The Commonwealth of Massachusetts 

 Department of Food and Agriculture 

 State Reclamation and Mosquito Control Board

100 Cambridge Street, Boston 02202

J.Kenney DFA Chairman Margaret Havey, Secretary 

G.Gonyea DEP 617-727-3000 X 137 

C.Burnham DEM 

 October 14, 1998 

Enclosed is the "final" Generic Environmental Impact Report (GEIR) 

for the Massachusetts Mosquito Control Projects. The use of 

quotation marks around "final” denotes the Board's intention that 

there never will be an actual final version of this report. It 

is our goal to update this document on a yearly basis as new ideas 

and approaches to mosquito control become known, new pesticides or 

equipment come on the market or improved techniques are made 

available. 

This GEIR will become a living document, which will change and 

improve over the years, rather than be a static report becoming 

outdated in a few short years. As these improvements come to the 

Board's attention, and are reviewed and found to be valid and 

useful, addendum will be issued in order to continually update the 

report. 

Yours truly, 

John Kenney 

Chairman 
TABLE OF CONTENTS 

I. CERTIFICATE OF THE SECRETARY OF ENVIRONMENTAL AFFAIRS 1-5 

II. EXECUTIVE SUMMARY 6-34 

III. INTRODUCTION, HISTORY, CURRENT ORGANIZATION, AND PRACTICE OF 

 MOSQUITO CONTROL IN MASSACHUSETTS 35-97 

A. Legislation and Regulation 

 1. Overview 

 2. State Laws 

 a. M.G.L. Chapter 252 as currently amended - Improvement of Lowlands. 

 b. M.G.L. Ch. 132B -- Pesticide Control Act (From the Code of Massachusetts 

 Regulations 333 CMR 2.00 -10.00) 

 c. 333 CMR 10.03 (21-23) - Amendments of 1983. 

 d. M.G.L., Chapter 91. Sections 1-63 -- Waterways 

 e. M.G.L., Chapter 40. Section 5 - Boards of Health and Supervision. 

 f. M.G.L., Chapter 131. Section 40 - Wetlands Protection Act. 

 g. Section 40A of Chapter 131. Inland Wetlands Restriction Act. Section 105 of 

 Chapter 130. Coastal Wetlands Restriction Act. 

 h. M.G.L., Chapter 131A. Massachusetts Endangered Species Act. 

 i. M.G.L., Chapter 132A. Sections 13-16, 18 of Ocean and Coastal Sanctuaries Act 

 j. Acts of Enabling Legislation Establishing Mosquito Control Projects 

 3. Federal Laws 

 a. Section 401. Clean Water Act: Water Quality Certification. 

 b. Section 404. Clean Water Act (1972). 

 c. Endangered Species Act. 

B. Current Mosquito Control Programs in Massachusetts 

 1. Formal Mosquito Control Projects 

 2. Non-Member Communities. 

 3. Other Programs 

 a. Department of Environmental Management 

 b. Department of Public Health 

 c. Federal Lands 

 d. Private Reserves. 

C. Historical Overview of Mosquito Control Practices in Massachusetts 

 1. Practices prior to 1980 

 2. Transitioning: from 1980 to 1995. 

D. Current Mosquito Control Strategies in Massachusetts 

 1. Overview 

 2. Current Practice 

 a. Saltmarsh Mosquitoes 

 b. Inland Freshwater Wetlands 

 c. Irrigated and Other Man-Made Reflood Habitats 

 d. Urban Habitats 

 3. Current Policies 

 a. Requests for Control 

 b. Documentation for Control Implementation 

 c. Selection of Control Strategies 

 d. Evaluation of Efficacy 

 e. Public Participation 

E. Eastern Equine Encephalitis 

 1. Responsibility for Surveillance and Control. 

 2.. Effect of EEE on Projects 
IV. DESCRIPTION OF MOSQUITO SPECIES AND ABATEMENT HABITATS 98-116 

 A. Mosquito Species 

 1. General biology of Massachusetstts mosquitoes 

 2. Salt marsh mosquitoes 

 3. Freshwater mosquitoes 

 a. Aedes canadensis 

 b. Aedes vexans 

 c. Additional Aedes species 

 d. Culex species 

 e. Culiseta species 

 f. Coquillettidea perturbans

 g. Other freshwater species 

 B. Habitats in which mosquito control takes place 

 1. Coastal Wetlands 

 a. Marine 

 b. Brackish 

 2. Inland Wetlands 

 3. Surface Water Bodies 

 a. Lakes and Ponds 

 b. Rivers and Streams 

 4. Recharge Areas 

 a. Wetland 

 b. Upland 

 5. Upland Areas 

 6. Agricultural Areas, with emphasis or sensitive areas such as apiaries and organic 

 farms. 

 7. Sensitive environments 

 a. Urban 

 b. Recreation 

 c. Sensitive individuals 

 d. Public and Private Wildlfie Refuges and Conservation Areas 

 e. ACEC and areas with rare or endangered species 

 f. Water supplies 

 C. Mosquitoes as disease vectors. 

 1. Easten Equine Encephalitis 

 2. California Encephalitis vectors 

 3. Dog heartworm 

V. CURRENT ABATEMENT STRATEGIES AND THEIR IMPACTS 117-219 

A. Chemical Control 

 1. Overview of Chemical Control 

 a. General Toxicity of Pesticides 

 b. Pesticides used for Mosquito Control in Massachusetts 

 c. General Properties of Registered Mosquito Control Insecticides in 

 Massachusetts, 1996 

 d. Pesticide Handling and Application 

 2. Larvicides 

 a. Biologicals: Bti and B. sphaericus

 b. Methoprene 

 c. Oils 

 d. Others 

 3. Adulticides 

 a. Pyrethrum and Synthetic Pyrethroids 
 b. Malathion 

B. Biological Control. 

 1. Introduction 

 2. Predators 

 a. Introduction 

 b. Vertebrate predators 

 c. Invertebrate predators 

 3. Parasites and Pathogens 

 a. mermithid nematode parasites 

 b. Microsporidia 

 c. Fungal Pathogens 

 c. Bacterial pathogens 

 d. Viral Pathogens 

 4. Pest Species Manipulation 

 a. Sterile Insect Technique 

 b. Incompatibility 

 c. Chromosomal Aberrations 

 d. Competitive Displacement 

 5. Other Control Approaches 

 a. Trap out techniques. 

 b. Repellents. 

C. Physical Control 

 1. Types of Habitat Modification 

 a. Open marsh water management (OMWM) 

 b. Other Modification Strategies 

 c. origination of Requests for Physical Control 

 2. Ecosystem changes of non-target biota as a result of physical controls. 

 a. Salt Marsh . 

 b. Freshwater Wetlands (exclusive of Vernal Pools) 

 c. Vernal Pools. 

 d. Rare and Endangered Species. 

D. Food Web Effects of Mosquito Control 

E. No Program 

VI. MOSQUITO CONTROL INTEGRATED PEST MANAGEMENT 220-236 

 A. Definition of IPM as it relates to mosquito control 

 B. 

 Aspects of IPM currently in place in Massachusetts mosquito control programs 

VII. STANDARDS FOR MOSQUITO CONTROL 237-244 

A. General policy regarding standard mosquito-control procedures 

 B. Standards for Monitoring and Control 

1. Larval Mosquito Populations 

 a. Larval indentification 

 b. Pre-control larval monitoring 

 c. Post-control monitoring 

 d. Additional water management requirements 

 e. Pre-hatch work 

 2. Adult Mosquito Populations 

 a. Monitoring for adulticiding 

 b. Further notes on complaint calls 

 c. Adult identification 

 d. Post-adulticide monitoring 
 C. Standards for Physical Control 

 1. Source Elimination 

 a. Tires 

 b. Blocked drainage 

 c. Residential problems 

 d. Drainage basin design 

 2. Source Maintenance 

 a. Stormwater runoff and ditch maintenance 

 b. Saltmarsh ditching 

 c. Waste disposal 

 3. Source Reduction 

 a. Open marsh water management 

 b. Freshwater wetlands 

 c. Cattail control 

 D. Standards for Biological Control 

 1. Larvivorous fish 

 2. Other biological control agents 

 E. Standards for Public Noltification, Public Awareness and Education 

 1. Public Notification 

 2. Public Awareness and Education 

 3. Staff Development 

 F. Standards for EEE Monitoring and DPH Liason 

 1. Role of programs in EEE Surveillance 

 2. Standard Operating Procedures during EEE Problem. 

VIII. SUMMARY AND RECOMMENDATIONS 245-250 

IX. WRITTEN COMMENTS ON GEIR 251 

 A. Comments on Notice of Project Change (1996). 

 B. Comments on Spring 1997, Rough Draft. 

C. Comments on Final Rough Draft (1997-98). 

X. LITERATURE CITED 252-260 

APPENDICES: 

A. Questionnaires, 1986 and 1996 261 

B. DPH EEE Program 262-269 

C. Sample Labels and Material Safety Data Sheets for pesticides currently in use 270 

D. North East Massachusetts MCP Standards for Open Marsh Water Management 271 

E. Stormwater Management 272-274 

F. North East Massachusetts MCP Standards for Ditch Maintenance 275 

G. Educational Flyers about Mosquito Control 276 

H. Preparer qualifications 277-278 
CERTIFICATE OF THE SECRETARY OF ENVIRONMENTAL AFFAIRS ON THE GENERIC 

ENVIRONMENTAL IMPACT REPORT 

PROJECT NAME Mosquito Control Program 

PROJECT MUNICIPALITY Statewide 

PROJECT WATERSHED Statewide 

EOEA NUMBER 5027 

PROJECT PROPONENT State Reclamation & Mosquito Control Board 

DATE NOTICED IN MONITOR: October 25, 1998 

As the Secretary of Environmental Affairs, I hereby determine that the Generic Environmental Impact 

Report (EIR) submitted on this project adequately and properly complies with the Massachusetts 

Environmental Policy Act (M.G.L. c. 30, ss. 61- 62H) and with its implementing regulations (301 CMR 

11.00). 

On September 23, 1996 the Secretary of Environmental Affairs issued a Certificate on a Notice of 

Project Change filed by the State Reclamation and Mosquito Control Board (SRMCB) requiring that a 

Generic Environmental Impact Report (GEIR) be completed, for mosquito control in the 

Commonwealth. The Certificate contained an extremely detailed scope for the GEIR, developed in 

coordination with SRMCB. This GEIR, by responding to all of the items in that scope, provides an 

extremely useful summary of' current data, practices, and standards for mosquito control statewide. In 

particular, the GEIR establishes that Open Marsh Water Management (OMWM) shall serve as the 

preferred practice for physical controls in salt marshes. The GEIR also highlights certain areas in which 

further research will be necessary, and it. 

1 - The State Reclamation and Mosquito. Control Board (SRMCB) is comprised of one representative 

each from the Departments of Environmental Management, Environmental Protection and Food and 

Agriculture proposes a system of annual updates, offering continued opportunities for review and 

comment on new information and proposals. 

Introduction

The SRMCB oversees nine organized mosquito control projects (Berkshire County, Bristol County, 

Cape Cod, Central Massachusetts, East Middlesex County' Norfolk County, Plymouth County, Suffolk 

County and the North East Massachusetts Mosquito Control and Wetlands Management District) and 

appoints the Board of Commissioners for each project. These mosquito control projects have a total of 

157 participating communities, primarily coastal. Thus, the focus of the GEIR and this Certificate are 

primarily upon salt marshes and their attendant pest mosquito problems. The remaining nonparticipating 

communities, mostly located in the central portion of the state practice no mosquito control, hire private 

contractors or have their own community-based mosquito control operations (e.g., the local public 

works department or health board). 

The intent of the GEIR was to gather, in single document information on methods of mosquito control 

and eradication in Massachusetts, and the environmental impacts of those methods. The GEIR has 

accomplished the goal of disseminating information on current mosquito control practices, and it has 

established the basis for viewing OMWM as the preferred control technique in salt-water marshes. 1
Comments received from the Department of Environmental Protection (DEP) and the Division of 

Fisheries and Wildlife (DF&W), in particular, will provide a good basis for future GEIR updates. 

However, the GEIR falls short of the ambitious goal of providing the basis for all future mosquito 

control projects implemented by the County Mosquito Control Projects. The SRMCB and, the GEIR 

acknowledge that additional study and research work is necessary to truly document ~he effectiveness 

of mosquito control techniques and their impact on the environment, particularly as they relate to 

freshwater projects. The report concludes that it will take a renewed and concerted effort, involving 

additional resources, to complete a mosquito control program "master guidance document" that best 

serves the public and protects the environment. To that end, the SRMCB plans to update the GEIR on a 

yearly basis as new ideas and approaches to mosquito control become known. 

Saltwater Marsh Regulation Issues and MEPA 

Established mosquito control projects are generally exempt from the Massachusetts Wetlands Protection 

Act (MWPA). However, Section 401 of the Federal Clean Water Act requires applicants wishing to 

discharge dredged of fill materials to obtain a certification or waiver from their state water pollution 

control agency. A Section 401 water quality certification is treated as a state permit for the purposes of 

establishing MEPA jurisdiction. Therefore, for projects involving new ditching such as that required for 

Open Marsh Water Management (OMWM), the MC proponent has been obliged to file an 

Environmental Notification Form (ENF) for, projects affecting at least 1,000 square feet of salt marsh or 

5,600-sf- of bordering-vegetated wetlands (BVW). The MEPA regulations require the filing of an 

Environmental Impact Report (EIR) for any particular work site that might require the alteration of one 

or more acres of salt marsh or BVW. 

In November 1995 the then-Essex County Mosquito Control Project (now the Northeast Massachusetts 

Mosquito Control and Wetlands Management District) filed an ENF requesting a waiver from the EIR 

requirement- (EOEA #10567). Based on a number of "findings and conditions" discussed below, a 

waiver from the EIR requirement was granted in February 1996. The most significant of those findings 

.was that the Essex County Mosquito Control Project established "Standards for Open Marsh Water 

Management" which were endorsed by the Environmental Protection Agency, the National Marine 

Fisheries Service, the Massachusetts Audubon Society and others. These standards are widely viewed as 

the least harmful to the environment (of the various control techniques) and most efficient non-pesticide 

method for controlling salt marsh mosquitoes. The-proponent also committed-' to conduct a review of 

ten years of OMWM in Essex County to provide a basis for comparison and evaluation of mosquito 

control effectiveness and impact to the environment. It is generally recognized that the principal concern 

associated with OMWM arises" from the disposal of the dredge material on the marsh and the potential 

for invasion of upland plants (particularly Phragmites) that can occur with even slight elevation 

increases (i.e." 1-2 inches). 

Open marsh water management (OMWM) projects are now underway in Essex (EOEA #10567), 

Norfolk, and Plymouth counties and are being expanded to include all problem marshes in those 

counties. The need to convert grid ditch systems is likely to continue and the salt marsh alterations will 

likely exceed the one-acre EIR threshold at several locations. Based on the success of OMWM, 

The establishment of "Standards for Open Marsh Water Management," the conclusions of this GEIR, -

and the commitment to continue to monitor the effectiveness of OMWM on the control of mosquitoes 

and, its impact on the environment, I am proposing, in a -forthcoming issue of the Environmental 

Monitor, to publish a Draft Record of Decision that would modify" the ENF and EIR thresholds for 

OMWM projects2, subject, at a minimum, to the following standards and conditions: 

2
2 The MEPA regulations at Section 11.01 (2) (b)"(3) under" Review Thresholds" state, in part, that the 

review thresholds do not apply to..." a project that is consistent with a Special Review Procedure review 

document, or other plan or document that has been prepared with the express purpose of assessing the 

potential environmental impacts from future Projects, has been reviewed under or approved by any 

Participating Agency, unless the' filing of an ENF and an EIR was required by a decision of the 

secretary on any such review document, plan or document." 

* That the Northeast Massachusetts Mosquito Control and Wetlands Management District "Standards 

for Open Marsh Water Management" be used as the statewide standard for OMWM projects. 

* That the salt marsh be inventoried for the presence of rare and endangered species as determined by 

the Natural Heritage and Endangered Species Program (NHESP) habitat maps. If a project falls within 

such an area, NHESP will then determine if the area to be altered is an actual wetland habitat for rare 

species. 

* Compliance with Section 401 of the Federal Clean Water Act and Federal Coastal Zone Consistency. 

* Improved record keeping with respect to treatment location, type, efficacy and post treatment 

monitoring. For example, there are old ditches that still effectively control mosquitoes therefore their 

effectiveness should be monitored prior to going ahead with OMWM. 

MC Projects Impact on Freshwater Wetlands

Freshwater wetlands are the dominant system in which freshwater physical control take place. 

Typically, this work consists of maintaining (i.e., moving blockages from previously ditched areas) 

existing ditches designed to remove standing water from the wetland. Though reducing standing water 

reduces mosquito breeding, there has been little research concerning the overall effects of these 

alterations on the modified wetland. Therefore, increased efforts are necessary to examine the 

environmental effects of draining surface water from wetlands. 

As stated above, most of the freshwater mosquito control projects are geared to removal of blockages, 

be they natural or influenced by man, in wetland areas earlier identified as significant mosquito 

breeding habitats. These projects usually are classified as maintenance projects and are therefore exempt 

from MEPA review pursuant to Section 11.01 (2) (b) (3). However, there is a significant amount of 

work that needs to be completed in order to determine whether such work is cost effective, and whether 

a specific alternative is the one least damaging to the environment. As the report acknowledges there 

has been no study to date of the costs and benefits of Massachusetts mosquito control programs. 

However, this work has been done in other states, most notably New Jersey, which should be helpful in 

answering the following questions raised in the GEIR: 

1) Establishing substantive human annoyance thresholds 

2) Documenting how human activity patterns relate to Human Annoyance Thresholds (HAT) and 

economic factors; 3) Determining the cost/benefit of control; and 

4) Correlating densities of immature mosquito (i.e., larvae) with future levels of biting annoyance. 

These issues should be addressed and reported on in future GEIR updates. EOEA is prepared to help in 

this regard. 

3
Standards for Freshwater Wetland Physical Control 

The GEIR indicates that the SRMCB still needs to determine the appropriate control measure standards 

for MC projects in freshwater wetlands (described in the report as Upland Water Management 

operational procedures). These standards will need to 

 The current provocations for execution of mosquito control techniques are generally as follows: 

1. Larval populations - by dip count (up to 20 per sampling area) and based on the population #s/10 or 5 

dips then a decision is made to either use a pesticide or water management strategy. 

2. Adult populations - No adulticiding is to take place at a regularly scheduled or prescribed time or 

place. Instead spraying is done based on annoyances, such as five bites per night; more than one landing 

per minute; or two complainant calls per square mile of area be coordinated with the DEP's Storm water 

Policy Handbook and Storm water Technical Handbook. In addition, many physical control projects 

lack adequate records, both with respect to the justification of a specific project, and with respect to site 

plans. Therefore, the SRMCB should work toward requiring better record keeping and notification 

practices, as discussed in the DEP comment (and the Coastal Zone Management letter for salt marsh 

alterations). 

Integrated Pest Management (IPM) 

The GEIR indicates that the strengths of the Massachusetts mosquito control IPM include the 

availability of and willingness to use least-toxic materials and willingness of existing control programs 

to try new strategies. In addition, a successful IPM program requires strong control programs and good 

pretreatment monitoring. The weaknesses of the IPM have been linked to a lack of funds for research 

and implementation and a lack of basic ecological data on the effects of control strategies in use or 

being planned. I do note that all of the pesticides -(larvicides and pesticides) used by MC projects have 

been approved by and are registered with the US Environmental Protection Agency. Given the rigorous 

process to gain market approval for a pesticide as well as the evolving nature of pesticide development, 

I agree with the conclusions of the GEIR that, for now, advances in reducing the risk of chemical use 

must come from improved targeting and increased use of water management and/or biological control 

techniques as encouraged by the IPM technique. 

Eastern Equine Encephalitis (EEE) 

The Massachusetts Department of Public Health (DPH) is responsible for surveillance for EEE Virus, 

risk assessment, public information and education on EEE disease. DPH is also responsible for 

recommendations for wide aerial vector control, interventions. DPH published its "Vector Control Plan 

to Prevent Eastern (Equine) Encephalitis" on (August 7, 1991). That protocol will govern when the next 

EEE outbreak occurs. The DPH has also developed a monitoring program that should bring EEE into 

the IPM framework. I urge that this work continue in order to avoid the adversity that accompanied the 

1990 aerial spraying. 

GEIR Recommendations and Conclusions 

In addition to the issues discussed above, GEIR updates should emphasize how MC programs will 

incorporate the IPM strategy of keeping human annoyance below specified thresholds. Standards for 

control methodology should favor source reduction (e.g., OMWM in salt marshes) whenever possible, 

and employ larvicide control only when source reduction is not effective. Projects should work closely 

with the DEP water quality certification program and the NHESP to improve notices and 

documentation, and to minimize negative impacts of source reduction. 4
It is clear that the SRMCB and the MC projects have a good handle on their data and research needs. 

The stumbling block to successful completion of the analysis appears to be primarily fiscal in nature. I 

am pleased with the SRMCB's commitment to provide yearly updates, and I expect that issues brought 

forward in this Certificate, as well as the comments from the DEP and DF&W, will be addressed in the 

first yearly update. The SMRCB should meet with MEPA prior to finalizing the content of the GEIR 

update. 

5
State of Massachusetts 

Generic Environmental Impact Report on Mosquito Control 

Executive Summary 

I. Introduction 

A Generic Environmental Impact Report (GEIR), covering mosquito control activities within the State 

of Massachusetts, was mandated under the provision of Massachusetts General Laws Chapter 30A Section 61 by

the Massachusetts Environmental Policy Act (MEPA) Regulation 301 CMR 10.32(5)(b) adopted on January 25, 

1979. The State Reclamation and Mosquito Control Board (SRMCB), the state agency that oversees all local and 

regional mosquito control programs in Massachusetts, administers the GEIR. The SRMCB consists of one 

representative each from the Departments of Environmental Management, Environmental Protection, and Food and 

Agriculture. The latter member presently serves as the Chairman of the Board. 

This GEIR serves five purposes: 

1. It provides a historic summary of all public activities in Massachusetts related to mosquito control, 

including an account of how mosquito control in Massachusetts has rapidly evolved over the past

ten years. 

2. It describes and quantifies Massachusetts mosquito problems and assesses the effectiveness of 

past and current control programs. 

3. It assesses the real and potential environmental impacts of past and current control practices and 

describes and evaluates alternative strategies. 

4. It gives an IPM framework for mosquito control in Massachusetts and provides a series of 

operational standards for mosquito control practices. 

5. It makes recommendations relative to the future organization and practice of mosquito control in

Massachusetts. 

6
II. History, Organization and Practice Of Mosquito Control In Massachusetts

A. Legislation and Regulation 

 1. State Laws 

 The first Act of major importance is Chapter 252 of the Massachusetts General Laws (MGL), 

which establishes the State Reclamation and Mosquito Control Board (SRMCB) and procedures for creating local

control projects. As now amended, 252 includes the important earlier provisions of Chapters 199 and 699 of the 

Acts of 1960. The word improvement (of wetlands) as frequently used in the narrative for this Act is misleading. 

Modification or alteration would have been a more appropriate and objective term to describe wetland drainage and 

filling activities. 

The second Act is the Wetlands Protection Act (Chapter 131 of MGL) which regulates activities in the 

aquatic and brackish habitats where most mosquitoes breed. However, organized mosquito control is generally

exempt from the provisions of this State Law. Hence, the Federal Clean Water Act as administered by the U. S. 

Corps of Engineers, is the principal regulating mechanism for mosquito-control alterations in wetlands. Regardless 

of the general exemption, mosquito control is not exempt from checking for the presence of rare and endangered 

species through the Massachusetts Natural Heritage Atlas, which lists estimated habitat maps for all rare and

endangered species as developed by the Natural Heritage Endangered Species Program (NHESP). 

The third Act which influences mosquito control in the Endangered Species Act (Chapter 131A of MGL) 

which prohibits the “taking” of rare and endangered species. It also protects “significant habitats,’ requiring a 

permit request for any work done in such areas. 

The fourth Act of importance to mosquito control activities is the Pesticide Control Act (Chapter 132B of 

MGL) which regulates pesticide use by mosquito control practitioners. 

Three additional Acts have the potential to impact mosquito control. M.G.L., Chap. 91. Sections 1-63 -- 

Waterways does not deal specifically with mosquito control but it does cover variety of activities associated with

wetlands. Mosquito control is specifically exempted from the provisions of Sections 19A, 59 and 59A of this law 

but not from other provisions. M.G.L., Chapter 40. Section 5 - Boards of Health and Supervision, contains clauses 

that address the issue of appropriating money at the municipal level for mosquito abatement. M.G.L., Chapter 

132A. Sections 13-16, 18 -- Ocean and Coastal Sanctuaries Act, Section 14, is designed to is to protect designated

ocean sanctuary from any "...exploitation, development, or activity that would seriously alter or otherwise endanger the 

7
ecology or the appearance of the ocean, the seabed, or the subsoil (of the sanctuaries), or the Cape Cod National 

Seashore." Mosquito control does not take place in these sanctuaries. 

 2. Federal Laws 

 Federal laws which directly impact on mosquito control activities are Sections 401 and 404 of the Clean 

Water Act and the Endangered Species Act. All other federal restrictions governing wetlands and pesticides are 

covered by Massachusetts laws which impose restrictions and requirements that are equal to or greater than those in

comparable federal law. The exception in the case of Section 404 arises because the state laws governing the 

ditching of wetlands exempt mosquito control but the Federal Clean Water Act does not. 

Section 401 (Clean Water Act: Water Quality Certification) requires applicants wishing to discharge 

dredged or fill materials to obtain a certification or waiver from their state water pollution control agency 

(Massachusetts Bureau of Resource Protection, Division of Wetlands and Waterways). The U. S. Army Corps of 

Engineers will not permit a mosquito-control project that does not have a water quality certification.

Section 404 of the Clean Water Act (1972), calls for a system of permitting to be carried out by the U.S. 

Army Corps of Engineers with a review of al! permit applications by appropriate state and federal agencies. The 

activities that involve mosquito control which require a permit under Section 404 are cutting or clearing new 

mosquito ditches in tidal areas below mean high water and/or placing material excavated from existing or new 

ditches on salt marshes or freshwater wetlands. 

The Endangered Species Act is designed to protect threatened and endangered species as listed on the 

Natural Heritage Atlas. To date, several programs have had to modify their control effort to take into account

endangered species. 

B. Current Mosquito Control Programs in Massachusetts

 1. Formal Mosquito Control Projects 

 Of the 351 Towns in Massachusetts, 157 (or 44.7%) currently belong to the 9 organized mosquito control

projects. Each project is managed by a superintendent who is hired and supervised by a Board of Commissioners 

representing the towns included in the project. Board members are appointed by the Board of Reclamation for 

designated terms (usually 3-5 years). Boards generally meet once or twice monthly to authorize major expenditures 

and to review policy and program progress. 

The SRMCB is made up of three members, one each from the Departments of Food and Agriculture, 

8
Environmental Management and Environmental Protection, and exercises responsibility over all 9 projects. All 

projects have a Board of Commissioners appointed by the SRMCB. They represent the various towns within each 

project and exercise general control over the project. 

The Nine Mosquito Control Projects of Massachusetts are Berkshire County, Bristol County, Cape Cod, 

Central Massachusetts, East Middlesex County, Norfolk County, Plymouth County and Suffolk County Mosquito

Control Projects and the North East Massachusetts Mosquito Control and Wetlands Management District (formerly

Essex County MCP). Nantucket conducts saltmarsh mosquito control including larviciding and open marsh water 

management. 

 2. Other State Agencies 

The State Division of Forests and Parks discontinued its own mosquito control program in. The North East

Massachusetts Mosquito Control and Wetlands Restoration District (NEMMCWRD) adulticides Salisbury Beach 

State Park and Bradley Palmer State Park in Hamilton as the need arises. 

The Massachusetts DPH is responsible for surveillance for EEE Virus, risk assessment, public information 

and education on EEE disease, as well as providing advice to the State Reclamation and Mosquito Control Board on 

appropriate risk management for EEE. DPH is also responsible for recommendations for wide area aerial vector 

control interventions in the event of an EEE Public Health Emergency. 

 3. Federal Property

No mosquito control is carried out by the U.S. Department of Interior on any government-owned land in

Massachusetts. The Cape Cod National Seashore is perhaps the U.S. Park Service property with the most

significant mosquito populations. Park Service biologists have conducted their own studies on the environmental

impact of Cape Cod mosquito control activities (Portnoy 1983, 1984a, 1984b) in adjacent estuaries and have 

lobbied against certain ditch cleaning practices on environmental grounds. 

The East Middlesex MCP has been controlling mosquitoes in Great Meadows National Wildlife Refuge 

since 1987. Annual aerial Bti applications targeted against spring Aedes species began in 1987 and applications to

control Aedes vexans began in 1990. The National Park Service reservation area (Paul Revere's Ride) in East 

Middlesex County has been declared off limits to any mosquito control activity (by East Middlesex MC project) 

except for ditch cleaning. 

The NEMMCWRD has completed OMWM projects on the Parker River Wildlife Refuge. 

9
C. Overview of Mosquito Control Practices in Massachusetts

Development and tourism along the Massachusetts coast is predicated on an ability to control the hoards of 

saltmarsh mosquitoes. Massive hand-ditching projects in East Coast marshes that took place during the WPA 

programs of the great depression. These ditching schemes, while quite effective in reducing saltmarsh mosquitoes, 

were engineered to make work rather than for optimum biological efficiency. 

 Early saltmarsh mosquito control projects, such as the one on Cape Cod in the 1930's, were organized prior 

to the availability of synthetic pesticides following World War II and these projects expanded and maintained the 

WPA-dug ditch system as their main strategy for mosquito control. After DDT, BHC, and other organochlorine 

pesticides became available, they were used to both supplement larval control and, for the first time, to conduct 

residual spraying for adults. Aerial application of these pesticides became commonplace in the 1950's and early 

60's. The commercial mosquito control oil, Flit ML0, was introduced and widely used during the 70's. 

Chemical control in freshwater marshes followed a similar pattern to that in salt marshes. Treatment of

catch basins, first with oils followed by organochlorines and organophosphates, dates back to the beginning of most

Massachusetts projects. 

Physical control was limited to drainage maintenance and expansion in both salt marshes and freshwater 

areas. Biological control was not conducted. 

By the early 1980s, concerns over pesticide use and wetlands loss began to encroach on mosquito control. 

Grid ditching for larvae and malathion for adults was no longer a desirable one-two punch. Control trends during 

the eighties and early nineties included: changing from traditional chemicals, such as Abate and Flit MLO, to Bti 

and methoprene for larval control, changing from malathion to permethrin or resmethrin for adult control, and 

changing from open tidal ditching to open marsh water management for saltmarsh mosquito control.

Source reduction remained a mainstay of the projects during this time period. Coastal communities shifted

away from ditch maintenance towards open marsh water management. An emerging difficulty for control programs 

is the rise in wet basins mandated by stormwater runoff regulations. 

The evaluation of control effectiveness by projects remained a combination of public complaints, adult 

counts, larval counts, and cases of human disease. 

Chemical control, including Bacillus products and IGRs, and source reduction, including open marsh water 

management, now dominate mosquito control in Massachusetts. Aerial applications of larvicide have been used by

10
several programs and are increasing. Biological control has not been emphasized except to the extent that OMWM

creates conditions under which biological control operates. Public education is a minor component of most

programs. 

Saltmarsh mosquitoes are the primary target of coastal programs, whereas inland programs target springbrood and summer-reflood Aedes. Coquillettidea perturbans is restricted by larval habitat to areas near cattail 

marshes but is a big problem in those areas. It complicates control efforts because controlling the larval stage with 

methoprene is expensive and adulticiding provides only short-term control. 

Vector mosquitoes are not the primary targets of Massachusetts control programs, though projects can 

respond to requests for aid from DPH in times of EEE emergencies. Culiseta melanura larval populations may be 

incidentally reduced by treatment programs that target swamp areas. 

At present, policy issues revolve around wetlands protection, water quality preservation, and endangered 

species. A chronic source of discussion is mosquito control’s exemption from many of the state-level wetlands 

protection acts, making the Federal Section 401 Water Quality Certification (administered at the state level) and the 

state and federal Endangered Species Acts the primary means of “controlling” source-reduction work. Stormwater 

runoff regulations have increased the number of wet basins (retention, wet detention) in many areas, on occasion 

creating breeding habitat

The EEE outbreak in 1990 highlighted a need for stronger DPH policies regarding emergency mosquito 

control. As a result, the Massachusetts Department of Public Health published “Vector Control Plan to Prevent 

Eastern (Equine) Encephalitis” (August 7, 1991) and implemented an extensive Public Education Program in 1991. 

 

The combination of large, affluent human population (both permanent residents and visitors) and prolific

pest mosquito populations near Massachusetts coastal marshes suggests that the public may always demand control

programs to deal with this problem. 

Open Marsh Water Management (OMWM) projects now underway in Essex, Norfolk, and Plymouth 

counties are being expanded to include essentially all problem marshes in those counties. The trend to convert gridditch systems to OMWM is likely to continue. 

 There are certain salt marshes where old ditches are effectively controlling mosquito production and 

perhaps where new OMWM activities might actually disrupt the marsh more than maintaining the status quo. Thus, 

11
OMWM plans should not be automatically prescribed for every saltmarsh without first examining this issue. 

Larviciding is still carried out in salt marshes. 

Inadequate budgets, the inability to conduct more source reduction work and a lack of applied research 

into more environmentally sound mosquito-control practices continue to restrict the actions and effectiveness of 

mosquito control programs in Massachusetts. 

III. Current Abatement Strategies and Their Impacts 

 A. Chemical Control 

Twenty-six different insecticide formulation distributed among fifteen product lines were used for 

mosquito control in Massachusetts between 1993 and 1995 (Table 1). Eight of these formulations used Bti as the 

active ingredient, five were methoprene-based, three were resmethrin-based, two each were pyrethin-based or 

malathion-based, and there were one each of temephos, isoctedecanol, and mineral oil. Of these, Acrobe (Bti) and 

Vectobac AS (replaced by 12AS) are no longer produced. Arosurf-MSF (Isoctadecanol) was off the market for 

several years but is now available under the name Agnique MMF. Abate 4E was not used in either 1994 or 1995 

and both the Malathion 10EC and the Resmethrin product (EPA reg. # 4-339-53853) were used in small amounts 

only

Of the insecticides used, all of the larvicides were classed as Category IV (Category I is the most toxic, 

Category IV the least) materials by EPA. Bonide Mosquito Larvicide, available but not used, is border line between 

Category III and IV. VectoLex CG, a new Bacillus sphaericus product, is Category IV. All adulticides are in 

Category III, with permethrin and resmethrin having essentially replaced malathion. 

Chemical impacts include acute, direct impacts to target and non-target organisms, and chronic or indirect

effects to target and non-target organisms. In general, acute toxicity effects are generally easiest to measure and 

avoid, particularly when the organism is large and the effect is death. However, less visible acute toxicity, such as

12
Table 1. Chemicals used in Massachusetts mosquito control, 1993 through 1995

Trade Name EPA Registration Active % Active Toxicity Other 

 Number Ingredient(s) Ingredient Class Warning Statements

LARVICIDES

Abate 4E 241-132 Temephos 43 IV 

Acrobea

 62637-1-241 Bti

b

 IV 

Arosurf-MSFc

 42943-8 Isooctadecanol 100 III 

Altosid

Briquets 2724-375-64833 Methoprene 7.9 IV 

 XR Briquets 2724-421-64833 Methoprene 1.8 IV 

 Pellets 2724-448-64833 Methoprene 4.0 IV 

Bactimos

Briquets 43382-3 Bti 10 IV 

 Granules 37100-43-2217 Bti 0.2 IV 

 Pellets 37100-42-2217 Bti 0.4 IV 

GB-1111 8898-16 Petroleum Hydrocarbons 

GB-1356 8898-16 

Teknar HP-D 2724-365-64833 Bti 0.8 IV 

Vectobac 

 AS 275-52 Bti IV 

 12AS 275-66 Bti 1.2 IV 

 Granular 275-50 Bti 0.2 IV 

ADULTICIDES

Malathion 8EC 34704-119 Malathion 8 III 

Permanone 10EC 4816-688 Permethrin 10 III 

Permanone 31-66 4816-740 Permethrin 31 III 

Resmethrin 4-339-53853 Resmethrin III 

Scourge 4+12 432-716 Resmethrin 4 III ⎫ ⎧RESTRICTED USE 

 PBO 12 ⎬ ⎨ CLASSIFICATION 

Scourge 18+54 432-667 Resmethrin 18 III ⎪ ⎪Due to acute fish toxicity 

 PBO 54 ⎭ ⎪Retail sale to and use only by 

 ⎪Certified Applicators or 

 ⎪persons under their direct 

 ⎪supervision and only for those 

 ⎪uses covered by the Certified 

 ⎩Applicators Certificate 

MATERIALS REGISTERED BUT NOT USED - LARVICIDES

Altosid

 Liquid 2724-392-64833 Methoprene 5 IV 

 Liquid Con 2724-446-64833 Methoprene 20 IV 

Bonide Mosquito

 Larvicide 4-195 Mineral Oil 98 III-IV 

VectoLex CG 275-77 B. sphaericus 50d

 IV 

MATERIALS REGISTERED BUT NOT USED - ADULTICIDE

Fyfanon ULV 4787-8 Malathion 95 III a

No longer marketed b

Bacillus thuringiensis var. israelensis c

Now marketed as Agnique MMF

13
methoprene toxicity to Chironomid larvae in duck-breeding habitat (SPRP 1996), may cause harm in the short term, 

and, since it often goes unnoticed, may be harmful in the long run as well. Mosquito Control Programs have 

limited, but not removed, the threat of acute impacts to non-targets by using pesticides that are more specific to the 

target, less toxic to non-targets, and/or have a shorter persistence in the environment. The amount of pesticide used, 

as in the case of ultra-low-volume sprays versus mist sprays, has also been reduced. 

 Chronic effects that may occur include the long-term effect of the chemical on targets (development of 

resistance to the chemical) and non-targets (reduced reproductive success), and long-term effects caused by a 

change in the ecosystem brought about by removal of the target organism. The current assumption is that the 

mosquitoes controlled are those which have escaped the food web and which, therefore, may be eliminated without

undue risk to the food web itself. That mosquitoes are remarkably productive cannot be denied. That removing 

millions of larvae from the food web of a salt marsh by the application of Bti has no effect on that ecosystem

deserves additional study, as does the role of mosquitoes in the ecosystem, and the effect of mosquito control on 

that ecosystem. 

Control personnel should take care to avoid chemical applications where mosquito larvae are not present or 

are present in very small numbers, should use control measures that do not harm existing predator complexes, and 

should limit control to areas where control is necessary, allowing natural cycles to continue in areas where human 

activity and the risk of disease transmission is slight. One argument made in favor of Altosid is that it does not kill 

the young larvae, leaving them available as food for the existing predator complex. 

Barring the discovery of new materials, both adulticiding and larviciding are presently be conducted with 

the least risk imposing materials available for the foreseeable future. Advances in reducing the risk of chemical use 

must therefore come from improved targeting and increased use of water management and/or biological control

techniques. 

B. Biological Control.

Biological control includes attacks on the pest species by other species and manipulation of the pest species 

itself. Only the former has been used in Massachusetts. Note that, for the purposes of this GEIR, Bti, Bacillus 

sphaericus and methoprene are classified as chemical controls and open marsh water management is classified as a 

physical control. A case can be made for classifying each of these strategies as a type of biological control. 

Biological control agents are grouped into three categories: predators, parasites and pathogens. Predators 

14
include both vertebrates and invertebrates and may attack both adult and immature stages of mosquitoes. In 

general, biological control is much more feasible in managing permanent water mosquitoes than temporary water 

forms. 

There are three basic strategies for utilizing all biological control agents: 1) increasing existing natural 

enemy populations by habitat improvement, 2) one-time introduction of sustainable exotic agents from other regions 

or habitats, and 3) augmentation of natural or exotic enemy populations by repeatedly releasing non-sustainable, 

lab-reared (or field collected) organisms. To date only the first, increasing fish habitat through OMWM, has been 

used in Massachusetts. Bti could arguably be classified as a biological control agent but its application technique 

and mode of action functioning as a stomach poison more closely resemble a pesticide than a biological control 

agent per se. Bacillus sphaericus may more closely fit the model of repeatedly releasing non-sustainable lab-reared 

organisms as there is evidence to suggest that it recycles within the environment.

There are important reasons why biocontrol is not more widely used against mosquitoes. First, the 

differences in biology of the various species of mosquitoes make it unlikely that any one control agent will operate 

across a wide range of species. Second, mosquito breeding is wide spread, making it difficult for a biological

control agent to find, or be placed in, all breeding areas. Third, predators such as bats and purple martins, may eat 

mosquitoes but prefer to eat other, larger insects. Finally, there is a high cost associated with sustained releases of a 

biological control agent and there are not, at this time, control agents available that require a single, or a few, 

releases to become established. 

The impacts on biological control have not received much attention because biological control has not been 

exercised to any great degree in Massachusetts. However, one of the primary reasons Gambusia are not being used 

in Massachusetts is the fear that they might displace native species of fish, thus altering the natural biota, not by 

predation but by competition for the same resource. 

C. Habitat Modification (Physical Control)

1. Salt Marshes. Open Marsh Water Management was originally developed for New 

Jersey salt marshes (Ferrigno 1970, Ferrigno and Jobbins 1968, Ferrigno et al. 1969), this strategy basically

attempts to overcome the limitations of ditching by incorporating other water management strategies. Reservoirs 

(which permanently hold water and sustain larvivorous fish) are created in selected tidal pools or large shallow pans 

and are connected via small shallow ditches to surrounding mosquito breeding depressions. This customized 

15
approach to marsh management represents the least deleterious and most efficient non-pesticidal method for 

controlling saltmarsh mosquitoes. 

New England coastal wetlands have been heavily impacted by man (Shisler 1990). However, evidence 

concerning the negative impact of saltmarsh ditch maintenance activity is mixed. The principal concern is with

disposal of the spoil on the marsh and the alleged invasion of upland plants that can occur with even slight elevation 

increases (i.e. 1-2 inches). OMWM effects are apparently limited (Wolfe 1996) but all alterations must be designed 

so that raised patches of marsh elder and other boundary plants are not created. 

2. Freshwater Wetlands (exclusive of Vernal Pools). Palustrine wetlands, including 

emergent, scrub-shrub and forested wetlands, are the dominant system in which Massachusetts freshwater physical 

control take place. Typically, this work consists of maintaining existing ditching designed to remove standing water 

from the wetland, thereby reducing mosquito-breeding habitat. For most MCPs, this type of work (source 

reduction) makes up a large percentage of their control effort. Though reducing standing water certainly reduces 

mosquito breeding, there has been little research concerning the overall effects of these alterations on the modified

wetland. Ditch systems can become problems in their own right, producing mosquitoes if left unmaintained. Most

of these systems were never designed specifically for mosquito control and their other, primary function, such as 

removing runoff from large parking lots, may cause considerable damage to the ecosystem, leaving the MCP to

clean up, or at least deal with, someone else’s mess. 

The majority of drainage systems currently maintained by MCPs were not initially constructed for 

mosquito control and the effort of MCPs today is almost entirely restricted to removing blockages to existing flows, 

rather than enlarging or straightening channels to increase flow. Road sand and yard waste represent two of the 

most common obstructions MCPs are called upon to remove from existing drainage networks. New developments

also can cause dramatic changes in the sediment load in streams, despite regulations designed to prevent such 

problems. Road sand, yard waste and increased sediment load from development can all have impacts on a stream

that are as greater or greater than regular ditch maintenance. Because MCPs are often involved in removing 

manmade sediments from streams, a system under appropriate ditch maintenance may function more closely to a 

natural system than one in which manmade wastes are allowed to accumulate unabated. 

The three broad categories of wetlands alteration are outright loss, changes in the abiotic system and 

changes in the biotic community. Filling and/or draining wetlands to convert them to upland is a mosquito-control 

16
practice that has been all but eliminated in Massachusetts. There is no indication that MCPs are intentionally 

reducing wetland acreage in order to control mosquitoes. However, the fact that the wetlands boundary remains 

essentially unmoved by a mosquito-control alteration does not mean that changes to the ecosystem have not 

occurred. 

Changes in the abiotic system and biotic community are deeply intertwined, though physical control most

often causes abiotic changes which then cause biotic changes. For channels changes in flow rates, microhabitats, 

sediment load, sedimentation, and groundwater interactions can all occur. For wetlands (outside of channels) 

changes can include lost water-storage capacity, increased sedimentation and pollutant load, changes in water depth, 

and changes in groundwater hydrology. 

When a stream is altered to improve water flow for the purpose of removing standing water, either within

the stream or from adjacent wetlands, a number of changes may take place. By definition, improving water flow 

increases runoff. This, in turn, may decrease the surface-water storage capacity of the wetland system and decrease 

the capability of the wetland to retain load (suspended solids). This may increase the load of the water moving

through the stream (Brown 1988). Increasing runoff into a given stream tends also to increase erosion, which 

further increases load (Williams & Feltmantle 1992). Not only may total flow be increased, but alteration tends to 

increase peak flow, which is associated with reductions in faunal diversity (Hynes 1972). Increased peak flow may

also lead to faster drying in intermittent streams. 

Maintenance for the purpose of reducing mosquito breeding also includes removing obstructions within

streams. Tree branches and fallen trees are a particularly important part of the stream environment, providing food, 

living space, concealment from predators, protection from abiotic conditions and emergence sites (Ward 1992). 

Removing these obstructions diminishes the variability of the stream ecosystem. 

The hyporheic zone, the interstitial space between the substrate particles in a stream bed, is an important 

part of the habitat for many stream species (Williams & Feltmantle 1992). Excessive drying can reduce the viability 

of the hyporheic zone. 

Sedimentation, both within stream beds and in wetlands into which streams flow, is a problem because it 

can alter the stream bed composition, thereby altering the fauna, and can clog interstitial spaces, thereby reducing 

the hyporheic zone and/or reducing groundwater recharge. Sediments can also increase exposure to pollutants as 

they provide additional sites for pollutant binding while suspended, and then carry the pollutants to the benthic 

17
fauna. Sedimentation, however, results most often from sources other than mosquito-control activities, and it is the 

primary cause of maintenance work. 

When new channels are constructed, they are typically designed to change standing-water wetlands to soilsaturated wetlands (New Jersey DEP 1997). Though this reduces mosquito breeding it can also adversely affect

other organisms that require standing water for periods other than peak flow. 

Increased drainage also has an effect on groundwater. Precipitation and inflow determine the amount of 

water initially available to a wetland for ground water recharge (Todd 1972). Increasing the amount of water 

removed from the wetland and/or stream prior to percolation downwards may decrease groundwater recharge. 

What is most needed is a comprehensive understanding of the true ecological costs of physical alterations 

for mosquito control. This is particularly important because, although the environmental effects of pesticides 

receive the lion’s share of concern, it is likely that the long-term effects of physical controls have a more profound 

effect on the environment than does pesticide use (Buchsbaum 1994). This may be especially true today with the 

switch from broad-spectrum, more-persistent pesticides to methoprene and Bti.

3. Vernal Pools. Vernal pools form in contained depressions in which water stands for a 

period of several months, generally from mid- to late winter through the spring. Water either comes in the form of 

snow melt or spring precipitation or can be a result of a rising water table. Some pools dry down within two or 

three months, others may only dry when the water table is lower than normal, resulting in a pool that is semipermanent. Regardless, a key feature of vernal pools is that they undergo periods of dry down. Vernal pools may

have permanent inlets but do not have permanent outlets (Kenney 1995). There are numerous obligate species for 

vernal pools, the most visible of which include fairy shrimp, the wood frog (Rana sylvatica) and several species of 

salamander (Ambystoma spp.). 

Mosquito species such as Ae. canadensis and Ae. excrucians also use vernal pools for breeding. From a 

control perspective, vernal pools are important because, due to increasing protection, vernal pool habitat is often left 

undeveloped while the land adjacent to the pool is built up. As a result, many new developments surround known 

breeding sites. Regardless of the wisdom of developing so close to vernal pools, mosquito-control personnel are 

charged with controlling the mosquitoes coming from the pool. 

4. Rare and Endangered Species. Operating under the assumption that it is rare and 

endangered species which are most likely to be lost from a wetlands system first, then reductions in habitat 

18
diversity, alterations from the natural state, and frequent disturbances will all work against these species. 

Channelization of streams reduces diversity by removing obstructions, straightening the channel and increasing 

flood levels. Wetlands changed from standing-water to saturated-soil regimes have been drastically changed from

their natural state. Maintenance is ongoing, as is the disturbance it causes. 

However, to what extent does mosquito control contribute to the these problems? First, Massachusetts

MCPs do not channelize streams, as their certification manual calls for following the existing meanders. Second, 

MCPs work neither in historically undisturbed, nor currently undisturbed streams. There is good reason to argue 

that there is no specific “natural” state that can be assigned a ditch dug by man and intermittently filled with road 

sand and grass clippings. Even with natural streams, the “natural” habitat in which they flow has long been altered 

and continues to be altered. 

The Natural Heritage and Endangered Species Program (NHESP) was created in order to conserve and 

protect those plants and animals not hunted, fished, trapped or commercially harvested in the state. The program’s 

highest priority is to inventory rare and endangered species and to develop conservation plans through research, 

management and habitat protection for those species 

The NHESP also reviews proposed alterations to wetlands habitats under the Wetlands Protection Act

(M.G.L. c. 131, s. 40 and regulations 310 CMR 10.00). NHESP has produced a series of estimated habitat maps for 

rare and endangered species (Massachusetts Natural Heritage Atlas) which proponents of a given alteration are 

required to check. Should a project fall within an estimated habitat, NHESP will then determine if the area to be 

altered is actual wetland habitat for a state-listed species. The results of the NHESP determination are given to the 

inquiring MCP. 

In Massachusetts, the species that have caused modifications in mosquito control practices are the Bluespotted salamander (Ambystoma laterale), Mystic Valley amphipod (Crangonyx aberrans), and banded bog 

skimmer (Williamsonia lintneri). In addition, ditch maintenance in vernal pond areas has been curtailed to protect

this type of habitat. Other animals for which concerns have been raised are the yellow-spotted turtle and osprey. 

Under the current system mosquito-control maintenance activities are exempt from the Massachusetts 

Wetland Protection Act, leaving the federal 401 Water Quality Certification Act and both the Massachusetts and 

Federal Endangered Species Acts as a method for regulating maintenance. Unfortunately, water quality, while 

important, does not address the issue of changing habitat and the presence or absence of a rare or endangered 

19
species has little to do with the merits of a given drainage project. Again, a more comprehensive understanding of 

the true ecological effects of mosquito control is required to better determine the cost/benefit ratio for different

types of mosquito control, including their effect on rare and endangered species. 

Physical control by water management may increase predation, as in OMWM, or may eliminate predator 

and prey as when wetlands are drained to soil saturation. Mosquito breeding must be thoroughly documented 

before new work is done. Because disturbances may displace some species, and because predator species tend to 

rebound more slowly than their prey, maintenance work should be conducted only when necessary. 

 D. No Program

Many communities in Massachusetts have chosen to forego mosquito control. These town are usually 

outside of the enzootic EEE zone so the risk of human diseases transmitted by mosquitoes is viewed as practically 

nil by these communities. In addition, they are not located near salt marshes and their attendant pest mosquito

problems. The mid-section of Massachusetts, where most no-control communities occur, also has a more rural 

character, less wetland , lower human populations, and a lower mean family income than most eastern areas with

organized MCPs. 

In addition to risk-benefit considerations, other criteria for weighing the control/no control option are 1) 

the feasibility of successfully reducing annoyance below the human annoyance threshold, and 2) the adequacy of 

community resources for reducing annoyance to acceptable levels. 

It is difficult to measure the impact of choosing the no control option. The example of towns that have left, 

and later rejoined, mosquito control projects is perhaps the only available basis for estimating public opinion 

concerning such impact. However, no documentation of annoyance levels, cases of disease, recreational dollars 

spent, etc., was ever attempted in these towns when they had mosquito control versus when they did not. 

The number of towns in MCPs declined in the late eighty’s. Economic factors, not environmental

concerns, were the dominant reason given for withdrawal. This trend has reversed itself significantly in the last 

several years. The 1990 EEE problem is probably one reason, coupled with the fact that several coastal programs 

tried the no-control option and found mosquito numbers rose quickly. 

IV. IPM as it Relates to Mosquito Control. 

A. Definition of IPM 

20
At its most basic IPM is: 

A system designed to reduce the negative impact of a pest species to an acceptable level while avoiding 

unnecessary additional problems (Virginia Cooperative Extension Service 1987). 

For mosquito control in general the negative impacts of mosquitoes are reduction in outdoor use, 

particularly recreational, and disease transmission. These negative impacts are all ongoing in Massachusetts. 

Problems that have developed in the past are loss/degradation of valuable habitat, exposure of non-target organisms 

to pesticides, creation of new, sometimes worse, breeding habitat, and resistance of mosquitoes to pesticides in use. 

 Other than exposure of non-targets to pesticides (unavoidable) none of these problems have been documented in

Massachusetts. 

Before an IPM program can be put in place, a strong organization must be in place. The organization must 

be adequately funded, adequately trained and provided with the materials to do the job correctly. At a minimum

expertise in mosquito biology, wetlands ecology, and program administration are required. 

Adequate staffing and resources are only the first steps in creating an IPM program. The main step is in 

creating the analytical process whereby control decisions are made, evaluated and modified. This process can be 

divided into four steps: 1) Surveillance and Monitoring, 2) establishing Thresholds for Action, 3) Prevention and

Control, and 4) Evaluation. 

1. Surveillance and Monitoring. For mosquitoes, adult populations are monitored for their 

direct impact on people whereas larval populations are monitored for their potential impact after they emerge as 

adults. For adult populations, monitoring is used to determine if adulticiding is required and to identify the species 

of mosquito in a given area so that future larval control efforts can be directed at the appropriate breeding sites. 

Larval populations are monitored to determine if larviciding is required and/or if physical or biological controls are 

working. 

The habitats in which breeding occurs or in which the adult mosquitoes are most numerous must also be 

identified. Wetlands should be mapped as should drainage basins. 

A third component of monitoring is to classify the area in which control is to take place by human usage. 

Unless funding is not a constraint, the goal of surveillance and monitoring should be to produce a site list prioritized 

by the level of mosquito breeding and its proximity to humans. 

2. Establishing Thresholds for Action. The goal of IPM is to keep pest levels below the 

21
Economic Injury Level (EIL). This is the level where the economic loss from pest damage exceeds the cost of 

control. In mosquito control, this is the Human Annoyance (or Disease) Threshold (HAT) and represents the 

highest biting density (or Disease Incidence) that most citizens in a community find tolerable. Intolerance is 

usually exemplified by people moving indoors, putting on repellent, leaving a campground etc.. HAT is generally 

the biting level above which most people prefer to pay to have the level reduced than put up with the annoyance. 

This level will vary from community to community and may be influenced by the species biting (Sjogren, 1977), the 

time of day when annoyance occurs, and the duration of the period when HAT is exceeded. 

The choice of control measures to use, and the extent to which a given control measure is used, is

determined by the pest species and population, the environment in which the pest population is located, and human 

factors expressed in political and economic terms. Determining which control options are available and how much 

funding will be allocated to each, coupled with an understanding of the pest population, should allow action 

thresholds to be created. 

3. Prevention and Control. Prevention refers to maintaining a pest population below the 

action threshold for control, whereas control refers to bringing a pest population back under the threshold for 

control. Source reduction is the primary prevention technique for mosquito control in that it directly reduces the 

area in which mosquitoes can breed. Maintaining water flow through drainage networks is the primary freshwater 

mosquito control technique while ditching used to be the primary prevention in salt marshes. Programs that do not

stress source reduction cannot make long-term reductions in mosquito populations. 

Public education is a second vital component of prevention. An educated public should be more willing to 

cooperate in eliminating man-made breeding habitats, should better understand the trade-offs between the various 

available control techniques, and should be more willing to fund more expensive approaches if the expense can be 

justified by a better long-term benefit.

Control, in the sense of killing mosquitoes, is dominated by chemical use for adult mosquito control. For 

larvae a combination of chemical control and OMWM (biological/physical control) is used. 

Thresholds are vital to the control process because only through thresholds can a rational response be made 

to unusual circumstances. A quality IPM program cannot “fail” in the strict sense because it has control techniques 

available for each step in pest population increase (or, in the case of a disease threat, each increase in the risk of 

contracting the disease). 

22
4. Evaluation. Each control step is evaluated for efficacy and future actions modified to 

improve control or reduce negative impacts. Field evaluation will generally use the same monitoring techniques 

described above and the important criteria will be changes in the mosquito population and/or environment. Over 

time, a steady state should develop where realistic thresholds trigger effective responses. 

B. IPM for Mosquitoes as it is Currently Practiced in Massachusetts. 

The strategy of IPM as developed for agricultural ecosystems is an ecologically-based concept (Axtell 

1979). It has yet to be fully applied to mosquito management programs. IPM is a strategy for managing insect

populations not a method for controlling them. It is more than integrated control which is simply the combining of

several control methods. Mosquito control has a long history of integrating different control methods. 

The general feeling among most MC practitioners is that any significant larval population within flight 

range of residential areas will probably result in some human annoyance and therefore should be controlled. No 

Project in Massachusetts has undertaken such an effort. 

Although many MC programs regularly monitor adult population levels (with light traps and landing 

counts) they do it to evaluate larval control effectiveness and the need for adulticiding; not to determine when 

immediate larval control is needed as in the case of agricultural IPM programs. However, light trap counts, landing 

rates and complaint calls are used to create a general picture of the need for mosquito control and projects with

long-term experience develop larviciding plans based on this historical data. 

There is no study to date of the costs and benefits of Massachusetts mosquito control programs. There is

good reason to believe, even if such studies were done, that the results would reflect local, current thought, as 

opposed to some underlying “true” cost/benefit for mosquito control. Regardless of the underlying variability of 

any cost/benefit analysis, working towards an understanding of the costs and benefits of mosquito control is

desirable. The following information would aid in such work:

1) Establish human annoyance thresholds (HAT) 

2) Document how human activity patterns relate to HAT and economic factors 

3) Determine cost/benefit analysis of control (willingness to pay) 

4) Correlate HAT with a standard non-biting sampling method (e.g. light trap) 

5) Correlate densities of immatures with future levels of biting annoyance. 

The cost/benefit of various control options (e.g., permanent vs. temporary control) also has been evaluated 

23
(Ofiara & Allison 1986a, 1986b) but this should not be confused with the cost/benefit of control programs. 

One major advance already underway is vastly improved mapping through Geographic Information Systems 

(GIS). GIS wetlands mapping can both aid mosquito control agencies in determining control priorities but can be used

by mosquito control agencies to integrate their work with other land-use agencies (Guthe 1993). Very detailed maps 

can also be made when planning water management projects (Gettman 1995). 

Overall, Massachusetts mosquito-control IPM strengths include, strong control programs, good pretreatment monitoring, the availability of and willingness to use least-toxic materials and a willingness of existing 

control programs to try new control strategies. Weaknesses include a lack of funds for research into new strategies, 

a lack of funds to implement new strategies and a lack of basic ecological data on the effects of control strategies in

use or being planned. A final wildcard is EEE which dramatically increases the stakes when attempting to 

determine the correct response. DPH has developed a monitoring program that should bring EEE into the IPM 

framework. 

V. Standards For Mosquito Control

A. Standards for Monitoring and Control. Pesticide applications in an IPM program require 

monitoring insect populations and comparing data with pre-established thresholds for treatment. In addition, posttreatment evaluation is required to ensure the treatment worked as planned and did not have unintended side-effects. 

1. Larval Populations: The primary technique for larval population counts is the dip 

count. It is hard to standardize dipping technique but, for the purposes of this document, it is assumed that dips are 

taken in undisturbed pools (the field person is aware that disturbing the water and/or casting a shadow over the 

water will cause mosquitoes to dive, thereby lowering counts) known by the field personnel to be typical of the 

breeding area being monitored. For large-scale work, dipping will be done at permanent, marked (or easily located) 

 dip stations. For small sites such as drainage basins and woodland pools, dips will be taken at random throughout 

the site. Up to twenty dips per site will be taken unless the count for treatment and/or water management is 

exceeded with a smaller number of dips. Specifics for various types of work are given in Table 2. 

Table 2. Specifics for monitoring larval (& pupal) populations of mosquitoes for determining control.

No Treatment Pesticide Water management # Sites for large-scale work

 Application 

Salt Marsh <1 per 10 dips 1+ per 10 dips 5+ per dipa 1 dip station per 250 acres 

24
 

Freshwater 

 Ground <1 per 5 dips 1+ per 5 dips Variable Not applicable

 Aerial <1 per 10 dips 1+ per 10 dips Not applicable 1 dip station per 250 acres 

a

Numerous additional factors go into determining water management options for OMWM. 

Projects have an obligation to ensure that all alterations function as intended without adverse effects on the 

environment. Post-alteration work for water management will also monitor vegetative re-growth, changes in fauna

and notes on whether or not the hydrology of the site is as intended. When projects have historical data that

establishes a pattern of breeding at a given site, they may conduct pre-treatment work. 

2. Adult Populations. No adulticiding program will be conducted on a routine, prescheduled basis (i.e. once per week, regardless). 

 a. Monitoring for Adulticiding

Table 3. Adult mosquito monitoring techniques and thresholds for adulticiding.

Monitoring Mechanism Rate to trigger adulticiding

Light traps Human-biting mosquito counts exceed five per night 

Landing counts Landing count rates exceed one per minute 

Complaint calls When complaint calls exceed two per geographical area 

(this area will vary but assume approximately one square mile) 

Projects should increase their efforts to understand the impact of adulticiding on mosquitoes. Projects 

should cross-reference complaint calls with adulticide applications and record the number of calls coming in the 

week before an application and in the following week (this work may be done during the winter for the previous 

season). In addition, projects should conduct before and after landing counts and/or light-trap counts for ten percent

of their adulticide applications. Landing counts should be taken within 48 hours pre- and post-application at the 

same location both times. Light trap samples should be from the same trap and for the same time period before and 

after treatment. Where possible, non-treated areas similar to the treated area should be checked to determine 

population trends outside the spray zone. 

B. Standards for Physical Control. Altering or eliminating mosquito breeding sites range from

proper disposal of tires through analyzing drainage systems to creating entire new open marsh water management

systems. Physical Control refers specifically to alterations to breeding habitat to prevent mosquitoes from maturing

25
to adulthood. Physical Control is divided further into three types:

Source Elimination: Completely eliminating the breeding site not just the mosquito breeding. Source 

elimination is generally limited to breeding habitats created by humans in non-wetland areas. 

Source Maintenance: Maintaining potential breeding sources in such a way that mosquitoes cannot become

a problem. 

Source Reduction: Reducing the ability of an area to breed mosquitoes. It differs from source 

maintenance in that the existing habitat is breeding mosquitoes whereas, if a maintenance program

is running as designed, mosquito breeding should not occur. Once a source reduction project is

completed, it will, in most cases, require at least some source maintenance in order not to return to

being a mosquito-breeding habitat.

The Massachusetts DEP has recently (March 1997) issued a Stormwater Policy Handbook and a 

Stormwater Technical Handbook. These provide guidelines for stormwater management and should be used to

determine appropriate control measures that MCPs should implement. Currently, the primary causes for concern 

regarding physical control is that there aren’t always adequate records of the reasons for a specific maintenance 

project nor are there also adequate site plans by which it can be determined that increases in ditch cross-section 

and/or length are not occurring. 

C. Standards for Chemical Control. 

 Projects must comply with regulations for aerial applications of pesticides. 

For truck-mounted adulticiding, projects should notify the public through the print media, between March 

1st and May 1st of each year, as to the areas that may be treated, the pesticide to be used and a number to contact for 

more information or to request exclusion from treatment. 

As education is a primary aspect of an IPM program, projects are encouraged to develop educational flyers 

covering such aspects of their work as pesticide use, water management, and property-owner mosquito control. 

Flyers may either be developed in-house or be obtained from the state or other agencies. Aside from the pesticide 

applicator recertification requirements, programs are urged to provide opportunities for staff to increase their 

knowledge about mosquitoes, wetland, and mosquito control.

D. Standard Operating Procedures during EEE problem. 

When surveillance data points to increasing levels of EEE risk, DPH notifies the SRMCB and regional 

MCP superintendents. The EEE Surveillance Program informs MCP superintendents of isolations of EEE in their 

districts and the districts, in turn, provide feedback to DPH regarding population and life stage indices for critical 

mosquito species. At certain defined interim levels of risk as outlined in the “Vector Control Plan,” MCPs may be

26
asked to increase their ground control larvicide and/or adulticide applications in response to increased EEE virus 

activity. The SRMCB is responsible for contracting with appropriate mosquito control applicators in the event that

aerial EEE vector control is recommended by DPH.

VI. Recommendations

A. Legal, Organizational and Fiscal Aspects of Massachusetts Mosquito Control

The organizational structure and funding for Massachusetts mosquito control programs, be they regional or 

town based, rests predominately at the level of town government, although the state legislative bodies have a direct

influences over eight of the nine MCPs’ annual budgets (only East Middlesex is not so affected). In contrast, the 

overseer of mosquito-control activity in Massachusetts is the State Reclamation and Mosquito Control Board. This 

is a loose arrangement for delivering a public service that is best applied at a regional level. Lack of control effort

in one town can greatly effect the efficiency of control efforts in neighboring towns. 

Enabling legislation has been written in a patchwork manner so that there is currently little consistency 

from project to project. For example, towns in Barnstable County (and formerly in Berkshire) are all members of 

their respective regional MC project and no individual community may withdraw from the program without

changing the legislation as did Chap. 119 of the Acts of 1982 in the case of Berkshire County. This provides an 

assurance of fiscal and organizational stability that is lacking in other programs. For example, the Essex County 

and Central Massachusetts projects both went through considerable upheavals in membership between 1988 and 

1993. Fortunately, the other projects have remained remarkably stable over the past decade. Maintaining and 

improving stability, both in membership and funding, is a desirable goal. 

This uncertain fiscal picture is further compounded by the fact that all MC projects in Massachusetts are 

seriously under-funded. In other states, with progressive MC programs, the per capita expenditure varies from $2 

upward. In Massachusetts, it averages about $0.50 (based on $2 per household of 4 people). In addition, many 

other states provide supplemental state funds to encourage non-chemical control efforts and for supportive research 

and educational activities. No such state support exists in Massachusetts. When supplemental state support has 

come, it has been for chemical adulticiding in the wake of EEE threats. 

To a large extent, funding dictates the control approaches that can be pursued. IPM, source reduction, 

1arval control, and adult control represent the four major options in their order of decreasing cost and efficiency. 

27
Thus, poorly funded programs are forced into more reliance on less efficient and more controversial techniques. 

Larger, better-funded, and stable regional projects can invest in better paid and trained employees, better 

surveillance and public education programs, and expensive equipment such as helicopters which can broaden the 

options for safer and more efficient larval control (e.g., granular larviciding with Bti and methoprene). 

Given the fact that several different state agencies are concerned with mosquito control activities, the 

current system of interagency responsibility for overseeing MC activities (i.e., State Reclamation and Mosquito 

Control Board representing 3 different state agencies) is perhaps the best compromise arrangement. On the other 

hand, the level of general support services that projects and towns receive from this Board seems to be inadequate. 

Recommendations

That new and comprehensive enabling legislation be drafted, reviewed, appropriately revised, and passed 

into law, which will bring all MC control activity in Massachusetts under the same organizational, fiscal and 

operational guidelines. This legislation should provide for the following:

1. The State Reclamation and Mosquito Control should have the following personnel:

a. An Executive Director @ approximately $45,000 per year 

b. An Engineer @ approximately $35,000 per year 

c. An Entomologist @ approximately $35,000 per year 

Not only would this staffing permit the state to conduct research into mosquito control, it would 

provide a team for rapid response to EEE threats in communities that are not members of 

established MCPs. This staff would also provide services such as incorporating DEP stormwater 

management guidelines into Massachusetts MCP Upland Water management operational

procedures. 

2. An operations budget, above and beyond the normal needs of the SRCMB, for research and 

development. A minimum of $50,000 per year is suggested. 

3. A competitive grant fund (funded by the state, administered by the Executive Director of SRMCB 

and advised by an ad hoc panel of outside experts) to support IPM related research and delivery

programs within the state mosquito control enterprise. This should provide support for studies 

such as: cost/benefit analysis of mosquito-control programs; development of human annoyance 

thresholds (HAT); improved methods for monitoring and predicting mosquito population levels;

28
development, evaluation, and implementation o£ new, non-chemical mosquito management

techniques (e.g., open marsh management and biological control); management of pesticide 

resistance, drift and other use exposures; impact of MC activities on surface and ground water, 

and on non-target organisms; and the biology and role of selected species in disease transmission. 

4. The SRMCB should establish a committee to work with their staff to develop best management 

practices (BMPs) for all aspects of mosquito control, the results of their work being used to

update the GEIR on a regular basis. The committee should include four mosquito-control 

superintendents, four representatives of environmental agencies (federal, state or private) and one 

at-large member to serve as chairperson. Their first order of business should be to develop a set

of BMPs for freshwater drainage maintenance for mosquito control. These BMPs should 

establish strict definitions for projects in which the mosquito control exemption from the 

Wetlands Protection Act may be applied. 

5. MCPs must have the authority to deny requests for maintenance work that does not have a 

mosquito-control component. Because these requests are often made by the same persons or 

municipalities which provide funding to the MCPs, the SRMCB must be willing to act as an 

appeals board, to which a request for work may be sent by an applicant in the event the mosquito

control program denies the request. 

6. Limit mosquito control activity to regionally based regional mosquito control programs which can 

be organized by the appropriate public vote. The SRMCB should organize the regional based 

mosquito control programs and appoint project or district commissioners. The SRMCB should 

select Commissioners from candidates proposed by authorized Boards/individuals from the cities 

and towns of the mosquito control projects or districts. 

7. A flexible and appropriate system of tax assessment which allows for budgets that are adequate to

provide for the implementation of the most contemporary and least risky strategies for controlling 

mosquitoes. 

8. A legal system whereby all major zoning and construction plans in the Commonwealth are 

reviewed by the executive director of SRMCB and the appropriate county MC director for their 

potential impact on mosquito populations and human health. 

29
B. Operational Aspects of Massachusetts Mosquito Control

 Operational programs in Massachusetts could legally be using chemicals (approved by EPA and the 

Massachusetts Pesticide Board) that are significantly more hazardous than those used in current practice. This 

suggests that knowledge and sensitivity for the environment and human safety are generally being considered by the 

existing control programs. As already indicated, funding levels seldom allow projects to follow the optimum

operational course. Despite these fiscal constraints, projects have significantly changed their operational methods in

recent years toward more source reduction work such as the Open Marsh Water Management projects in Essex, 

Norfolk and Plymouth Counties. Most projects also use more selective and environmentally compatible larvicides 

such as Bti and methoprene. 

The operational recommendations that follow are predicated on additional and adequate funding being 

available for implementation. 

Recommendations

1. All MC Projects should build their programs around the IPM strategy of keeping human 

annoyance below threshold levels as given in the Standards of this GEIR. 

2. Control methodology should be source reduction whenever possible and larvicidal control when it

is not. Projects should work closely with the DEP water quality certification program and the 

Natural Heritage Endangered Species Program to minimize negative impacts of source reduction 

to wetland habitat and/or rare or endangered species. The most target-selective and 

environmentally compatible larvicides (e.g., Bti, methoprene) should be used whenever possible 

regardless of cost considerations. 

3. Saltmarsh mosquito control efforts should emphasize OMWM. All OMWM proposals should 

include plans for filling many of the old grid ditches in Massachusetts salt marshes which do not

function in a productive way and which must regularly be cleaned in order to prevent breeding in

the ditches themselves. This will gradually eliminate the controversy over the continuing need to

clean these ditches and the problem of what to do with the resulting spoil that is created. 

4. Document location, length, and cross-section(s) of all drainage systems maintained by the project

and have that information available in an easily understood format for public inspection. 

30
Exemption from the permitting process extents only to those drainage systems for which adequate 

historical records of maintenance work exist. 

5. The SRMCB should create a list of pesticides approved for mosquito control in Massachusetts. 

Adulticides should be from Categories III and IV and larvicides should be from Category IV. 

6. Adulticiding should only be carried out in emergency situations involving disease threats or pest 

densities which consistently exceed the human annoyance threshold. 

7. For large-scale adulticiding, only ULV-cold fogging should be used. For spot treatment around 

recreation areas or other areas where public events are to be held, portable mistblowers using 

permethrin as a residual pesticide can be used. 

8. Aerial applications should be restricted to granular formulations in areas where drift could be a 

significant problem. Sometimes some drift is desirable so as to reduce the chance of gaps 

between application swathes. In such cases a liquid formulation may be a better choice. At this

time liquid formulations are also significantly cheaper, making larger applications, and more 

effective control, easier. Increased use of helicopters for aerial larviciding in coordination with

the use of drift-suppression agents and technologies should be encouraged (particularly for 

enhanced larval control in inaccessible habitats such as salt marshes, wooded swamps, vernal 

pools, etc.). 

9. Projects should file a post-treatment report for aerial applications with the Pesticide Bureau which 

gives location and acreage actually treated. The pre-application forms do not always accurately 

represent what actually happened. 

10. Chemical-use reporting needs to be monitored to ensure uniformity and accuracy in reporting. 

Previous reports contained such problems as no units are given on the 1993 through 1995 Cape 

Cod report for Bactimos (BTI), two different EPA registration numbers for Bactimos are given in

the 1993 Cape Cod and Central Massachusetts MCPs reports, and briquets are variously reported 

in terms of number of briquets, pounds of briquets or pounds of active ingredient. The Pesticide 

Bureau should insist that yearly chemical-use reports be filled out according to standardized 

procedures. Reports should be checked as they come in to ensure that standardized reporting 

procedures are followed. 

31
11. All pesticide storage areas should be equipped with smoke, fire and security systems. A standard 

procedure should be developed for the disposal of all insecticidal materials used in Massachusetts

for mosquito control. The State Pesticide Board should encourage manufacturers of such products

to market reusable containers. A standard procedure should be developed for the clean-up of 

accidental spills of insecticides. Proper use of absorbent materials and the disposal of such 

materials are necessary. Proper attire during formulation and application of insecticides should be 

made mandatory for all individuals involved in these processes. 

 C. Research Needs 

There is a need in the mosquito control process in Massachusetts for a strong, operationally focused, 

research effort in freshwater wetlands, exclusive of chemical application techniques. This is not to condemn current

research efforts, for we know more about EEE mosquitoes than ever before, have improved saltmarsh mosquito 

control dramatically, and have made improvements in both chemicals used and methods of chemical use over the 

past decade. But there is a need for research to assess the environmental impacts and efficacy of the current MCP 

programs relative to the freshwater environment. 

Additional research on topics such as long-term effects of OMWM, economically viable control of Cq. 

perturbans, and mosquito control in endangered species habitats also require attention.

Recommendations

1. For water management practices, monitor impacts on animals on a case-by-case basis, depending 

on the site and establish vegetation transects to document changes in wetland vegetation. 

2. Develop a unified data base that documents mosquito populations on an ongoing basis from

regular monitoring sites. Establish state standards for monitoring mosquitoes and provide training 

to mosquito control project staff in data collection and management. 

3. Conduct comparative studies with different management approaches (e.g. pesticide applications 

vs. water management). 

4. Develop a Geographic Information System (GIS) with known breeding sites and areas of 

historical water management activities. 

5. Qualify sites on the basis of need for control, based on breeding (potential or actual), mosquito

32
species, proximity to human activity, level and type of human activity, and type of wetland habitat

affected. 

6. Create an ongoing research partnership with NHESP to document wetland types, etc.. Mosquito

Control Projects have knowledge and expertise about wetlands that could be invaluable to

NHESP. 

33
Literature Cited

 

Axtell, R.C. Principles of integrated pest management (IPM) in relation to Mosquito Control. Mosq. News 39,710 

(1979). 

Brown, R.G. Effects of wetland channelization on runoff and loading. Wetlands 8,123-133 (1988). 

Buchsbaum, R. Coastal marsh management. in Applied wetlands science and technology, D.M. Kent (Ed.) pp. 331-

361. Lewis Publishers, Boca Raton, Florida (1994). 

Ferrigno, F. Ecology of marsh and coastal impoundments. Job Progress Rpt. N.J. Div. Fish, Game & Shell

Fisheries. Proj. No. W-34-R-16. Job No. II-A, 19pp. (1970). 

Ferrigno, F. and D.M. Jobbins. Open marsh management. Proc. N.J. Mosq. Exterm. Assoc. 55,104 (1968). 

Ferrigno, F., L.G. MacNamara and D.M. Jobbins. Ecological approaches for improved management of coastal

meadowlands. Proc. N.J. Mosq. Exterm. Assoc. 56,188 (1969). 

Gettman, A.D. Mapping Block Island salt marshes for OMWM conversion. Proc. 41st Ann. Meeting of the 

Northeastern Mosq. Contr. Assoc. 24-25 (1995). 

Guthe, W.G. GIS: a new tool for mosquito control. Wing Beats 4(1),4-6 (1993). 

Hynes, H.B.N. The ecology of running waters. University of Toronto Press, Toronto, Canada (1972). 

Kenny, L.P. Wicked bug puddles; a guide to the study and certification of vernal pools. Vernal Pool Association 

and EPA. U. S. Government Printing Office (1995). 

New Jersey DEP. Best management practices for mosquito control and freshwater wetlands management. Office of 

Mosquito Control Coordination, New Jersey Department of Environmental Protection. Trenton, NJ (1997). 

Ofiara, D.D. and J.R. Allison. On assessing the benefits of public mosquito control practices. J. Am. Mosq. Contr. 

Assoc. 2,280 (1986a). 

Portnoy, J.W. Oxygen Depletion, Stream Clearance and Alewife Mortality in the Herring River, Summer 1984. 

National Park Service Report (1984a). 

Portnoy, J.W. Herring River Mosquito Surveys, 1984. National Park Service Report (1984b). 

Shisler, J.K. Creation and restoration of coastal wetlands of the northeastern United States. in, Wetland Creation

and Restoration J.A. Kusler and M.E. Kentula, (Eds). pp. 143-163. Island Press, Washington, DC. 1990 

Sjogren, R.D. Metropolitan Mosquito Control District Final Environmental Impact Statement: Options for Control 

to the year 2000. St. Paul, MN, 464 pp. (1977). 

SPRP. An assessment of non-target effects of the mosquito larvicides, Bti and methoprene, in metropolitan area 

wetlands. Scientific Peer review Panel, St. Paul, Minnesota (1996). 

Todd, D.K. Groundwater Hydrology, second edition. John Wiley & Sons, NY (1980). 

Virginia Cooperative Extension Service. The national evaluation of extension’s integrated pest management (IPM)

programs. Virginia Cooperative Extension Service 123pp. 

Ward, J.V. Aquatic insect ecology 1. Biology and habitat. John Wiley & Sons, NY (1992). 

Williams, D.D. and B.L. Feltmate. Aquatic Insects. CAB International, Wallingford, England. (1992). 

Wolfe, R.J. Effects of open marsh water management on selected tidal marsh resources: a review. J. Amer. Mosq. 

Contr. Assoc. 12,701-712 (1996). 

34
II. INTRODUCTION 

 

A Generic Environmental Impact Report (GEIR), covering mosquito control activities within the State 

of Massachusetts, was mandated under the provision of Massachusetts General Laws Chapter 30A Section 61 by

the Massachusetts Environmental Policy Act (MEPA) Regulation 301 CMR 10.32(5)(b) adopted on January 25, 

1979. The State Reclamation and Mosquito Control Board (SRMCB), the state agency that oversees all local and 

regional mosquito control programs in Massachusetts, administers the GEIR. The SRMCB consists of one 

representative each from the Departments of Environmental Management, Environmental Protection, and Food and 

Agriculture. The latter presently serves as the Chairman of the Board. 

A special committee designated as the Citizen's Advisory Committee (CAC) was established under MEPA 

Regulation 301 CMR 10.10(3) to assist the SRMCB and the MEPA office in developing a scope of what should be 

included in the GEIR. Following the committee's preparation of the GEIR scope and SRMCB approval of this

document, potential GEIR contractors were invited to submit proposals in 1985. A subcommittee of the CAC was 

appointed to screen GEIR proposals and make recommendations on the awarding of the contract. A contract

agreement with the University of Massachusetts (Dr. J. D. Edman) was signed in September of 1985, and the initial 

Draft GEIR was prepared. 

The CAC received comments on the initial Draft GEIR but no action was taken on the comments nor was a 

Final GEIR published. In 1995 this situation was brought to the attention of the Executive Office of Environmental

Affairs and the SRMCB was instructed to complete the GEIR. Due to the substantial time lag between the original 

Draft GEIR and the renewal of the process, a Notice of Project Change was filed with the Massachusetts

Environmental Policy Act Unit in July, and the revised Scope (Section I above) was approved September 23rd of 

the same year. Mr. George Christie, a private mosquito-control consultant, was hired by the SRMCB committee to

rewrite the GEIR to conform with the new scope. 

This GEIR serves five purposes: 

1. It provides a historic summary of all public activities in Massachusetts related to mosquito control, 

including a account of how mosquito control in Massachusetts has rapidly evolved over the past

ten years. 

2. It describes and quantifies Massachusetts mosquito problems and assesses the effectiveness of 

35
past and current control programs. 

3. It assesses the real and potential environmental impacts of past and current control practices and 

describes and evaluates alternative strategies. 

4. It gives an IPM framework for mosquito control in Massachusetts and provides a series of 

operational standards for mosquito control practices. 

5. It makes recommendations relative to the future organization and practice of mosquito control in

Massachusetts. The recommendations were formed in collaboration with the CAC and the 

SRMCB and were based on a joint review of the background information summarized Sections III 

through VII of this report.

36
III. HISTORY AND CURRENT ORGANIZATION AND PRACTICE OF 

MOSQUITO CONTROL IN MASSACHUSETTS 

A. Legislation and Regulation 

1. Overview 

 There are four basic legislative Acts which regulate mosquito control activities in Massachusetts. Often

associated with each of these Acts are regulations (or CMR), which are developed by the state agency charged with 

administering the provisions of the legislative acts. These serve as the rules or policy used in the day-to-day 

enforcement of the Acts. 

The first Act of major importance is Chapter 252 of the Massachusetts General Laws (MGL), which 

establishes the State Reclamation and Mosquito Control Board (SRCMB) and procedures for creating local control

projects. As now amended, 252 includes the important earlier provisions of Chapters 199 and 699 of the Acts of 

1960. The word improvement (of wetlands) as frequently used in the narrative for this Act is misleading. 

Modification or alteration would have been a more appropriate and objective term to describe wetland drainage and 

filling activities. Although the word “improvement” will be used in this report, in order to maintain continuity with 

the Act, the reader should be aware that “modification” would be a more accurate description. 

The second Act is the Wetlands Protection Act (Chapter 131 of MGL) which regulates activities in the 

aquatic and brackish habitats where most mosquitoes breed. However, organized mosquito control is generally

exempt from the provisions of this State Law. Hence, the Federal Wetlands Protection Act as administered by the 

U. S. Corps of Engineers, is the principal regulating mechanism for mosquito-control alterations in wetlands. 

Regardless of the general exemption, mosquito control is not exempt from checking for the presence of rare and 

endangered species through the Massachusetts Natural Heritage Atlas, which lists estimated habitat maps for all rare 

and endangered species as developed by the Natural Heritage Endangered Species Program (NHESP). NHESP also 

overseeing vernal pool certification, not by actively certifying pools itself, but by certifying pools brought to its

attention by individuals or organizations such as the Vernal Pool Association. 

The third Act which influences mosquito control in the Endangered Species Act (Chapter 131A of MGL) 

which prohibits the “taking” of rare and endangered species. It also protects “significant habitats,’ requiring a 

permit request for any work done in such areas. 

37
The fourth State Act of importance to mosquito control activities is the Pesticide Control Act (Chapter 

132B of MGL) which regulates pesticide use by mosquito control practitioners. Except as already mentioned, 

Federal Laws do not generally influence local mosquito control practices except where Federal lands are involved. 

This is true because Massachusetts State Laws are generally more restrictive than their Federal counterparts. 

What follows is a brief summary of State and Federal Laws and regulations which may relate to mosquito

control activities. 

 2. State Laws 

 a. MGL Chap. 252 as currently amended - Improvement of Lowlands. it should be noted 

that there are ongoing efforts to modify this law, one in particular is designed to require IPM practices in mosquito

control.

Sections 1-4. The State Reclamation and Mosquito Control Board (SRMCB) consists of 3 members 

representing the Departments of Food & Agriculture (DFA), Environmental Management (DEM), and 

Environmental Protection (DEP). The SRMCB is housed in the Department of Food & Agriculture. Members of 

the SRMCB (appointed by the commissioners of their respective departments) receive no additional compensation 

for their service on the SRMCB, but are entitled to any expenses incurred in the performance of their duties. 

Although not required by this statute, the SRMCB elects one member to serve as Chairman. The SRMCB has the 

authority, under this chapter, to (1) drain or flow (flood) a lowland with multiple ownerships, (2) remove 

obstructions in rivers or streams leading to low lands, or (3) eradicate (abate) mosquitoes in infested areas whenever 

it considers such activities to be necessary or useful. This chapter requires that the SRMCB make an annual report. 

Employees (engineers, assistants, agents, etc.) may be hired by the SRMCB to carry out the provisions in this

chapter. These parties are empowered to enter any private land which the SRMCB wishes to examine or survey. 

 Section 4A. The Commonwealth, acting through a State department or the Metropolitan District 

Commission, and any municipality, may, in its proprietary capacity, take part in lowland improvements described in

this chapter. In their governmental capacity, these agencies/municipalities may take such action when the public 

health, safety, or convenience will be promoted by lowland improvements. The improvements made must be in 

accordance with Section 5A of this chapter. A petition by proprietors for lowland improvement does not require a 

majority rule. The governing bodies of the agencies/municipalities must act on the petition. Notice of a hearing 

before the SRMCB will be given to all petitioners, governing bodies, and to all known proprietors whose land 

38
would be affected by such improvements. Municipalities are authorized to raise and appropriate money for the 

improvements. 

 Section 5. The majority (in either value or area) of proprietors of any area, may petition the SRMCB to

improve the area. Upon receipt of the petition and appropriate fees, the SRMCB will investigate and survey the 

land to determine the practicability and advisability of the proposed improvements. If the improvements are 

deemed practicable and advisable, the SRMCB will give public notice of the petition in a regional newspaper and 

by registered mail to each known owner, stating the date of a hearing to be held by the SRMCB. After the hearing 

and upon the SRMCB's approval of the proposed improvements, the SRMCB will determine whether a reclamation 

district is necessary. 

 If a district is recommended, the SRMCB will appoint 3, 5, or 7 district commissioners to form a 

reclamation district. Commissioners will receive no more than ten dollars for each day of actual service plus 

compensation for expenses incurred in the performance of their duties. The district is responsible for paying such 

compensation and expenses, as well as the actual cost of improvements. The district must reimburse the SRMCB's 

contributors the money that was expended for improvements. However, this does not include any money that was 

given to the district for improvements, but returned to the SRMCB because it was not needed or used. The SRMCB 

may fire and hire commissioners for cause. 

 Section 5A. The SRMCB may determine that although improvements should be made, a reclamation 

district need not be formed. When the SRMCB is petitioned by an agency/municipality (as described in Section

4A), it will notify the petitioners of the estimated expense of the proposed improvements. Once money is received 

to cover the expense, the SRMCB will designate a name under which improvements will be made and sends the 

money to the State Treasurer who holds it in a special fund. When needed, the money may be disbursed on 

warrants drawn by the SRMCB. The SRMCB will appoint one or more commissioners to oversee the 

improvements. The commissioner(s) receive a compensation (fixed by the SRMCB), plus expenses incurred in the 

performance of their duties. The SRMCB has the authority to hire and fire commissioners for cause. Any excess 

funds are returned to the contributors (in proportion to their contributions). If funds contributed are insufficient to

complete the improvements, the SRMCB will notify the contributors of their shares of the additional cost. 

Improvements will not continue until these additional funds are received by the SRMCB. In order to carry out the 

improvements, the SRMCB will have the powers conferred under Sections 2, 3, 4, 5 (except reimbursement of 

39
expenses), and 8. Commissioners have the powers conferred under Sections 12 and 13 (provided any property

taken by eminent domain is taken in the name of the municipality, and the municipality (1) authorizes the taking, (2) 

assumes liability for damages, and (3) has complied with all laws concerning land taking). Money for which the 

municipality is liable may be contributed by persons benefited by the improvements, in proportion to their 

respective benefits, or otherwise. Any municipality which has withdrawn from a mosquito control project may, 

with approval of the board and upon such conditions as the board my prescribe, rejoin by public vote. 

 Section 5B. Local Boards of Health (in areas not in mosquito control districts), and mosquito control

district commissioners may determine a mosquito breeding area to be a public nuisance. They may give the owner 

of the area a written notice stating that a mosquito breeding area exists on their land, causing a public nuisance. The 

notice should also give treatment methods and set a deadline for abatement. If the owner refuses to abate, the Board 

of Health or the mosquito control district commissioners may abate the nuisance (in a manner approved by the 

SRMCB). In doing so, they may hire all necessary assistants who may enter upon the land for abatement purposes. 

 Section 6. For the purpose of organizing a mosquito control district, the district commissioners will call a 

meeting of the proprietors of the lands to be improved. A majority in interest (in either property value or area) must

be present at the meeting, otherwise the meeting will have no power to act. At the meeting, a temporary clerk and a 

moderator are elected. The moderator submits the question of organizing a reclamation district (under the 

provisions of this chapter) to the proprietors. If accepted by a majority vote, the proprietors will then elect, by 

ballot, a district clerk and treasurer (one year terms), as well as 3-member prudential committee (three years terms; 

one member is replaced every year). At each annual meeting, elections will be held to replace the clerk, the 

treasurer, and one member of the prudential committee. At meetings, the district may borrow money for necessary

expenses, and may issue notes, payable in not more than two years. These notes are subject to the provisions of 

Section 10 and MGL Chapter 44. The proceeds will be held by the district treasurer. 

 Subsequent meetings will be called by the clerk at the request of the commissioners or at least two

proprietors. If the clerk neglects or refuses to call the meeting, the meeting may be called upon a warrant from a 

justice of the peace. Notices of meetings must be posted in two or more public places or should be mailed to each 

proprietor 7 days before the meeting. Vacancies in the office of clerk, treasurer, or member of the prudential 

committee may be filled at any legal meeting. If necessary, the prudential committee may appoint a person to 

temporarily fill a position until an election can be held or until the officer is no longer disabled. 

40
 The prudential committee is in charge of expenditures for maintenance of the improvements, and exercises 

the authority conferred upon the district by law. 

 The treasurer receives the district's money (except as otherwise specified in Sections 6 to 14A). He/she 

makes payments under the direction of the district or the prudential committee, in accordance with the requirements 

of Sections 1 to 14B and MGL Chapter 44. 

 By-laws may be adopted by a district formed under this section. These by-laws are subject to the approval

of the SRMCB. The district has the rights and powers authorized to it under Section 14A for carrying out and 

maintaining improvements. The members of the district are the owners of land lying within its limits. 

 A district will not be dissolved without authorization by the General Court. This authorization will not be 

given until a provision has been made for payment of the obligations of the district. 

 Section 6A. Any district established under this chapter may buy the following insurance coverages: 

(1) liability for bodily injuries and damage to property; 

(2) liability for workmen's compensation; 

(3) fire insurance (covering, among other things, loss by destruction or damage to buildings or personal

property); 

and (4) motor vehicle collision insurance. 

Section 7. Once a district is organized, the commissioners will make surveys and investigations and will 

prepare a plan delineating district boundaries and proposed improvements. They will determine the total expense of 

the proposed improvements, along with the percentage to be paid by each proprietor (determined by estimating the 

benefits less any damages caused by the improvements. The proprietor will be awarded any damages in excess of

the benefits. The commissioners will report their plan and estimates to the SRMCB who will approve, disapprove

or modify them. 

 The commissioners must also submit a copy of their determination to each proprietor (hand-delivered or by 

registered mail). A proprietor has 15 days in which to file any objections with the SRMCB. The SRMCB will 

notify all proprietors of the receipt of any objections within 30 days; and at least 7 days after this notice is given, the 

SRMCB will hold a meeting to consider the objections and to make a decision. If the proprietors are not satisfied

with this decision, they may petition the County Superior Court. 

 Once the percentages to be paid by each proprietor have been determined, the SRMCB will record in the 

41
Registry of Deeds (1) a description of the area to be improved; (2) a copy of a plan; and (3) an estimate of the 

amount to be assessed from each parcel. 

 Section 8. If the SRMCB feels that certain improvements will benefit public health as a whole and should, 

therefore, be paid by the Commonwealth, the SRMCB must separately estimate that part of the expense, to be 

included with other estimates under MGL Chapter 29, Section 4. 

 Section 9. After recording the description, plan and estimate (from Section 7), the commissioners will call 

a meeting to decide on the method of financing (options are included in Sections 10 and 11). Approval of proposed 

expenditures requires a majority vote of a body of proprietors representing a majority interest in both acreage and 

value of the district's area. 

 The district commissioners may petition the county commissioners to vote to pay for the first expenditures 

involved in making improvements. Upon approval, the county treasurer may issue bonds or notes, payable within

25 years to defray expenses. Payment of principal and interest will be made by the county and repaid to the county 

by the district. 

 Section 10. The district may vote to adopt any of three methods of financing. It may raise money, by

assessment or contribution, and deposit the funds required to cover the estimated expenses with the State Treasurer 

(payments are made as provided in Section 14). The district may take out a temporary loan in anticipation of 

assessments from district members and, thereby, pay for the improvements as the work is performed. The district 

may issue notes or bonds, payable for the amount of the estimated expense, on condition that the initial payment is 

made within 5 years of the issue date, and that the entire amount is paid within 25 years. 

 Indebtedness is subject to MGL Chapter 44 and other MGL's applicable to notes and bonds of districts. 

Money received from the sale of notes and bonds will be deposited with the State Treasurer. The State Treasurer 

will credit the district account for any district expenses that benefit the public health of the Commonwealth. Money 

remaining after payment of the total expenses will be paid to the district treasurer to redeem outstanding notes and

bonds. 

 Section 11. The district clerk will certify to the assessors the amount of money voted to be raised and paid 

annually (on account of the interest and principal due) along with the amount to be paid by each proprietor. A copy 

of this certification must be filed with the SRMCB. The certified amount will be assessed from the land of the 

proprietors and will be committed to the local tax collectors. Each week, the tax collectors will remit the money 

42
collected from the assessments to the district treasurer. Assessments will be considered a financial obligation under 

law, upon the recording of the description, plan and estimate (under Section 7), and will continue for two years as of 

July 1 of the year of assessment (i.e., reassessments are made every 2 years). 

 Section 12. If Sections 1-7 have been complied with, and payments for expenses have been arranged, the 

commissioners will carry out the improvements, as approved by the SRMCB. The commissioners may hire persons

to perform the work under their direction. If improvements are for public use, the commissioners may take lands, 

easements, and rights in lands (under MGL Chapter 79), and may purchase and convey property within and beyond 

the limits of the Commonwealth if necessary. Any person damaged in his property (by an action under this and the 

following section), may recover damages from the district (as provided in MGL Chapter 79). These damages will 

constitute a part of the total expense of the improvements. 

 If the commissioners find it necessary to regulate water levels by operating floodgates or dams on the land 

of a person not a party to the proceedings (e.g., a person outside the district), the commissioners must give 

reasonable notice to the proprietor. The proprietor may appeal this work by petitioning the County Superior Court 

within 30 days after receipt of the notice. Until the appeal is determined, the commissioners must suspend the work. 

The commissioners are required to submit to the SRMCB the bills incurred in meeting the cost of required

improvements (under Section 14B), on a monthly basis. Once inspected and approved by the SRMCB, these bills 

will be rewarded to the County or State Treasurer who will make payment from available funds. The SRMCB must 

also approve bills for maintenance or further improvements reported by the prudential committee and the 

commissioners (as provided in Section 14A). Once approved, payment will be made by the district treasurer. 

Section 14A. A reclamation district organized under this chapter may vote to undertake further 

improvements, and to incur debt (as provided in Section 10). Original improvements must be completed before this 

vote is passed. The district may also vote to request the SRMCB to appoint commissioners to carry out these 

further improvements (as provided in Section 5). Or, the district may authorize its prudential committee to carry

out. these further improvements. In either case, both the prudential committee and the commissioners acting under 

this section will have the same powers as authorized under Section 5. The district will notify the SRMCB of their 

vote and the prudential committee/commissioners will submit to the SRMCB its/their plans for carrying out the 

improvements. Assessments from district members to pay for the improvements (modifications) will be made in

the manner provided in Section 11. 

43
 Section 14B. No person obtaining additional water power or water by the work contemplated in Section 1 

- 14B will gain the right to its use, nor may a person be entitled to compensation if the additional water is reclaimed.

 No water power may be developed by a district under this chapter except by vote of the district and approval of the 

SRMCB. 

Anyone who obstructs or injures any structure constructed under the provisions of Sections 1 - 14B will be 

fined not less than ten dollars. In addition, the SRMCB may attempt to recover from the perpetrator any damages 

incurred. The provisions in Section 5A will govern the disposition of money recovered. 

The mayor and aldermen or selectmen will receive two dollars for each day of service. The city or town 

clerk will receive (for recording the petition), the fee provided by Clause (68) of Section 34 of MGL Chapter 262. 

 Any party aggrieved by the mayor's and aldermen's or selectmen's refusal to make such an order, may

petition the county commissioners. The county commissioners will proceed as if the petition had been originally 

filed with them. 

Section 24. Greenhead fly control projects may be established, with the approval of the SRMCB, in any

town or city along the seacoast, by vote of the city council/selectmen. By the same vote, any two or more adjoining 

cities or towns may form a district within their combined areas. 

For these areas, the SRMCB will appoint 3 district commissioners. They will be paid a fixed 

compensation, not exceeding five dollars per day, along with other expenses incurred in the performance of their 

duties. Compensation and expenses will be paid by the district. The SRMCB may fire and hire Commissioners for 

cause. The duties of the commissioners will be established by the SRMCB. 

Votes to form a district are binding for five years. Any city or town may vote to withdraw from the 

district within 60 days, but not less than 10 days, of any "anniversary date" of its original vote. They must notify

the SRMCB within this time frame, as well. 

Any city or town may vote to join an existing district, with the approval of the SRMCB. 

Each project will determine its maximum annual budget, and will report its determination to the SRMCB. 

In the case of districts, the commissioners will make this determination. The SRMCB will, in turn, determine the 

proportionate share of the budget that each member municipality is to be held accounted for. The SRMCB will then 

report its determination to the treasurer of each member municipality. 

 One third of the budget will be paid by the member municipalities within a district in proportion to the salt 

44
marsh area within its boundaries. Another third will be paid by the Commonwealth. The final third will be paid by 

the member towns/cities within a district in proportion to their respective taxable valuations. A project consisting of 

a single municipality is not entitled to subsidy by the Commonwealth. 

Payments of each municipality’s share of the budget will be made to the State Treasurer. Towns/cities may 

also raise money in advance to anticipate its liability. These funds would be held by the State Treasurer, as well, 

and would be credited against the municipality’s liability. 

Projects will be allocated funds annually from the State Treasury to eliminate or control Greenhead flies in 

accordance with the predetermined control strategy (prepared and devised by the SRMCB to effect the greatest 

measure of relief). Such work must be performed under the direction and control of the SRMCB. Additional 

control efforts may be carried out as long as additional funding is provided, such as funds voluntarily deposited with 

the State Treasurer for such purposes. 

 b. MGL Chap. 132B -- Pesticide Control Act (From the Code of Massachusetts Regulations 

333 CMR 2.00 -10.00) 

General Information

 The Massachusetts Pesticide Control Act was inserted as MGL Chap. 132B of the Acts of 1978 (Chapter 3) 

as an emergency law and took effect immediately. The purpose of the Act is to have the laws of the Commonwealth

conform with federal requirements on registration and certification of pesticides as set forth in the Federal 

Insecticide, Fungicide, and Rodenticide Act, Public Law 92-516, as amended, (FIFRA), and the federal regulations 

thereunder. To this end, the Massachusetts Pesticide Control Act creates administrative mechanisms to regulate the 

labeling distribution, sale, storage, transportation, use and application and disposal of pesticides. The Massachusetts

Act also establishes standards and sets forth prohibitions with regard to each regulatory function. The responsibility 

for implementing the commands of the Massachusetts Pesticide Control Act is distributed by the Act among three 

governmental bodies:

 i. Department of Food and Agriculture (DFA). The DFA has been designated as the state 

lead agency for implementation and administration of the Act and the Massachusetts pesticide program. 

 The Act charges the DFA with a wide range of specific regulatory functions and empowers it to

promulgate and adopt regulations, standards and forms as are necessary for implementation and administration. 

Among the duties assigned to the DFA by the Act are:

45
a. Entering into cooperative agreements and contracts in matters related to the Act and FIFRA. 

b. Taking actions necessary to secure for the Commonwealth the benefits of FIFRA and other 

federal 

 legislation. 

c. Establishing advisory councils. 

d. Declaring pests and devices to be subject to the provisions of the Act.

e. Establishing the fee and preparing and accepting the applications for experimental use permits. 

f. Establishing requirements for licensing and supervising pesticide dealers. 

g. Establishing requirements for certifying, licensing and supervising various categories of pesticide 

 applicators. 

h. Controlling both storage and disposal of pesticides. 

i. Issuing administrative orders to prevent unreasonable adverse effects on the environment or 

violations under the Act.

j. Right of entry and inspection as needed to administer the Act. Within the DFA, the pesticide 

regulatory functions shall be under the administrative supervision of a Pesticides Program

Director. 

ii. Pesticide Board. The Act creates within the DFA a Massachusetts Pesticide 

 Board.

 The Board's responsibilities entail advising the Commissioner of Food and Agriculture with respect to the 

implementation and administration of the Act The Board also hears appeals of those aggrieved by the actions or 

decisions of the DFA or the Subcommittee of the Pesticide Board. The Act, additionally, assigns the Board the 

responsibility for approving a variety of departmental actions within the DFA. Among the actions requiring Board 

approval are:

a. All regulations, standards and forms proposed by the DFA to implement and administer the Act.

b. Appointment of the Pesticides Program Director. 

c. Cooperative agreements and contracts with respect to the Act and FIFRA. 

d. Establishment of advisory councils. 

e. Declarations of pests and devices to be subject to the provisions of the Act.

46
 The Commissioner of Food and Agriculture or his designee serves as the Chairman of the Pesticide Board. 

Other members include the Commissioner of Environmental Protection or his designee, the Commissioner of 

Fisheries, Wildlife and Recreational Vehicles or his designee, the Commissioner of Environmental Management or 

his designee, the Commissioner of Public Health or his designee, the Director of the Division of Food and Drugs or 

his designee and the seven persons appointed by the Governor, one of whom has been engaged in the commercial

production of a plant-related agricultural commodity for at least the preceding five years on land owned or rented by 

him, one of whom has been an active commercial applicator of pesticides for at least the preceding five years, one 

of whom has expertise in the health effects of pesticide use, one of whom is a physician, one of whom is

experienced in the conservation and protection of the environment, and two of whom represent the public at large. 

Each member is appointed for a period of four years, except for persons appointed to fill vacancies, who serve for 

the unexpired term. 

 The appointive members of the Board receive fifty dollars for each day or portion thereof spent in the 

discharge of their official duties and are reimbursed for their necessary expenses incurred in the discharge of their 

official duties. 

iii. Subcommittee of the Pesticide Board. The Act creates a subcommittee within

the 

 Pesticide Board of the DFA. 

 The subcommittee is responsible for registering all pesticides for use in the Commonwealth and for issuing 

all experimental use permits. 

 The Director of the Division of Food and Drugs serves as the Chairman of the Subcommittee. Other 

members include the Commissioner of Food and Agriculture or his designee, the Commissioner of Environmental

Management or his designee, and the Commissioner of Public Health or his designee, and one person appointed by

the Governor, who has been actively engaged in commercial application of pesticides for at least the preceding five 

years who is a member of the Pesticide Board. 

c. 333 CMR 10.03 (21-23) - Amendments of 1983. 

 Amendment (21) to the Pesticide Regulations provides a list of conditions that must be met prior to all nonagricultural pesticide applications by aircraft. It calls for public notification of abutting Landowners 2-10 days

before the application as well as notification of the Department of Food and Agriculture and the contractor. 

Application sites must be recorded on U.S.G.S topographical maps and records kept for 2 years. Amendment (22) 

47
deals with the right of exclusion from pesticide applications of property owners and their tenants. Methods are 

outlined for requesting exclusion and for properly marking the boundaries of property to be excluded. Exclusion 

requests are not honored if public health or agricultural threats exist or if a recently introduced pest is being 

contained. 

 Amendment (23) requires a permit from the Department of Food and Agricultural for all private 

applications of pesticide by aircraft. Aerial applications for mosquito control are specifically exempted from this 

provision along with a few other classes of applications. 

 d. M.G.L., Chap. 91. Sections 1-63 -- Waterways 

 This law does not deal specifically with mosquito control but it does cover variety of activities associated

with wetlands. Mosquito control is specifically exempted from the provisions of Sections 19A, 59 and 59A of this

law but not from other provisions. As amended by Chap. 373 of the Acts of 1969, the Act makes provisions so that

the use of oil for mosquito control in any lakes rivers, or tidal waters or flats under MGL 252 is exempt from the 

provisions of Section 59 and 59A of Chapter 91, provided it conforms to the rules and regulations and of the State 

Pesticide Board.

e. M.G.L., Chapter 40. Section 5 - Boards of Health and Supervision. 

 Clause (36) and (36C) have MGL Chapter 40 Section 5 refers to the appropriation of money by towns for 

mosquito abatement: 

 (Clause 36). At any town meeting, a town, whether or not a member of a mosquito control project, may

appropriate money for lowland improvement (modification) and mosquito abatement. Outside agencies may be 

contracted by the Board of Health to carry out mosquito control, provided the SRMCB is notified. This outside 

agency is responsible for filing a detailed annual report of their mosquito control program with the SRMCB. 

(Clause 36C). A town or city that is a member of a mosquito control project may appropriate money in

addition to the amount assessed by the project for mosquito abatement. The abatement activities must, however, be 

carried out under the supervision and control of the mosquito control project. 

f. M.G.L., Chapter 131. Section 40 - Wetlands Protection Act.

The Wetlands Protection Act controls the use of freshwater and coastal wetlands by establishing a public

review and decision-making process through which certain activities affecting wetlands may be regulated. The Act 

is administered by local conservation commissions (or the mayor or selectmen of towns without conservation 

48
commissions), and the Department of Environmental Protection (DEP). Any proposed project that may affect a 

wetland area must be approved by the local conservation commission. The proponent must apply for a permit with

the conservation commission and the DEP, who will evaluate the proposed project to determine whether any land is 

subject to the jurisdiction of the Act. The Act is complemented by 310 CMR 10.00, which provides the 

conservation commission, and DEP with standard definitions and procedures by which to implement the Act. 

Proposed alterations to wetland habitats of rare wildlife must also be reviewed by the Natural history & Endangered 

Species Program (see Endangered Species Act below). 

 Mosquito control activities are exempt from the provisions of the Wetlands Protection Act, provided that 

the activities are carried out in compliance with Clause (36) of Section 5 of MGL Chapter 40, MGL Chapter 252, or 

of any special act. Nonetheless, there is still some debate concerning whether the exemption applies only to the 

maintenance of existing structures or also includes new structures. (see page 25) 

g. Section 40A of Chapter 131. Inland Wetlands Restriction Act. Section 105 of Chapter 

130. Coastal Wetlands Restriction Act.

The Inland Wetlands Restriction Act, together with the Coastal Wetlands Restriction Act makes up the 

statutory basis of the Massachusetts Wetlands Restriction Program. The objective of both Acts is to promote and 

protect the public safety, property, wildlife, fisheries, water resources, flood plain areas, and agriculture by

restricting or prohibiting the altering or polluting of inland and coastal wetlands. Although the areas and interests 

protected are basically the same as those protected by the Wetlands Protection Act, the Wetlands Restriction Acts

set forth a planning program that is not dependent on a proponent's initiative to apply for a permit. Through the 

Massachusetts Wetlands Restoration Program, inland and coastal wetlands are mapped out in each city and town. 

After a public hearing, a Restriction Order is issued by the administering agency, which prohibits certain activities 

in the wetland areas. The Order is then recorded in the Registry of Deeds and is binding to all present and future 

owners of the property.

Two regulations, which correspond to the Acts, are 302 CMR 4 and 6. These regulations contain the rules 

for adopting coastal and inland wetland orders. The Department of Environmental Management is the legal

authority for both Restriction Acts. However, the administrative responsibility has been taken on in recent years by 

the DEP. A statutory transfer of the Massachusetts Wetlands Restriction Program is pending. 

Mosquito control, as authorized by MGL Chapter 252, is exempt from the Wetlands Restriction Act.

49
h. M.G.L., Chapter 131A. Massachusetts Endangered Species Act.

This Act prohibits the “taking” of rare plants or animals. This includes all plants or animals listed as 

Endangered, Threatened, or Special Concern by the Massachusetts Division of Fisheries and Wildlife. Fines and 

jail terms may be imposed for illegally taking a rare species. This Act also protects “significant habitats,” which can

be so designated after a public hearing process. Permits must be issued for any work in significant habitats. 

The primary agency for determining rare species status and significant habitats is the Massachusetts

Natural History & Endangered Species Program (NHESP) run from the office of the Division of Fisheries & 

Wildlife. NHESP has developed a series of Estimated Habitat Maps for state-listed rare species (contained in the 

Massachusetts Natural Heritage Atlas), which assist mosquito-control programs in determining the presence or 

absence of rare or endangered species. 

Mosquito control activities are not exempt from the Endangered Species Act and care must be taken to

ensure programs are in compliance with the Act. Both pesticide applications and storm water drainage are 

considered alterations and require permitting. 

 i. M.G.L., Chapter 132A. Sections 13-16, 18 -- Ocean and Coastal Sanctuaries Act 

The following areas in Massachusetts are protected under the Act: the Cape Cod Ocean Sanctuary, the Cape 

Cod Bay Ocean Sanctuary, the Cape and Islands Ocean Sanctuary, the North Shore Ocean Sanctuary, and the South 

Essex Ocean Sanctuary. Section 13 of the Act demarcates the ocean sanctuaries, all of which extend approximately 

three miles seaward from a point on the mean low water line. The purpose of the Act, as described in Section 14, is to

protect each ocean sanctuary from any "...exploitation, development, or activity that would seriously alter or otherwise 

endanger the ecology or the appearance of the ocean, the seabed, or the subsoil (of the sanctuaries), or the Cape Cod 

National Seashore." 

The Ocean Sanctuaries Act does not require the issuance of permits other than those already required by law. 

In consequence, the Department of Environmental Management, the State agency authorized to oversee the Act, serves 

as a trustee rather than as a permitting agency. All other State and local permitting agencies are responsible for 

conducting their activities in conformation with the Act. Regulation 302 CMR 5.00 complements the Act. 

Although not specifically exempted from the provisions of the Act, mosquito control activities are not 

performed within the boundaries of the ocean sanctuaries. 

 j. Acts of Enabling Legislation Establishing Mosquito Control Projects 

50
 Except for Cape Cod, all 10 current and disbanded MC Projects in Massachusetts were established after 

World War II when mosquito control first appeared both technically and economically feasible on a wide scale. 

The most recent were the Central Massachusetts and Suffolk County projects formed in 1973/74. Almost without 

exception, these projects were created as a result of lobbying efforts by local citizen groups who were concerned 

about both outbreaks of mosquito-borne disease (i.e. EEE) and biting annoyance created by high densities of 

mosquitoes. Local legislators and city selectmen or boards of health played roles in shepherding through the 

necessary legislation. The Cape Cod Chamber of Commerce was instrumental in the creation of the MC Project on 

the Cape. The Board of Reclamation often assisted local citizens and legislature with their efforts. especially in the 

case of the more recently established projects. 

 The East Middlesex and South Shore (disbanded in 1981) projects were formed under Chapter 252 of the 

General Laws. The remaining eight were created by special legislation (individual project descriptions below). An 

important change in the entering and leaving procedure was made in 1991 when state legislation required towns, 

upon joining a project, to commit to a minimum of a five-year membership. This provides both stability of funding 

to the projects and enables a more comprehensive pest management plan to be put in place (single-year 

memberships place emphasis on immediate results; multi-year memberships place emphasis on long-term results). 

3. Federal Laws 

 Federal laws, which directly impact on mosquito control activities, are Sections 401 and 404 of the Clean 

Water Act and the Endangered Species Act. All other federal restrictions governing wetlands and pesticides are 

covered by Massachusetts’s laws, which impose restrictions, and requirements that are equal to or greater than those 

in comparable federal law. The exception in the case of Section 404 arises because the state laws governing the 

ditching of wetlands exempt mosquito control but the Federal Clean Water Act does not. 

a. Section 401. Clean Water Act: Water Quality Certification. 

This section requires applicants wishing to discharge dredged or fill materials to obtain a certification or

waiver from their state water pollution control agency (Massachusetts Bureau of Resource Protection, Division of 

Wetlands and Waterways). Section 401 is a federal mandate that is implemented by the state, resulting in some

friction over precisely what does and does not require a water quality certificate and what issues the certification can

and cannot address. The issue is rendered moot for mosquito control, however, as the U. S. Army Corps of 

Engineers will not permit a mosquito-control project that does not have a water quality certification. Section 401 

51
provides DWW with the power to influence permit applications in two ways: by denial of the required water quality 

certification, and by issuing the water quality certification with limitations attached. To date, obtaining water 

quality certifications has not been particularly difficult for Massachusetts mosquito control programs. 

 b. Section 404. Clean Water Act (1972). 

This Federal Act calls for a system of permitting to be carried out by the U. S. Army Corps of Engineers 

with a review of all permit applications by appropriate state and federal agencies. The mosquito-control activities, 

which require a permit under Section 404, are as follows:

a) Cutting or clearing new mosquito ditches in tidal areas below mean high water. 

b) Placing material excavated from existing or new ditches on salt marshes or freshwater wetlands. 

 The Corps developed a draft plan in the early 1980's outlining procedures for issuing general permits for 

maintenance work (i.e. ditch cleaning) in existing mosquito ditches in each MC project. This plan was eventually 

shelved pending the preparation of a GEIR to serve as a guide. According to 1986 correspondence to the Norfolk

County MCP from the Section Chief of the Regulatory Branch of the Operations Division, the Corps does not

require a permit under Section 404 for ditch cleaning provided the spoil is scattered at a depth of no more than 3 

inches. 

 The question of permit requirements for new construction in Massachusetts’s salt marshes, such as the 

OMWM projects in Essex and Plymouth Counties, remains an ambiguous issue. The Audubon OMWM Manual (p. 

2-2) indicates that, in addition to the Corps permit, permits are required from the Division of Waterways, Office of 

Environmental Affairs and a Letter of Consistency from the Office of Coastal Zone Management. Interagency

correspondence suggests that even agency heads are unclear about the legality of any of these requirements when 

mosquito source reduction work is involved. However, in current practice the Corps is not issuing permits for 

OMWM projects without these two documents. 

 c. Endangered Species Act.

This act is designed to protect threatened and endangered species as listed on the National Historic Register 

 Suffolk County has had to use Bti instead of Altosid in areas where the Blue-spotted salamander (Ambystoma 

laterale) and the banded bog skimmer (Williamsonia lintneri). Other projects, such as Bristol County MCP, have 

requested advice on osprey (Horseneck Beach in Westport) and the yellow-spotted turtle but have not had to modify 

their proposed work because of these animals. In both cases Bristol County was doing ditch maintenance. Should 

52
the project have been proposing larviciding or more extensive source reduction work, there is a chance that their 

request would have been denied. 

With the Suffolk County larviciding program, the issue of the effects of Altosid, an insect hormone mimic, 

on reproduction in amphibians has been the driving force behind the decision to not allow its use. The scientific

claims for such effects are limited and more research in this area is required. 

In Plymouth County, proposed drainage maintenance was halted by the local conservation commission 

because they felt that the drainage threatened the pools themselves, regardless of the presence of endangered 

species. Whether or not all vernal pools deserve complete protection remains a matter for research and debate. 

 The net effect of the Endangered species act on mosquito control has been small, but has provided another 

means of analyzing the environmental effects of mosquito control. research on the effects of source reduction on 

non-targets is lacking and this lack should be addressed. 

B. Current Mosquito Control Programs in Massachusetts

 1. Formal Mosquito Control Projects 

Of the 351 Towns in Massachusetts, 158 (or 45%) currently belong to the 9 organized MC. These projects 

and the towns included in each are illustrated topographically in Fig. 1. Each project is managed by a superintendent 

who is hired and supervised by a Board of Commissioners representing the towns included in the project. Board 

members are appointed by the Board of Reclamation for designated terms (usually 3-5 years). Members are unpaid

except for up to $75 per meeting in expenses. Boards generally meet once or twice monthly to authorize major 

expenditures and to review policy and program progress. 

Questionnaires were sent to each MC Project in both 1985 and in 1996 (copies in Appendix 1). The 

projects’ responses to the questionnaire formed the basis for the following summaries. 

 The State Reclamation and Mosquito Control Board exercises responsibility over all 9 projects. This 

responsibility includes, but is not necessarily limit to, the following: 

1. Review and approve budgets

2. Administer project funds (payroll, process purchases, etc.) 

3. Review program plans 

4. Appoint commissioners 

5. Issue control policies and recommendations 

53
6. Administer emergency control funds provided to projects from the governor's or legislators 

 emergency funds 

7. Provide advice and guidance when requested by projects or towns 

8. Moderate disputes 

9. Assist towns seeking to join or organize a formal project or to withdraw from an existing project

10. Serve as a liaison between projects and other state and federal agencies and in legislative matters 

 Most projects indicated satisfaction with the administrative arrangement and the current functioning of the 

SRMCB. Suggestions for improvement centered around the Board providing more comprehensive services to the 

projects (this would require more staff) and more efficient and responsive staff for dealing with project budgets. 

More formal meetings with all projects to foster better communication and occasional attendance of Board 

representatives at project commission meetings were a common theme. 

 All projects have a Board of Commissioners appointed by the SRMCB. They represent the various towns 

within each project and exercise general control over the project. Their specific role involves, but is not necessarily 

limited to the following:

1. Appoint the project superintendent

2. Approve the appointment of all permanent project personnel

3. Approve payroll and sign all invoices prior to processing by the SRMCB

4. Review and set policy

5. Review budgets and salaries 

6. Serve as liaison between the project and the towns they represent 

7. Provide advice to project superintendent

8. Moderate disputes 

 The projects find this administrative structure to be responsive and appropriate. The wide range of 

expertise represented by the commission membership brings a broad information base to bear on important financial

and operational issues. The superintendents make all day-to-day operational decisions concerning when and where 

to institute control and what methods to use. 

 The Nine Mosquito Control Projects of Massachusetts (see Tables 1 and 2 for budget figures presented in

descriptions):

54
Berkshire County Mosquito Control Project

Created under: Chapter 456 of the Acts of 1945 

Area included: The towns of Becket, Hinsdale, Lanesboro, Otis, Richmond, and Sheffield 

 and Stockbridge. 

Annual Assessment: 35 cents on each one thousand dollars of taxable valuations; sums so 

expended in proportion to their respective valuations. 

Amendment to Assessment: Chapter 459 of the Acts of 1970--20 cents on each one thousand dollars 

of the equalized valuations; sums so expended in proportion to their said 

 valuations. 

Formed in post-War 1945 under the leadership of the State Senator from Pittsfield. This countywide 

project originally had 32 member towns. All except 8 of these towns withdrew in the early 80's after the passage of

Proposition 2 1/2 and considerable negative publicity. One additional town left later on. Since 1985, four towns 

have joined the project and four have withdrawn. Of these one (Hinsdale) withdrew and then rejoined and another 

(Pittsfield) joined and then withdrew. The reasons for withdrawing centered on cost, while the reasons for joining

centered on municipalities responding to resident complaints. 

 Spring hatch Aedes are the major problem experienced in this mountainous terrain. Some reflood Aedes

and Cq. perturbans problems also exist. In 1985 approximately 70% of the budget was devoted to source reduction 

through hand cleaning of ditches. By 1996, approximately 70% of the budget is devoted to larviciding and 

adulticiding. The program is evaluated by all four standard monitoring methods. 

Over the past decade increasing citizen concern regarding pesticide use has been the most important 

change faced by the project. At present, providing the desired control services under very tight funding is given as 

the most important challenge facing the project. 

Bristol County Mosquito Control Project 

Created under: Chapter 506 of the Acts of 1956 

Area included: All the cities & towns comprising Bristol County 

Annual Assessment: 15 cents on each one thousand dollars of taxable valuations; sums so 

 expended in proportion to their respective valuations. 

Amendment to Assessment: Chapter 638 of the Acts of 1970--8 cents on each one thousand dollars 

of the equalized valuations; sums so expended in proportion to their said

 valuations. 

All twenty towns in Bristol County make up this control project, which was formed in 1959 during a 

period of high pest densities and threat from EEE. Senator Parker of Taunton played a key role in organizing the 

55
project. Only one town (Dartmouth) subsequently withdrew from the project following negative publicity. It

rejoined several years later during another EEE active period. 

There are approximately 67,000 acres of fresh water swampland in Bristol County. As in the case of 

Norfolk and Plymouth Counties, this presents some unique problems. It has resulted in a large source reduction 

effort (78% of budget in 1995) and adulticiding (19%) over larviciding. Salt marsh mosquitoes have become an 

increasingly important part of the control program. Spring Aedes and Cq. perturbans are major pest problems and 

concern with EEE transmission is ever present. Light trap counts and cases of human/animal disease are used to 

evaluate the effectiveness of the program. 

Over the past decade Bristol MCP has been faced with the double squeeze of increasing concern over 

wetlands alterations and increasing concerns over pesticide use. With source reduction and adulticiding being the 

two primary control techniques used by Bristol MCP, such concerns go to the heart of the project’s effectiveness. 

As an example, Bristol MCP switched from malathion to resmethrin for adulticiding due to public pressure to end 

the use of malathion. However, resmethrin is more costly, which brings to the fore the continuing difficulties of

budgets. Bristol MCP, like many other projects, faces difficulties in implementing newer control strategies due to 

tight budgets. 

Cape Cod Mosquito Control Project 

Created under: Chapter 379 of the Acts of 1930 

Area included: The town comprising Barnstable County

Annual Assessment: 25 cents on each one thousand dollars of their respective valuations. 

Amendment to Assessment: Chapter 209 of the Acts of 1975--9 cents on each one thousand dollars 

of the equalized valuations; sums so expended in proportion to their 

 said valuations. 

The Cape Cod project was organized through the efforts of the Cape Cod Chamber of Commerce, 

beginning in 1928. Their motivation was the enhancement of the recreational resources of the Cape. All 15 towns 

in Barnstable County have belonged to the project continuously since its formal creation in 1930. There are 

approximately 20,500 acres of salt marsh and 2,600 acres of freshwater wetlands on the Cape capable of supporting 

mosquito development.

The Cape Cod project has chosen not to use adulticides as part of their program. Larviciding and source 

reduction (maintenance on existing water systems) form the backbone of the project. The Cape project is currently

56
conducting research into the use of native fish as biological control agents for mosquitoes. While larval surveys and 

larvicide applications are conducted during half of the year, the other half of the year is spent maintaining the 

current ditch systems (including work on pipes, culverts and sluiceways). Many towns’ DPWs and Conservation 

Commissions utilize the project’s expertise to help keep drainage systems open and running properly. Further, the 

Cape Cod project’s work is recognized by the National Flood Insurance Program’s Community Rating System as 

meeting the flood-plain maintenance requirements for towns to obtain lower flood insurance rates. 

The Cape Cod project utilizes a Geographical Information System (GIS) that includes maps of all potential 

larval habitat, documentation of work done including larvicide application, and data from adult and larval surveys 

conducted at all mosquito development sites. Information from this system is used to write an annual report and is

made available to the member towns. 

This project also runs a greenhead fly control program. Over 600 blue box traps are placed on the salt 

marshes of Barnstable County every spring. Research was conducted by the project in the summers of 1992-1995 

to determine the effectiveness of adding Octenol, an olfactory attractant to these traps. Success with that research 

has resulted in this project and others incorporating octenol into their greenhead fly trapping programs. 

As an indication of the stability of the Cape Cod Project, all eighteen employees have over 4 years of

experience with 50% of the employees having worked in mosquito control for over 15 years 

Central Massachusetts Mosquito Control Project

Created under: Chapter 583 of the Acts of 1973 

Area included: The area in Middlesex and Worcester Counties including the cities of

Fitchburg, Leominster, and Marlborough and the towns of Ashland, Ayer, 

Berlin, Billerica, Blackstone, Boxborough, Chelmsford, Clinton, Dracut, 

Holliston, Hopedale, Hudson, Littleton, Lunenburg, Milford, Natick, 

Northborough, Sherborn, Shrewsbury, Southborough, Stow, Tewksbury, 

Westborough, Westford, and Wilmington. 

Annual Assessment: 8 cents on each one thousand dollars of the cities' and towns' equalized 

valuations; sums so expended one quarter in proportion to their valuations 

and three quarters in proportion to their respective areas. 

Twenty-eight towns make up this large project. It was organized in 1973 through the efforts of several

town boards of health and concerned citizen groups. The Project has experienced significant turnover in

membership. Two towns withdrew from the project early on but then rejoined. Seven other towns withdrew 

permanently prior to 1986, primarily as a result of Proposition 2 1/2 fiscal constraints and concern over pesticide 

57
use, though concerns about mosquitoes coming into the town from areas not being treated played a role in

Hopkinton’s decision to withdraw. However, Fitchburg, Lunenburg, and Leominster were joining during the same

period, in each case due to a desire to be a part of a regional approach to mosquito control. Since 1986, an 

additional seven towns have withdrawn (Harvard, Lancaster, Boylston, Grafton, Groton, Northbridge and Shirley). 

The towns left for budgetary reasons and environmental concerns. Five towns have joined the project since 1989, 

two (Wilmington and Natick) because town programs were abandoned, one (Blackstone) because of bad mosquito 

problems, one (Dracut) because of positive feedback from member towns, and the fifth (Stow) because they liked 

the environmentally responsible control techniques of the Project. Towns can withdraw or rejoin by a vote at town 

meeting but joining towns also must be approved by the SRMCB, which may impose special stipulations. 

Up to 10,000 acres of mixed, freshwater wetlands and a large number of catch basins and tires are treated 

with larvicide’s (35% of total budget) and/or have source reduction work done (40% of budget). Spring hatch and 

reflood Aedes, and Cq. perturbans account for the bulk of the pest problems in this project. All standard 

monitoring methods are used to evaluate program effectiveness. 

Central Mass has assembled an impressive staff, with six staff members holding BS or BA degrees and 

several personnel having more than 15 years of mosquito-control experience. 

Over the past decade the Project has worked to reduce its use of adulticides and increased its applications 

of larvicides such as Bti. Water management has been geared towards maintenance but wetlands restoration is

playing an increasing role. Given that many towns have withdrawn from the project due to budget constraints, 

developing a modern, cost-effective control program is the highest challenge currently facing the Project. 

East Middlesex Mosquito Control Project

 Created under: MCL Chapter 252, section 5A in 1945. There is no specific Massachusetts 

Law or Act which names the East Middlesex Control Project. 

Area included: Twenty cities and towns in Middlesex and Norfolk Counties including 

Arlington, Bedford, Belmont, Brookline, Burlington, Cambridge, Framingham, Lexington, Lincoln, Melrose, Newton, North Reading, Reading, 

Sudbury, Wakefield, Waltham, Watertown, Wayland, Wellesley, and Weston. 

Annual assessment: Cities and towns voluntarily appropriate funding each year for mosquitocontrol services. Funding is carried over from one fiscal year to the next. 

This project was organized in 1945 as a trust agency to provide mosquito control for 6 cities and towns. 

The original goals for the Project cited by the representatives of the 6 municipalities were to form a cooperative 

58
mosquito control program under the auspices of the State Reclamation Board. Policies for the Project were set by

the Commission that would be comprised of representatives, appointed by the State Reclamation board, from each 

municipality. The primary reasons cited in 1945 for organizing the Project were the vector potential and nuisance 

caused by mosquitoes. 

Currently the Project has 20 members. The newest municipalities to join the project have been North

Reading (1991) and Melrose (1997). The twenty-member commission meets twice a year. Five Commissioners 

serve on the Executive Committee, which meets regularly. Funding is derived through voluntary appropriations. 

The Commission has a policy, which allows municipalities flexibility in choosing control methods. The Project 

recommends a control program for each municipality. The municipality then has control over which services it 

chooses to fund. Although this process has resulted in stable growth since 1983, the Project has historically had 

funding limitations because 33% of its area is urban with relatively minor mosquito pest problems. 

 Spring Aedes species, Ae. vexans, and Cq. perturbans are the major concerns in the district. Culex in urban 

areas are also a concern. Aerial larviciding against spring Aedes and Aedes vexans is the largest program in the 

district. Other programs include larviciding with a truck-mounted hydraulic sprayer and portable sprayers, catch 

basin larviciding in urban areas and adulticiding with truck-mounted ULV aerosol sprayers and portable aerosol and 

backpack mistblowers. Beginning in 1994, the Project entered into a cooperative agreement with the Essex County

Mosquito Control project to use a backhoe and operator for East Middlesex ditch-maintenance operations. The 

Project continues to maintain ditches by hand in woodland areas. The Project maintains an extensive surveillance 

operation, which includes monitoring adult mosquitoes at 50 locations. The Project records extensive larval survey 

data to support it’s larval control program. Beginning in 1995 the Project augmented its surveillance and record 

keeping programs by adding GIS mapping software. 

North East Massachusetts Mosquito Control and Wetlands Management District

formerly Essex County Mosquito Control Project

Created under: Chapter 516 of the Acts of 1958 

Area included: The area in Essex County not including any city or town already a member 

of an organized mosquito control project. 

Annual Assessment: 15 cents on each one thousand dollars of taxable valuations; sums so 

expended one quarter in proportion to their valuations and three quarters 

in proportion to their respective areas. 

Amendment of Assessment: Chapter 679 of the Acts of 1970 -- eight cents on each thousand dollars of 

equalized valuation; on quarter in proportion to there said valuations and 

three quarters in proportion to their respective areas. 

59
This seventeen-town project was established in 1965 after lobbying efforts by citizen groups who were 

concerned about pest mosquitoes. Prior to 1986 four towns (Essex, Merrimac, North Reading, Lynnfield) 

subsequently withdrew from the project by town meeting vote due to fiscal constraints and some negative publicity. 

One of these towns (Lynnfield) rejoined the following year due to a perceived increase in pest densities and threats 

to public health. Ten towns withdrew from the project in the late ‘eighties, primarily because of budget constraints. 

Four towns (Ipswich, Newburyport, Salisbury and Amesbury) have since rejoined, all because of public demand 

following the halt of control activity (length of time out of project varied from one to three years). 

A high proportion of the Essex County MCP budget is devoted to salt marsh mosquito problems (60%) and 

this project has taken the lead in working with environmental interests to develop OMWM plans and studies in

some of its marshes. Catch basins are treated with Altosid briquettes and all other larviciding is carried out with the 

bacterial toxin Bti. This is mostly in woodland vernal pools in the spring and in unmanaged salt marshes. The 

project does little adulticiding. It also administers a greenhead fly control program using box traps in several 

coastal towns. All monitoring methods (i.e., complaints, and light emergence traps, and landing/larval counts) are 

used to evaluate the effectiveness of the program and for daily decision-making. 

Essex County has been a leading project in developing Open Marsh Water Management as a mosquitocontrol and marsh-restoration technique in the Northeast, and has pushed to develop a set of standards for mosquito

control in such areas as uplands ditch maintenance that will both standardize control throughout New England and 

provide a better framework for the permitting process. 

Not surprisingly for a Project with a forward thinking approach, Essex County’s program, over the past

decade, has reduced adulticiding while implementing OMWM and increasing its ties with environmental agencies 

and groups. The loss of several towns has required a change in strategy from a regional to a municipal approach, a 

change not particularly desirable for area-wide control problems like mosquitoes. However, the challenge of 

revising the Project’s strategies and techniques has been met and its most important challenge today is meeting the 

demand for marsh restoration work while continuing to maintain a high standard for mosquito control.

Essex County MCP changed its name in 1996 to the North East Massachusetts Mosquito Control and 

Wetlands Management District, but it will be referred to as Essex County in this report as the name is new and may 

not be recognized by readers at this time. 

60
Norfolk County Mosquito Control Project

Created under: Chapter 341 of the Acts of 1956 

Area included: The area in Norfolk County not including any city or town already a 

member 

of an organized mosquito control project. 

Annual Assessment: 20 cents on each one thousand dollars of taxable valuations; sums so e 

expended on half in proportion to their valuations and one half in 

proportion to their respective areas. 

Amendment of Assessment: Chapter 496 of the Acts of 1975--8 cents on each thousand dollars of 

equalized valuations; sums so expended one quarter in proportion to their 

valuations and three quarters in proportion to their respective areas OR 

three quarters in proportion to their valuations and one quarter in proportion 

to their respective areas, WHICHEVER IS THE LESSER AMOUNT. 

Twenty-two towns formed this project in 1956 and three more joined in the early 80's after the South Shore 

project disbanded. Two towns (Milton and Norfolk) later withdrew by a vote at town meeting or city council.

Norfolk rejoined just one year later only to withdraw and rejoin again about 10 years later. Withdrawal votes were 

fueled by environmental concerns over pesticide use and negative publicity. Efforts to rejoin were precipitated by

public health threats, biting complaints, and ineffective in-house control programs. Norfolk did not lose towns 

during the late eighties, so has had stable membership for more than a decade. 

Over half of the project budget is spent on source reduction work. In the ‘80’s adulticiding was stressed 

over larviciding but this has changed and now larviciding, including aerial applications, far exceeds adulticiding. It 

is estimated that there are over 30,000 acres of freshwater swampland in Norfolk County, which can breed 

mosquitoes, but only 1,087 acres are treated for spring-hatch and 523 acres (there may be overlap) for summer 

reflood mosquitoes. Thirty-eight acres of salt marsh are under active control. All 4 standard surveillance methods 

are used to evaluate program effectiveness. 

Over the past decade the project has faced increasing pressure from the public concerning pesticide use. 

The project has responded by providing a more localized response to fogging requests (no more town-wide 

applications are done), by increasing larval monitoring to better target larvicide applications, and by using Bti and 

IGR formulations for larviciding. In 1996, the Project purchased a third excavator for source-reduction work, went

from five to nine field staff positions, hired two seasonal employees to improve their database information on 

wetlands and purchased computer mapping equipment to better target their control efforts. 

These changes, while desirable environmentally, have their cost, and funding remains a primary concern. 

61
In addition, environmental regulations likewise cause concerns, specifically when fueled less by scientific reason

and more by emotional appeal. 

Plymouth County Mosquito Control Project

Created under: Chapter 514 of the Acts of 1957 

Area included: The area in Plymouth County not including any city or town already a 

member of an organized mosquito control project. 

Annual Assessment: 25 cents on each one thousand dollars of taxable valuations; sums so 

expended on half in proportion to their valuations and one half in

proportion 

to their respective areas. 

Amendment of assessment: Chap. 544 of Acts of 1970 -- 13 cents on each thousand dollars of 

equalized valuations; one-half in proportion to said valuation and one-half 

in

proportion to their respective areas. 

Twenty-one towns formed this project in 1958 during a period of major EEE threat. The Plymouth County 

Selectman's Association and local legislators led this movement to organize. Seven additional towns joined the 

project in the early 1980's when the South Shore project disbanded. Four of the original member towns withdrew 

by town meeting vote in the mid-sixties. Towns must have been a member for at least 3 years before they can vote 

to leave the project. Towns that withdrew did so primarily over concern for the impact of the wide-scale aerial 

spraying that the project was carrying out in the mid-sixties. The town of Halifax rejoined the project in 1985 after 

they determined that the Plymouth County project was more environmentally sound than the in-house program they

had developed. Since that time, Abington, Hanover, Kingston, and Whitman have also rejoined. Bridgewater 

withdrew in 1990, due to budgetary concerns. 

About 20% of the concern of this Project is with salt marshes. Water management, including OMWM

efforts, is used to control most salt marsh Aedes. Spring and reflood Aedes receive a substantial amount of 

attention. Cq. perturbans, the cattail mosquito, causes a very significant problem but there are no recommended 

larvicides for this species at present. Although several projects contract for some aerial larviciding (and adulticiding 

in emergencies), Plymouth County is the only project, which owns fixed winged aircraft for doing its own aerial

work. Ground adulticiding with resmethrin is still an important control strategy in this project because of inability to 

control the cattail mosquito, and other species developing in large woodland swamps, with larvicides. Up to 7,860 

acres of Plymouth County's large acreage of swampland are treated with larvicide’s (Bti), targeted mainly against

spring Aedes. The project evaluates its control effectiveness from complaints, landing counts, and larval counts. 

62
The past decade has clearly been one of change at Plymouth. Malathion for adulticiding gave way to 

resmethrin and the larvicide Temephos was replaced by Bti. There has also been an increase in the number of 

member towns and increased service requests. Dr. Ludlam further notes that the State Reclamation Board has 

become stronger and there have been improved ties with the Massachusetts Department of Public Health. The most

important challenge facing Plymouth today is the continued lack of a control strategy for Cq. pertubans in the larval 

stages. 

 

Suffolk County Mosquito Control Project 

Created under: Chapter 606 of the Acts of 1973 

Area included: The area of Suffolk County comprising the cities of Boston and Chelsea. 

Annual Assessment: 5 cents of each one thousand dollars of equalized valuations; sums so 

expended one quarter in proportion to their valuations and three quarters in

proportion to their respective areas. 

The Suffolk County project is the smallest in land area and encompasses Boston and Chelsea. The two 

other towns in Suffolk County, Revere and Winthrop, are members of the Essex County project, which predates this

project. The project was organized in 1974 with strong leadership from legislators who were residents of the 

district and felt that a pest problem existed. Member town can withdraw from the project through a majority vote of 

the city council and mayor. Prior to the organization of the project, the Department of Housing Inspection 

contracted with a private applicator to do aerial spraying of salt marshes and the Parks Department did adulticiding

with mistblowers. 

About 30% of the mosquito problem is associated with salt marsh Aedes but no marsh management

activities are carried out in the project’s 200 acres of breeding salt marsh. Control is done with larvicide’s. Another 

130 acres of freshwater wetland breeding sites are also treated with larvicides, as are storm sewer catch basins. 

About 40% of the projects budget is devoted to adulticiding, the highest percentage of all the projects, but down for 

the 1980s. Program effectiveness is evaluated by complain levels, light traps, landing rates, and larval counts are 

used to evaluate the effectiveness of the program. 

Over the past decade the project has used more Altosid for larviciding and reduced malathion use for 

adulticiding. Public pressure, both for increased spraying (to eliminate mosquitoes) and decreased spraying (to

protect the environment) plays a strong role in the day-by-day operation of this populous project. There are also 

two MDC Reservations in which mosquito-breeding areas overlap endangered species habitat. Currently the project

63
can use Bti in these areas but would prefer to switch to Altosid. Permission to make this switch has not been 

granted. 

Budgets

 Budgets for all projects for 1993 and 1994 fiscal years are provided in Tables 1 and 2. The standard break 

down by category as used by the SRCMB is adopted in these Tables. The data used in these Tables were provided 

by the projects themselves. 

 2. Non-Member Communities. 

 For the initial GEIR, all Massachusetts Town Boards of Health were sent a concerning their town's 

mosquito control activities and 326 (93%) eventually responded. Fifty-seven towns (about 38% of those 

responding) indicated they do some mosquito control: 34 carry out the control work themselves using town 

personnel and 23 contracts with private applicators. Nineteen (83%) of the 23 towns with contracted control

provided detailed information on costs and pesticides used; 23 (68%) of the 34 town-operated programs provided 

this information.

 The decision by non-member towns to do mosquito control work (which in almost all cases was temporary,

chemical control) is made by a variety of authorities: 68% by the BOH, selectmen, mayor or other town officials, 

and 32% by a public vote. Citizen complaints and a perceived health threat both weighed heavily in decisions to do 

control work. Approximately 1/4 of the towns had some mosquito survey information available as an aid in the 

decision-making process. The major criteria used to assess the effectiveness of the control work undertaken was the 

post-treatment level of citizen complaints (95% of all towns). Other considerations were, in order of importance: 

larval counts, light trap counts, level of disease, and human landing counts. 

 Table 1. Budgets for Mosquito Control Projects for Fiscal Years starting in 1993 and 1994. 

 Budget Item 1993 1994 

Berkshire County MCP 

 Administration 

a. Personnel (wages & benefits) 30,000 30,000 

b. Other (office supplies, travel, etc.) 500 500 

 Field Operations 

a. Personnel (wages & benefits) 10,700 10,700 

64
 b. Pesticides 5,792 0 

c. New equipment 0 0 

d. Other (gas, suppli 20,000 25,792 _______ _______ es, etc.) 

TOTAL $66,992 $66,992 

Bristol County MCP 

 Administration 

a. Personnel (wages & benefits) 75,370 75,518 

b. Other (office supplies, travel, etc.) 46,918 47,888 

 Field Operations 

a. Personnel (wages & benefits) 260,615 255,550 

 b. Pesticides 34,377 31,610 

c. New equipment 6,125 17,412 

d. Other (gas, supplies, etc.) 24,121 20,162 _______ _______ 

 TOTAL $447,526 $448,140 

65
Table 1. Budgets for Mosquito Control Projects for Fiscal Years starting in 1993 and 1994 (continued). 

 Budget Item 1993 1994 

Cape Cod MCP 

 Administration 

a. Personnel (wages & benefits) 585,000 585,000 

b. Other (office supplies, travel, etc.) 5,000 5,000 

 Field Operations 

a. Personnel (wages & benefits) 204,495 204,495 

 b. Pesticides 38,000 38,000 

c. New equipment 35,000 35,000 

d. Other (gas, suppli _______ _______ es, etc.) 

 TOTAL $918,511 $918,511 

Central Mssachusetts MCP 

 Administration 

a. Personnel (wages & benefits) 123,201 125,817 

b. Other (office supplies, travel, etc.) 36,546 17,241 

 Field Operations 

a. Personnel (wages & benefits) 286,348 286,144 

 b. Pesticides 15,000 37,527 

c. New equipment 18,154 18,970 

d. Other (gas, supplies, etc.) 84,181 77,731 _______ _______ 

 TOTAL $563,430 $563,430 

East Middlesex MCPa

 Administration 

a. Personnel (wages & benefits) 64.190 64,995 

b. Other (office supplies, travel, etc.) 27,507 24,804 

 Field Operations 

a. Personnel (wages & benefits) 119,156 116,734 

 b. Pesticides 18,422 21,508 

c. New equipment 0 11,927 

d. Other (gas, supplies, etc.) 18,843 23,159 _________ _________ 

 TOTAL $248,118 $263,126 a

Rounded to the nearest dollar from reported figures. 

Essex County MCP 

 Administration 

a. Personnel (wages & benefits) 47,320 53,000 

b. Other (office supplies, travel, etc.) 7,000 7,000 

 Field Operations 

a. Personnel (wages & benefits) 188,105 188,737 

 b. Pesticides 10,000 28,000 

c. New equipment 0 13,000 

d. Other (gas, supplies, etc.) 25,685 37,231 _______ _______ 

 TOTAL $278,110 $326,968 

66
Table 1. Budgets for Mosquito Control Projects for Fiscal Years starting in 1993 and 1994 (continued). 

 Budget Item 1993 1994 

Norfolk County MCP 

 Administration 

a. Personnel (wages & benefits) 184,427 161,640 

b. Other (office supplies, travel, etc.) 60,482 60,472 

 Field Operations 

a. Personnel (wages & benefits) 79,040 121,939 

 b. Pesticides 4,617 186 

c. New equipment 19,520 26,369 

d. Other (gas, suppli 57,331 45,556 _______ _______ es, etc.) 

 TOTAL $405,417 $416,162 

Plymouth County MCP 

 Administration 

a. Personnel (wages & benefits) 127,217 144,700 

b. Other (office supplies, travel, etc.) 37,388 40,000 

 Field Operations 

a. Personnel (wages & benefits) 243,318 256,514 

 b. Pesticides 30,590 31,500 

c. New equipment 54,625 32,100 

d. Other (gas, suppli 71,311 59,635 _______ ______ es, etc.) 

 TOTAL $564,449 $564,449 

Suffolk County MCP 

 Administration 

a. Personnel (wages & benefits) No Figures supplied 

b. Other (office supplies, travel, etc.) 

 Field Operations 

a. Personnel (wages & benefits) 

 b. Pesticides 

c. New equipment 

d. Other (gas, supplies, etc.) _______ _______ 

 TOTAL 

67
Table 2. Total Budgets for the nine MCPs. 

County 1993 1994 

Berkshire County 66,992 66,992 

Bristol County 447,526 448,140 

Cape Cod 918,511 918,511 

Central Massachusetts 563,430 563,430 

East Middlesex 248,118 263,126 

Essex County 278,110 326,968 

Norfolk County 405,417 416,162 

Plymouth County 564,449 564,449 

Suffolk County No Figures Supplied 

 

 _________ _________ 

TOTAL $3,492,553 $3,567,778 

The choice of control strategy to be used was generally made by the town BOH or town personnel directly

responsible for control activities. About 1/4 of the towns left this decision to the private applicator contracted to do 

the control work. One-third consulted outside public advisor such as the Board of Reclamation or neighboring MC

project superintendents. About 1/6 sought advice from private sources such as pesticide salespersons. A similar 

breakdown of sources was used by towns to make decisions concerning when, where and how to apply the 

prescribed pesticides, except in the case of public and private consultants who were used less (only by 1/4 and 1/10 

of the towns respectively). The choice of chemical to be used for control was based largely on its safety to the 

environment. Two-thirds of the towns predicated their decision on this consideration. Other concerns such as cost, 

effectiveness, and ease/safety of application were much less important. None of these criteria were used in selecting

pesticides by more than 10 of responding towns. Decisions on when and how often to apply larvicides were based 

on larval sampling in about 2/3 of the towns and on a calendar spray schedule in 1/3 of the towns. Adulticide 

applications were mainly based on public complaints or pre-established calendar schedules, but a little over 50% of

towns were prepared to modify their application schedules depending on weather conditions. Twenty-nine percent

of towns indicated that scheduled pesticide treatments had actually been canceled due to adverse weather or for 

other reasons. 

 Most towns (ca. 80%) rely on newspaper and TV/radio announcements to inform the public of pending 

pesticide treatments. Twelve percent make no effort to inform the public at all. Fifty-three percent keep a list of

beekeepers whose hives should be avoided but only 3% personally notify beekeepers of pending spray schedules. In 

68
most towns, beekeepers must rely on the same information provided to the general public, which means that 9-12% 

of towns provide beekeepers with no warning whatsoever. In contrast, 94% of towns polled make some provisions 

for people to request that their property not be sprayed. 

Nantucket is one town that has started a program in the time period between the first draft GEIR and this

draft. The program has included aerial and ground applications of Altosid, and extensive Open Marsh Water 

Management. Activity and expense peaked in 1992 and 1993 when the OMWM system was dug. Since then the 

town has conducted small amounts of larviciding in salt marshes. No work is done in freshwater areas and no 

adulticiding is done. 

 3. Other Programs 

 a. Department of Environmental Management

 The Division of Forests and Parks discontinued its own mosquito control program in 1978 at the 

suggestion of the MEPA office pending the completion of an Environmental Impact Report of statewide mosquito

control. From 1966-77, their mosquito control program consisted of adulticide treatments of state parks twice each 

summer coinciding with the heavy use periods of Memorial Day and July 4th. Applications were made with a mist

blower and a mixture of methoxychlor (9 gal of 25% EC), malathion (1 gal of 57% EC) and water (40 gal). There 

was no attempt to evaluate the effectiveness of these applications, which were presumably carried out at night. 

 The Essex County Mosquito Control Program adulticides as required at the Salisbury Beach State Park and 

at the Bradley Palmer State Park in Hamilton. 

 b. Department of Public Health

The Massachusetts DPH is responsible for surveillance for EEE Virus, risk assessment, public information 

and education on EEE disease, as well as providing advice to the State Reclamation and Mosquito Control Board on 

appropriate risk management for EEE. DPH is also responsible for recommendations for wide area aerial vector 

control interventions in the event of an EEE Public Health Emergency. The Process for Risk Assessment and 

Management of EEE is outlined in the “Vector Control Plan to Prevent EEE” (See Appendix B, Vector Control 

Plan: Risk Assessment Section VI). 

Every year DPH’s Eastern Equine Encephalitis Surveillance Program (EEESP) collects data to assess the 

risk of EEE. This is an on-going program, which is carried out at the State laboratory Institute in Jamaica Plain. 

Key variables used to determine the risk of EEE include precipitation levels, mosquito population abundance, and 

69
presence of EEE virus in mosquitoes, horses, and humans. The purpose of the DPH EEE surveillance effort is to 

assess risk and use this information to advise the SRMCB and the public of the relative risk of EEE in any given 

season. In addition, the DPH chairs the Pesticide Review Board, which regulates pesticide use in the state. 

In 1956 the EEESP was established in southeastern Massachusetts by the U. S. Public Health Service 

(CDC), in cooperation with the Massachusetts DPH, for the study of EEE. A surveillance program has continued 

since 1957 to the present, with funding solely from DPH beginning in 1970. Surveillance for EEE consists of 

monitoring mosquitoes to determine population levels in relation to previous years’ levels, especially Cs. melanura, 

Ae. vexans, Ae. canadensis, Cq. perturbans, and Ae. sollicitans, testing samples of mosquito populations for the 

presence of EEE and Highland J (HJ) virus (HJ is an arbovirus which does not cause human disease but which is an 

indicator of arboviral activity in the bird population), testing suspected EEE horse cases and screening suspected 

human cases of encephalitis, meningoencephalitis or other cases of clinical disease that may mimic symptoms of 

EEE virus infection. Information is also compiled on precipitation, groundwater levels, and surveillance data from

other sites. The surveillance program keeps abreast of new developments in the study of EEE and has expanded its 

trapping effort in response to these developments. 

In recent years DPH has funded studies in collaboration with local universities aimed at furthering our 

understanding of EEE. These have included an assessment of the focality of EEE transmissions; Cs. melanura host

preferences studies and research aimed at identification of the principal avian reservoir host species for the 

amplification and perpetuation of the EEE virus. In 1997, mosquito trapping was expanded to include several bird 

roost studies postulated to be critical foci for amplification of EEE virus (Komar et al., unpublished). 

Each year the EEESP prepares a summary of the past season’s surveillance activities in November, and

provides an early prediction of the next season with regard to the likelihood of the presence of EEE virus in the 

environment and the potential for transmission to humans based on key variables of precipitation, mosquito

populations and prior years’ EEE activity in mosquitoes, birds, horses and humans. This information is provided to 

the SRMCB, EOEA agencies, the State Legislature, Boards of Health and the general public. Vector control

meetings are held as needed with eastern Massachusetts Mosquito Control District Superintendents and the SRMCB

throughout the season. 

Surveillance provides an early warning of the presence of EEE in the environment. The EEE Surveillance 

Program begins no later than the first week in June and continues through early October, unless a killing frost brings 

70
the mosquito season to an end earlier. This is a continuing program with an objective to provide epidemiological

information on EEE virus and potential vectors of this disease to guide public health actions. EEE surveillance 

reports are issued weekly throughout the trapping season and provide a summary of weekly laboratory analyses for 

mosquitoes, horses and humans. 

When EEE is found in trapped mosquitoes, supplemental surveillance activities are initiated. These may 

include increased trapping of bridge vector species (species that transmit the disease from birds to horses or 

humans) utilizing a variety of trapping methods, estimation of vector species larval abundance, and age structure 

determinations. Isolation of EEE also may trigger health alerts and advisories when appropriate. 

The first emergency effort to control mosquitoes during a disease outbreak occurred in 1956 when $90,000 

was made available from the governor’s emergency fund for aerial adulticiding. In this effort 150,000 acres were 

sprayed with DDT. The EEE disease outbreak of 1973 led to an aerial ULV application of malathion in the late 

summer, when approximately 1.7 million acres in eastern Massachusetts were treated. In 1974 and 1975 

approximately 82,000 acres were aerially treated. The cost of the 1973-75 vector control interventions was over 

$700,000. In the EEE outbreak of 1982-84, no state-funded aerial application was conducted, however, $150,000 

was allocated from the governor’s emergency fund to support intensified ground spraying. In 1990 another 

emergency aerial ULV malathion application occurred over the southeastern part of Massachusetts. In this

intervention 524,096 acres were treated at a cost of approximately $800,000. All interventions were based upon the 

likelihood of multiple human cases of EEE. While the cost of EEE vector control interventions may appear high, 

the lifelong costs associated with just one residual case of EEE have been estimated at $3 million dollars (Villari et 

al. 1995). 

 c. Federal Lands 

 In general, states have no jurisdiction over federal property. Any mosquito control activity on U. S. 

government property in Massachusetts is only subject to federal laws and not to the laws of the commonwealth. 

Thus, the following description will be brief and informational only. 

71
 i. Parks, monuments, refuges, etc. 

 No mosquito control is carried out by the U. S. Department of Interior on any government-owned land in

Massachusetts. The current philosophy of the U. S. Park Service and U. S. Fish and Wildlife Service seems to be 

adverse toward the initiation of pest control except in unusual circumstances, e.g., the campground in Everglades 

National Park, the Island Wildlife Refuge, etc. The Cape Cod National Seashore is perhaps the U. S. Park Service 

property with the most significant mosquito populations. Park Service biologists have conducted their own studies 

on the environmental impact of Cape Cod mosquito control activities (Portnoy 1983, 1984a, 1984b) in adjacent 

estuaries and have lobbied against certain ditch cleaning practices on environmental grounds. 

The East Middlesex MCP has been controlling mosquitoes in Great Meadows National Wildlife Refuge 

since 1987. Annual aerial Bti applications targeted against spring Aedes species began in 1987 and applications to

control Aedes vexans began in 1990. Prior to each application, the Eat Middlesex MCP submits data on preapplication larval populations. Following receipt of the data each year, Great Meadows National Wildlife Refuge 

issues a permit for the aerial application. The National Park Service reservation area (Paul Revere's Ride) in East 

Middlesex County has been declared off limits to any mosquito control activity (by East Middlesex MCP) except

for ditch cleaning. 

The Essex County MCP has completed OMWM projects on the Parker River Wildlife Refuge. 

 ii. Military Bases. 

 All U. S. Military bases have a pest control section, which often engage in some mosquito surveillance and

control activity. In Massachusetts, Fort Devens has routinely carried out both larval and adult control. In the 1980s 

this has consisted of mist blowing with Malathion for adult control and Altosid briquettes for larval control. 

Hanscom Air Force Base joined the East Middlesex MC project in 1985 but still assists with surveillance and some

control activities. None of the other military bases in Massachusetts (i.e., Barnes in Westfield, Westover in

Chicopee, and Otis on the Cape) reported mosquito control activities in recent years. 

 d. Private Reserves. 

 There are several private reserves and estates in Massachusetts (e.g., Cranes Beach), which are frequently 

used by the public in one capacity or another. There is no indication that mosquito control is regularly practiced on 

any of these properties. It seems unlikely; therefore, that this represents a significant category of undocumented 

pesticide use or habitat modification for mosquito control, past or present. Certain MCPs include, by request, some

72
reservation properties in their overall program but those activities are included in their program summaries. 

C. Historical Overview of Mosquito Control Practices in Massachusetts 

1. Practices prior to 1980 

Development along the Eastern Seaboard, especially for tourism, was predicated on an ability to control the 

hoards of salt marsh mosquitoes. The earliest experimental work took place in New Jersey salt marshes in the late 

teens and early 1920's. These successes encouraged the massive hand-ditching projects in East Coast marshes that 

took place during the WPA programs of the great depression, with some 3,000 miles of ditching being dug in 

Massachusetts’s salt marshes alone. These ditching schemes, while quite effective in reducing salt marsh

mosquitoes, were engineered to make work rather than for optimum biological efficiency. Moreover, the value of 

estuarine ecosystems was unrecognized at the time. 

 Early salt marsh mosquito control projects, such as the one on Cape Cod in the 1930's, were organized 

prior to the availability of synthetic pesticides following World War II and these projects expanded and maintained

the WPA-dug ditch system as their main strategy for mosquito control. After DDT, BHC, and other organochlorine 

pesticides became available, they were used to both supplement larval control and, for the first time, to conduct 

residual spraying for adults. Aerial application of these pesticides became commonplace in the 1950's and early 

60's. However, coastal projects that were organized after the introduction of these modern pesticides still relied 

heavily on source reduction to manage salt marsh mosquitoes. Paris Green (an arsenical) and petroleum oils were 

developed as mosquito larvicide’s for malaria control during World War II and also became popular in the U. S. 

after the war. Waste crank case oil was not infrequently used in mosquito control despite the fact that thin oils (e.g., 

diesel fuel) with a spreading agent provide for the greatest and most effective surface coverage. The commercial 

mosquito control oil, Flit MLO, was introduced and widely used during the 70's, but was taken off the market in the 

mid-80’s. Arosurf-MSF, a monomolecular surface film was available for several years, starting in the mid-80, but 

was taken off the market. It is now (1997) being returned to the market as Agnique MMF (Henley, personal

communication). 

Abate (temephos), one of the few organophosphates registered for aquatic use, was introduced a few years 

later and shared the larvicide market with surface oils. The first new generation pesticide introduced for mosquito 

control was the growth regulator Altosid (methoprene), a juvenile hormone mimic. It has been widely used in

mosquito control since the mid-l970's. Projects in the Northeast were slow to switch to this highly selective 

73
material, perhaps due to its delayed response and narrow window for control. 

The choice of which larvicide to use is based equally on effectiveness and safety to the applicator and to 

the environment. Adulticiding is often predicated on public complaints. Weather conditions and field surveys also 

play a role in deciding when to schedule applications in most projects. 

Chemical control in freshwater marshes followed a similar pattern to that in salt marshes. Treatment of

catch basins, first with oils followed by organochlorines and organophosphates, dates back to the beginning of most

Massachusetts projects. 

Physical control was limited to drainage maintenance and expansion in both salt marshes and freshwater 

areas. Biological control was not conducted. 

 Controlling Cs. melanura larvae in large white cedar/red maple swamps was generally considered an 

impossibility so aerial adulticiding was adopted as the strategy of choice for vector control during epidemic threats. 

Projects within the main focus of EEE in southeastern Massachusetts were the only ones to routinely do aerial 

spraying. This work was gradually discontinued in the 1970’s due to environmental concern over aerial

adulticiding.

Projects have intermittently had the support service of a SMRCB entomologist. During 1976-81, a period 

when the projects had no entomological support from the SMRCB, an extension biting-fly specialist was available 

through a cooperative agreement with the University of Massachusetts. Each project contributed 0.5% of their 

annual operating budget as their share of support for this position, which was jointly funded by Massachusetts 

Cooperative Extension. The specialist developed control recommendations, evaluated new control methods, set up 

a statewide light trap surveillance program, and carried out other support services to the projects. Some controversy 

developed among projects, particularly over the control recommendations made by the specialist. Following his 

resignation, the SMRCB again hired an entomologist and the University position was discontinued.

2. Transitioning: from 1980 to 1995. 

By the early 1980s, concerns over pesticide use and wetlands loss began to encroach on mosquito control. 

Grid ditching for larvae and malathion for adults was no longer a desirable one-two punch. Control trends during 

the eighties and early nineties include: 

z Changing from traditional chemicals, such as Abate and Flit MLO, to Bti and methoprene for 

larval control (Table 3). 

74
z Changing from malathion to permethrin or resmethrin for adult control (Table 3). 

z Changing from open tidal ditching to open marsh water management for salt marsh mosquito 

 control.

z Reduction in the number of towns belonging to Projects in the late 1980s. This trend has reversed 

in the past several years. 

Table 3. A comparison, between the early 1980’s and the mid-1990’s of chemicals used by Massachusetts MCPs. 

Active Ingredient Toxicity Class Used Betweena

1981-1985 1993-1995 

 AS LARVICIDES

Bacillus thuringiensis var. israelensis IV + +++ 

 Fenthion II - N 

 Isooctadecanolb

 Malathion III + N 

 Methoprene IV o ++ 

 Methoxychlor IV ++ N 

 Mineral Oil III-IV +++ o 

 Permethrin III - N 

 Temephos IV + - 

 

 AS ADULTICIDES

 

 Dibrom II + N 

 Fenthion II o N 

 Malathion III +++ - 

 Methoxychlor IV + N 

 Permethrin III N ++ 

 Resmethrin III - +++ 

 a+++ = Primary pesticide used 

 ++ = Significant use 

 + = Common but minor use 

 o = Infrequent use 

 - = Rarely used 

 N = Never used bDiscontinued product (Arosurf) 

Altosid had come onto the market but acceptance was slow, both because it was hard to monitor the 

efficacy (larvae do not die for some time) and because of restrictions on the label against using in fish habitat. By 

the early ‘90s, however, it was in general use throughout Massachusetts. The extended-residual briquet form of 

Altosid was tested against Cq. perturbans, as was Arosurf-MSF, but results were mixed and the briquet’s high cost 

prevents it from being an attractive control agent for large cattail areas. Trials with Altosid pellets were 

75
encouraging but this control technique is not being used in Massachusetts. 

In contrast to Altosid, the biological pesticide Bacillus thuringiensis var. israelensis was quickly accepted 

by Massachusetts’s projects when introduced in the early 80's. It is a mainstay of most programs, despite some

problems in salt marshes and aquatic habitats high in organic matter. The latter problem may be solved by the recent 

(1996) introduction of Bacillus sphaericus, a new biological pesticide that is designed specifically for Culex 

breeding in high-organic-matter habitats. 

Flit-MLO disappeared from the market and was replaced by Golden Bear oils. Arosurf-MSF was used in 

small amounts for several years before it too was taken off the market. It has recently returned to the market as 

Agnique MMF. Bonide Mosquito Oil (Mineral oil) is now available but not used. Source reduction 

remained a mainstay of the projects during this time period but coastal communities shifted away from ditch

maintenance towards open marsh water management. An emerging difficulty for control programs was the rise in

wet basins mandated by storm water runoff regulations. If improperly designed these can breed considerable

numbers of spring-brood and/or summer reflood mosquitoes. 

The evaluation of control effectiveness by projects remained a combination of public complaints, adult 

counts, larval counts, and cases of human disease. 

All projects maintained a public education component and several expanded their programs. 

Throughout this period, outside of inadequate budgets and the inability to do more source reduction work, 

the main operational problems voiced by most projects has been the lack of applied research support to assist them

in evaluating new technology and solving certain ever-changing problems. For example, the cattail mosquito, Cq. 

perturbans, is a major pest and potential epidemic vector of EEE in most projects but there is presently no 

recommended method for controlling this mosquito. 

D. Current Mosquito Control Strategies in Massachusetts

 1. Overview 

Chemical control, including Bacillus products and IGRs (Table 4), and source reduction, including open 

marsh water management, dominate mosquito control in Massachusetts (Tables 5 and 6). Aerial applications of 

larvicides have been used by several programs (Table 7) and is likely to increase. Biological control has not been 

emphasized except to the extent that OMWM creates conditions under which biological control operates. Public

education is a minor component of most programs. 

76
Salt marsh mosquitoes are the primary target of coastal programs, whereas inland programs target springbrood and summer-reflood Aedes (Tables 8 and 9). Coquillettidea perturbans is restricted by larval habitat to areas 

near cattail marshes. However, in those areas its populations can be extremely high. 

Vector mosquitoes are not the primary targets of Massachusetts control programs, though projects do 

respond to requests for aid from DPH in times of EEE emergencies. Culiseta melanura larval populations may be 

incidentally reduced by treatment programs that target swamp areas. East Middlesex MCP did conduct trials with

Altosid pellets aerially applied in April, 1992 for Cs. melanura control and were successful (Henley 1992). This

work has not been repeated in Massachusetts. 

Policy issues have revolved around wetlands and water quality preservation and endangered species. A 

chronic source of discussion is mosquito control’s exemption from many of the state-level wetlands protection acts, 

making the Federal Section 401 Water Quality Certification Act (administered at the state level) and the state and 

federal Endangered Species Acts the primary means of “controlling” source-reduction work. Storm water runoff 

regulations have increased the number of wet basins (retention, wet detention) in many areas, on occasion creating 

breeding habitat. Engineers and public officials involved in designing and approving such basins have been slow to

acknowledge mosquito control as design criteria, though the relevant sections of the Storm water Policy Handbook 

and Storm water Technical Handbook released by DEP in March 1997 should be incorporated into MCP practices 

(see Appendix E for listing of relevant information). 

The EEE outbreak in 1990 highlighted a need for stronger DPH policies regarding emergency mosquito 

control. As a result, the Massachusetts Department of Public Health published “Vector Control Plan to Prevent 

Eastern (Equine) Encephalitis” (August 7, 1991) and implemented an extensive Public Education Program in 1991. 

 

77
Table 4. Pesticide use by Project, 1993 through 1995. 

Pesticide Catagory Amount Used 

 1993 1994 1995 

Berkshire MCP 

Altosid Briquets IV 24.3 lb 5.8 lb 1.8 lb

Bactimos Granules IV 534.0 lb 2124.0 lb

Bactomos Pellets IV 232.0 lb 2026.0 lb 2093.0 lb

Abate 4E III 0.6 gal 

Arosurf-MSF III 16.0 gal 5.0 gal 

Scourge 18+54 III 10.1 gal 25.0 gal 20.1 gal 

Bristol County MCP 

Altosid Briquets IV 0.57 lb 45.6 lb

Bactomos Pellets IV 1593.0 lb 80.2 lb 2300.5 lb

Scourge 12+36 III 151.9 gal 190.6 gal 173.4 gal

Cape Cod MCP 

 Altosid Briquetsa IV 9.5 lb 8.4 lb 11.0 lb

Bactomos Pellets IV 20,710.0 lb 41,497.0 lb 43,174.0 lb

GB 1111 III 671.0 gal 704.0 gal 330.0 gal aTotals reported as briquets coverted to lbs 

Central Massachusetts MCP 

Altosid Briquets IV 231.9 lb 192.7 lb 106.2 lb

Bactimos Granules IV 281.1 lb 115.9 lb 2829.1 lb

Bactomos Pellets IV 1223.0 lb 3313.0 lb 81.0 lb

Vectobac Granules IV 96.9 lb

Vectobac 12AS IV 225.7 gal 171.7 gal

Witco GB-1356 III 65.1 gal 95.2 gal 5.6 gal

Witco GB-1111 III 23. 5 gal

Scourge 18 + 54 III 342.6 gal 398.5 gal 388.5 gal aDry and liquid ounces as reported coverted to pounds or gallons respectively

East Middlesex MCP 

 Acrobe IV 125.0 gal

Altosid Pellets IV 15.0 lb 10.9 lb

 Altosid Briquetsb IV 69.9 lb 20.7 lb 33.7 lb

Altosid XR Briquetsb

 IV 17.1 lb

Arosurf MSF III 2.3 gal 3.0 gal 

Bactimos Granules IV 12,880.0 lb 6,785.0 lb

Bactimos Pellets IV 2,324.0 lb

Vectobac G IV 8,062.0 lb 720.0 lb

Vectobac 12AS IV 8.4 gal 22.9 gal 169.2 gal

Permanone 10EC III 2.4 gal 2.1 gal 1.7 gal

Scourge 18 + 54 III 20.2 gal 26.0 gal 18.1 gal aDry and liquid ounces as reported coverted to pounds or gallons respectively

78
Table 4. Pesticide use by Project, 1993 through 1995 (continued). 

Pesticide Catagory Amount Used 

 1993 1994 1995 

Essex County MCP 

Altosid Pellets IV 70.5 lb

Bactimos Granules IV 3.8 lb 252.2 lb

Bactomos Pellets IV 1993.1 lb 4439.6 lb 887.5 lb

 Permanone 31-66a III 39.0 gal 42.5 gal 12.8 gal 

Scourge 18 + 54a III 10.1 gal 25.0 gal 20.1 gal aOunces as reported converted to gallons 

Norfolk County MCP 

Altosid XR Briquets IV 0.1 lbb 2.8 lb 254.8 lb

Bactimos Briquets IV 0.6 lb 1.8 lb 48.8 lb

Vectobac 12AS IV 79.0 gal 2.6 gal

Vectobac AS IV 52.3 gal

Arosurf-MSF III 406.7 gal 83.1 gal 149.0 gal

Scourge 18 + 54 III 45.8 gal 53.2 gal 52.7 gal aRounded to the nearest tenth from reported values bReported value = 0.038 lb

Plymouth County MCP, Ground-application Pesticide Usea 

Altosid XR Briquets IV 17.5 lb

Bactimos Pellets IV 357.0 lb 500.0 lb 50.0 lb

Bactomos Briquets IV 1.8 lbb

 10.3 lbb 17.2 lb

Vectobac 12AS IV 17.5 gal 2.5 gal

Teknar HP-D IV 17.5 gal 20.0 gal

Scourge 18 + 54 III 110.0 gal 85.0 gal 70.0 gal aSee Table 7, Aerial Application of Pesticides for information regarding aerial applications. bTotal reported as briquets converted to lbs. 

Suffolk County MCP, Ground-application Pesticide Usea 

 Altosid Briquetsa IV 3.5 lb 4.8 lb 3.3 lb

Altosid XR Briquetsa IV 57.5 lb 0.1 lb 11.4 lb

Bactimos Pellets IV 25.8 lb 31.0 lb

 Vectobac 12ASb IV 3.9 gal 7.9 gal 5.1 gal

 Malathion 8ECb III 1.5 gal 1.9 gal 0.2 gal 

 Permanone 10ECb III 0.1 gal 1.4 gal 0.8 gal 

 Resmethrinc

 III 11.2 gal 

Scourge 18 + 54b III 6.3 gal 12.1 gal 3.5 gal a

Totals reported as briquets converted to lbs. bRounded to the nearest tenth from reported values. cEPA reg #4-339-53853 

79
Table 5. Project distribution of operations by control method as expressed as a percentage of the budget allocated 

(average for 1981-1985) or as a percentage of the project’s operations (1994 and 1995). 

Berkshire MCP 

 % of Budget % of Operations 

 1981-1985 1994 1995 

Source reduction (excluding OMWM) 20 20 

S Open Marsh Water Management 0 0 ource reduction 33 ⎨

Biological larviciding (Bti) 5 40 40 

Chemical larviciding/pupiciding(excluding IGRs) 0 0 

C IGR larviciding (methoprene) 5 10 hemical larviciding/pupiciding 50 ⎨

Adulticiding 10 30 20

Public Education 2 5 10 

Bristol County MCP 

 % of Budget % of Operations 

 1981-1985 1994 1995 

Source reduction (excluding OMWM) 75 78 

S Open Marsh Water Management 0 0 ource reduction 60 ⎨

Biological larviciding (Bti) 6 2 2 

C

hemical larviciding/pupiciding 3 ⎨ hemical larviciding/pupiciding(excluding IGRs) 0 0 C IGR larviciding (methoprene) 0 0 

Adulticiding 30 22 19

Public Education 1 1 1 

Cape Cod MCP 

 % of Budget % of Operations 

 1981-1985 1994 1995 

Source reduction (excluding OMWM) Information 

S Open Marsh Water Management ource reduction 70 ⎨

Biological larviciding (Bti) 21 not

Chemical larviciding/pupiciding(excluding IGRs) C IGR larviciding (methoprene) Supplied 

hemical larviciding/pupiciding 4 ⎨

Adulticiding 0

Public Education 5 

Central Massachusetts MCP 

 % of Budget % of Operations 

 1981-1985 1994 1995 

Source reduction (excluding OMWM) 40 40 

S Open Marsh Water Management 0 0 ource reduction 70 ⎨

Biological larviciding (Bti) 5 25 25 

Chemical larviciding/pupiciding(excluding IGRs) 5 5 

C IGR larviciding (methoprene) 5 5 hemical larviciding/pupiciding 5 ⎨

Adulticiding 15 15 15

Public Education 5 10 10 

80
Table 5. Project distribution of operations by control method as expressed as a percentage of the budget allocated 

(average for 1981-1985) or as a percentage of the project’s operations (1994 and 1995) (continued). 

East Middlesex MCP 

 % of Budget % of Operations 

 1981-1985 1994 1995 

Source reduction (excluding OMWM) 26 42 

S Open Marsh Water Management 0 0 ource reduction 34 ⎨

Biological larviciding (Bti) 28 44 37 

Chemical larviciding/pupiciding(excluding IGRs) <1 0 

C IGR larviciding (methoprene) 4 4 hemical larviciding/pupiciding 27 ⎨

Adulticiding 10 25 16

Public Education 1 1 1 

Essex County MCP 

 % of Budget % of Operations 

 1981-1985a 1994 1995 

Source reduction (excluding OMWM) 20 15 

S Open Marsh Water Management 29 28 ource reduction -- ⎨

Biological larviciding (Bti) -- 40 50 

C

hemical larviciding/pupiciding -- ⎨ hemical larviciding/pupiciding(excluding IGRs) 0 0 C IGR larviciding (methoprene) 0 1 

Adulticiding -- 10 5

Public Education -- 1 1 a

No response 

Norfolk County MCP 

 % of Budget % of Operations 

 1981-1985 1994 1995 

Source reduction (excluding OMWM) 50 50 

S Open Marsh Water Management 0 0 ource reduction 54 ⎨

Biological larviciding (Bti) 4 25 20 

C

hemical larviciding/pupiciding 13 ⎨ hemical larviciding/pupiciding(excluding IGRs) 0 0 C IGR larviciding (methoprene) 14 20 

Adulticiding 25 10 8

Public Education 4 1 2 

Plymouth County MCP 

 % of Budget % of Operations 

 1981-1985 1994 1995 

S

ource reduction 25 ⎨ ource reduction (excluding OMWM) 45 53.0 S Open Marsh Water Management 0 0.0 

Biological larviciding (Bti) 5 30 25.5 

Chemical larviciding/pupiciding(excluding IGRs) 0 0.0 

C IGR larviciding (methoprene) 0 0.5 hemical larviciding/pupiciding 25 ⎨

Adulticiding 40 20 16.0

Public Education 5 5 5.0 

Table 5. Project distribution of operations by control method as expressed as a percentage of the budget allocated 

(average for 1981-1985) or as a percentage of the project’s operations (1994 and 1995) (continued). 

81
Suffolk County MCP 

 % of Budget % of Operations 

 1981-1985 1994 1995 

Source reduction (excluding OMWM) 5 5 

S Open Marsh Water Management 0 0 ource reduction 1 ⎨

Biological larviciding (Bti) 26 30 30 

C

hemical larviciding/pupiciding 25 ⎨ hemical larviciding/pupiciding(excluding IGRs) 0 0 C IGR larviciding (methoprene) 15 15 

Adulticiding 46 40 40

Public Education 2 10 10 

Table 6. Types of Control Activity,

1 by Habitat 

 Salt Marsh Spring Summer Cattail 

 Brood Re-Flood 

Berkshire County C,F C,F 

Bristol County A C C F 

Cape Cod MCP A,C,D,E A,C,D,E A,C,D,E A,C,D,E 

Central Massachusetts A,C,E,F A,C,D,E,F A,C,D,E,F 

East Middlesex A,C,D A,C,D 

Essex B,C A,C A,C 

Norfolk A,C,D,F A,C,F A,C,D,F F 

Plymouth A,C,D,F A,C,F A,C,F F 

Suffolk C,D,F A,C,D,F A,C,D,F F 1

Types of control activities -- indicate the types of control activities carried out on each wetland type using the 

following categories:

 A -- Source reduction 

 B -- OMWM

C -- Biological larviciding 

D -- IGR larviciding 

E -- Larviciding, non-IGRs 

F -- Adulticiding

82
Table 7. Aerial application of Pesticides, 1993 through 1995 

Project/Town Dates Time of day Acreage Pesticide Rate Target Area 

1993 

East Longmeadow 4/26 - 5/12 Daylight 1,000 Vectobac 12AS 1 qt/acre 

E. Middlesex MCP April 12-22 6 AM - 8 PM 2,017 Vectobac G 1 pt/acre 

Bactimos Pellets 5 - 7.5 lb/acre 

Plymouth MCPa April 12-16 4 AM -Noon 1,360 Vectobac 12AS 1 pt/acre Spring Brood 

May 3-7 4 AM - Noon 1,400 Vectobac 12AS 1 pt/acre Spring Brood 

May 10-14 4 AM - 9 AM 1,920 Vectobac 12AS 1 pt/acre Spring Brood 

1994 

Chelmsford April 16-22 Dawn - 11 AM 700 Bactomis Granules 5 - 7.5 lb/ac 

East Longmeadow May 5 - 12 Daylight 1,000 Vectobac 12AS 1 pt/acre 

E. Middlesex MCP April 19-28 6 AM - 8 PM 2,700 Vectobac G 5 - 7.5 lb/ac Wetlands 

Bactimos Granules 5 - 7.5 lb/ac 

August 23-27 6 AM - 8 PM 1,000 Vectobac 12 AS 1 pt/acre Flood Plain/

 Wetland

 Acrobe 1 pt/acre 

Plymouth MCPa April 18-22 4 AM - 9 AM 8,000 Bactimos Pellets 8 lb/acre Spring Brood 

April 25-29 4 AM - 9 AM 16,000 Bactimos Pellets 8 lb/acre Spring Brood 

 May 2-6 4 AM - Noon 8,000 Teknar HP-D 1 pt/acre Spring Brood 

1995 

Chelmsford April 16-22 Dawn - 11 AM 700 Bactomis Granules 5 - 7.5 lb/ac 

East Longmeadow May 5 - 12 Daylight 1,000 Vectobac 12AS 1 pt/acre 

E. Middlesex MCP April 12-22 6 AM - 8 PM 2,800 Vectobac 12 AS 1 pt/acre 

Bactimos Granules 5 lb/acre 

Essex MCP June 10-17 5 AM - Noon 1,400 Vectobac 12AS 1 qt/acre Salt Marsh 

June 20-24 5 AM - Noon 1,000 Vectobac 12AS 1 qt/acre Salt Marsh 

July 8-22 5 AM - 8:30 PM 1,000 Vectobac 12AS 1 qt/acre Salt Marsh 

August 5-19 5 AM - 8:30 PM 1,400 Vectobac 12AS 1 qt/acre Salt Marsh 

Plymouth MCP April 10-14 4 AM - Noon 11,000 Teknar/Acrobe 1 pt/acre Spring Brood 

April 18-21 4 AM - Noon 11,000 Teknar/Acrobe 1 pt/acre Spring Brood 

April24-28 4 AM - Noon 11,000 Teknar/Acrobe 1 pt/acre Spring Brood 

May 1-5 4 AM - Noon 11,000 Teknar/Acrobe 1 pt/acre Spring Brood 

May 8-12 4 AM - Noon 5,500 Teknar/Acrobe 1 pt/acre Spring Brood a

These are actual treatments for Plymouth County. Forms filed with SRMCB were for more dates and larger areas 

 than actually treated. 

 83
Table 8. Estimated wetlands acreage affected, by habitat, exclusive of adulticiding.

 Salt Marsh Spring Summer Cattail 

 Brooda

 Re-Flooda

Berkshire County 0 500 250 0 

Bristol County — no figures given 

Cape Cod MCP — no figures given 

Central Massachusetts 0 10,000 5,000 to 10,000 2,000 

East Middlesex 0 2,767 1,192 0 

Essex 5,000 500 1,000 0 

Norfolk 38 1,087 523 0 

Plymouth 100 7,860 1,000 0 

Suffolk 240 130 130 5 

TOTAL 5,378 22,844 9,095 2,005 a

There is overlap between acreage affected by spring brood and summer re-flood 

Table 9. Percentage of control effort, from monitoring through adulticiding (includes source reduction), 

by breeding habitat by Project. 

Habitat % Effort _______________ 

 1994 1995 Species targeted 

Berkshire MCP 

 Salt marsh 0 0 

 Freshwater 

 Spring re-flood 90 90 spring brood Aedes

 Summer re-flood 10 10 Ae. vexans

 Cq. perturbans 0 0 

Bristol County MCP 

 Salt marsh 50 50 Ae. sollicitans, Ae. cantator

 Freshwater 

 Spring re-flood 30 40 Ae. canadensis, Ae. excrucians, Ae. cinereus

 Summer re-flood 15 10 Ae. vexans

 Cq. perturbans 5 0 

Cape Cod MCP 

 Salt marsh 50 50 

 Freshwater 

 Spring re-flood 50 50 

 Summer re-flood 0 0 

 Cq. perturbans 0 0 

 84
Table 9. Percentage of control effort, from monitoring through adulticiding (includes source reduction), 

by breeding habitat by Project (continued). 

Habitat % Effort _______________ 

 1994 1995 Species targeted 

Central Mssachusetts MCP 

 Salt marsh 0 0 

 Freshwater 

 Spring re-flood 40 40 Ae. absrratus, Ae. excrucians

 Summer re-flood 30 20 Ae.vexans, Ae. canadensis

 Cq. perturbans 30 40 

East Middlesex MCP 

 Salt marsh 0 0 

 Freshwater 

 Spring re-flood 45 52 Ae. abserratus, Ae. aurifer, Ae. canadensis

Ae. cinereus, Ae. excrucians

 Summer re-flood 37 28 Ae. vexans, Ae. trivittatus

 Cq. perturbans 13 14 

Essex County MCP 

 Salt marsh 50 60 Ae. sollicitans

 Freshwater 

Spring re-flood 5 5 spring brood Aedes

 Summer re-flood 45 35 Aedes species 

 Cq. perturbans 0 0 

Norfolk CountyMCP

 Salt marsh 10 10 Ae. sollicitans, Ae. cantator

 Freshwater 

 Spring re-flood 60 60 Ae. excrucians, Ae. abserratus, Ae. cinereus 

Ae. canadensis, Ae. vexans

 Summer re-flood 15 15 

 Cq. perturbans 15 15 

Plymouth County MCP 

Salt marsh 20 20 Ae. sollicitans, Ae. cantator

 Freshwater 

 Spring re-flood 60 60 Ae. excrucians, Ae. abserratus

 Summer re-flooda

 10 10 Ae. vexans, Ae. cinereus, Ae. canadensis

 Cq. perturbansa

 10 10 a1994 and 1995 were extremely dry years which resulted in lower than normal control efforts toward summer 

 reflood and Cq. perturbans. 

 85
Table 9. Percentage of control effort, from monitoring through adulticiding (includes source reduction), 

by breeding habitat by Project (continued). 

Habitat % Effort _______________ 

 1994 1995 Species targeted 

Suffolk CountyMCP

 Salt marsh 30 30 Ae. sollicitans, Ae. cantator

 Freshwater 

 Spring re-flood 22 22 Ae. excrucians, Ae. abserratus, Ae. canadensis

 Summer re-flood 42 42 Ae. cinereus, Ae. vexans

 Cq. perturbans 6 6 

 2. Current Practice 

a. Salt marsh Mosquitoes 

The combination of large, affluent human population (both permanent residents and visitors) and prolific

pest mosquito populations near Massachusetts coastal marshes suggests that the public may always demand control

programs to deal with this intense annoyance problem. Most salt marshes that breed Aedes mosquitoes are now 

under management and, in most cases, the strategy is source reduction. 

 Open Marsh Water Management (OMWM) projects now underway in Essex, Norfolk and Plymouth 

counties are being expanded to include essentially all problem marshes in those counties. OMWM plans are 

developed and tailored to the specific circumstances of each individual estuary. The permitting and review process 

for these projects is time consuming. Thus, it will be some time before all marsh management will consist of this 

strategy even though it is currently the most environmentally sensitive and rational marsh management strategy for 

most situations. Public and State agency support for OMWM is solid. Wolfe’s (1996) review article on the effects 

of OMWM provides a strong basis for accepting OMWM as the best salt marsh mosquito control technique 

currently available. Wolfe makes the interesting point that salt marsh mosquitoes are an increasing problem not 

because they are breeding in greater numbers than before, but because more people are choosing to live near the 

coast. 

 Regardless of the benefits of OMWM, maintaining grid ditch networks is still an important part of coastal 

programs. Grid ditches are aesthetically unattractive and some have clearly had some negative impact on the 

 86
normal high salt marsh ecosystem. In contrast, evidence suggests that some ditched marsh may be more productive 

than unditched marshes (Shisler & Jobbins 1975). No qualitative studies on the impacts of grid ditching in 

Massachusetts have been done but clearly the habitat has been dramatically changed. Converting open systems to

OMWM systems does create a more-nature, though still highly managed, system. In the interim, current ditch 

cleaning practice seems preferable to the increased use of larvicides. 

 There are certain salt marshes where old ditches are effectively controlling mosquito production and 

perhaps where new OMWM activities might actually disrupt the marsh more than maintaining the status quo. Thus, 

OMWM plans should not be automatically prescribed for every salt marsh without first examining this issue. 

 Larviciding is still carried out in salt marshes that are unditched or in which ditches are ineffective or 

unmaintained. Larvicides in current use include the biological pesticide Bti, the insect growth regulator Altosid, 

and surface oils. These are all pesticides that have lower risks associated with their use. Bti and Altosid have the 

least potential non-target effects because of their high selectivity for certain dipterous insects. Bti is not always as 

effective in highly organic salt marshes as it is in other habitats. 

Adulticiding in coastal areas is often necessary because of the huge numbers of mosquitoes that breed on 

the marsh (a 99% kill with larvicide can still leave a lot of mosquitoes). Truck-mounted ULV application is the 

standard response, as is the case for freshwater adult mosquitoes discussed below. 

b. Inland Freshwater Wetlands 

 Most projects do a considerable amount of source reduction work in freshwater wetlands. This activity

consists primarily of ditch and culvert cleaning to discourage ponding along natural waterways and the resultant

production of spring and reflood Aedes. Routine maintenance generally involves hand-cleaning of debris from

drainage systems and brush removal where it is encroaching on the flow system. Machinery is not used for routine 

maintenance but is used where deteriorating conditions (a build-up of such sediments as road sand being a common 

example) require work that cannot be done by hand. 

Larviciding is done with Bti products, Altosid or Golden Bear oil. The vast majority of larviciding is done 

after mosquito breeding has been documented. Most applications are made from the ground by backpack sprayer or 

by hand (briquets). Aerial applications to freshwater areas are limited, but increasing (Table 7). Pre-hatch work is 

done by several projects. In general the area must have a lengthy history of mosquito breeding. 

Mosquito breeding in vernal pools, large acid swamps, and cattail/water willow ponds cannot be readily 

 87
controlled by source reduction work. Even larviciding is often difficult in large or deep permanent swamps. 

Projects with a large acreage of these habitats (i.e., Norfolk, Plymouth and Bristol) still depend more on adulticiding

than do projects whose larval sources are more accessible to larviciding. Helicopter application of granular 

larvicides is perhaps the only way to reach many of these habitats with larvicides, but this practice has been 

hampered in the past by the fact that flight plans had to be filed too far in advance. This problem was overcome by

the East Middlesex MCP by filing the flight plan when flooding started, not when larvae were first seen. This

carried the risk of requesting a treatment that turned out to be unnecessary but the predictability of Ae. vexans 

breeding after flooding is high. Regardless, changes made to the Pesticide Board regulations at the start of 1997 

season to make it easier to conduct aerial work. Norfolk MCP is actively increasing its aerial application program. 

Coquillettidea perturbans remains a problem for larval control. Slow-release Altosid formulations looked 

promising for the control of cattail mosquitoes (Walker 1987) but this technique is not being used today, most likely

because of high cost. Altosid pellets have been used with some effect (Ranta et al. 1994) and this approach may 

make expanding Cq. perturbans larval control possible. Fortunately, this mosquito has not been a significant pest

over the last several years in most projects (see Table 9 for low % of effort directed towards Cq. perturbans). In 

East Middlesex MCP, however, Cq. perturbans has continued to greatly exceed nuisance threshold levels, being the 

main nuisance species between mid-June and mid-July. In nine cities and towns of the East Middlesex MCP, there 

is at least one light trap site which annually records greater than 500 Cq. perturbans per night during the peak 

period for that species. Dry the dry summers of 1993, 1995, and 1997, Cq. perturbans has been the only significant

mid-summer mosquito problem. 

No source reduction programs are in place for the maple/cedar swamps in which Cs. melanura breeds. 

Larviciding these areas has had some success (Henley 1992, Woodrow et al. 1995). 

No control programs target permanent-water breeding Culex or Anopheles except in cases where Aedes are 

breeding as well and in urban habitats (see below). With the exception of minor work with dumped tires, Ae. 

triseriatus is not targeted for control. 

Freshwater wetlands have been the sites most likely to have control restrictions due to endangered species. 

 Salamanders, turtles and dragonflies have all been cited as reasons to either forego work or to restrict larvicide 

choice. In at least one case, the existence of vernal pools alone, regardless of endangered species presence, was 

sufficient for the local conservation commission to halt drainage maintenance in the area. 

 88
 c. Irrigated and Other Man-Made Reflood Habitats

 Very little agricultural land in Massachusetts is irrigated. Those lands which are irrigated tend to have

sandy soils with good percolating characteristics. Golf courses, athletic fields, etc., which temporarily flood and 

produce reflood Aedes are generally very accessible and larvicidlng is the common practice for dealing with the 

habitats. Source reduction is occasionally used to eliminate or limit breeding in these poorly graded and drained 

grassy habitats. 

d. Urban Habitats

 Most projects do both source reduction (cleaning and repairing) and larviciding work on storm drain catch 

basins to control Culex breeding. Slow release larvicide formulations are popular in these small enclosed habitats. 

This urban mosquito control activity is non-controversial. It is effective, but the real impact of these mosquitoes on 

biting annoyance is not clear (see Part IV). 

Wet basins have emerged as a primary problem in areas of new development. Shallow-water basins often 

hold water long enough in the spring to breed Ae. canadensis. Basins that have deep water in the spring (one-plus 

feet) may not breed mosquitoes then but may dry down in July and be perfect Ae. vexans breeding sites after a 

heavy August rain. Basins that are deep all year round may have invasive cattail on which Cq. perturbans can 

develop. Only basins that hold water for a week or less, even during the wet spring months, will probably not

produce mosquitoes and even these require maintenance to avoid wetlands type vegetative growth that eventually 

causes longer pooling. Two other problems with basins is that many are fenced off, so that they are difficult to

monitor, and ownership is often hazy so that maintenance lapses. Prevention of mosquito breeding in basins must

become a design consideration. 

 3. Current Policies 

 a. Requests for Control

Requests for control are almost invariably for adult mosquito control, though individuals may request that

wetlands on or adjacent to their property be checked and larvicided. Requests for adulticiding are handled in 

varying ways by the projects (Table 10). In most projects, complaint calls are considered a valid form of 

determining spray schedules, if not on an immediate basis, certainly over the long term. Responding rapidly to

complaint calls is considered a primary objective of many projects, as they are service organizations. Of course, 

their service is to the common public good, and individual requests should be judged on that basis. Whether all

 89
programs do so is not known. 

Table 10. Adult Mosquitoes: Monitoring and Adulticiding Policies 

Techniques used to trigger adulticiding

Project Light Traps Landing Count Complaint Calls Post-treatment Monitor 

Berkshire No No Yes (for local treata

) Reduction in calls 

Berkshire also stated that adulticiding is done on a pre-scheduled basis 

Bristol County Not for Spray No Yes Reduction in calls

Reduction in light traps 

Cape Cod Yes, but no Adulticiding is done by Cape Cod 

Central Mass Yes 3/min Do landing count Random re-checks 

East Middlesex 100 human-biting 4/min (for local treat) Supplement LT data Not done 

Essex No 10+/min 5/square mile Landing counts 

Norfolk Yes 2/min (for local treat) Yes (for local treat) Limited landing counts 

 Reduction in calls 

Plymouth No Informal Yes Staff observations 

 Reports from residents 

Suffolk Yes Yes Do landing count Informal checks a

Local treatment by hand-held or backpack sprayer only

Larviciding requests do not make up the majority of calls to MCPs. But, for example, East Middlesex 

MCP does receive calls for both larval control and information on how residents can control mosquitoes. In general 

these come as a result of their newspaper releases concerning larviciding or from residents who observe control

crews in wetlands in the past (Henley, personal communication). Other programs most likely receive similar calls. 

In general, though, monitoring is based on historical knowledge and survey work by the MCP itself. When larvae 

are found, larviciding typically occurs. 

Pre-hatch work, is an exception to the rule that larvae must be present and is conducted when the project

superintendent feels there is sufficient historical data to justify applications prior to larval hatch. 

b. Documentation for Control Implementation 

 90
All Projects keep records of complaint calls, most conduct light trapping and most conduct some landing 

counts (Table 10). Of the three, landing counts are the most casual, often being little more than a report that there 

are a lot of mosquitoes biting the field staff in a certain area. However, Berkshire County, Central Mass and Suffolk

investigate each complaint call and take landing-count data. 

Field workers record larval counts at the sites they visit. In some cases, they bring larvae back either for 

larval identification or for rearing to adults for ID. In many cases, the larvae are sight-IDed to genus and more 

specific identification is not done. Counts for aerial application and/or OMWM are much more detailed and 

generally involve taking a specific number of dips at a permanently situated sampling station. 

An area that needs improvement is record keeping regarding aerial applications of larvicide. The general

plans filed by projects with the state are not specific enough, as they tend to describe the maximum possible 

application acreage, rather than acreage actually treated. Projects do keep records of actual treatments and these 

should be filed with the state as a post-treatment report,

Record keeping for freshwater drainage maintenance is spotty and needs improvement. Without baseline 

data on channel cross-sections, it is impossible to monitor maintenance work to ensure that channels are not

becoming larger. 

c. Selection of Control Strategies 

Control strategies may be selected at the project level for both short- and long-term work, and at the field 

worker level for short-term work. Examples of project-level long-term selections are the absence of adulticiding by 

the Cape Cod project and the strong push into wetlands restoration by the Essex County MCP. Short-term, project

level decisions revolve around the choice of larvicides made available to field workers, aerial work, and the 

distribution of personnel among, surveillance, source reduction and pesticide application work. Project 

Superintendents use their experience, the input of their staff, professional journals, and any other resource that can 

guide them in creating a quality program. 

 An under-emphasized aspect of the selection process is the cost of each strategy. Strategies that cost 

more than is available will not be implemented. Ground application of larvicide is possible in larger areas than it is 

currently being done, however the manpower requirements are high. Altosid applications for Cq. perturbans 

populations control seem to be limited primarily due to cost. 

Field staff are responsible for determining the need to treat a given site, the type of material to use (for 

 91
example, briquets versus a liquid treatment in a series of vernal pools), and whether or not physical control

(removing debris clogging a culvert) should be done immediately or can wait for non-breeding periods. The 

effectiveness of any program is directly linked to the skill of the field staff in determining the most appropriate 

response to current local conditions and their motivation to carry out the appropriate response effectively. 

One of the goals of the GEIR is to help establish procedures for determining which control technique to

use. However, a large amount of basic research into mosquito and wetlands ecology needs to be done to improve 

our basic understanding of the cause and effect relationships among the environment and the control procedures 

available. 

d. Evaluation of Efficacy 

 No project has developed a comprehensive and comparable data base on mosquito densities to document 

the long term impact of control efforts on annoyance levels in their communities. While they might be faulted for 

this failure, such an effort requires resources that many projects do not have. Nearly all projects routinely operate

light traps or make landing rate counts in order to monitor adult population levels. Just how these data are analyzed 

and used is not clear. No publicity or publications utilizing quantitative data on mosquito populations have been 

produced by any project. All projects seem to keep good records of how many complaints they receive annually 

from each section of their jurisdiction. Statistical treatment of these data would be difficult and appears to have not 

been attempted.

 Larval sampling is routinely carried out by all projects before pesticide applications. Post-treatment checks 

are less common. However, one of the reasons the projects did not accept Altosid very quickly was that it was hard 

to tell if the treatment had worked (the larvae can take up to a week to die). From this it can be inferred that posttreatment monitoring was occurring. This is an area where a state-level entomologist would be of considerable help

as she could carefully monitor larvicide applications with an eye towards developing more accurate delivery 

techniques and application rates for varying situations. 

Post-treatment monitoring of adulticide applications is done on an ad hoc basis (Table 10). A drop off in

complaint calls is the primary criteria by which adulticiding efficacy is judged. While aerial ULV applications are 

effective (Mount et al. 1996), truck-mounted ULV treatments depend heavily on proper weather conditions and on 

there being an adequate road network. The general attitude, with the notable exception of Cape Cod, is that the 

residents pay for mosquito control and adutlciding kills mosquitoes. Developing better evaluation techniques for 

 92
efficacy of truck-mounted adulticiding would be a major step in improving mosquito control in Massachusetts. 

 e. Public Participation

All projects notify residents by press release or public notice of their intended control operations for the 

coming season. Most towns also notify the Departments of Health and the chief executive’s office of the 

municipalities for which they do work of their plans for the season. In Norfolk, each health board receives a notice 

of which days of the week the project may be treating in their town. Maps are included. Suffolk takes the process 

one step further and notifies the mayor’s office before each adulticide. With minor variations all projects do the 

same type of notification. 

Requests for exclusion are handled virtually identically by all projects, with a list of exclusion sites given 

to drivers so that they know where to not treat. Maps of excluded properties are made available to the spray crews. 

Multiple Chemical Sensitivity (MCS) is becoming an increasingly important concern to health officials as 

the number of individuals reporting disabilities linked to chemical exposure has increased dramatically over the past 

decade. Regardless, MCS has yet to become a major issue for mosquito control. In most cases, an individual with 

MCS can be accommodated by the standard exclusion request since most mosquito control programs do not, as a 

general rule, ask why an exclusion is requested. This lack of conflict, however, should not be taken to mean that

MCS is a non-issue. Mosquito control programs are designed to protect people, not harm them, and individuals

suffering from MCS deserve to have their needs addressed. At the same time, control programs must take into

account the needs of those who do not suffer from MCS, yet do suffer from mosquito problems. So long as 

programs continue to work honestly and above-board with MCS suffers (and any other group which requests 

exclusion), and receives the same level of cooperation from those requesting exclusion, mutually acceptable 

solutions should continue to be the norm.

 93
One source for additional information on MCS is:

MCS Referral & Resources, Inc. 

 508 Westgate Road 

Baltimore MD 21229-2343 

 Telephone 410-362-6400 

 fax 410-362-6401 

Public education is a vital component of a complete program but current education efforts represent only a 

tiny part of most projects (Table 5). Programs vary from distribution of handouts upon request to full-scale 

educational presentations, including videos and other visual aids (Table 11). In general, but not absolutely, the 

extent of the education program is a function of program size. It is not clear that all projects use the Fact Sheets 

currently available from DPH. These include “Eastern Equine Encephalitis”, “Insect bites and Insect repellents”, 

and “Mosquito Repellents” as well as a pamphlet “Bugged by Mosquitoes?”

E. Eastern Equine Encephalitis 

1. Responsibility for Surveillance and Control. 

Eastern Equine Encephalitis (EEE) is an alphavirus endemic to many passerine bird species found in 

freshwater swamp habitats. The virus is transmitted among wild bird populations in these areas by Cs. melanura, a 

mosquito species that feeds almost exclusively on birds. The freshwater swamp is the enzootic focus of EEE and 

under normal conditions the virus is restricted to this habitat, Occasionally, however, due to factors which include 

seasonal and yearly rainfall levels and temperatures, mosquito virus may “spill over” into mammalian populations. 

This phenomenon is due to the transmission of the virus from infected birds to mammals by one of more mosquito

species which feed on both humans and birds. Species that transmit disease from normal reservoirs to accidental 

hosts are known as “bridge vectors”. The Massachusetts mosquito species traditionally thought to be likely bridge 

vector species are Cq. perturbans, Ae. vexans, Ae. sollicitans, and Ae. canadensis. Recently published studies also 

suggest that Anopheles species and Cx. salinarius may be possible epidemic vectors (Edman et al. 1993;

Vaidyananthan et al. 1997). EEE virus has been isolated from all of these species. The bridge vector(s) 

responsible for EEE transmission to humans has not, however, been unequivocally identified. 

EEE is a rare form of encephalitis with a high rate of mortality. The overall case fatality rate is now about 

30% and survivors often suffer lifetime disabilities. The severity of illness tends to be most grave at the extremes of

age. Fatality rates are highest among the elderly and intermediate in children. Infants and children who survive the 

 94
Table 11. Public Education Programs. 

Project Visit Complaint Give Talks Notes on Programs/Pamphlets Available 

 Callers

Berkshire Yes Yes UMss Coop Extension Leaflet “Mosquitoes” 

the “Ten Commandments of Mosquito Control” 

 Bookmark for schools 

Bristol County Yes No Supply information upon request

Cape Cod Yes Yes Conducts school programs for all age groups, 

have developed and distribute an informational 

pamphlet, and routinely appear in local press. 

Central Mass Yes Yes News releases to member municipalities’ press 

Project staff attend various meetings 

A video “Working for You”, a display and a 

slide show are all available 

Pamphlets are distributed to Boards of Health

and other offices and anyone else who 

 requests them. 

School program for elementary schools. 

East Middlesex Yes Yes School eduation program (three grade groups:

1-3, 4-6, and 7+) 

Give talks upon request. 

 20-minute video 

 DPH fact sheets 

Pamphlet on Mosquito IPM

Essex Not mentioned Not mentioned Fact sheets available on request

3-panel display available to environmental groups 

Outreach through environemental groups 

Norfolk Sometimes Yes Fact sheets: IPM, Bti, Methoprene, The Facts 

 about Mosquito Spraying 

Materials supplied to local Boards of health

Provides interviews on Local Cable TV 

Personnel always available for town-sponsored 

 meetings 

Has extensive school program

Attend local health fairs 

Plymouth Sometimes Yes Speaker program: spokesperson available 

year-round for any community group 

Utilizes community channel on cable TV 

Pesticide information distributed to towns and

available to residents upon request

DPH fact sheets and pamphlet 

“Homeowner Mosquito Control” pamphlet

Suffolk Yes Yes (Schools) Press releases in the spring 

Faxes to mayor prior to treatment

infection are most likely to be permanently neurologically impaired and often require lifelong supportive care. 

 95
Horse cases of EEE have been described as early as the nineteenth century in Massachusetts and human 

cases were likely to have occurred, although they were not recognized as EEE prior to 1938. Since the first 

recognized outbreak of human EEE in 1938, 74 cases have occurred in Massachusetts with cases disproportionately 

concentrated in the south-central and southeastern parts of the state. 

Four multi-year outbreaks of human EEE have been recorded in the central-eastern and southeastern areas 

of Massachusetts,. Thirty-four (46%) cases were identified in 1938. Subsequent years of human EEE cases have 

been 1939 (1 case), 1955 (4 cases), 1956 (12 cases), 1970 (1 case), 1973 (2 cases), 1974 (3 cases), 1975 (1 case), 

1982 (2 cases), 1983 (6 cases), 1984 (2 cases), 1990 (3 cases), 1992 (1 case), 1995 (1 case) and 1997 (1 case). 

The two worst years for human cases of EEE (1938 and 1956) occurred before there was an EEE 

Surveillance Program. However, it is assumed that the virus carriage of mosquitoes, and mosquito populations, 

would have been unusually high compared to average levels of these indicators. Since the beginning of a 

prospective EEE Surveillance Program, there have been two years of extraordinarily high levels of virus carriage in 

mosquitoes, in 1973 and 1990. Although only a small number of human EEE cases were identified in 1973 (2 cases) 

and 1990 (3 cases), there were significant control interventions in each of the two outbreak years. Wide-area 

spraying with ULV malathion was done to reduce populations of the vector species. 

In 1990, in response to surveillance data showing alarmingly high and increasing EEE virus levels in 

mosquitoes, multiple horse cases, and the risk of multiple human cases, the largest aerial application (ULV) of

malathion in years was made over much of southeastern Massachusetts. Three people contracted the illness prior to

the treatment and one died. 

As a result of this outbreak, the Department of Public Health and the State Reclamation Board sought to

strengthen ties between state and project officials and to better define their response to future outbreaks. While

there was considerable controversy over what some felt to be an extreme response by the state, there can be no 

question that mosquito populations were effectively reduced by the application and that no new human cases of 

EEE occurred after the treatment. Mount et al. (1996) provide an excellent review of aerial applications of 

insecticide for mosquito control and conclude that ULV applications are efficacious, cost effective and can work 

over dense foliage or open housing. The results in 1990 in Massachusetts support these conclusions. 

2. Effect of EEE on Projects 

Of the nine Projects, Berkshire is outside the EEE risk area and Cape Cod and Essex County are defined as 

 96
low-risk areas. The other Projects provide significant support for EEE monitoring and mosquito control. When 

requested larval and adult monitoring data are also supplied by the Projects to DPH. Bristol, Norfolk, Plymouth and 

East Middlesex MCPs traditionally increase truck-mounted aerosol applications in areas of high public use when 

DPH indicates elevated risk of EEE. These Projects also supply support for, or actually conduct, aerial applications 

for larval (Bti) or adult (malathion) mosquito control at the request of DPH. 

Though the Projects do not target EEE vectors specifically, unless so directed by DPH, their general 

operations permit surveillance and control work to be carried out against vector species as necessary. As an 

example, East Middlesex has 50 CDC light traps set up through out its district, a portion of which monitor Cs. 

melanura populations. East Middlesex has also conducted aerial applications of Altosid pellets to control Cs. 

melanura. Emphasizing the problem of Cq. perturbans, however, East Middlesex has been unable to develop a 

larva control program to adequately deal with this potential vector. 

A continuing source of friction is the definition of a nuisance versus a health threat. While several projects 

were formed as much because of the possibility of EEE as the nuisance factor, no project today considers preventing 

EEE to be their primary goal. Fortunately, DPH and the Projects in EEE areas work well together and a system of 

graduated responses (from regional ground control up to state-mandated aerial adulticiding) has been put in place. 

 97
IV. DESCRIPTION OF MOSQUITO SPECIES AND ABATEMENT HABITATS 

A. Mosquito Species 

1. General Biology

Mosquitoes belong to the family Culicidae of the Order Diptera (true flies), insects with one pair of clear 

wings. There are 167 North American species in 13 different genera (Darsie and Ward 1981). Of these, 46 in 9 

different genera have been found in Massachusetts (Table 12). About one-half of these (from 5 different genera) 

may at times cause significant human annoyance in certain localities; the majority belong to the genus Aedes. No 

mosquito species feeds exclusively on humans. Those species that annoy humans feed on a wide variety of other 

mammals and occasionally on birds as well. Some non-human-biting species such as Cs. melanura, Cs. morsitans

and Cx. restuans can be important in the maintenance of enzootic disease cycles in wildlife. Some of these diseases, 

e.g., Eastern equine encephalomyelitis (EEE), occasionally spill over into human populations via transient epidemic 

vectors. 

Mosquito life cycles can be grouped into two basic types: permanent-water and temporary-water (or flood-water). 

Temporary-water species generally belong to the genus Aedes or Psorophora and present the major pest problem in

Massachusetts. Adult females can readily be distinguished from permanent water forms because their abdomen 

terminates in a sharp point formed by the extended cerci. This group overwinters as dormant eggs laid singly by

females (usually ca. 75-150/female) in the band of moist soil surrounding the evaporating temporary pools in which 

the larval stages developed. Hatch (stimulated by increased temperature or reduced O2) occurs when these 

depressions are flooded by tides, rains, irrigation or flooding rivers. The eggs of most temperate flood-water 

species must undergo a prolonged cold-conditioning period prior to hatch so there is normally only a single 

generation early each season (univoltine species). In a few species such as the eastern saltmarsh mosquito, Ae. 

sollicitans, eggs laid in the earlier part of the season will hatch after only 2-4 weeks of conditioning so multiple 

generations (multivoltine) are commonplace. The terms generation and brood are not always synonymous because 

not all eggs hatch when flooding occurs, so that multiple broods may sometimes occur from a single generation of 

overwintering eggs. In Massachusetts, reflood species like Ae. vexans, Ae. sticticus, and Ae. trivittatus (and perhaps 

late spring-hatch species like Ae. canadensis and Ae. cinereus) may have multiple generations or just multiple 

broods caused by delayed egg hatch. In spring, larval development of temporary-water mosquitoes may require two 

98
months or more 

Table 12. Systematic Index of the Culicidae of Massachusetts

Taxon Taxon 

Genus AEDES Genus CULEX 

 Subgenus Aedes Subgenus Culex 

 cinereus (Meigen) pipiens Linnaeus 

 restuans Theobald

 Subgenus Aedemorphus salinarius Coquillett 

 vexans (Meigen) 

 Subgenus Neoculex 

 Subgenus Ochlerotatus territans Walker

 abserratus (Felt & Young) 

 atropalpus (Coquillett) Genus CULISETA 

 aurifer (Coquillett) 

 canadensis (Theobald) Subgenus Climacura

 cantator (Coquillett) melanura (Coquillett) 

 communis (De Gerr) 

 decticus Howard, Dyar & Knab Subgenus Culicella

 diantaeus Howard, Dyar & Knab morsitans (Theobald) 

 dorsalis (Meigen) minnesotae Barr 

 ercrucians (Walker) 

 fitchii (felt & Young) Subgenus Culiseta

 implicatus Vockeroth impatiens (Walker) 

 intrudens (Dyar) inornata (Williston)

 provocans (Walker) 

 punctor (Kirby) Genus ORTHOPODOMYIA 

 sollicitans (Walker) signifera 

 sticticus (Meigen) 

 stimulans (Walker) Genus PSOROPHORA 

 taeniorhynchus (Wiedemann) 

 trivittatus (Coquillett) Subgenus Grabhamia

 columbiae (Dyar & Knab) 

 Subgenus Protomacleaya 

 hendersoni Cockerall Subgenus Janthinosoma

 triserlatus (Say) ferox (von Humboldt) 

Genus ANOPHELES Subgenus Psorophora 

 ciliata (Fabricius)

Subgenus Anopheles 

 barberi Coquillett Genus URANOTAENIA 

 crucians Weidemann Subgenus Uranotaenia

 earlei Vargas sapphirina (Osten Sacken) 

 punctipennis (Say) 

 quadrimaculatus (Say) Genus WYEOMYIA 

 walkeri Theobald

 Subgenus Wyeomyia

Genus COQUILLETTIDIA smithii (Coquillett) 

 Subgenus Coquillettidea

 perturbans

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while in summer it may be as brief as 4-6 days. Permanent-water mosquitoes deposit their eggs (generally a 

multi-egg raft of ca. 100-250 eggs except in the Anopheles) on the surface of permanent or semi-permanent (i.e. 

persists for several weeks) water and hatch occurs within 1-3 days. Populations are asynchronous compared to

flood-water species (with several overlapping generations), and larval development tends to be longer. Some

permanent water species (e.g., Cq. perturbans, Cs. melanura and Cs. morsitans) overwinter in a diapausing larval

stage, but most overwinter as hibernating adult females that are fertilized, nulliparous (never having produced eggs), 

and non-blood-fed. 

Mosquitoes metamorphose into the winged adult stage within the nonfeeding pupal stage. The pupa is

active and aquatic (called tumblers) and is resistant to most chemical control measures (suffocating surface films are 

an exception). It normally lasts only 2-4 days. Males generally pupate and emerge about 1 day ahead of females of 

the same cohort.

Mating most commonly occurs in twilight swarms within 2-3 days after females emerge. Most, but not all,

females mate before they take blood. Both sexes feed frequently on plant nectar; females take blood in order to

obtain protein for egg development. A few species are autogenous, meaning they do not need a blood meal to

produce eggs. One Massachusetts species, the pitcher plant mosquito (Wy. smithii), never takes blood. Most

females begin seeking hosts 2-4 days after emergence but some species (e.g., Cs. morsitans) may delay feeding for 

2 weeks or more. Thus, the time period between adult emergence and the first egg laying (first gonotrophic cycle) 

is usually 7-10 days. Subsequent host-feeding to egg-laying cycles in most temperate species require 4-6 days. 

Species that transmit disease (vectors) must feed at least twice, once to acquire the infection, and once to

transmit it, unless the infection is acquired transovarially (into the egg while in the ovary) from their mother. This 

means that females must normally survive for 12-14 days in order to be a vector. If the extrinsic incubation period 

of the pathogen/parasite in the mosquito is longer than the gonotrophic cycle, as is often the case, the survival time 

required for transmission is even longer. 

Most females do not survive beyond the first oviposition but a few individuals in all mosquito populations 

live a long time (i.e., several weeks). Exceptionally, overwintering adults live 5-7 months. Males generally survive 

for shorter periods than females and never overwinter. 

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 2. Saltmarsh mosquitoes 

The leading pest mosquito problem in coastal communities in Massachusetts is caused by two brackish

water species, Ae. sollicitans and Ae. cantator. The latter species is abundant only in the early part of the season 

(mid-May to mid-June); Ae. sollicitans is the major target of most saltmarsh mosquito control efforts. Both species 

develop in pans in the high salt marsh (dominated by Spartina grasses) which are normally only flooded by moon 

tides. Heavy rains or high tides caused by unusual winds can also cause intermittent flooding in the high marsh. 

Ae. cantator tends to occur more in the extreme upland edge of the high marsh. This area is often quite fresh and 

may include plants such as cattails. Unmaintained mosquito ditching can become an important breeding area, as 

Spartina alterniflora prevents the ditches from draining and shallow water is held between moon tides. 

 Aedes taeniorhynchus is a third species that occurs in salt marshes, often in conjunction with Ae. 

sollicitans. Complicating the control picture further is Cx. salinarius which sometimes breeds in after heavy, latesummer rains. As a result, salt marshes generally require monitoring at least twice a month (once after the fullmoon high tide and once after the new-moon high tide) as well as after any major rain event. With regard to

saltmarsh mosquito control, one should always assume that there are huge numbers of eggs available to hatch after 

any flooding; any other assumption will result in broods being missed and adult mosquitoes swarming in numbers 

not easily understood by one who has not experienced them. 

Uncontrolled populations of salt marsh Aedes often reach extremely high biting densities (i.e., 100+ 

females landing/minute). Adults may not be particularly long lived, but because moon tides occur so regularly and 

often, multivoltine Ae. sollicitans can be a problem throughout the summer season. Because the economies of 

coastal areas affected by this mosquito often depend heavily on summer tourism, the impact of saltmarsh

mosquitoes is greatly magnified. This is reflected in the percent effort coastal projects spend on saltmarsh Aedes

control (Table 9). 

Salt marshes and the estuaries they feed are the principal nursery grounds for a variety of marine and 

brackish water organisms, including several commercial forms. Disrupting these vital wetlands to control saltmarsh

mosquitoes can cause unintended, long-term problems. 

3. Freshwater mosquitoes. The most severe and predictable late-spring to early-summer mosquito

annoyance in all inland (and many coastal) areas is caused by several species of Aedes collectively referred to as 

spring-hatch or snow-pool mosquitoes, the most common of which is Ae. canadensis. These mosquitoes tend to

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develop in similar aquatic situations (i.e., temporarily flooded woodland depressions including the flooded borders 

of permanent swamps and bogs) and have similar life cycles. They overwinter as dormant eggs and have a single, 

spring generation each year (univoltine). Adult mosquitoes are most active from late spring to mid summer; the 

females taking blood meals and depositing their eggs in the moist soil and leaf litter around the edges of the 

evaporating woodland pools in which they developed as larvae. They are part of a larger grouping of mosquitoes 

called temporary-water or flood-water species which all have eggs that hatch synchronously when flooded by rain, 

tide, snow melt or rising rivers. In this case, snow melt and spring rain fill the woodland depressions that are 

stocked with eggs, usually causing hatch sometime in early March. Mild conditions in late February and early

March followed by severe cold, or spring precipitation, can reduce larval populations by freezing or flooding. As a 

result, considerable year-to-year population variation occurs. 

 Spring-hatch Aedes can be subdivided into two major groups, dark-legged and banded-legged, based partly

on the physical appearance of biting females and partly on some minor differences in their life cycles. The 

dark-legged group hatch and emerge about 1-3 weeks ahead of the banded-legged group and seem to survive as 

adults for a shorter period of time. Some members of this group (e.g., Ae. punctor) become more abundant at more 

northern latitudes (coniferous forest zone) and at higher elevations (e.g., near the top of the Holyoke Range). 

When people enter the densely shaded daytime resting places of these mosquitoes, females attack more aggressively 

than do members of the banded-legged group such as Ae. stimulans and Ae. canadensis. Dark-legged Aedes appear 

to be the principal vectors of California group encephalitis viruses. These viruses overwinter inside the eggs of 

their mosquito vector (Calisher & Thompson 1983). 

The banded-legged group often develop in the same pools and rest in the same wooded, daytime resting 

habitats as some species in the dark-legged group. However, they tend to disperse further from the larval habitat

and, during the early evening biting peak of both groups, banded-legged females feed more readily in open and 

semi-wooded habitats than to dark-legged females. Some banded-legged females survive into August, and this

group seems to be the principal vector of dog heartworm in Western Massachusetts. 

Although the general larval habitat of both groups is similar, considerable variation in habitat occurs and 

some species are more restricted than others. For example, certain dark-legged Aedes are mainly found in

association with cranberry (Ae. aurifer) or sphagnum (Ae. decticus) bogs. Spring woodland pools vary from small,

shallow depressions formed by fallen trees to large, deep ravines in mountain bedrock and natural swales in forested 

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flood plains. Permanent woodland or grassy swamps and bogs are also a common source of some members of the 

spring Aedes group. 

 a. Aedes canadensis. Aedes canadensis is perhaps the dominant spring-breeding mosquito

in the Northeast. It’s primary habitat is woodland vernal pools; pools that having standing water from snow-melt

until early summer. Larvae can be collected even before the last frosts but development is slow during the cool

spring months and adults usually do not emerge until near the end of May or in early June. Although Ae. 

canadensis is an active biter, it does not generally fly far from the woods in which it breeds. As residential areas 

have cut their way into the woods of Massachusetts, however, Ae. canadensis has become an increasing problem. 

 Aedes canadensis control is difficult because the pools in which it breeds are isolated from each other. A 

small woodlot can contain many pools, some of which may require field workers to cut through poison ivy,

multiflora rose, and bull brier just to reach. Ground application of larvicide under such circumstances is tedious 

and, regardless of intent, often less than complete. 

 Aedes canadensis is predominantly univoltine, but a second brood (either delayed hatch of over-wintering 

eggs or early hatch of spring-laid eggs) can develop in early fall if rainfall is sufficient to partially fill the woodland 

pools. In such cases, treatment is nearly impossible, as a summer’s growth of the above-mentioned plants, coupled 

with a dense canopy of leaves from the many shrubs that line the pools make getting to the pool, and placing the 

correct amount of pesticide in the pool, extremely difficult.

 b. Aedes vexans. Aedes vexans is the most ubiquitous floodwater mosquito in North 

America and is the predominant summer reflood mosquito in Massachusetts. Aedes vexans is found in lake and 

river flood plains, shrub swamps, flooded meadows, and shallow grassy depressions associated with open habitats

such as roadside ditches, pastures, golf courses and athletic fields. It will also breed in woodland pools and shallow 

cattail marshes, such as those that develop in some retention ponds. The first Ae. vexans are normally not on the 

wing before mid-June. Populations of Ae. vexans are unpredictable because they depend entirely on the frequency 

and spacing of major rains. Rainfall of 1 inch many produce some Ae. vexans but it usually requires 3” of rain

within a short period of time (several days) to produce a large brood. 

Larval broods of Ae. vexans have been observed as late as mid-September in Amherst. It is not always

clear whether such late season broods result from the delayed and staggered hatching of eggs that are a year or more 

old or from the hatching of non-diapausing eggs laid earlier the same season. Brust and Costello (1967) and 

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Horsfall et al (1973) have shown that many species such as Ae. vexans lay some eggs that will hatch without cold 

conditioning. Sequential hatching of eggs is also well documented in five reflood Aedes species (i.e., canadensis, 

cinereus, sticticus, trivittatus, and vexans). Larval development is rapid, 4-6 days, and the pupal stage lasts for 

about 2 days. Hence, the window for effective larval/pupal control is narrow. Moreover, a large number of 

scattered pools all need to be treated within the same brief time span following major rains. Control efforts suffer 

from the same difficulties as described for Ae. canadensis, as Ae. vexans will often breed in mid-summer in the 

same pools used by Ae. canadensis in the spring.

 c. Additional Aedes species 

Lesser, but at times significant, populations of Ae. triseriatus, Ae. trivittatus and Ae. sticticus do occur in

Massachusetts. Larvae of the latter two species are associated with ground pools in wooded or semi-wooded flood 

plains. Extremely heavy general rains sufficient to cause river flooding commonly proceed large populations of Ae. 

trivittatus and Ae. sticticus. 

 Aedes triseriatus is a treehole mosquito, breeding in the wild in holes left in trees when a branch breaks off 

 and/or insect damage causes a part of the tree to rot out. Within the shaded forest it is a ready biter but it does not

venture far from it’s breeding areas. Because it’s larval habitat is widely dispersed (and often well above the height 

that a person could reasonably be expected to reach), larval control is not possible. Fortunately, because it stays 

within the woods, control targeting Ae. triseriatus is rarely necessary. 

Aedes triseriatus overwinter as eggs in the larval habitat; hatching occurs in early spring and development

to the adult stage takes about 3 months. The first biting adults appear in late June in Massachusetts. Larval 

populations are often crowded and asynchronous so some emergence continues until early August. A second 

generation of larvae has been observed, especially in tires, where water is usually warmer and development is faster. 

 However, it is doubtful that many adults from this generation are successful at this latitude. This mammal-feeding, 

diurnal species does not normally disperse far from its sylvan larval habitats. Biting adults are particularly active in

the late afternoon, pre-twilight period (i.e., 4-7 PM). 

 If Ae. triseriatus stayed in the trees, it would be a minor pest, but it has become well adapted to breeding in

tires, particularly where they are shaded. As a result, Ae. triseriatus can be a locally important pest wherever 

rimless tires are stored. Tire removal, and the prevention of illegal tire dumping along wooded roads, is an 

important part of mosquito control.

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 Aedes atropalpus is another natural container breeder, but it is associated with rock pools, especially those 

in exposed riverbeds. The northern form is autogenous for the first egg batch so it is a less bothersome daytime pest

species than its southern sibling, Ae. epactius. This species has also become adapted to tires in the Midwest. 

A new Asian container breeder, Ae. albopictus, has recently been introduced into the Southern United 

States (Texas), apparently via imported used truck tires (Moore 1986). This diurnal urban pest throughout Asia has 

already spread as far north as Indiana and is likely to appear in Massachusetts at some point (Nawrocki & Hawley 

1987) Locations where used truck tires are brought in and stored for recapping are the most likely points of 

introduction. This species has mainly been found in tares in the United States to date. It is an efficient laboratory

vector of many Western Hemisphere arboviruses (Shorter 1986). 

 d. Culex species. Culex mosquitoes have an ambiguous place in mosquito control in 

Massachusetts. On the one hand, they are commonly encountered as larvae in storm drains, cisterns, drainage 

basins and other contain-type situations but, on the other hand, the extent to which they cause biting problems for 

people and are involved in the transmission of disease, for example encephalitis between birds, is unknown. 

Species such as Cx. territans and Cx. restuans are certainly not pests of humans, but Cx. restuans may be involved 

in transmission of EEE between birds (it is common to pick up EEE in Culex pools in areas where it is present in

Cs. melanura pools–the problem being that Culex pools are rarely sorted to species before testing). 

 Culex mosquitoes are multivoltine, having several generations per year. There can be considerable overlap

among the generations. Adult females overwinter and are among some of the first mosquitoes to be seen in the 

spring. Culex mosquitoes do not bite during the day and are more active later at night than are most Aedes species. 

The house mosquito, Cx. pipiens, breeds prolifically from mid to late summer in urban storm sewers, 

ornamental/wading/swimming pools, bird baths, plugged rain gutters, tires, car bodies, empty barrels, and other 

similar manmade containers. This species tolerates pollution, so the highest densities often occur in eutrophic water 

enriched by animal waste (e.g., sewage oxidation ponds). Multiple, overlapping generations (each requiring 8-10 

days) occur in the same habitat. Mated but non-blood-fed females produced late in the season overwinter in

underground sewers, basements, and other protected places. 

The southern form, Cx. pipiens quinquefasciatus, feeds readily on both mammals and birds (Edman 1974), 

but the northern form, Cx. pipiens pipiens, which occurs in Massachusetts, is mainly associated with avian hosts. In

large urban centers in the North, a less common autogenous form (Cx. pipiens molestus) exists. It readily attacks 

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humans after the initial blood-free gonotrophic cycle is completed. This form has been documented in Boston, 

where it is associated with underground sewers and subway tunnels (Spielman 1973). Cx. restuans is often found in

some of the same container habitats as Cx. pipiens. 

 Culex salinarius differs from the above-mentioned Culex species in that it is an active human biter and can 

occur in significant numbers. It’s breeding habits are poorly understood as it is generally classed as a permanentpool breeder but dense larval populations have been found in rain-fed pools in salt marshes in Rhode Island 

(salinities close to 0 ppm) and large adult populations existed in the coastal residential area of Bonnet Shores, RI in 

1986 (Christie, personal communication). 

The extent to which Culex species require control can be debated. Species such as Cx. territans almost 

certainly play no role whatsoever in either pest or disease problems. However, the ability to identify mosquito

larvae to species is often not well developed and field identification can be difficult (though separating Aedes from

Culex requires little more than direct observation). Under such circumstances, treatment of any larval population is 

the general rule. Defining the role of Culex species in the magnification of EEE within the bird population would 

aid in determining the extent to which larval control of Culex should take place. 

 e. Culiseta species 

 Culiseta melanura occupies an interesting position in Massachusetts mosquito control in that it is the only 

known vector species in Massachusetts that is not also a significant pest. Therefore, controlling Cs. melanura in the 

larval stage, especially prior to documentation of EEE in adult Cs. melanura populations, is controversial in that the 

MCPs, as established, are not expected to target vector mosquitoes as a part of their routine work. The decision as 

to whether or not to attempt larval control would be made easier if Cs. melanura bred in habitats occupied by other 

pest species such as Ae. vexans or Ae. canadensis. Unfortunately, Cs. melanura breeds in a very specific habitat, 

the holes that develop around the roots of trees with cedar/maple swamps and is not routinely affected by treatment

work for other species. In fact, because the holes are not interconnected and are often have only small openings, 

they are extremely difficult to treat even when the decision has been made to attempt larval Cs. melanura control.

 Other Culiseta species exist in the state but have not been identified as vectors of disease or pests of 

humans. 

 f. Coquillettidea (formerly Mansonia) perturbans. Among a group of insects already

disliked by humans, Cq. perturbans stands out as being particularly disliked by mosquito-control personnel. First,

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it is a large, aggressive biter that sparks complaint calls like few other mosquitoes and, second, because the larva 

lives attached to the stems of cattail, it is exceedingly difficult to monitor and control 

 In Massachusetts, Cq. perturbans has one generation per year. It overwinters in the larval stage (3rd instar) 

and adults begin to emerge in mid to late June, peaking in mid-July. Breeding occurs principally in

cattail/water-willow ponds. These ponds are often caused by road, railroad, pipeline, power line, and parking lot 

construction next to natural wetland or seepage areas. Adults feed primarily during evening twilight periods on 

larger mammals situated in open pastures or in transitional habitats (Edman 1971). Birds are also attacked when 

they are available in the foraging habitat of this mosquito. 

 Coquillettidia perturbans presents unique control problems because larvae and pupae remain attached to 

the base of emergent plants at the bottom of deep ponds. Oxygen is obtained directly from the plant cells in which 

the modified air tube is imbedded. At this time there is no known effective larval control for Cq. perturbans, 

making adulticiding the only real choice for control in residential areas located near cattail marsh. For this reason,

the present pollution-control fade of cattail ponds must be carefully monitored by mosquito-control programs. 

Wherever possible, manmade cattail drainage basins should be avoided or should be so constructed that, for a 

period of several weeks in late summer, no standing water is present in the basin. This will break the aquatic part of

the life cycle. 

 Coquillettidea perturbans is a vector of EEE, compounding the problem of it’s control by increasing the 

stakes in any decision not to control it. 

g. Other freshwater species. Mosquitoes of the genera Anopheles and Psorophora can 

also be pests in Massachusetts. Anopheles mosquitoes differ from the other genera of mosquitoes in that, as larvae, 

they lie, upside down, on the under-surface of the water. They commonly inhabit more permanent waters and can 

sometimes be found along the edges of slow-moving streams. They are also fairly common later in the summer in

puddles in dirt roads and other pools, often being found together with Ae. vexans and/or Culex species. Anopheles 

mosquitoes do not occur in the kinds of swarming numbers that Aedes mosquitoes do, but they enter houses more 

readily. They overwinter as adults and are some of the first mosquitoes to bite in the spring. Individual females are 

not uncommon in-house biters on the occasional warm day in spring. 

 Psorophora ferox, is a large, aggressive mosquito that breeds in the flood plains of overflowing summer 

rivers and streams. It is not common in the northeast but, where it is present, it is an unforgettable insect, both 

107
because of it’s size and the painful bite. 

B. Habitats in which mosquito control takes place. 

An understanding of where mosquitoes breed and feed is essential to understanding mosquito control. 

Perhaps one of the most frustrating things to the mosquito-control professional is the misunderstanding within the 

general public as to where mosquito breeding occurs and where mosquito control should take place. To anyone 

who works in coastal mosquito control, the new homeowner, experiencing her first summer brood of saltmarsh 

mosquitoes, is a familiar, and somewhat sorry, sight. Calls concerning, “...that pond of my neighbor’s” are far more 

common than, “I have some vernal pools in the wood lot behind me.” 

The following discussion will start with breeding areas (coastal and inland wetlands and, to some degree, 

surface water bodies) and progress to adult habitats (surface water bodies, recharge areas, upland areas and 

agricultural areas). Finally, sensitive environments will be discussed from both a breeding perspective and with

regard to adult mosquito control. 

 1. Coastal Wetlands

a. Marine. The marine habitat for mosquito breeding is restricted to salt marshes, 

generally between the level of mean high water and high high tide. Below mean high water tidal flushing is too 

frequent and too strong for mosquitoes to successfully breed and above high high tide the water longer has 

sufficient salinity to breed saltmarsh mosquitoes. The plant species most frequently associated with mosquito 

breeding are the short-form Spartina alterniflora, Spartina patens, and Juncus gerardii. Tall-form Spartina 

alterniflora generally defines the lower breeding edge (except in blocked ditching where the tall form edges the 

ditch) and Iva fructesens generally defines the upland edge. 

 Aedes cantator is the most common species when salinities are low (0 to 10 ppt) as occurs in the spring and

after heavy summer rains. Aedes sollicitans dominates the mid-summer months when salinities are high (10 ppt and

up). However, there is considerable overlap between the two species and it is not difficult to collect both in the 

same dip of water. Aedes taeniorhynchus is less common than above two species. Culex salinarius seems to be 

restricted to rain-fed pools at the upland edge. 

b. Brackish. Both Phragmites communis (tall reed) and Typha species (cattail) obscure 

the boundary between fresh and salt water. Salinities in the range of 1 to 5 ppt occur and Ae. cantator dominates 

this type of habitat. Cattail tends to indicate a fairly constant source of freshwater, such as a stream or spring, while 

108
Phragmites tends to indicate pooling of water for temporary periods at a level just high enough to avoid salt-water 

influence except under storm conditions. 

 2. Inland Wetlands. 

Freshwater wetlands vary tremendously in size and hydrology, from small damp spots in isolated wood 

lots, to broad wooded swamps to sheet flow of spring water down the sides of hills. Mosquito breeding tends to be 

maximized in areas of temporary, standing water but the number of species that breed in freshwater makes 

generalizations difficult at best. 

Red-maple swamps are a significant source of Ae. abserratus and Ae. canadensis. Flood plains, flooded 

meadows and shrub swamps produce Ae. excrucians and Ae. vexans. 

Vernal ponds have received particular attention both because they breed mosquitoes and because they are 

an important breeding site for amphibians and other semi-aquatic animals. These ponds are rarely more than oneto-two-hundred square feet in surface area, and remain flooded from snow melt until drydown in mid to late June. 

They breeds Ae. abserratus, Ae. excrucians, Ae. canadensis, Ae. cinereus and, if dry down is late or the pool is

reflooded by rain, Ae. vexans and Anopheles species. If such a pool is located in a flood plain, it can breed Ps. ferox 

as well. 

Larger, deeper swamps cause considerable difficulty because, although the number of mosquito larvae per 

square foot may be low than in the vernal ponds, the size of the swamp more than makes up for the difference. 

Further, access to the central areas of the swamp is extremely limited, making aerial application the only practical 

control technique. Aedes abserratus and Aedes canadensis are two primary pest mosquitoes that emerge from these 

swamps. As the swamps dry down, innumerable pockets of water are left among the tree roots and Cs. melanura

becomes increasingly easy to find as the swamps dry.

Flood-plain marshes, wet meadows and swamps produce Ae. excrucians in the spring and Ae. vexans in the 

summer. Flood plains are ideally suited for Ae. vexans as peak flooding is delayed for a day or more after rainfall

and areas remain flooded longer than in other areas. This creates ideal conditions for breeding. In the summer East 

Middlesex MCP has recorded up to 5,000 Aedes vexans per night at collection sites in close proximity to river flood 

plains. 

Shrub swamps are much less common than forested swamps so are less a target for mosquito control on 

that basis. Aedes excrucians seems to be the pest mosquito most likely to be found in such sites, and Cu. restuans is 

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also common. 

The mosquito problem associated with marshes depends on water depth and the presence of cattail. A 

marsh more than a foot deep with an extensive stand of cattail will breed Cq. perturbans and be a constant source of 

difficulty to control personnel. If water levels are lower, and cattail is replaced by emergent grasses and rushes, 

then Ae. canadensis and Ae. vexans may be present. Again, Culex and Anopheles species are fairly common in this 

type of marsh. 

A less-common type of wetland is the sloping, forested wetland caused by water seepage and typically

having a ground cover of skunk cabbage. Mosquito breeding is not high in such places, the slope preventing 

significant pooling, but manmade disturbances, such as cutting a dirt trail across the face of the slope, can pool 

water and provide breeding habitat.

3. Surface Water Bodies. As opposed to the wetlands described above, in which surface water 

often disappears for at least part of the year, surface water bodies generally have standing or moving water yearround and have an extensive, open water surface. 

a. Lakes and ponds. Few mosquitoes breed in the open water of lakes and ponds. 

Breeding does occur in the wetlands, particularly cattail, that border the lake or pond. In East Middlesex MCP, 

flood plains and cattail marshes located on the edges of lakes and ponds produce massive populations of Ae. 

Excrucians, Ae. vexans, and Cq. perturbans (Henley, personal communication). Small ponds which become

covered with floating plants such as duckweed can breed Culex territans and Anopheles mosquitoes. Small, 

manmade ponds lacking fish populations can also breed mosquitoes, especially where emergent vegetation exists. 

Although not significant breeding sites, lakes and ponds are areas where adult mosquitoes congregate. 

Several reasons probably play a role, from the availability of water to drink, to the fact that mammals and birds tend

to come to water to drink also and, that there are often wetlands immediately adjacent to more open bodies of water. 

 One important point to make is that there are numerous types of gnats and midges that, to the untrained 

observer, look much like mosquitoes. These insects breed in the sand or mud edging ponds and lakes and can give 

the appearance of huge numbers of mosquitoes as the adults swarm among the vegetation. Early-season complaint

calls are often based on observations of these, no-biting, insects. 

The fauna of all open bodies of water, including rivers and streams discussed below, are particularly

susceptible to broad-spectrum pesticides such as malathion and the pyrethroids group. Larval control is rarely an 

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issue, but adulticiding near open water always carries some risk of non-target kills. 

b. Rivers and streams. The current in the open water of rivers and streams makes 

mosquito breeding impossible in all but the slowest moving sections. Even here the predator complex in most cases 

is too well developed for mosquitoes to survive in any numbers. Again, however, the wetlands bordering the river 

are significant breeding sites. Some breeding also can take place in intermittent streams, once they have stopped 

flowing and before they dry down completely. 

4. Recharge Areas. Recharge areas are those in which surface water percolates down to recharge 

aquifers or drains into reservoirs. The obvious concern in such cases is that pesticides used in such areas may move 

along with the water, causing contamination of the aquifer or reservoir. The primary pesticides for mosquito

control, resmethrin and Bti, break down quickly and do not pose a water-quality risk to reservoirs. Of course, 

adulticiding over wetlands can kill wetland species directly, though ULV rates are low enough that such kills are 

infrequent. 

a. Wetland. Because wetlands are wet due to the impermiability of the substrate, their 

addition to recharge areas is often less than that of surrounded, drier areas. Pesticides applied to wetlands, 

therefore, are not likely to cause contamination by percolation. However, because wetlands do store water which 

can then move out of the wetland as runoff, pesticides applied to such areas may move off-site, including into 

reservoirs. 

b. Upland. Upland recharge areas rarely have significant mosquito breeding, because the 

water percolates downward quickly. The primary concern in such areas would be heavy rainfall immediately after a 

treatment for adult mosquitoes. In such cases there could be overland flow of runoff contaminated by pesticide 

washed from leaf surfaces. 

5. Upland Areas. This is a catch-all category for all lands not defined as wetlands. Obviously, the 

majority of human developments are located on uplands and the majority of adulticiding takes place within upland 

areas. Perhaps unconsciously, pesticides used for adult mosquito control are designed to be relatively benign to the 

plants and vertebrate animals of Massachusetts. No material that caused robins or squirrels to drop in their tracks, 

or which killed maple trees, would ever be permitted for use in Massachusetts. This makes ULV sprays in such

areas appear reasonably benign. However, simply because the larger species do not exhibit acute effects, does not 

mean that no effects occur. One clear question that cannot be answered is what long-term effects do regular 

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adulticide treatments have on the less-visible fauna of the typical suburban woodlot-meadow habitat in 

Massachusetts. 

6. Agricultural Areas. The muddy hoof-prints of the milk cows around the water hole may well

breed Ae. vexans, but the proper control in such cases must take into account the fact that food for human 

consumption is the primary purpose of the land in question. The Bti and IGR larvicides currently available are 

unlikely to cause problems in meat, dairy or crop production, but adulticides are a different story. Pesticide residues 

are limited even on non-organically grown produce and a late-summer application has the potential to cause 

problems for growers. Of particular concern are the backyard gardens of homeowners which cannot help but

receive the drift from pesticide applications. 

Agricultural enterprises of particular concern are apiaries and organic farms. Bees are susceptible to 

pesticides but the exposure to bees caused by mosquito control applications of resmethrin at night is minimal since 

the bees have already returned to their hives. 

During the EEE vector control aerial applications of malathion, beekeepers were advised to cover their 

hives. The applications were scheduled for 2.5 hour windows after dawn and before dusk. The criteria used in

determining the period of the spray window included daylight periods when mosquito activity would be optimal and 

bee activity would be minimal.

The owners of properly run organic farms have gone to great lengths to become certified as pesticide free. 

In most cases the farms are small and the business, at least in the first years, marginal. The problem with organic 

farms, under normal circumstances, is knowing they exist, not avoiding them once known. Massachusetts MCPs 

have systems in place so that organic farmers can heave their land excluded from pesticide applications. Problems 

can develop when the question of drift from nuisance spraying occurs, or when there is a public-health threat. 

7. Sensitive environments and populations. Certain environments and populations have special 

considerations which require a more cautious approach to mosquito control. Some of these have been discussed 

above but there are others worthy of mention. 

a. Urban. The urban environment requires special care due to the increased population 

density and the difficulty in ensuring that people know the benefits and the dangers associated with mosquito

control. b. Recreation. People who enjoy outdoor recreation areas often have a higher 

tolerance for mosquitoes and a lower tolerance for spray vehicles than does the population at large. On the other 

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hand, resort communities may demand higher than normal levels of mosquito control in order to make their site 

more enjoyable to the public. In any event, areas in which summer recreation takes place tend to polarize the debate 

over control and provide increased political headaches for MCPs, even where mosquito control itself is relatively 

straightforward. 

c. Sensitive individuals. There are several groups of people who are sensitive to pesticide 

applications. Some individuals with emphysema or asthma can be adversely affected by airborne pesticide 

applications and such individuals sometimes request that their property be excluded from spraying. 

Individuals with Multiple Chemical Sensitivity (MCS) have contacted MCPs and requested exclusion from

spraying. No project has reported difficulty working with these individuals to create acceptable no-treatment zones. 

 The causes, systems, diagnosis, and treatment of MCS all remain in a great state of flux, so MCPs are well advised 

to work carefully with MCS individuals and pay attention to the changing medical knowledge concerning MCS. 

d. Public and Private Wildlife Refuges and Conservation Areas. These areas are often 

excluded from mosquito control at the request of the property owner because mosquito control runs counter to the 

goal of preserving the area in as natural a state as possible. Exclusion is not always absolute, however, as 

sometimes environmentally friendly pesticides like Bti can be used or water management may be practiced where 

pesticide applications are not permitted. The best way to approach such areas is to contact property owners and

discuss with them possible mosquito-control alternatives. 

e. ACEC and areas with rare or endangered species. Whenever rare or endangered species 

are present, pesticide applications and/or wetland alterations need to be approved by the appropriate agencies (see 

discussion under Rare and Endangered Species under impacts of physical control below). In many cases they will 

be rejected out of hand. 

f. Water supplies. As stated above under surface water bodies and recharge areas, open 

water and water that is destined for drinking supplies, whether through percolation into the groundwater or by flow 

into reservoirs, must be very carefully protected. Fortunately, it is rare indeed that water supplies are held in such a 

way as to breed mosquitoes. For water supplies in general, therefore, mosquito control must consist of influencing 

the design of such systems to avoid creating habitats that would produce mosquitoes. 

C. Mosquitoes as Disease Vectors 

Most of the 9 organized mosquito control projects in Massachusetts justify their activities (and claim

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benefits) in part on the disease threat to human and animal populations posed by vector mosquitoes. Control

programs in Berkshire County and Cape Cod (Fig. 1) lie outside of the area historically affected by outbreaks of 

Eastern equine encephalomyelitis (EEE) and therefore do not justify or plan their programs to address this disease 

problem. Dog heartworm is recognized throughout the Commonwealth (Arnott & Edman 1978). California group 

viruses have also been found in mosquitoes. To date human illness attributable to these agents has not been 

identified in Massachusetts.. 

A major practical difficulty in addressing the vector mosquito problem in Massachusetts stems from the 

fact that the specific species responsible for transmission of disease agents to humans and domestic animals are 

often unknown. The enzootic vector of EEE among birds is clearly Cs. melanura, but the vector(s) to horses and 

humans is unknown. The cattail mosquito, Cq. perturbans, and the most common reflood species, Ae. vexans, are 

prime suspects. Other mammal-feeding Aedes such as Ae. canadensis also may be involved and perhaps even Cs. 

melanura feeds sufficiently on mammals under unusual circumstances to cause some transmission to these dead-end 

hosts (Nasci & Edman 1981a). 

Based on isolations in other states (Calisher & Thompson 1983) and a few in Massachusetts (Walker 

1984), it seems likely that the important California group viruses in the Northeast, i.e. LaCrosse and Jamestown 

Canyon, are transmitted by the treehole mosquito, Ae. triseriatus, and spring, woodland Aedes, respectively. Dog 

heartworm also may be spread primarily by spring Aedes but reflood Aedes (e.g., Ae. sticticus and Ae. trivittatus),

Cq perturbans, Cx. salinarius and Anopheles spp. also may be involved in transmission of this parasite (Arnott & 

Edman 1978). 

1. Eastern Equine Encephalitis 

MCP's in Southeastern Massachusetts, i.e., Norfolk, Bristol and Plymouth Counties, face the greatest threat 

from this disease. During major epidemic years, virus activity extends northward from this enzootic focus into

southern New Hampshire and westward into Rhode Island, Connecticut and Central Massachusetts. All projects 

except Berkshire County give considerable continuing attention to this potential problem. Upon occasion, projects 

may submit mosquitoes to the SLI for EEE virus analysis. 

The enzootic foci of EEE are red maple/white cedar swamps. The largest adult populations of the enzootic 

vector, Cs. melanura, occurs in or near the localized swamps where this species develops. Most human and horse 

cases also occur in the immediate vicinity of these same swamp habitats. Still, at times this mosquito may disperse 

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several miles from its larval habitat (Morris et al. 1980. Nasci 1980. Nasci & Edman 1984) and human/horse cases 

occasionally occur in upland areas. This mosquito is unusual in that it overwinters in the larval stage (4th or 3rd 

instar). Adults from this generation emerge in late spring (i.e., mid to late May). Two to three summer generations

occur about one month apart, e.g., in late June, July and August, depending on water levels and temperature (Nasci

1980). EEE virus is generally not isolated from this mosquito until late summer. During epidemic years it tends to 

be isolated earlier, i.e., beginning in early July, but apparently never from the overwintering generation. The 

location of the virus from November to July remains a mystery. Culiseta melanura feeds only after dark and the 

vast majority of blood meals are obtained from passerine birds (Nasci & Edman 1981a). This sylvan mosquito

feeds equally at ground level and at higher elevations in the tree canopy. Activity is concentrated just after dark and 

just before sunrise (Nasci & Edman 1981b). The morning flight activity peak does not seem to involve 

blood-feeding but rather the return to suitable daytime resting sites. 

The isolation of EEE virus from the cattail mosquito Cq. perturbans during disease outbreaks (Crans, 

personal communication) has focused suspicion on this species at the most likely epidemic vector to horses and 

humans. Ae. vexans and Ae. canadensis are two other prime suspects for EEE virus transmission to humans and 

horses in Massachusetts. Like Cq. perturbans, they are major pests. Their biologies will be described along with 

the other pest species. 

A new EEE threat may be developing in New England as Ae. sollicitans, long a known vector in New 

Jersey (Crans et al. 1991), was, for the first time, found to be EEE-positive in Connecticut in 1996 (Andreadis 

1996). Crans (1991) gave a suggested cycle for EEE transmission to Aedes sollicitans in which Cs. melanura

infected night-roosting glossy ibis, which were then fed upon by Ae. sollicitans while feeding in the salt marsh. 

Though the link between glossy ibis and Ae. sollicitans is tentative, there can be no question that Ae. sollicitans is a 

potent vector in New Jersey and could be an important vector in Massachusetts as well. 

2. California encephalitis vectors 

Jamestown Canyon virus has been isolated from both dark-legged and banded-legged spring Aedes in

Massachusetts and neighboring New York State (Walker 1984, Calisher & Thompson 1983). LaCrosse virus is

associated with the tree-hole species Ae. triseriatus in Eastern New York State, but it has not yet been found in

Massachusetts. All suspect human cases of arboviral disease which are found not to be EEE are sent by the SLI to 

the CDC for a full arbovirus analysis. No California Group virus infections have been identified. 

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 3. Dog heartworm

A wide variety of mosquito species are capable of vectoring this debilitating nematode parasite of canines. 

 Coin lesions in human lungs can occur from accidental infection with this parasite (Adkins & Dao 1984, Deren & 

Feinberg 1984). Felines are more susceptible to infection than was previously thought because they apparently do 

not produce microfilaria (Fukushima et al. 1984). Natural infections have been found in three different species of 

spring Aedes in Massachusetts but other potential vectors cannot be discounted (Arnott & Edman 1978). The 

treehole mosquito, Ae. triseriatus, and three permanent water species, Cx. salinarius, An. punctipennis and An. 

quadrimaculatus, are all possible late season vectors. 

King and Munro (1989) reported on a questionnaire sent to Plymouth County veterinarians concerning dog 

heartworm. Infect rates were reported as generally less than 5% but one veterinarian reported rates above 20%. 

With between 25,000 and 30,000 dogs in the reporting area, the estimated cost of yearly preventative treatments 

was $750,000. 

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V. CURRENT ABATEMENT STRATEGIES AND THEIR IMPACTS 

A. Chemical Control 

1. Overview of Chemical Control 

a. General Toxicity of Pesticides. 

Pesticides are placed in one of four categories based on their acute toxicity (Table 13). Category I 

pesticides are extremely toxic while Category IV materials can range from mildly toxic to non-toxic. 

Pesticides are also classified as either “General Use” or “Restricted Use” materials. General Use pesticides 

are available for use either by the general public or by licensed applicators. Restricted Use materials may only be 

applied by certified applicators or licensed applicators working directly under the supervision of a certified 

applicator. While Restricted Use materials are generally more toxic than General Use ones, toxicity is not the only

issue. For example, resmethrin-based ULV products (Scourge) have recently been placed on the Restricted-use list, 

not so much because of toxicity but because the mode of application (ULV area-wide treatments) means that 

incorrect applications can have wide-ranging effects. 

Table 13. Toxicity Category of Pestcides used in Mosquito Control 

Category Signal Word Categories of Acute Toxicity Probable Oral Antidote Statement 

 Required on LD50 LC50 Lethal Dose Other Cautionsa

the label Oral Dermal Inhalation for 150 lb. man 

 mg/kg mg/l 

I DANGER 0 thru 50 0 thru 200 0 thru 0.2 A few drops Skull and Crossbones 

Highly Toxic 1 to a teaspoon- “Call Physician Imme- 

 POISON ful diately”

 Antidote Statement 

II WARNING from 50 from 200 from 0.2 >1 teaspoonful

Moderately thru 500 thru 2000 thru 2 to one ounce 

Toxic 

III CAUTION from 500 from 2000 from 2.0 >1 ounce 

Slightly Toxic thru 5000 thru 20,000 thru 20 to one pint or 

 one pound 

IV CAUTION >5000 >20,000 >20 Over one pint

Relatively or one pound 

Non-toxic a

All pesticide labels are required to include the statement, “Keep out of reach of Children.” 

 

from: pesticide Applicator Trainging Core Manual: Northeastern Regional Pesticide Coordinators 

and Manual 2, Vectorborne Disease Control Homestudy Counrse 3013-G: Center for Disease Control

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Newer pesticides have muddied the pesticide classification system. Bti and Bacillus sphaericus are 

biological organisms yet their mode of action is through the creation of a toxin that is activated in the insect’s 

midgut. For the purposes of pesticide classification and this GEIR, therefore, they are considered pesticides, not

biological control agents. Methoprene is also a case of a material (an insect growth regulator) that, while not

directly toxic, so alters the life cycle of the insect that death results. Again, methoprene (Altosid) is classified as a 

pesticide but is far removed from the classic chlorinated hydrocarbon and organophosphate pesticides of the past. 

b. Pesticides used for Mosquito Control In Massachusetts 

Twenty-six different insecticide formulation distributed among fifteen product lines were used for 

mosquito control in Massachusetts between 1993 and 1995 (Table 14). Eight of these formulations used Bti as the 

active ingredient, five were methoprene-based, three were resmethrin-based, two each were pyrethin-based or 

malathion-based, and there were one each of temephos, isoctedecanol, and mineral oil. Of these, Acrobe (Bti) and 

Vectobac AS (replaced by 12AS) are no longer produced. Arosurf-MSF (Isoctadecnol) was removed from the 

market but has just reappeared under the name Agnique MMF. Abate 4E was not used in either 1994 or 1995 and 

both the Malathion 10EC and the Resmethrin product (EPA rep # 4-339-53853) were used in small amounts only

(Table 4 gives a break-down by Project of chemical use). 

Of the insecticides used, all of the larvicides were classed as Category IV materials by EPA. Bonide

Mosquito Larvicide, available but not used, is border line between Category III and IV. VectoLex CG, a new 

Bacillus sphaericus product, is Category IV. All adulticides are in Category III. 

Many pesticides have dual actions. They are important in controlling injurious pests, but they may also 

present a hazard to species not considered to be pests in the environment. As a result, the concepts of "target” and 

"non-target” organisms have arisen. For example, in many freshwater systems, control measures may be taken 

against undesirable target organisms such as mosquito larvae or unwanted algae. Non-target organisms are those 

whose destruction is not intended but which may be affected. These non-target organisms may play key roles in

aquatic ecosystems. 

The distinction between target and non-target species is not absolute, because the same group may be nontarget organisms in one area of the country but target organisms, under certain circumstances, in another area. For 

example, larvae of caddisflies (Trichoptera) and naiads of mayflies (Ephemeroptera) are important food sources for 

118
 Table 14. Chemicals used in Massachusetts mosquito control, 1993 through 1995

Trade Name EPA Registration Active % Active Toxicity Other 

 Number Ingredient(s) Ingredient Class Warning Statements

LARVICIDES

Abate 4E 241-132 Temephos 43 IV 

Acrobea

 62637-1-241 Bti

b

 IV 

Arosurf-MSFc

 42943-8 Isooctadecanol 100 III 

Altosid

Briquets 2724-375-64833 Methoprene 7.9 IV 

 XR Briquets 2724-421-64833 Methoprene 1.8 IV 

 Pellets 2724-448-64833 Methoprene 4.0 IV 

Bactimos

Briquets 43382-3 Bti 10 IV 

 Granules 37100-43-2217 Bti 0.2 IV 

 Pellets 37100-42-2217 Bti 0.4 IV 

GB-1111 8898-16 Petroleum Hydrocarbons 

GB-1356 8898-16 

Teknar HP-D 2724-365-64833 Bti 0.8 IV 

Vectobac 

 AS 275-52 Bti IV 

 12AS 275-66 Bti 1.2 IV 

 Granular 275-50 Bti 0.2 IV 

ADULTICIDES

Malathion 8EC 34704-119 Malathion 8 III 

Permanone 10EC 4816-688 Permethrin 10 III 

Permanone 31-66 4816-740 Permethrin 31 III 

Resmethrin 4-339-53853 Resmethrin III 

Scourge 4+12 432-716 Resmethrin 4 III ⎫ ⎧RESTRICTED USE 

 PBO 12 ⎬ ⎨ CLASSIFICATION 

Scourge 18+54 432-667 Resmethrin 18 III ⎪ ⎪Due to acute fish toxicity 

 PBO 54 ⎭ ⎪Retail sale to and use only by 

 ⎪Certified Applicators or 

 ⎪persons under their direct 

 ⎪supervision and only for those 

 ⎪uses covered by the Certified 

 ⎩Applicators Certificate 

MATERIALS REGISTERED BUT NOT USED - LARVICIDES

Altosid

 Liquid 2724-392-64833 Methoprene 5 IV 

 Liquid Con 2724-446-64833 Methoprene 20 IV 

Bonide Mosquito

 Larvicide 4-195 Mineral Oil 98 III-IV 

VectoLex CG 275-77 B. sphaericus 50d

 IV 

MATERIALS REGISTERED BUT NOT USED - ADULTICIDE

Fyfanon ULV 4787-8 Malathion 95 III a

No longer marketed b

Bacillus thuringiensis var. israelensis c

Now marketed as Agnique MMF 

119
trout and other valuable freshwater fish. In certain areas, these species of insects can occur in such large numbers 

that they become nuisance pests, and their immature stages are the target of planned control operations with

pesticides. 

The ideal situation in most control operations is to be able to destroy the undesirable species at pesticide 

concentrations that will have minimal adverse effects on the rest of the biota. However, some degree of

contamination and hazard is assumed with nearly all pesticide use. The hazard to aquatic organisms and other 

wildlife species depends on the chemical and physical properties of the pesticide, type of formulation, rate and

method of application, and characteristics of the receiving ecosystem system (Nimmo 1985). 

Looking at the change in pesticide use by MCPs over the past decade (Table 3), all Category II insecticides 

have been phased out and Methoxyclor, the only organochlorine compound on the list in the early eighties, has 

likewise been dropped. Using malathion and permethrin for larviciding has also been discontinued and Bti and 

methoprene have taken over from Mineral Oil (Flit-MLO) as the dominant larvicides. For adulticiding, permethrin 

and resmethrin have essentially replaced malathion. Theses changes indicate that MCPs have responded to the 

desire of the public at large (including the staff of the MCPs incidentally) for materials with the lowest risks. The 

other conclusion to be drawn is that, until the discovery of new materials, both adulticiding and larviciding are 

presently be conducted with the materials that have the least overall risk. Advances in reducing the risk of chemical

use must therefore come from improved targeting and increased use of water management and/or biological control

techniques. 

c. General Properties of Registered Mosquito Control Insecticides in Massachusetts, 1996. 

Physical Properties. Using both water solubility and KoW, the following insecticides are classified as water 

insoluble or practically water insoluble; Bti, isooctadecanol, methoprene, petroleum oil/Flit MLO, pyrethrin I, 

resmethrin and temephos. Malathion is the most water soluble insecticide used (145 ppm). Nevertheless, it still has 

a relatively high partition coefficient (KoW 779) and because of its rapid environmental and metabolic degradation 

is not expected to bioaccumulate in any appreciable fashion as discussed below. 

 Insecticides which have little or no volatility are; Bti, B. sphaericus, malathion, methoprene, and temephos. 

 Isooctadecanol and mineral oil are slightly volatile. Although pyrethrin I and resmethrin have appreciable vapor 

pressures, they are most likely to be bound to suspended organic matter or soil particulate in natural systems. If 

volatilization occurs, they are rapidly photodegraded. 

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 Four of the insecticides have vapor densities less than 1.0 (relative index to air) and so could concentrate 

near the surface, resulting in increased exposure via inhalation. However due to the low vapor pressure of 

isooctadecanol and methoprene, these compounds are mot likely to be available for concentration. The pyrethroid

insecticides, as discussed above, are rapidly degraded by photolysis if they become available which is not likely

 from environmental surfaces. 

For specifics on a given insecticide, the reader should refer to the sample labels and Material Safety Data

Sheet (MSDS) for that material, located in Appendix C.

Analytical Methodology (from: The Pesticide Manual 7th ed. Worthing & Walker, British Crop Protection 

Council. Lavenham, UK. 1983. For more detailed methods consult The Agrochemical Handbook, 2nd ed. 1983). 

 1. Bti and B. sphaericus are measured in international toxicity units/mg product (i.u.) relative to that

of an appropriate standard product against Trichoplusis ni or Aedes egypti in standard bioassays. 

Assays based on the number of spores are not satisfactory.

2. Methoprene is analyzed by GLC or HPLC w/UV detection. 

3. Isooctadecanol is analyzed by GLC.

4. Pyrethrin I is analyzed by GLC. 

5. Resmethrin is analyzed by GLC. 

6. Temephos is analyzed by GLC.

7. Malathion is analyzed by GLC. 

8. Petroleum Oil is analyzed by GLC. 

Transport, Persistence and Degradation in Soil, Air and Water. None of the insecticides used for mosquito control 

in Massachusetts are included on the 1987 EPA lists (I + II) of the 51 priority pesticide leachers. 

Synergists and Inerts in Pesticide Products. 

Synergists are compounds added to a pesticide that increase the efficacy of that pesticide. Relatively few 

combinations of insecticides and synergists lend themselves to practical use, either because the degree of improved 

performance is small or because too much of the expensive synergist is required, or both (Casida 1970). By the 

same token, no example of increased toxicity to man or useful animals under practical conditions has been reported 

(Hayes 1982). 

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In mosquito control, the synergistic effect of various compounds on pyrethrum and synthetic pyrethroids is

well known. piperonyl butoxide (PBO) is the sole synergist used in Massachusetts. It acts as a substrate for the 

microsomal enzyme-NADPH2 system, which also metabolizes many drugs and insecticides. By serving as an 

alternative substrate for the detoxification enzyme of the insect, PBO prolongs the persistence of the insecticide so 

that a lower initial dose is effective (Casida et al. 1966, Kamienski & Casida 1970, Casida 1970). 

“Inert” materials which are used as formulation aids in the insecticides applied by towns/BOHs and

Projects for mosquito control in Massachusetts are categorized as follows: Powders, granular carriers, solvents and 

special effects materials. 

Dustable powders generally contain l-l0% a.i. mixed with powdered minerals as carriers and diluents. For 

wetable powders, the same diluents and carriers can be used as for dusts. However for dispersible powders, a finer 

particle-size spectrum is necessary, the proportion above 40 um not exceeding a few percent. No powdered 

materials are currently in use in mosquito control in Massachusetts. 

Granular formulations are made by either impregnation (soaking or coating) of granular carriers or by

granulation of powdery mixtures of active ingredient and formulation aids. These two types differ in the active 

ingredient concentrations attainable. For both types, an active ingredient content of 20% is the maximum

technically feasible. Included in the grouping are Bactimos briquets, granules and pellets (Bti), Vectobac granules 

(Bti) and Altosid briquets, XR briquets, and pellets (methoprene). 

Liquid formulations such as emulsifiable concentrates, soluble concentrates and ULV use various organic 

solvents as diluents. Aliphatic hydrocarbons are poor solvents for most active ingredients and are therefore 

normally only used for very dilute formulations. Aromatic hydrocarbons are used frequently, the fractions C6 to

C12 being favored (e.g., from technical xylene mixtures to substituted naphthalenes). Apart from the toxicity of

benzene, their high flammability prohibits the use of lower aromatics. On the other hand, phytotoxicity frequently 

increases with increasing molecular weight. Ketones are excellent solvents for many organic compounds. Most of 

them are at least partially water soluble, so they are mainly suitable for formulating water-soluble and liquid-active 

ingredients. When they are used for the formulation of emulsifiable concentrates of solid, water-insoluble active 

ingredient, the active ingredient often crystallizes out during the preparation of the spray mix. This is caused by the 

solvent passing into the aqueous phase whereupon the active ingredient is precipitated in the "oil droplets" of the 

emulsion. Here ketones can normally only be used together with other, water-insoluble solvents as cosolvents. 

122
This is also valid for alcohols and glycols and their ethers and esters as well as for highly polar aprotic solvents such 

as dimethylsulfoxide and dimethylformamide. Chlorinated solvents are only used to a very slight extent. 

Chlorobenzene is used occasionally; dichlormethane is used more frequently as a relatively non-toxic, highly 

volatile, and nonflammable solvent for hygiene and stored-product agents and for aerosols. 

Emulsifiable concentrates used for mosquito control include the larvicide Abate 4E and the adulticides 

Malathion 10EC, Permanone 10EC, Permanone 31-66, Resmethrin, and the Scourge products. 

With increasing public concern of off-site deposition of pesticides (e.g. aerial drift) and the movement of 

the pesticide industry away from organic compounds to biological insecticides, new formulation technology has 

emerged. Flowable concentrates not only reduce drift, but provide better coverage and greater adhesion to the 

substrate. Dried active ingredients are ground to a uniform particle size (usually 10 um) as either a dry, wet (H2O) 

or oil suspension (which then is diluted with water for application). Included in this grouping are the Bti products

Teknar flowable (Bti) and Vectobac AS and 12AS. 

None of the direct nerve toxins (pyrethrin and resmethrin) have inert ingredients which appear on 

EPA/SAP List 1. Scourge (resmethrin) contains a List 2 compound (0.025% xylene) and 4-12% PBO and 12% 

Chevron 100 (a soybean oil diluent) as additional active ingredients. 

None of the indirect nerve toxins (malathion and temephos) have inert ingredients which appear on the 

EPA/SAP List 1. Of the products which contain malathion, malathion 57% EC contains a List 2 compound, 31.5% 

and 36.55% xylene range aromatics, respectively. Temephos (Abate 4E) contains 39% Chevron 100 as an 

additional active ingredient. 

None of the selective insect toxins (Bti and methoprene) contain any List 1 or 2 compounds. No other 

additional active ingredients are listed.

None of the physical toxins (isoocadecanol (Arosurf MSF/Agnique MMF and petroleum oils) contain any

of the List 1 or 2 compound. Petroleum hydrocarbons as a group are included on List 2 as potential toxic inerts of 

pesticide products.

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d. Pesticide Handling and Application 

Pesticide storage varies considerably from project to project. Cape Cod uses only bagged Bti so no 

formulation work is necessary nor are there stringent storage requirements. Five projects store and formulate 

chemicals in an area within the main garage, generally separated by a wire cage (cabinets within a metal shed at 

Suffolk) from the main garage area. Ventilation fans operate either continuously or whenever the lights in the 

garage are turned on. Bristol, Central Mass and Essex all have separate buildings for pesticide storage and 

formulation. Central Mass mentioned that their structure was built in consultation with the local fire department and

the State Pesticide Board. East Middlesex constructed its storage area from Department of Defense specifications. 

All projects use pickup-truck mounted ULV sprayers for adulticiding. No thermal foggers remain in use. 

Backpack sprayers are used to apply liquid larvicides and, in some projects, adulticides. Granular materials are 

applied by hand or with cyclone-type spreaders. Briquet formulations are applied by hand. Additional information 

on the pesticides may be found on the sample labels and MSDS sheets in Appendix C.

Applicator certification is done by the Pesticide Bureau of the Department of Food and Agriculture. 

Mosquito control applicators are certified under the “Mosquitoes and Biting Flies” subcategory of “Public Health 

and Nuisance Control”. Aerial Applicators are licensed separately. Ongoing training is required and many

mosquito-control personnel attend annual meetings of the Northeastern Mosquito Control Association for such 

training. Specifics for certification and other applicator issues are covered in CMR 333: Pesticide Board. 

Most of the pesticides used are extremely safe, so handling instructions are minimal. For Bti, mineral oil 

or Golden Bear oil, and metheprene products, work areas should be ventilated and eye protection and impervious 

gloves worn. With these materials applicators should also wash thoroughly after handing or applying them. With

malathion, permethrin and resmethrin products safety goggles, chemical resistant gloves and a respirator should be 

worn when formulating spray material. Eyes should be flushed immediately and skin washed with soap as quickly

as possible if accidental contact occurs. Vomiting should not be induced for resmethrin and permethrin products 

but should be induced for malathion. In all cases where resmethrin, permethrin or malathion is ingested, a physician 

should be contacted immediately.

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 2. Larvicides 

a. Biologicals: Bti and B. sphaericus 

 i. Bacillus thuringiensis var. israelensis

Mode of Action. Bacillus thuringiensis (Bt) is a naturally occurring, gram positive, rod-shaped, spore-forming

bacterium, which is pathogenic to the larvae of a number of insects species, especially Lepidoptera, when ingested 

by the larvae. Bti is also a pathogen to the larvae of some insects in the order Diptera (e.g., mosquitoes and 

midges). Bacillus thuringiensis var. israelensis Serotype H14 (Bti) is a biological insecticide produced during 

sporylation of this bacterium. The protein product of the H14 serotype (e.g., Bactimos, Vectobac and Teknar) is

used to selectively control the larvae of mosquito and blackflies. It is a stomach poison which alters gut

permeability to salts under alkaline conditions. This decreases feeding and development and eventually causes 

death by starvation (Hartley & Kidd 1983). 

Fate in the Environment. The residual period for Bti has been estimated at 48 hr in water, as it gradually settles out

or adheres to suspended organic matter (SCAMP 1987). As a natural part of the ecosystem, Bti degrades to

complex but non-toxic organic compounds which are ultimately mineralized (Hartley & Kidd 1983). 

Effects on Non-target organisms. There is no evidence of acute or chronic toxicity of the spore-crystal complex to

amphibians (tree frog tadpoles, toad tadpoles, California newt), fish (mosquito fish, rainwater kill fish, two-spine 

stickleback) or birds. It is non-toxic to bees. Groups of organisms that have been reduced by Bti applications are 

from the suborder Nematocera of the order Diptera which includes species of the families Dixidae, Chironomidae, 

and Ceratopogonidae (Fisher & Rosner 1959, Garcia et al. 1980, Hartley & Kidd 1983, Worthing & Walker 1983). 

 A recently completed study in Minnesota found Bti reduced chironomids, tipulids, ceratopogonids and 

stratiomyids. There is reason to believe this may have negative impacts on nesting ducks and their ducklings, for 

which chironomids make up a significant part of their diet (SPRP 1996). 

When a small stream was treated at 0.5 ppm/15 min. (13°C) with an aqueous suspension of unformulated 

Bellon primary powder of Bti, in contrast to the sharp reduction (89%) in black fly larvae in the 20-350 m area 

below the treatment point, Surber samples indicated increases in mayfly (35%), caddisfly (47%), stonefly (75%), 

chironomid (19%), and elmid (242%) populations. No adverse effect on any of these non-target populations was 

evident following stream treatment (Molloy & Jamnback 1981). In laboratory and field studies conducted with Bti

to determine its effect upon Ae taeniorhynchus and non-target organisms in a salt marsh, Bti killed over 99% of the 

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mosquito larvae at concentration of 4.5 IU/ml and above. Out of 39 species collected prior to treatment, only a 

homipteran (true bugs), Notonecta indica, showed a significant decrease in population. However, this genus is

known to fly from deteriorating habitats (Purcell 1981). Experimental testing has demonstrated no adverse effect

against other aquatic insects including dragonflies, damselflies, mayflies, stoneflies, caddisflies, water beetles or 

true bugs. Other invertebrates such as Daphnia, cyclops, rotifers and crustaceans are also unaffected (SCAMP 

1987). 

Many acute toxicity/pathogenicity studies with various varieties of Bt have been conducted using several

routes of administration in rats, rabbits, and guinea pigs. Among the various studies reviewed, the highest dose 

tested was 6.7 x 101l spores per animal. There were no significant adverse effects associated with these studies 

(Castillo 1986). No acute toxicity was observed in rats gavaged with the maximum dosage of 2 billion spores of Bti 

H-14. No erythema or edema formation were observed after dermal exposure to 1.6 billion spores. All other 

parameters of the test animals were normal. There was no evidence that Bti H-14 multiplied on the abraded

epidermis. No adverse effects were observed in rats given 80 million viable spores by instillation into the lungs. 

There was no histological evidence of multiplication of the organism in lung tissue. Instillation of 10 million Bti 

spores into the ocular cavity produced no eye irritation beyond 48 hr. No multiplication occurred in the ocular 

cavity (Castillo 1986). Acute, oral and dermal toxicity (LD50) of Bti H-14 (Vectobac) is in excess of 30,000 mg/kg. 

No allergenic response to B. thuringiensis was elicited in guinea pigs by introcutaneous injection, 

inhalation, or topical application to the intact or abraded skin (Hayes 1982). 

Each of 18 persons ingested 1 g of a commercial B. thuringiensis preparation containing approximately 3 x 

109

 spores daily for 5 days on alternate days. In addition to ingestion, five of them inhaled 100 mg of the powder 

daily for 5 days. There were no complaints and no positive findings by physical and laboratory examination (Fisher 

& Rosner 1959). When Bt was applied by aircraft at a rate of 2 kg of preparation (3 x 109

 organisms/g) per hectare 

(6 x 1012 organisms/hectare) the concentration of viable organisms in the air over the field exceeded background by 

42.5 times on the day of application and by 22.5 times 5 days later (Castillo 1986). No complaints were received 

from eight men exposed for 7 months to fermentation broth moist bacterial cake, effluent, and the final powder in

the course of commercial manufacture of the pesticide (Fisher & Rosner 1959, Hayes 1982). 

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A dose of 107

 (i.e., 10 million) Bti organisms killed the test animals when injected introcerebrally (IC). 

Death was probably due to the massive i.c. inoculum and not any infective process. Most of the animals died within

24 hours (Castillo 1986). 

The EPA's review of the toxicological data on Bti determined that no data gaps exist in the toxicology

data base and no major environmental mammalian safety concerns (except for certain endangered species of 

Lepidoptera) were identified (Castillo 1986). Toxicological data specially required for biochemical and microbial 

pesticide registration including: immunotoxicology studies, infecticity studies, intracerebral test, tissue culture tests 

and virulence enhancement studies (EPA 1984, Marquis 1986). Bti is effective only against dipteran larval

(mosquitoes and black flies) and is safe to the environment (Worthing & Walker 1983). 

Bti is non-phytotoxic and has shown no effects on seed germination or plant vigor (SCAMP 1987). 

 ii. Bacillus sphaericus

Mode of Action. . Bacillus sphaericus is a naturally occurring bacterium, which is pathogenic to the larvae of many

genera of mosquitoes. There are a number of strains of B. sphaericus, that being most toxic to mosquitoes is B. 

sphaericus 2363. Like Bti, it produces a toxin that must be ingested and partially digested before it becomes 

activated. Aedes mosquitoes are generally less susceptible to B. sphaericus. It is currently marketed as a granular 

larvicide by Abbot Labs under the trade name VectoLex CG and is of interest because it works better than Bti in 

highly organic waters often favored by Culex species (Abbott Laboratories 1996). Also of interest is the fact that it

is not toxic to other dipterans, including blackflies. Its limited range of toxicity, while a blessing in some respects, 

has slowed development as the market for B. sphaericus is likely to remain small (Federici 1985). 

Fate in the Environment. Bacillus sphaericus has a field life of between two and four weeks. The spores settle out

of the water column in as little as two days though they settle more slowly than Bti, as they adhere less to suspended 

particulates. The spores can remain viable for months in the field (Yousten et al. 1992). Bacillus sphaericus may

undergo limited recycling (reproducing itself within the larval gut of Culex species), especially in rich organic 

environments (Abbott Laboratories 1996, Karch et al. 1990). 

 Bacillus sphaericus is ingested by other filter-feeding arthropods (Daphnia pulex and Cypris sp.) It can 

germinate within the gut of these animals and may be spread by them through the environment. It does not seem to

adversely affect them and they may play a role in recycling B. sphaericus, thereby increasing the length of control

achieved from a single application. Bacillus sphaericus does not affect populations of the predator species Cleon 

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dipterium, Corixa punctat and Nepa cinerea. (Karch et al. 1990). Bacillus sphaericus can be used in conjunction 

with the fungus Lagenidium gigateum (Orduz and Axtell 1991). 

Effects on non-target organisms. Bacillus sphaericus, technical material, had acute oral and dermal LD50 values 

for rats of >5g/kg and >2g/kg respectively, making it a class IV larvicide. The technical material can be moderately 

irritating to the skin and eyes of people. 

Toxicity tests on mallards, bluegills, and rainbow trout showed the material to be extremely save to these 

animals. Acute toxicity tests on freshwater invertebrates (daphnia and mayfly larvae) and salt marsh and bay

species (sheephead minnow, shrimp and oysters) all indicate that the material is essentially non-toxic. Honey bees 

are not affected by B. sphaericus (Abbott Laboratories 1996). 

 Bacillus sphaericus is not phytotoxic (Abbott Laboratories 1996). 

 b. Methoprene 

Mode of Action. Methoprene is an insect growth regulator (i.e., a synthetic analog of the juvenile hormone) which 

does not allow insects to mature from the larval stages into reproductively capable adults. It shows little or no effect 

on the adult or pupal stages of insect development. Unlike ordinary insecticides, this relatively non-persistent

chemical exhibits morphological rather than direct toxic activities. Although its exact mode of action is not 

completely known, three modes have been investigated: 1) methoprene binds JH receptors resulting in extended 

juvenile forms which are not reproductively competent, 2) methoprene competitively inhibits catabolic metabolism

of JH which extends juvenile forms etc., and 3) methoprene binds to its own receptors and extends juvenile forms 

(Matsumura 1985). 

Fate in the Environment. Methoprene is relatively stable but nonpersistent in the environment (SCAMP 1987). It

does not biologically magnify. In soil, methoprene rapidly degrades with a half-life of approximately 10 days. In 

plants its degradation principally involves ester hydrolysis, Odemethylation, and oxidative clearage of the double 

bond of the C4-position. In lucerne and rice, the principle metabolite is 7-methoxycitronellal. Methoprene is very 

susceptible to photolytic decomposition under environmental conditions. It is degraded to many photoproducts 

which are present in relatively low yield (<10%). The rapid degradation of methoprene and multiplicity of 

photolytic products are indicative of extensive photodegradability in the natural environment (Quistad et al. 1975). 

Technical grade methoprene is stable >4 yr. in glass in the dark at 43° (Worthing & Walker 1983). Sterile

aqueous 0.5 ppm solutions at 98% pure [C5-

14C] methoprene, buffered at various pH values, were found to be 

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extremely stable to hydrolysis over 4 weeks at 20°C in the dark. No degradation (detectable limit 1%) was seen in

sterile water at pH 5.7 methoprene was rapidly photoisomerized (t1/2-30 min.) to a final 2E:2% isomeric mixture of 

44:56. The 2% isomer of methoprene has a much lower biological activity than 2E-methoprene itself, hence 

photoisomerization of methoprene in the field should quickly result in a nondegradative loss of about half the 

biological activity. Solutions of methoprene (0.5 ppm) were found to undergo photoinitiated decomposition to more 

polar products, to the extent of 15% in 2 days and 332 in 3 days at 20°C. Earlier experiments at 0.1 ppm at two 

temperatures (24 and 40°C) had shown no breakdown at 24°C and only 5% breakdown at 40°C, in 1 day (Schooley

et al. 1975). 

In pond water, the half-life of methoprene is approximately 30 hr at 0.001 ppm and 40 hr at 0.01 ppm. 

Incubation of (2E)-[C10-

14C] methoprene for 3 days at 0.42 ppm generated three primary metabolites, the result of 

ester hydrolysis and/or O-demethylation. These metabolites and recovered methoprene were photoequilibrium

mixtures of 2-ene double bond isomers (e.g., E and %). In another incubation experiment with (2E)-[C5-

14C] 

methoprene at 0.66 ppm in a pond water sample of presumably different microflora, a completely different

metabolite was identified as resulting from oxidative scission of the 4-ene double bond. The principle metabolite in 

the latter experiment was 7-methoxycitronellic acid. 

Methoprene was rapidly degraded when a thin film (0.1 u) on glass was exposed to sunlight through glass. 

 The half-life under these conditions was 6 hr. After exposure to sunlight for 27 hr, only 3% of the applied dose 

remained as methoprene and it was isomerized to a 50:50 mixture of (2E,4E) and (2%,4E)-methoprene. The 

recovery of only 72% of the applied radioactivity after 27 hr suggested photolysis of methoprene to volatile 

products which were lost by vaporization. Collection of vapors above the photolysate resulted in recovery of 13% 

of the applied radioactivity. The volatile constituents were resolved into methoxycitronellal (4%), methoprene 

(0.2%) and 14C02 (6%). Since only a trace amount of methoprene (0.2%) was detected in the condensed vapors, 

volatility of methoprene is not considered a major route for loss of radioactivity. 

Effects on Non-target Organisms. Methoprene is non-toxic to bees, and relatively non-toxic to non-target species 

but shrimp and crabs may be killed (Hartley & Kidd 1983, SCAMP 1987). Methoprene does have some toxicity to 

the saltmarsh copepod Apocyclops spartinus, but the concentration of methoprene in the water required to cause 

transient reductions in the early life stages of the copepod is above that which should occur during routine mosquito

control (Bircher & Ruber 1988). Methoprene did not adversely affect the copopods Cyclops vernalis and Cyclops 

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navus in a Minnesota study but did reduce chironomids, tipulids, ceratopogonids and stratiomyids (SPRP 1996). As 

for Bti applications, reducing chironomid populations may have a long-term effect on nesting ducks. 

The acute toxicity (96hr-LC50) of methoprene to a variety of fish ranged from 1.6 ppm for rainbow trout to

greater than 100 ppm for channel catfish (Johnson & Finley 1980). 

In a model ecosystem study on the uptake and degradation of methoprene by bluegills, the fish had a 

surprisingly large amount of radioactivity after 4 to 6 weeks of exposure. If the radioactivity was due to the 

presence of parent methoprene, one would have concluded that the compound was bioaccumulated several thousand 

times. However, less than 0.l% of the measured radioactivity was in the form of methoprene and its primary

metabolites, with the rest being present in such natural products like cholesterol, proteins, free fatty acids, and 

glycerides. With this correction factor, methoprene was bioconcentrated by bluegills to a moderate extent. In clean 

water, bluegills eliminated 93 to 95% of the accumulated body burden of methoprene in less than 2 weeks. 

Two formulations of methoprene were applied aerially (0.1 lb a.i./acre) to rice fields in the Sacramento

Valley of California. The level of control of Cx. tarsalis was assessed in emergence cages established before and 

after spraying in these and control fields. After spraying, the treated fields had about one half the rate of Cx. 

tarsalis emergence as did control fields. None of the non-target organisms examined exhibited population 

fluctuations which could be statistically attributed to the methoprene applications (Case & Washino 1978). 

Locomotor activities of mosquitofish (Gambusia affinis) and goldfish (Carassus auratus) were 

monitored for a 2-week period in the presence of methoprene at concentrations approximately 10-fold greater than 

those generally recommended for application. Methoprene, the active ingredient in Altosid SR-10, at 0.2 ppm did 

not significantly alter the locomotor activity of either mosquitofish or goldfish (Ellgaard et al. 1979). 

The acute oral toxicity (LD50) of methoprene to mallard ducks was assessed as greater than 2000 ppm. 

However, treatment levels as low as 520 ppm produced signs of intoxication in mallards (Smith 1987). The eightday dietary LC50 for chickens was greater than 4640 ppm (Hartley & Kidd 1983). Thus, methoprene shows only

slight toxicity to fish and birds and is relatively non-toxic to non-target species (SCAMP 1987). 

When the metabolic fate of methoprene was studied in a guinea pig, a steer, and a cow, a rather large 

percentage of the radiolabel was incorporated in the tissues and respired by the animals. In the urine and feces, a 

small amount of radiolabel was metabolized into free primary metabolites, somewhat more was incorporated into 

simple glucuronides, and a considerable quantity of radiolabel was found in polar compounds, possibly complex 

130
conjugates or polar biochemicals. No parent methoprene was found in the urine, but approximately 40% of the 

radiolabel in feces was contributed by unmetabolized methoprene. The formation of conjugates and the metabolism

of methoprene was more extensive in the steer than in the guinea pig (Chamberlain et al. 1975). Samples of fat,

muscle, liver, lung, blood, and bile from a steer which received a single dose of [C5-

14C]methoprene were analyzed 

for radioactive residues. No primary methoprene metabolites could be characterized, but the majority (16-88%, 

depending on tissue) of the total tissue radioactivity was positively identified as [14C]-cholesterol. Seventy-two 

percent of the bile radioactivity was contributed by cholesterol, cholic acid, and deoxycholic acid. Radioactivity

from catabolized methoprene was also associated with protein and cholesteryl esters of fatty acids (Quistad et al. 

1975). 

Acute oral toxicity (LD50) of methoprene in rats is greater than 34,000 mg/kg. That for dogs is greater than 

5000-10,000 mg/kg. Dermal LD50 values of methoprene are greater than 3500 mg/kg for rabbits. It is nonirritating 

to both the skin and eyes of rabbits (Hartley & Kidd 1983, Worthing & Walker 1983). Methoprene has an 

inhalation LC50 value of greater than 210 mg/l in rat (Sine 1984). In 2-yr feeding trials, no methoprene-related 

effects were observed in rats at 5000 mg/kg diet and in mice at 250 mg/kg diet. No effects were observed at the 

highest rates tested: in 3-generation reproduction studies in rats (2500 mg/kg diet); teratogenicity in rabbits (500 

mg/kg) or rats (1000 mg/kg); mutagenicity in rats (2000 mg/kg) (SCAMP 1987). Hollingsworth calculated the VSR 

for methoprene to be greater than 1,730,000. Methoprene is one of the most selective insecticides presently

available (Wilkinson 1976). 

Methoprene is not phytotoxic. 

 c. Oils 

Petroleum oils are also known as mineral oils and refined grades have been called white oil. Petroleum oils

are prepared by the distillation and refinement of crude mineral oils. Those used as pesticides generally distill 

>310°C to 335°C, namely; "light" (67-79%), “medium” (40-49%), and “heavy” (10-25%) (SCAMP 1987). They

consist largely of aliphatic hydrocarbons, both saturated and unsaturated, the content of the latter being reduced by

refinement. Recently, highly refined oils have been used as adjuvants to increase the effectiveness of some other 

pesticides (Hartley & Kidd 1983). Petroleum oils may be used as diluents for pesticides or by themselves 

Petroleum oils are also used alone as insecticides. Inhalation of oils from the surface of water attacks 

mosquito larvae through their respiratory system. Death occurs due to reduced oxygen levels (hypoxia) and lack of 

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feeding. Petroleum oils also enhance penetration of the insect cuticle by the insecticide. In bioassays of insecticidal 

compounds, selective toxicity has been noted to vary for the same compound depending on the nature of the carrier 

solvent and site of application. The degree to which a solvent induces rapid penetration through the insect cuticle

has been termed its carrier efficiency. This carrier efficiency can be directly related to and is dependent on the 

physical properties of the solvent-insecticide combination. Differences in carrier efficiency have been attributed to

the ability of the solvent to dissolve the outer layer of the insect epicuticle (Schouest et al. 1983). 

Petroleum oils are used as surface treatments to prevent mosquitoes from breathing at the surface. 

Petroleum oils have been shown to be phytotoxic to plants so use instructions should be followed and oil used only

during the dormant period (Hartley & Kidd 1983). 

Petroleum oils/Flit ML0 are mineral oils used as diluent/adjuvant oils or as a physical toxicant which kills 

mosquito larvae via suffocation. Both are prepared by the distillation and refinement of crude mineral oils. Those 

used as pesticides generally distill >310°C. They may be classified by the proportion distilling at 335°C, namely: 

'light' (67-79%), 'medium' (40-49%), and 'heavy' (10-25%) (Worthing & Walker 1983). Acute oral LD50 for rats 

and mice >4300 mg 'Actipron'/kg. No toxicological problem due to petroleum oils has been reported in practice. 

Tests have shown there is no risk of polynuclear aromatic compounds entering the food chain using mineral oils for 

insect control (Hartley & Kidd 1983). 

In 1968, the Medical Research Council in the United Kingdom published its report, "The Carcinogenic 

Action of Mineral Oils," based on work done in several British universities. The most biologically active fractions 

(boiling range of 300-400°C) were distilled further. The carcinogenic activity appeared to occur in materials which 

boiled above 350°C (presence in lower-boiling fractions was possibly the result of azeotropism), and activity was 

still present in fractions boiling at 420°C. Over 40 chemical compounds were isolated from mineral-oil fractions, 

many for the first time, by repeated chromatography, complexing with picric acid and trinitrobenzene, and 

fractional crystallization. Further studies of the nature of the active compounds did not identify any single highly

potent carcinogen. Several of the compounds separated were structurally similar to very potent carcinogens, and the 

total activity of the oil could be caused by the combined effect of several individually weak carcinogens (Kipling & 

Cooke 1984). 

132
Albino rats were dosed orally by stomach tube at varying rates up to 10,000 mg FLIT MLO/kg BW and 

observed for mortality and signs of systemic toxicity for 14 days. The LD50 was never reached and it was 

concluded that the LD50 for FLIT MLO is above 10,000 mg/kg BW. A dose of one pint of FLIT MLO administered 

to a horse by stomach tube showed no gross reactions. 

FLIT MLO was applied to the exposed abdominal skin of albino rabbits at dosage levels up to 3.16 g/kg 

BW. After 24 hr, the residue was removed, and the animals were observed for a total of 14 days after application. 

There were no deaths or signs of systemic toxicity at any dosage level tested. There was no dermal irritation to

unabraded skin on any of the animals. A slight to moderate redness appeared on abraded skin. At the end of the 

14-day period, the skin of all animals was completely clear of any signs of irritation. 

Albino rats (10 male and 10 female) were exposed continually for 1 hr to an atmosphere containing an 

average of 200 mg FLIT MLO (aerosol) per liter (1) of air. Observations of mortality or signs of acute toxicity 

were made at intervals throughout the exposure, and the animals were observed for 14 days after exposure. There 

were no deaths during exposure or in the 14 days thereafter. During the post-exposure period the respiration rates 

of the animals seemed elevated initially, but returned to normal within 24 hr. A slight loss of fur occurred after a 

few days, but this effect had disappeared in all but four animals by the end of the study. Other superficial effects 

(exudate around the eyes, etc.) were observed but quickly disappeared. 

FLIT MLO (0.1 ml) was placed in the left eyes (the right eyes served as a control) of nine albino rabbits. 

The eyes of three of the rabbits were irrigated after two seconds; those of another three after four seconds; the eyes 

of the remaining three were left unirrigated. Periodic observations for signs of eye irritation were made, with the 

last observation made 7 days after application. There was no evidence of systemic effect due to any of the 

applications. Eye irritation was slight and transient in all animals. All signs of the effect had cleared within four 

days following application. Examination on the seventh day confirmed the absence of any corneal damage. Ratings 

on the Draize scale, a common scoring system, were as follows: 4 at one and four hours, 2 at 24, 48, and 72 hours, 

and zero thereafter (Exxon 1973). 

Bonide Mosquito Larvicide is a low-order, low-viscosity, highly saturated petroleum hydrocarbon mineral

oil that enters mosquito larval breathing tubes and spreads over main tracheal trunks. These respiratory pathways

twist and collapse reducing oxygen levels to tissues. Death is by hypoxia and lack of feeding. It is virtually

identical to Flit MLO. 

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The residual periods of petroleum oils are relatively short. Tests have shown there is no risk of 

polynuclear aromatic compounds entering the food chain. No toxicological problems due to the use of petroleum

oils for mosquito control have been reported in practice (Worthing & Walker 1983). It has some hazard to fish but 

little or no hazard to birds. Flit MLO has been evaluated to determine its effects on the aquatic environment. In a 

series of laboratory tests on grass shrimp, fiddler crabs, goldfish, bluegill, sunfish, fathead minnows, coho salmon, 

killifish, and domestic ducks, in which field applications of the larvicide were simulated and exaggerated, Flit MLO 

was found to have no adverse effects even at concentrations well above the recommended application rates of 1 to 5 

gallons per acre (Exxon 1973). 

Little or no hazard has been associated with the application of petroleum oils to beneficial and non-target 

invertebrates. Other Diptera that land on pools treated with oils will be pulled into the water due to the loss of 

surface tension and water beetles can often be observed crawling out of treated pools (Christie, personal 

observation). The flies clearly die, the beetles probably do not. Some hazard has been determined for honey bees. 

Isooctadecanol (Arosurf MSF), is a surface-acting ethoxylated fatty alcohol (i.e., a nonionic surfactant) 

which forms a thin film over the surface of water creating a physical barrier due to reduced surface tension. This 

results in the suffocation of aquatic larvae and pupae (EPA 2/15/84). Foliar absorption, translocation in plants, and 

metabolism and persistence in plants is not available (EPA 2/15/84). Data on microbial breakdown shows that

Arosurf MSF is degraded by unacclimated, mixed cultures of microorganisms from natural sources by shake culture 

methods. Although not available for Arosurf MSF, similar ethoxylates degrade under field conditions with the 

major route of degradation being hydrolysis at the ether linkage and subsequent oxidation of the alkyl chain to

lower molecular polyethylene glycole-like materials which are ultimately mineralized to C02 and H2O. The 

resultant average persistence for isooctadecanol has been determined to be 2-10 days (EPA 2/15/84). Although 

incomplete, the 96 hr - LC50 for Daphnia is reported as 1.9 ppm. Bioaccumulation data is also lacking but studies 

on closely related fatty acid and fatty alcohol ethoxylates in shellfish support the contention that the compound is

rapidly cleared from aquatic invertebrates as inert metabolites. 

Arosurf MSF was used in small amounts for several years in the late 80’s and early 90’s and is not

currently being sold. It is included here both for historical purposes and in the off chance that it might become

available again. As a surfactant, it forms a thin film over the surface of the water. Its mode of action is physical 

rather than chemical in that it reduces the water surface tension resulting in suffocation of the larvae and pupae. 

134
These nonionic surface-active films spread into uniform, nearly monomolecular layers, and can not be seen because 

they are too thin to absorb light or cause iridescence due to reflective interference. Periodic observations indicated 

that wind velocity as low as 2-3 mph can push the film over the water surface to the downwind side or corner of a 

pond within minutes after treatment, thereby establishing areas of highly compressed film and areas of essentially

no film (Levy et al. 1980). Average persistence for Arosurf MSF has been determined to be 2 to 10 days at

recommended dosage rates (Miller 1984). Monomolecular films are biodegradable and have shown no adverse 

effects on mammals and several species of vertebrate and invertebrate aquatic organisms so these materials should 

not pose a threat to the environment or a health hazard to man. 

An exemption from the requirement of a tolerance for the pesticide in or on fish, shellfish, irrigated crops, 

meat, milk, poultry and eggs, when used as a mosquito control agent in aquatic areas has been established under 40 

CFR 18Q.1078. Studies on closely related fatty acid and fatty alcohol ethoxylates having various degrees of 

ethoxylation supported the clearance of the chemical as an inert ingredient and were also used in support of the 

exemption as an active ingredient (EPA 1984). Arosurf MSF demonstrates low mammalian toxicity (category III). 

Isooctadecanol has demonstrated low toxicity to fish, birds and other wildlife and non-target organisms. Acute 

toxicity (96hr-LC50) of isooctadecanol to fish range from 98 ppm (rainbow trout) to 290 ppm for bluegill (Miller 

1984). 

Qualitative data on non-target animals and plants exposed to various dosages of Arosurf MSF during field 

trials to control mosquitoes have indicated that this film will cause little or no adverse effects to the environment. 

Some mortality of pupae and/or emerging adults of certain midge species (Chironomidae) breeding in aeration and 

decomposition ponds at sewage treatment systems was noted. However, significant mortality of midges was also 

observed in some control (untreated) sewage ponds containing a similar layer of natural surface scums. Therefore, 

the true impact of Arosurf MSF on the reduction of the midge population is not known. Adult dragonflies were 

observed to oviposit in water treated with Arosurf MSF and a Gambusia sp. was observed eating large lenses of 

floating Arosurf MSF with no apparent adverse affects. Field and laboratory tests indicated that predation and 

asexual reproduction of the mosquito planarian Dugesia dorotocephala (Woodworth) and the infectivity and 

development of the mosquito nematode Romanomermis culicivora (Ross and Smith) were not adversely affected by

Arosurf MSF at surface dosages of 0.4-0.5 ml/m2

. Although no quantitative data were obtained concerning the 

135
effects of Arosurf MSF on the natural populations of animals and plants, general observations indicated that there 

appeared to be few long-term effects (Ward 1966). 

Arosurf MSF was effective in reducing 3rd and 4th instars of Ae. nigromaculis and Ae. melanimon

populations at 0.5 and 1.0 ml/m2 surface rates, averaging 88% and 96% mortality reduction, respectively. Nontarget arthropods which showed acute lethal effects were corixids (Corisella spp.). Notonectids (Notonecta 

unifascfata), clam shrimp (Eulimnadia sp.), and Tropisternus lateralls beetle adults. Non-targets that did not

exhibit mortality were mayfly (Callibaetis spp.) naiads, chironomid larvae and copepods (Takahashi et al. 1984). 

Under field conditions, this film-forming substance produced a high level of control (90%+) of larvae and 

pupae of Cx. tarsalis at the rate of 0.5 to 0.75 gal/acre with no apparent effect on non-target organisms such as 

mayfly naiads, diving beetle adults, ostracods and copepods (Mulla et al. 1983). 

 d. Others 

Temephos (Abate) is a non-systemic insecticide used as a relatively selective larvicide against mosquitoes, 

midges, gnats, punkies sand flies, thrips and black flies (SCAMP 1987). It has not been used in Massachusetts for 

several years. It is non-phytotoxic when used as recommended but is not generally used on plants (Hartley & Kidd 

1983. SCAMP 1987). It has relative long residual action but short residual time in soils and water (SCAMP 1987). 

 In plants, temephos is oxidized to the sulfoxide and, to a lesser extent, to the sulfone and mono- and diorthophosphates. Further degradation proceeds very slowly (Hartley & Kidd 1983). In insects, the thiophosphate 

group and sulfur atom in the sulfide group of temephos undergoes a step wise oxidation. The oxidative compound 

is then hydrolyzed, and the final metabolite is 4,4'-dihydroxy diphenyl sulfone (Aizawa 1982). These reactions are 

highly species dependent which provides temephos's selective action. 

Temephos has some hazard to non-target and beneficial insect but is highly toxic to honeybees by direct 

contact (topical LD50 is 1.55 ug/bee). It is also hazardous to crustaceans such as shrimp and crabs (SCAMP 1987). 

At 100-1000 ppb, temephos causes some reduction in °2 evaluation by algae (Verschueren 1983). The 96 hr - LC50

for temephos to crustaceans range from 45-82 ppb and the median threshold limit (TLm) for shrimp range from 249 

ppb 2550 ppb. The LC50 values of temephos to non-target aquatic insects range from 1-2 ppb (Ephemeroptera) to

500-1000 ppb (Tricoptera) (1 hr-LC90-95). The 96hr-LC50 value for stoneflies is 10 ppb (Verschueren 1983). 

Temephos (Abate 4E) did reduce populations of copepods and cladocerans in a test in man-made ponds but the 

populations recovered within several weeks. Ostracods were not affected (Fortin et al 1987). 

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Temephos is stable when stored at room temperature, moderately stable to hydrolysis in contact with

aqueous alkali, but the rate of hydrolysis increases with pH. Optimum stability is at pH 5-7 with increased

hydrolysis occurring at 2>pH>9 at rates depending on temperature. Temephos may be oxidized to the sulfoxide, the 

sulfone, and the mono- and dioxygen analogs. The sulfoxides and sulfones of the oxygen analogs have not been 

observed. Hydrolysis products include the thiophenol and the corresponding sulfoxide and sulfone (Reed 1982). 

In a study using 3H-labeled temephos topically applied to bean plants, unchanged temephos comprised 

more than 70% of the terminal residues after 28 days. The sulfoxide comprised about 4% of the residues. The other 

oxidative metabolites were present in very small amounts. Conjugates of the hydrolysis products comprised the 

remaining residues. More than 90% of the applied activity remained after 28 days, indicating that residue decline is

primarily the result of growth dilution (Reed 1982). 

 In laboratory studies, temephos has a half-life of 108 days in aqueous media. However, temephos degrades 

more rapidly in samples of reservoir, polluted brook, and puddle waters with half-lives ranging from 9-32 days. 

Temophos rapidly photodegrades to the sulfoxide and then to other oxidative and hydrolytic products. Sanders et

al., (1981) reported concentrations ranging from 0.15 ug/l to 10 ug/l in small freshwater ponds 24 hr after 

application. Henry et al. (1971) measured temephos concentrations after simulating saltmarsh application rates (26 

to 131 ug/l) and reported disappearance rates as a function of temperature. Temephos concentrations ranging from

16 ug/l to 34 ug/l were found in stagnant ponds after application by helicopter, with a half-life of approximately 5 hr 

(Lores et al. 1985). Peak concentration of temephos in water during early May occurred within 1 hr of treatment of 

a 4 EC formulation (mean approx. 20 ug/l) and within 8 hr of treatment with the 2G formulation (mean approx. 9 

ugtl). The rate of degradation in water appeared to be affected by the initial solubility of temephos which is itself 

influenced by the application site, the water temperature and the formulation applied. These findings support a 

general half-life disappearance of 24 hr for the active ingredient under conditions found in local spring Aedes

breeding habitat (Mackenzie et al. 1983). 

Little data exists for soil degradation, but there are indications that certain soil bacteria are capable of

causing rapid degradation of temephos to water-soluble hydrolysis products. The mean peak concentrations of 

temephos residues in sediments were in the 250-500 ug/kg range following a single early spring application of 90-

100 g/ha and declined to negligible levels in 10 days (Mackenzie et al. 1983). 

137
From an animal metabolism study, data from cattle indicate that temephos and its sulfoxide are 

interconvertible in animals. The sulfoxide was present in the milk of cows fed 20 ppm temephos and temephos was 

present in the milk of cows fed 5 ppm of the sulfoxide (EPA 1986). All of the oxidative metabolite of temephos 

are expected ChE inhibitors, but terminal residues appear to consist primarily of temephos and its sulfoxide (EPA 

1981). When 3H-temephos was orally administered to rats, radioactivity reached a peak in the blood between 5 and 

8 hrs and then dissipated with a half-life of about 10 hrs. Appreciable radioactivity was found only in the 

gastrointestinal tract and fat. Both in feces and in fat, most of the activity came from unchanged insecticide, but 

small amounts of the sulfoxide were present also. While traces of temephos were found in the urine, the principal 

urinary metabolites were sulfate ester conjugates of 4,4'-thiodiphenol, 4,4'-sulfinyl-diphenol, and 4,4'-

sulfonyldiphenol. At least 10 other components could be extracted but were not identified. In the guinea pig, 

absorption apparently was less than in the rat, and biliary excretion of metabolites was demonstrated (Hayes 1982). 

Temephos was dermally applied to cattle as a 0.l% spray and the cattle were slaughtered 7, 14, 28, 42, and 

56 days after treatment. Temephos was not detected (<0.05 ppm) in any sample of muscle or liver, but was detected 

in the kidney at 0.08 and 0.13 ppm in 2 of the 3 animals slaughtered after 7 days. Temephos averaged 1.19 ppm in

the fat of the 3 animals killed at 7 days and declined thereafter with a half-life of 6 days. Temephos sulfoxide was 

detected at levels of 0.39 and 0.09 ppm only in the fat of cattle killed 7 and 14 days, respectively, after treatment. In

a study where 14C-labeled temephos was sprayed on lactating goats, residues in the back fat were predominantly

temephos. Residues in omental fat and milk were predominantly the sulfoxide with some sulfone and, in liver, 

residues of the sulfoxide and the sulfone were roughly equal. Other oxidative and hydrolytic metabolites were 

present in only small amounts. Therefore, metabolism and elimination of temephos is rapid with about 95% of a 

single oral dose eliminated in the urine and feces within 96 hours (EPA 1981). 

The acute oral toxicity (LD50) of temephos in rats is 770-13,000 mg/kg t8600 mg/kg), and 4000 mg/kg for 

mouse. Temephos has an acute dermal toxicity (LD50) for rabbit of 1300-1930 mg/kg and greater than 4000 mg/kg 

for rats (Hartley & Kidd 1983, Worthing & Walker 1983). Temephos and malathion showed an approximately

fourfold potentiation in rats when they are given together at levels approaching their LD50 values (Gaines et al. 

1967). However, under other conditions no potentiation was observed between temephos and 23 other organic 

phosphorus compounds (Levinskas & Shaffer 1970). Temephos has a TWATLV value of 10 mg/m3. The 

threshold limit value of 10 mg/m3 indicates that occupational intake at a rate of 1.4 mg/kg/day is considered safe. 

138
In a neurotoxicity study, hens were fed 230, 460, and 920 ppm temephos for 30 days. Microscopic 

examination of nerve tissues revealed no demyelination (Reed 1982). Temephos in a dosage of 500 mg/kg 

produced a rapid onset of leg weakness in chickens, from which survivors recovered within 36 days or less. An 

intake of 125 mg/kg produced very mild leg weakness, followed by prompt recovery. This sign was produced in 30 

days at a dosage of 15.3 mg/kg/day but not in 108 days at a level of 7.4 mg/kg/day (Gaines et al. 1967). Thus, the 

effect of temephos in chickens is similar to that of malathion, and the lack of myelin loss in hens fed the compound 

at a dietary level of 920 ppm (about 53 mg/kg/day) for 30 days, as reported by Levinskas & Shaffer (1970), would 

be expected (i.e., low OPIDN hazard). 

The subacute and chronic toxicity of temephos is detailed below. Temephos has been shown to inhibit

ChE activity in vivo. In rats, subchronic oral doses as low as 6 ppm resulted in depressed red blood cell ChE 

activity. In dogs, subchronic oral doses of 500-700 ppm caused depressed red blood cell, plasma, and brain ChE 

activities. Subchronic oral dosing with temephos caused no observed effect on survival, food consumption, or 

tissue and organ histopathology in rats given up to 350 ppm in the diet, and in dogs given 500 or 700 ppm in the 

diet for 90 days. Weight gain was reduced in rats given 350 ppm in the diet. In a 30-day study with male rats fed 0, 

250, 500, and 1000 ppm technical temephos, the NOEL was 250 ppm (which is equivalent to 12.5 mg/kg B.W./day) 

for any effect other than ChE inhibition, which was noted at all dose levels. Weight gain depression was the effect

noted at 500 ppm and above. No adverse effects were noted at feeding levels up to 300 ppm in a 2-year rat study. 

However, ChE activities were not measured (EPA 1981). 

Over a 90-day period, rats tolerated a diet containing 9 ppm of the sulfoxide with no apparent effect except

inhibition of RBC ChE activity. No inhibition occurred at 3 ppm (Levinskas and Shaffer 1970). In a study with 

human volunteers, increasing doses of temephos (2 to 256 mg/day) or constant doses of 64 mg/day were ingested 

over a four week period. No alterations in red blood cell or plasma ChE activity and no clinical symptoms were 

observed (EPA 1981). 

The reproductive and teratogenic effects of temephos are as follows. Male and female rats were started on 

diets containing 500 ppm temephos at mating. Dosage was maintained throughout mating, gestation, parturition, 

and lactation. There were no significant differences in number of litters produced, litter size, viability of young or 

the incidence of congenital defects between treated and control groups even though the dosage caused signs of 

poisoning in some rats (Gaines et al. 1967). In a second reproduction study, no compound-related effects on 

139
reproductive capacity were noted in rats fed 25 or 125 ppm of temephos. No effects were noted in the offspring 

(EPA 1981). Temephos at oral dosage levels as high as 2.5 mg/kg/day for 422 days or at 5 mg/kg/day for 186 days

caused no ill effects in sheep or their lambs (McCarty et al. 1968). 

No oncogenic effects were noted in a 2-year study with rats fed 0, 10, l00, and 300 ppm. There exists no 

mutagenicity data for temephos. The EPA Registration Standard for temephos states that toxicological data gaps 

related to reregistration of temephos for the food uses are a second oncogenicity study (in mouse) and teratogenicity

and mutagenicity testing. 

Acute toxicity (96hr-LC50) of temephos in a variety of fish species range from 0.16 ppm (rainbow trout) 

to 34.1 ppm (fathead minnow). Test conditions and size did not appreciably change the toxicity of temephos to fish. 

 Variations in pH from 6.0 to 9.0, hardness from 40 to 162 ppm, or size from 1 to 20 g gave a range of less than 4 

mg/1 in 96hr-LC50 values. Flow-through tests for up to 15 days with cut-throat trout and lake trout produced 

TILC50 (time-independent LC50) values for temephos of 0.20 and 1.05 mg/1 (ppm) and cumulative toxicity indices 

(96hr-LC50 value divided by TILC50 value) of 5.0 and 1.0, respectively. This indicates little or no cumulative action

of temephos in fish (Johnson & Finley 1980). 

Following the treatment of the Upper Volta River with Abate for the control of Simulium larvae, no fish

died, but fish in the treated area were prone to easy capture. The catch per unit effort, and the number of species 

captured in the 24-hr period following treatment, were higher. Evidently, sublethal stress leading to under- or 

hyper-activity, make the fish an easy prey in nature and affect the stability of the population. When Abate was 

applied to River Oti in Ghana to control Simulium larvae, fish 300 m upstream from the point of application were 

normal, whereas fish at the site of application swam erratically. Fewer numbers and species were collected in the 

24-hr period following application than before application, suggesting possible avoidance reaction of fish to Abate. 

Exposure to 96hr-LC50 of fenitrothion for 24 hr completely inhibited the learning ability of salmon perr; Abate at 5

mg/l retarded learning (Murty, Vol. II, 1986). 

Acute oral toxicity (LD50) of temephos for the bullfrog is greater than 2000 ppm (Smith 1987). 

Acute oral toxicity (LD50) of temephos for a variety of birds ranges from 18.9 ppm (California quail) to

270 ppm (chukar). Its dietary LC50 values range from 92 ppm (northern bobwhite) to 894 ppm (mallard duck). 

There are few data on its dermal toxicity. Mallard ducklings (12-24 hr of age) were fed diets treated with temephos 

140
for 7 days and housed in either heated or unheated brooders. High mortality occurred in the 100 ppm group housed 

in unheated brooders, but diets containing up to 10 ppm did not affect duckling survival (Fleming et al. 1985). 

A reproductive study conducted with game-farm mallards fed 0, 1, and 10 ppm Abate 4E (temephos) did 

not result in treatment effects for hatching success, clutch size, fertility, nest attentiveness of incubating hens, and

duckling avoidance behavior. However, the mean interval between eggs laid was greater for the 10 ppm group, and 

duckling survival to 21 days was significantly lower for both treatment groups than for controls (Franson et al. 

1983). 

There have been no published accounts of wildlife die-offs that have been related to field applications of 

temephos (Smith 1987). However, the 30-day EMLD (empirical minimum lethal dose, lowest daily oral dosage that

produces 1-2 deaths over a 30 day period) for mallards (n - 22) is 2.5 mg/kg per day for both sexes. The resulting 

cumulative toxicity index for temephos is 79.4/2.5 - 32, indicating a high degree of cumulative action for an 

organophosphate in birds (Hudson et al. 1984). 

3. Adulticides 

a. Pyrethrum and Synthetic Pyrethroids 

Pyrethrin I is insoluble in water, has appreciable vapor pressure but an extremely large partition coefficient 

(KoW) indicating that it is immobile in soil and migrants slowly, if at all. It is unstable in sunlight and rapidly 

hydrolyzed by alkali with loss of insecticidal properties. Photodecomposition of pyrethrin I as thin films on glass 

yields 11-15 products, none of which are insecticidal or of toxicological significance. Saponification 

(alkalihydro1ysis) of the pyrethrum mixture of ester products liberates 12-16 acids, again with the subsequent loss 

of insecticidal activity. 

 Many invertebrates and microorganisms are capable of metabolically detoxifying this natural insecticide. 

Although the levels of Pyrethrin I in water, air, and soil are not known, little is expected to persist because of its 

photolabile and biodegradable nature. 

 Similar to pyrethrin I, resmethrin decomposes rapidly on exposure to air and sunlight and is unstable in

alkaline media. However, photolysis of the ester bond is a significant reaction for trans- and cis-resmethrin but 

apparently not for pyrethrin I. Resmethrin and other type I pyrethroids generally yield a large number and great

variety of photoproducts, most of which originate from further reactions of the primary cleavage products. For 

example, the alcohol moiety liberated on photolysis of resmethrin degrades further to benzyl alcohol, benzaldehyde, 

141
benzoic acid and phenylacetic acid, the latter contributing to the unpleasant odor of photodecomposed resmethrin. 

The environmental and toxicological impact of these breakdown products are unknown at this time but due to the 

low rates and quantities used in mosquito control, they are not expected to be particularly significant. 

 As with pyrethrin I, resmethrin is rapidly biodegraded by invertebrates and microorganisms by established 

metabolic pathways. Although the levels of resmethrin in water, air, and soil are not known, little is expected to 

persist because of its photolabile and biodegradable nature. 

Pyrethrins are potent, non-systemic contact insecticides causing rapid paralysis and knockdown with death 

occurring at a later stage of intoxication. Insecticidal activity is markedly increased by the addition of synergists 

such as PBO. Pyrethrins are not phytotoxic. Although toxic to bees, pyrethrins show less hazard than indicated by 

topical bioassays (approximately 1 ug/housefly) due to their repellent effect (Hartley & Kidd 1983). Pyrethrins are 

degraded in the environment by sunlight, chemical hydrolysis and by many invertebrate organisms via hydrolytic

and oxidative metabolism. The approximate residual period for pyrethrins is 1-3 days on plants and similar short

duration in soil and water (SCAMP 1987). No biological magnification has been shown. Degradative products

have not been determined to be as toxic or more toxic than the parent pyrethrin compounds. Its toxicity (96hr-LC50) 

to crustaceans range from 11 to 42 ppb and for nontarget aquatic insects approximately 1.0 ppb (Verschueren 1983). 

The synthetic pyrethroid resmethrin is also a non-systemic, contact insecticide with fast knockdown similar 

in action to the natural pyrethrins (Hartley & Kidd 1983). Although sometimes formulated with synergists (e.g., 

piperonyl butoxide), resmethrin's toxicity is not enhanced in their presence (SCAMP 1987). Resmethrin is not

phytotoxic if used as recommended. Resmethrin is toxic to bees, but field data indicates that ULV sprays of 

resmethrin are not hazardous to honeybee colonies in the area treated for adult mosquito control (Scourge Tech. 

Bull. 1986). Daphnia magna has an LC50 of 0.1 ppm (48 hr), Penaeus shrimp 1.25 ppb and the American oyster 

1.79 ppm. 

Piperonyl butoxide (3,4-methylene-dioxy-6propylbenzyl(heptyl) diethylene glycol ether) is used as a 

synergist in conjunction with pyrethrins and pyrethroids such as resmethrin. It is relatively stable to hydrolysis and

UV irradiation. It is not toxic to bees or other beneficial insects and is degraded by invertebrates by oxidative attack 

on the carbon atom of the methylenedioxy group forming dihydroxyphenyl compound. Side-chain oxidations also 

occur. Elimination is by glucoside or amino acid conjugations (SCAMP 1987, Hayes 1982). 

142
Pyrethrum and the synthetic pyrethroid resmethrin share a common mode of action as direct nerve toxins 

which interfere with nerve impulse generation via modulation of voltage-gated ion channels, particularly sodium

and possibly calcium channels (Narahashi 1987, Clark & Brooks 1988). 

As summarized by Hayes (1982), pyrethrum may be absorbed from the gastrointestinal tract and by the 

respiratory route. It is not absorbed to a significant degree through the skin. However, allergic reactions may result 

from this route of exposure. The esters constituting pyrethrum mixtures are rapidly detoxified by hydrolysis in the 

gastrointestinal tract and to some extent in the tissues of adult warm-blooded animals. The chrysanthemum

monocarboxylic acid formed is excreted in the urine. Pyrethrins or their metabolites are not known to be stored in 

the body or to be excreted in the milk, but no study of the matter has employed modern methods. Partly because of 

their ready excretion, these compounds exhibit little clinical effect in animals following repeated exposure to 

moderate doses, but they or their metabolites do lead to liver changes in rats. Studies describe the very extensive 

metabolism that pyrethrins undergo, mainly in the liver. Various active ingredients undergo significantly different

biotransformation. For example, within 48 hours of oral administration of 14C-pyrethrin II to rats, 53% of the 14C 

was recovered as exhaled C02, whereas only 0.3% of 14C pyrethrin I was recovered in that form under the same

circumstances. The corresponding proportions of 14C recovered from the urine were 7 and 46%, for pyrethrins II 

and I, respectively. Some of the orally administered material is excreted in the feces, at least partially in 

metabolized form. Three compounds have been isolated from urine and identified by NMR and mass spectra. All

three are produced by both pyrethrin I and II. All three are the result of oxidation of both the acid and alcoholic

moieties leaving the main structure of the molecule intact (Elliott et al. 1972a, 1972b). So far the numerous 

compounds that result from hydrolysis of the esters have not been identified. The fact that the most severe cases of 

poisoning have been reported in infants suggests that very young children may not hydrolyze the pyrethrum esters 

efficiently. In any event, mammals show approximately the same susceptibility to injected pyrethrins as do coldblooded animals, including insects (Gaudin 1937). 

Acute oral LD50 values of pyrethrum in rats range from 584- 1500 mg/kg, 272-796 mg/kg for mice and 

1500 mg/kg for rabbit (Farm Chemical Handbook 1988, Hartley & Kidd 1983, Hayes 1982). Lehman (1952) 

estimated that the fatal human dose might be 100 grams (1430 mg/kg) for a 70-kg man. Acute dermal LD50 values 

for rats are greater than 1500 mg/kg and for rabbits 5000 mg/kg. Dermatitis is possible in sensitive individuals from

constituents of the flowers. Rats and dogs inhaled a concentration of 16 mg/m3

 of pyrethrins for 30 min. periods 

143
during 31 calendar days with only slight lung irritation (SCAMP 1987). Inhalation of pyrethrum at 6000 mg/m3

 for 

30 min. caused only moderate lung congestion (Carpenter et al. 1980). 

The subacute and chronic toxicity of pyrethrum is also low. Groups of 12 male and 12 female rats were 

fed pyrethrin in soybean oil at dietary levels of 0, 200, 1,000, and 5,000 ppm for 2 years. The daily dosages were, 

therefore, approximately 0, 10, 50, and 250 mg/kg, respectively. Even at the highest level pyrethrin had no 

significant effect on growth or survival. A slight though definite liver damage was observed, especially at the 

higher dosage levels (Lehman 1965). Dogs fed pyrethrins at a dietary level of 5,000 ppm for 90 days showed 

tremor, ataxia, labored respiration, and salivation during the first month of exposure (Griffin 1973). Ambrose & 

Robbins (1951) reported no effect in rats fed pyrethrins at a dietary level of 1000 ppm for two years, but tissue 

damage and gross signs of intoxication appeared at 5000 ppm. When pyrethrins were fed to rats at a dietary level of 

1,000 or 5,000 ppm for 2 years, the liver lesions included bile duct proliferation and focal necrosis of the liver cells

(Lehman 1965). Pyrethrins, especially synergized pyrethrins, produced enlargement, margination, and cytoplasmic 

inclusions in the liver cells of rats. At a dietary level of 1,000 ppm, pyrethrins and 10,000 ppm piperonyl butoxide, 

the changes were well developed in only 8 days, but were not maximal. The changes were proportional to dosage 

and similar to those produced by DDT. The effects of the two materials were additive (Kimbrough et al. 1968). No 

relevant pathology was detected in rats fed pyrethrins at a dietary level of 8,000 ppm for 5 weeks (Griffin 1973). 

The sensitizing property of pyrethrins is apparently more evident in humans than in other animal 

vertebrates (Hayes 1982). When 200 people (177 women and 23 men) were patch tested with a 1% water 

dispersion of pyrethrins, no evidence of primary irritancy or of sensitization was found (unpublished report cited by

FAO/WHO 1971). It must be noted, however, that both the formulation used and the duration of exposure were 

different from those that have caused the most severe dermatitis or sensitivity of any kind under practical conditions 

of exposure. There is little doubt that commercially available pyrethrin extracts are less sensitizing than native 

pyrethrum. However, apparently no study has been made to measure the difference in way that would be 

statistically valid. Mitchell et al., (1972) found all the active ingredients of pyrethrum, except pyrethin II, to be 

inactive on patch test in a patient who had a history of allergenic dermatitis to pyrethrum and who reacted positively 

to pyrethrum flower heads, powder extracts of the plant, and pyrethrosin. The no-effect level corresponds to a rate

of 3600 mg/man/day (SCAMP 1987). 

144
Pyrethrum has little or no reproductive or teratogenic hazard (Hayes 1982). Rabbits that received 

pyrethrins orally on days 8 to 16 of gestation at dosages as high as 90 mg/kg produced litters with no statistical 

increase in abnormalities (unpublished report cited by FAO/WHO 1971). When rats were fed pyrethrins at a dietary 

level of 5,000 ppm beginning 3 weeks before first mating, reproductive performance was not reduced, but the 

weights of weanlings were significantly lower than those of controls (Griffin 1973). 

 The synthetic compounds are more photostable, sometimes providing control for many weeks following a 

single field application. In addition, some of the synthetic pyrethroids are metabolized more slowly by both insects 

and mammals and hence have increased toxicity. Enhanced environmental and biological stability of these 

compounds have triggered needs for residue analysis and for understanding their potential toxicity to mammals

(Marquis 1986). 

Resmethrin was one of the first or "early" pyrethroid synthesized which is not halogenated nor does it

contain a cyanophenoxybenzyl alcohol. Thus, its metabolism and pharmacokinetics are more similar to the 

pyrethrins than the more stable type II pyrethroids (e.g., fenvaleratte, cypermethrin, deltamethrin). 

Resmethrin has an acute oral LD50 οf 2700 mg/kg in rats and 4250 mg/kg in rats exposed to technical

resmethrin (SBP-1382). The dermal LD50 value in rabbits is greater than 2000 mg/kg and greater than 3000 mg/kg 

in rats. Resmethrin was found to be non-irritating to skin and eyes (rabbits). SBP1382 is classified as a very mild

conjunctival irritant. The inhalation (4 hr) for rats and dogs is established at greater than 9.49 g/m3

. No effect level 

was 420 mg/m3 (4 hr). The NOEL in rats for a subchronic inhalation study (90 days) is 0.1 g/m3

. 

In 90 day feeding trials, rats receiving 3000 mg resmethrin/kg diet showed no ill effects. The NOEL (no 

observable effect level) for resmethrin in a 180-day subchronic feeding study in dogs is 10 mg/kg/day.

In three generation reproduction tests for resmethrin, the NOEL for rats is 500 ppm. No teratogenic effects 

are observed in rats receiving resmethrin at dosages up to 80 mg/kg/day, up to 25 mg/kg/day for rabbits and up to 

50 mg/kg/day for mice. The NOEL for fetotoxicity is 40 mg/kg/day.

Although limited, two studies support the contention that resmethrin has little carcinogenicity hazard. In 

an 85-week mouse feeding/oncongenicity study, SBP-1382 was not oncongenic at 1000 ppm. In a 2-yr rat chronic 

feeding/ oncogneicity study, SBP-1382 was not oncogenic at 5000 ppm, the highest dose tested. The above data

have been compiled from the following sources: Hartley & Kidd 1983, Worthing & Walker 1983, SCAMP 1987, 

145
Penick-Bio UCLAF Corp. 1986. Although overall evidence for chronic toxicity in mammals is limited, 

pyrethrin/pyrethroids still represents one of the safest classes of pesticides present available. 

Because piperonyl butoxide (PBO) is included in various pyrethrum and pyrethroid (i.e., resmethrin) 

products used for mosquito control, the following mammalian toxicology is included. The acute oral toxicity (LD50) 

for PBO in various mammal range from 3800 mg/kg (mouse) to 11,502 mg/kg in rat. Dermal LD50 for PBO in 

rabbit is greater than 1880 mg/kg. Although dermal absorption is poor, multiple inunction at 200 mg/kg may be 

fatal to animals. In a subchronic feeding study, rats tolerated without harmful effects 5000 ppm in the diet for 17 

weeks; 10,000 ppm were endured through 3 successive generations with moderate toxic effects and; 25,000 ppm in 

the diet were fatal to rats in from 4 to 46 weeks. In 2-yr chronic feeding trials, rats receiving 100 mg/kg diet 

suffered no ill-effect. PBO is noncarcinogenic and the safe human tolerance for chronic ingestion is estimated at 42 

mg/kg diet (Negherbon 1959, Worthing & Walker 1983). 

Pyrethrins (pyrethrum) are highly toxic to fish (Hartley & Kidd 1983). Acute toxicity of pyrethrum as 

judged by 96hr-LC50 ranged from 13 ppb (channel catfish) to 58 ppb (bluegill). Temperature and pH of test 

solutions affected the biological activity of natural pyrethrins. Toxicity to channel catfish was 12-fold higher at

18°C than at 12°C. Toxicity increased in acid water (low pH); the 96hr-LC50 for bluegills was 41 ug/l (ppb) at pH 

6.5 and 87 ug/l (ppb) at pH 9.5. Water hardness (44-314 ppm) had little influence on toxicity (Johnson and Finley 

1980). Excellent control of larvae of Cx. tarsalis in experimental ponds was obtained at the rate of 1 pyrethrin 

tossits/ m2 (44 B ai/ha). At the same rate, satisfactory control (92%) of Cx. peus larvae was obtained in dairy

waste-water lagoons in Riverside County, Ca. At the effective mosquito larvicidal rate (44 g/ha), mosquito fish, G. 

affinis, was affected when some tossits were placed with the fish in 0.9 m3

 screened cages. Five successive weekly 

treatments of G. affinis at the larvicidal rate and double that rate (44 and 88 g/ha) resulted in 37% and 67 % 

reduction of fish yield harvested 42 days after the first treatment compared to the yield obtained from the untreated 

ponds (controls), respectively. No marked effects on some of the non-target organisms such as dragonfly naiads, 

ostracoda, copepods, and Dixa midge larvae were noted. Mayfly naiads were eliminated at all rates applied, but

recovered within 2-3 weeks after treatment. 

Pyrethroids have very high insecticidal activity and have found wide use in the last few years. Though 

they are not persistent in the environment, their acute toxicity to fish is high. The cyano-substitution of the 

phenoxybenzyl alcohol moiety (as in cypermethrin and fenvalerate) enhances the toxicity of pyrethroids to fish. 

146
Similarly, pyrethroids with (lR)-cis-isomers for the acid moiety are more lethal than the corresponding cis-,transracemates. Fenvalerate and permethrin are more toxic than many OC compounds, the 96hr-LC50 being 0.5 to 12.0 

ug/l (ppb). Cold water fish were reportedly more susceptible than warm water fish to natural permethrins as well as 

synthetic pyrethroids. 

Pyrethroids are metabolized in fish by both hydrolytic and oxidative processes. It appears that, in general,

esterases are more important in metabolizing the trans-chrysanthemates of primary alcohols whereas oxidases are 

more important with the cis-chrysanthemates of primary alcohols. Pyrethroids are rapidly metabolized by fish 

(Murty, Vol. II 1986). Resmethrin (SBP-1382) is toxic to fish (Hartley & Kidd 1983) with an acute toxicity (96hrLC50) to freshwater fish ranging from 1.7 ppb (lake trout, bluegill) to 16.6 ppb (channel cat fish) (Johnson and 

Finley 1980). Resmethrin has a 96hrLC50 value of greater than 150 ppb for coho salmon (Verschueren 1983). 

Resmethrin was the least toxic pyrethroid against frogs (Rana pipiens pipiens) with a subcutaneous LD50 value of 

greater than 60 ppm (Cole and Casida 1983). 

The acute oral toxicity of resmethrin to California quail has been determined to be much greater than 2000 

ppm (Johnson and Finley 1980). 

 b. Malathion

Malathion is a non-systemic insecticide and acaricide that acts as a cholinesterase inhibitor. It is generally 

non-phytotoxic but may damage glasshouse cucumber, beans and certain ornamentals. Some varieties of apple, 

pear and grape may also be injured (Hartley & Kidd 1983). Its approximate residual period on plants is 5-10 days

but has a short residual time in soils. Malathion is rapidly degraded in vitro by saltmarsh bacteria to malathion

monocarboxylic acid (monoacid), malathion dicarboxylic acid (diacid) and various phosphothionates as a result of 

carboxyesterase cleavage. In addition, some expected phosphatase activity produces desmethyl malathion, 

phosphomono- and phospho-dithionates, 4-carbon dicarboxylic acids and the corresponding ethylesters 

(Verschueren 1983). In insects, malaoxon is the major metabolite formed by oxidative desulfuration at about 25% 

of all total. Predominant degradation is caused by hydrolysis in insects (Aizawa 1982). Biological magnification of 

malathion is not likely (SCAMP 1987). 

Malathion presents some toxicity to beneficial insects including honey bees (Hartley & Kidd 1983). The 

topical LD50 for honey bees is 0.71 ug/bee (SCAMP 1987). The 96 hr-LC50 for non-target aquatic insects range 

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from 1.1 to 10 ppb, and for crustaceans 0.76 ppb to 3000 ppb. The median tolerance limit (TLm) for the American 

oyster is 9070 ppb (48 hr) for egg and 2600 ppb (14d) for larval (Verschueren 1983). 

Degradation of malathion in soil is quite rapid. It was found that after the application of malathion at 5 

lb/acre only 15% of the applied dosage was recovered 3 days later. After 1 week, 95% of the applied malathion had 

disappeared. In Ludhiana, Palamput, and Kamma soils, malathion was 100% degraded 4 days with higher 

temperatures producing more rapid degradation (Laveglia & Dahm 1977). 

 Walker & Stojanovic (1973) also found that malathion was quite stable under neutral or acid pH conditions 

and that susceptibility to hydrolysis increased with increasing alkalinity. They demonstrated that malathion

disappeared more rapidly under nonsterile than sterile conditions and indicated that malathion disappearance is 

stimulated by various microbiological systems in soil. Under sterile conditions, the observed malathion remaining 

in the Trinity loam, Okolona clay, and Freestone sandy loam after 10 days of incubation was 91%, 77% and 95%, 

respectively. In nonsterile soil, complete disappearance of malathion had occurred. Getzin and Rosefield studied 

the degradation of malathion in nonsterile, heat-sterilized, and gamma-sterilized soil. After 1 day, 97% of the 

malathion was degraded in the nonsterile soil, 90% in the irradiated soil, and only 7% in the autoclaved soil. 

Because of the rapid degradation in nonsterile soil, it was suggested that microorganisms were partly responsible for 

the degradation of the compounds. The difference between the amount of malathion decomposed in irradiated soil

and autoclaved soil was attributed to nonviable, heat-labile substances. A stable, heat-labile enzyme, which 

catalyzed the hydrolysis of malathion to its monoacid, was partially purified. This esterase was extracted from

irradiation-sterilized soil as well as from nonirradiated soil. When the partly purified enzyme was applied to the 

soil, it possessed many of the characteristics necessary for prolonged activity in a cell-free state in soil. It was less 

heat-labile than most enzymes, lost little or no activity upon prolonged storage, and survived desiccation in the soil. 

 There have been many reports of microorganisms metabolizing malathion to various products. Carboxyesterase 

activity, which degrades malathion to its monoacid and diacid, is the predominant degradative pathway. 

Phosphatase activity also has been reported. Oxidative desulfuration and demethylation seem to be rather minor 

metabolic routes (Laveglia & Dahm 1977). 

Walker (1976) reported that malathion dissipated rapidly in both sterile and nonsterile water in that only

3% of the added insecticide could be detected after 18 days incubation. The similarities between malathion

degradation in the presence and absence of biologically active systems dictates that malathion disappearance is by

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purely chemical mechanisms. The effect of salinity on the degradation of malathion in estuarine water was 

determined by incubating the insecticide in sterilized seawater varying in salinity from O to 25 ppt. The 

degradation of malathion was found to be directly proportional to the length of incubation and to increasing salinity

in this sterile system indicating direct chemical hydrolysis. 

The organophosphate insecticides included in this classification share a common mode of action as potent

indirect nerve toxins via inhibition of cholinesterases (ChE). 

Acetylcholine (ACh), the neurotransmitter secreted by cholinergic neurons, allows for chemical 

transmission of nerve impulses across the synapse. Acetylcholinesterase (AChE) is the enzyme responsible for the 

breakdown of ACh, thereby terminating the electochemical connection between two nerve cells. Organophosphorus 

insecticides (OP) phosphorylate AChE in an irreversible reaction that inhibits the activity of AChE to hydrolyze the 

neurotransmitter at the nerve synapse. The accumulation of ACh results in continuous nerve firing and eventual 

failure of nerve impulse propagation. Respiratory paralysis is generally the immediate cause of death. Brain ChE 

activity is used in the diagnosis of OP poisoning with a reduction of 20% of normal activity indicating exposure. A 

ChE inhibition of 50% or more is considered the diagnostic threshold for determining the cause of death. Because 

of the irreversible nature of the pesticide-enzyme binding reaction characteristic of OP poisoning, recovery from a 

sublethal OP exposure depends on synthesis of more ChE. There is evidence that recovery of ChE activity in

plasma is as fast or faster than in the brain (Hayes 1982). 

In addition to anticholinesterase activity, some OP pesticides have other adverse biochemical effects. A 

number of have been determined to inhibit neurotoxic esterase, an enzyme that has not been isolated and whose 

biochemical and physiological functions in nerve tissue are unknown (Metcalf 1982). Organophosphate-Induced 

Delayed Neuropathy (OPIDN) has been recently reviewed (Marquis 1986). Little information is available on 

delayed neurotoxicity in wildlife species. However, species differences can be great and the capacity to produce 

delayed neurotoxicity is widespread among OP (Metcalf 1982). 

Other sublethal biochemical effects have been described for OP, such as impaired reproduction in birds 

through possible hormonal effects and reduced tolerance to cold stress (Rattner et al. 1982a, 1982b). 

Embryotoxicity and teratogenic effects have been demonstrated for some OP (Hoffman & Albers 1983), and some

have been shown to cause changes in brooding behavior or nest attentiveness of birds which could result in death of 

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the young (Grue et al. 1983, Smith 1987). Central nervous system toxicity and noncholinergic effects of OP in

mammals have been recently reviewed by Marquis (1986). 

As summarized by Hayes (1982), the most striking difference between the metabolism of malathion and 

that of the majority of organic phosphorus compounds used as insecticides depends on the presence of two carboxy

groups in malathion. Malathion is subject to the various kinds of metabolism that other organic phosphorus 

insecticides undergo, but the splitting of either carboxyester linkage renders the compound non-toxic. Details of the 

metabolism have been reported by O'Brien (1960) and by Heath (1961). 

The excretion of absorbed malathion is rapid. When 25 mg of 14C-labeled malathion was administered to

each of six male rats, activity appeared in the urine within 2 hr, and 91.72% was eliminated within 24 hr while an 

additional 7.75% remained in the gastrointestinal contents. Excretion was mainly via the urine (83.44%) and partly

by the feces (5.51%), but 2.77% was exhaled as carbon dioxide. No unmetabolized malathion could be detected 8 

hrs after dosing (Bourke et al. 1968). In in vitro studies of human and rat liver, no important difference was found 

in ability to degrade malathion (Matsumura & Ward 1966) concentrations of 1 ug/l (ppb) of methoxychlor or MDE, 

Daphnia exposed for three generations grew and reproduced normally, but the emergence of mayfly nymphs was 

drastically reduced. In ponds treated with 10 to 40 ug/l (ppb) of methoxychlor, the total number of benthic 

organisms increased and species composition changed with chironomids becoming the dominant species. Neither 

survival nor growth of bluegills in the treated ponds was affected. However, most of the fish examined showed 

nonspecific liver degeneration and an accumulation of a muco- or glyco-proteinaceous material inside the major 

blood vessels. Regression of these effects had occurred by 56 days after treatment (Johnson & Finley 1980). 

Greater sensitivity of young striped mullet than older juveniles to methoxychlor has been reported. Adult 

striped mullets had larger amounts of the residues, owing to the presence of a relatively higher percentage of body

fat in the adult when compared with the juveniles. That it is the lipid content that confers a greater degree of 

tolerance of the larger fish to the DDT-type compounds is confirmed by the toxic concentrations of DDT, endrin, 

and malathion, to brook trout, cut-throat trout, and coho salmon of 1-g size and 1- to 2-g size. With DDT and 

endrin, there was reduction in the toxicity with in-crease in size, whereas no such difference in the toxicity of

malathion to smaller and larger fish was found. Exposure to a 96hr-LC50 value of fenitrothion for 24 hr completely

inhibited the learning ability of salmon parr and Abate at 5 mg/l retarded learning. DDT (OC) at 0.07 mg/l mildly 

enhanced learning whereas methoxychlor had no effect (Murty, Vol II, 1986). 

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Organophosphate insecticides have negligible chronic toxicity, but some have moderate to high acute

toxicity in fish. The 96hr-LC50 of several organophosphate compounds to various species of North American 

freshwater fish are listed below: 

The acute toxicity (96hr-LC50) of malathion for a variety of fish species ranged from 62 ppb (red ear 

sunfish) to 12,900 ppb (black bullhead). In lake trout, fry (0.3 g) were twice as sensitive as fingerlings (4.5 g) to 

malathion. An increase in temperature from 10° to 21°C caused an 11-fold decrease in toxicity to the daphnid 

Simocephalus. However, an increase from 7° to 29°C caused a fourfold increase in toxicity to bluegills. Variations

in water hardness did not appreciably alter the toxicity to fish or invertebrates. Mixtures of malathion with Baytex 

(fenthion), parathion, EPN, Perthane (ethylan), or carbaryl were synergistic in their toxicity to rainbow trout and 

bluegills. Combinations of malathion with DDT or toxaphene were only additive. Malathion has more-thanadditive toxicity with more than half of the pesticides with which it was combined (Murty 1986) and is no longer 

used as a larvicide in Massachusetts. 

Organophosphate compounds, because of their relatively higher water solubility, are in general taken up 

to lesser extent than organochlorines and eliminated faster. The time for achieving the highest levels of uptake and 

the extent of retention of OP residues by fish was directly related to the extent of persistence of a compound in

water. Motsugo fish exposed to 0.6 to 1.2 ppm malathion, attained the highest body concentrations 2.4 mg/kg of 

malathion after 1 day. No malathion residues were found 24 hr after the exposure of pinfish to 75 ppb 

concentration. Only malathion monoacid was recorded in the gut (Murty 1986). With DDT and endrin, there was 

reduction in the toxicity with increase in size, whereas no such difference in the toxicity of malathion to smaller and

larger fish was found. The natural degradation products of pesticides, in general, are less toxic than the parent

compounds. But occasionally, the primary degradation product may be more toxic. The hydrolysis product of 

malathion, diethyl fumarate, was more toxic than the parent compound to the fathead minnows (Murty 1986). 

Acute oral toxicity (LD50) of malathion is 4100 mg/kg for rabbits and greater than 4000 mg/kg for rats

(Hartley & Kidd 1983, Worthing & Walker 1983, Smith 1987). 

Based upon the low toxicity of this compound, it would appear that a time-weighted average TLV of 10 

mg/m3 is sufficiently low to prevent systemic effects (Hartley & Kidd 1983). Workers exposed to 84.8 mg/m3 

experienced moderate eye irritation (SCAMP 1987). Hollingsworth has established a VSR for malathion of 38 

(Wilkinson 1976). 

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Under subacute and chronic experimental conditions, malathion has been fed to rats for 104 weeks at levels

as high as 5000 ppm in the diet with no gross effects. In 1.75 yr trials rats receiving 100 mg tech./kg diet showed 

normal weight gain. There was no effect found on blood ChE when malathion was fed to human volunteers for 47 

days at the rate of 16 mg/man/day. Volunteers dosed dermally showed no change of blood ChE or other injury

while exceeding an average of 47 mg/man/day and a maximum of 220 mg/man/day. 

Whereas there is no evidence that malathion is teratogenic in mammals, it does cause a characteristic 

syndrome of deformity in chickens that apparently depends on tryptophan metabolism and may be peculiar to the 

egg, which is closed system (Hayes 1982). When 1.17 to 29.20 mg of malathion was injected directly into the yolk

of each egg, it often killed the embryo and deformed many of those that survived. When injections were made on 

days 8 to 12, half of the survivors lacked feathers or had only a few feathers on the abdominal region. When 

injections were made on days 6 or 7, 95% of the survivors were smaller than normal. When injections were made

on days 4 or 5, the legs were half the proper size and the phalanges were permanently flexed in 95% of the 

survivors, and the maxilla was curved downward over the shortened mandible in 50% of cases. All of the hatched

chicks had abnormal feathers, and some lacked feathers completely or in some areas. Most of the hatched chicks 

were about two-thirds normal size, and 6% were only one-fourth normal size (Greenberg & LaHam 1969). 

Tryptophan prevented the hind limb, beak, and feather defects and overall growth retardation in malathion-dosed 

embryos (Greenberg & LaHam, 1970). Application of 0.1 ml of 0.2 M nicotinamide or 0.1 ml of 0.1 M tryptophan 

simultaneously with malathion prevented development of the syndrome in all survivors, although the nicotinamide 

increased mortality. Tryptophan was also effective when injected into the yolk, and it was not toxic. It was 

speculated that malathion interferes with mobilization of tryptophan from yolk proteins, consequently decreasing 

synthesis of nicotinamide, which is essential for pyridine nucleotide-dependent reactions involved in differentiation 

of legs, beak, feathers, and other organs. Deformities of chicks can also be produced by feeding malathion to laying 

hens for 3 weeks at dietary concentrations up to 600 ppm (Ghadiri et al. 1967). However, the most likely problem

for poultry is not teratogenicity but simple toxicity. 

The hatchability of eggs was reduced when the hens were fed dietary levels of 1.0 ppm or higher but not

0.1 ppm (about 0.0058 mg/kg/day) (Sauter & Steele 1972). 

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Although malathion has been reported to produce delayed neuropathological syndrome in a human 

suicide attempt (Hierons & Johnson 1978), these findings are not substantiated in more sensitive animal models 

(Hayes 1982). 

None of the 8 mutagenicity studies reported in NCI were positive for malathion. In general 

carcinogenicity/oncogenicity studies carried out by NCI, malathion was not implicated as a carcinogen (personal

communication, Pesticide Bureau, DFA, Boston, MA). IARC concluded that malathion and its metabolite 

malaoxon were tested for carcinogenicity in mice and rats by administration in the diet. No evidence of 

carcinogenicity was found. Maddy (1984) ranks malathion in category 3 (negligible oncogenic potential,

controversy as to any such potential, or not oncogenic). 

Salmonids exposed to 120 to 300 ugtl (ppb) malathion showed AChE inhibition of 70 to 80%, and 

activity indices were reduced by 50 to 70% of that of unexposed fish. Goldfish exposed to sublethal levels of 

malathion showed a significantly reduced frequency of avoidance response at levels below that causing a reduced 

AChE activity. One-hour bath exposures of rainbow trout to sublethal levels of malathion caused severe tissue 

damage to the gills and minor nonspecific liver lesions. Ponds given four semi-monthly treatments during May-July 

at levels up to 0.02 mg/1 (20 ppb) produced no discernible effects on resident bluegill and channel catfish 

populations. Aquatic insect populations were significantly depressed at the high treatment level but not at the lower 

levels (Johnson & Finley 1980). 

Irrespective of the exposure time and exposure concentration, the AChE activity of dying pinfish was 

reduced by 72 to 79%. Enzyme inhibition was higher in lethal exposures than in sublethal exposures. The observed 

correlation between brain AChE activity and deaths was considered to be of diagnostic value. After 3.5, 24, 48, or 

72-hr exposure to 575, 142, 92, and 58 ppb of malathion, 40 to 60% of the pinfish died and the extent of inhibition 

of AChE was in the range of 72 to 79%. Following the exposure of brook trout and rainbow trout to malathion, the 

AchE levels were approximately 24 and 28% of those of the controls, and the fish had less than one third the ability 

of the controls to do work. Thus malathion, though not directly and immediately toxic, had a deleterious effect, 

owing to the impairment of the ability of the fish to maintain equilibrium, to search for food, and to avoid predators 

(Murty 1986). In their examination of population and ChE responses in Walleye exposed to malathion aerial

sprays, Lockhart et al. (1985) found that cholinesterase activity fell to about 25% of prespray values within 12 hr 

after the first spray, and then gradually recovered to about 80% of prespray values over 2 weeks. The same pattern 

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was evident after the second spray, but the inhibition of ChE activity was not quite as large. Fish captured for 

analysis showed no indication of the symptoms of OP poisoning. The population statistics indicated small

temporary decreases in both catch per unit effort and weight gains after the first spray. Evidently a reduction in

ChE activity to about 25% of preexposure levels was the approximate threshold for population effects caused by

malathion.

The acute oral toxicity (LD50) of malathion to various species of birds range from not toxic at 100 ppm

(European starling, red-winged black bird) to 1485 ppm for mallard duck. Dietary LC50 values range from 2639 

ppm (ringnecked pheasant) to greater than 5,000 ppm for mallard duck. Acute dermal LD50 values are not available 

(Smith 1987). 

Malathion applied at 0.6 to 1.1 kg/ha (0.5 to 1.0 lb/acre) resulted in no observed mortality of wild birds in

one study conducted, and bird counts after spraying were either higher or nearly the same as before spraying (Black 

& Zorb 1967). At applied rates of 852-1140g malathion/ha (12-16 oz/acre) to fields containing caged quail, no 

evidence of mortality or population changes of wild birds were observed (Smith 1987). After malathion was 

aerially applied to a forested watershed at the rate of 0.81 kg/ha, birds reacted to the spraying for 2 days without 

lasting effects and no effects on reptiles and amphibians were observed. However, populations of mice and 

chipmunks were reportedly reduced by at least 30% (Giles 1970). Tadpoles exposed to 5 mg/1 (5 ppm) malathion 

through a continuous-flow apparatus did not bioaccumulate levels that were toxic when fed to 2-week-old mallard 

ducklings in a single meal (Hall & Kolbe 1980). The predicted bioconcentration factor (BCF) for malathion is low. 

Thus, malathion has moderate to slight acute oral toxicity to birds and there are no published reports of 

wildlife die-offs that can be attributed to the use of malathion. Its persistence and toxicity to birds is relatively low. 

 However, malathion's toxicity has been reported to be potentiated by EPN treatment (Murphy 1969), and the 

interaction of these and other pesticides is not fully understood (Smith 1987). 

B. Biological Control.

1. Introduction 

Biological control includes attacks on the pest species by other species and manipulation of the pest species 

itself. The former includes the traditional biological control agents, predators, pathogens and parasites, whereas the 

later includes such techniques as sterile-male release and genetic manipulations. 

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Biological control agents are grouped into three categories: predators, parasites and pathogens. Predators 

include both vertebrates and invertebrates and may attack both adult and immature stages of mosquitoes. Helminth, 

protozoan and fungal parasites and microbial pathogens generally only invade immature stages, though mortality 

may not occur until the early adult stage. Parasitic water mites are an exception in that they attach to certain adults 

as they emerge from the pupal stage and apparently reduce adult survivorship if they are abundant (Lanciani & 

Boyett 1980) In general, biological control is much more feasible in managing permanent water mosquitoes than 

temporary water forms. 

There are three basic strategies for utilizing all biological control agents: (1) increasing existing natural 

enemy populations by habitat alteration, (2) one-time introduction of sustainable exotic agents from other regions or 

habitats, and (3) augmentation of natural or exotic enemy populations by repeatedly releasing non-sustainable, labreared (or field collected) organisms. To date only the first, increasing fish habitat through OMWM, has been used 

in Massachusetts. Bti is sometimes classified as a biological control agent but its application technique and mode of 

action as a stomach poison more closely resemble a pesticide than a biological control agent per se. Bacillus 

sphaericus may more closely fit the model of repeatedly releasing non-sustainable lab-reared organisms as there is

evidence to suggest that it recycles within the environment.

No other biological control agent is currently available for general field use, though experiments continue 

with may different organisms (see below). There are important reasons why biocontrol is not more widely used 

against mosquitoes. First, the differences in biology of the various species of mosquitoes make it unlikely that any

one control agent will operate across a wide range of species. Second, mosquito breeding is wide spread, making it 

difficult for a biological control agent to find, or be placed in, all breeding areas. Third, predators such as bats and 

purple martins, may eat mosquitoes but prefer to eat other, larger insects. Further, even when abundant, they do not

drive mosquito populations below levels that people generally find intolerable. Finally, there is a high cost

associated with sustained releases of a biological control agent and there are not, at this time, control agents 

available that require a single, or a few, releases to become established. 

Because of the limited application of biological control to mosquitoes in Massachusetts, the following 

discussion will focus primarily on the feasibility of control agents currently being studied for mosquito control. An

important point to make regarding biological control is that the mosquito control have limited research capabilities. 

While conducting field evaluations of new control techniques is a desirable practice for any mosquito control

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program, the projects should not be expected to find and bring forward biological control agents without substantial

help from research institutions such as the state university. 

2. Predators 

 a. Introduction 

In order for any predator to independently be an effective control agent, it must meet two important

criteria: (1) its size and abundance in relation to the target species must be sufficient for it to kill or consume a high 

percentage of the prey population within a relatively short time period, and (2) its feeding behavior should be 

selective toward the prey species when it is present but allow it to utilize other food items when the target species is 

absent. These criteria are rarely met in full. Predators that are sufficiently large and/or abundant to have a major 

impact, usually lack feeding specificity. Conversely, those with feeding specificity are usually less abundant

because their populations are regulated by a more restricted food supply. Vertebrate predators of insects have a 

clear size advantage but invertebrate predators tend to exist in much greater numbers. 

Because of the limitations of predators as biocontrol agents, it is normally essential to continuously raise 

and release the predator to achieve field densities high enough to cause real reductions in the prey species. 

However, in some cases, manipulation of the environment to the advantage of natural predator populations can 

provide an adequate augmentation effect. 

 b. Vertebrate predators 

Fish

Larvivorous fish are the oldest and perhaps most effective traditional biological control agent used against

mosquitoes. In certain habitats they may, by themselves, provide adequate larval control throughout the breeding 

season. If not, pesticides such as BTI or methoprene which are non-toxic to vertebrates can be used in an integrated 

fashion with fish. 

As already mentioned, the main reason open saltmarsh management strategies effectively control many

saltmarsh Aedes in the Northeast is because this method provides access for the abundant estuarine populations of 

larvivorous killifish (Fundulus spp.) into the mosquito breeding pools in the high saltmarsh (Hruby & Montgomery

1986). 

 The mosquitofish Gambusia affinis is distributed widely throughout the warmer parts of the world and is

the species most often reared and introduced into fresh water habitats for mosquito control. The biology and use of 

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this fish in mosquito control was reviewed by Meisch (1985). It is an opportunistic feeder and avidly eats pupae 

and late-instar larvae of culicines and chironomids. It is most effective against Culex in unvegetated, permanent

ponds but has been widely used in California and the Gulf States against ricefield Aedes and Psorophora. 

 Because Gambusia is so aggressive and fecund, it may replace important commercial or rare native fish 

species. This has raised environmental concern over the introduction of this fish into natural waters where it does 

not already occur. A recent article by Rupp (1996) has renewed this debate, both emphasizing real successes and 

real concerns over Gambusia use (see “Comments on ‘adverse Assessments of Gambusia affinis’” (JAMCA 1996) 

and Boklund 1997, Eliason 1997, and Rupp 1997). Because it is not a native species of Massachusetts it may not be 

imported and released in state waters. 

Outside of the mosquitofish, the common guppy (Poecilia reticulata) has received the most attention for 

mosquito control (Bay 1985). Comparative studies indicate that it is a less effective predator than Gambusia but it

is more tolerant of polluted waters. Many other native fish have been explored for their mosquito control potential

(Bay 1985). Studies in North Africa (Allo et al. 1985) suggest that malaria may be controlled through the annual

introduction of native fish from streams into the manmade water storage tanks which produce the vector Anopheles

in this region.

Birds

Many birds depend on insects as food and those which capture insects on the wing (e.g., the swallows), 

have been credited with consumption of significant numbers of mosquitoes. Purple martins specifically have been

promoted on the basis of the claim that they often consume 10-12 thousand mosquitoes per day but Kale (1968) 

concluded on the basis of existing evidence that all claims of martins significantly reducing mosquito populations 

were unsubstantiated and, because of several biological facts, were unlikely to ever be demonstrated. The facts on 

which these conclusions were drawn are as follows: 

(1) Mosquitoes were a negligible item in the diet of martins in the only two published studies in

which the contents of martin gizzards were examined. 

(2) None of the published statements appearing in the popular ornithological literature which 

attributes a mosquito-eating habit to martins is based on factual study or scientific reference. In

fact, there is evidence that martins feed more on larger insects including species of dragonflies 

which may be predators of adult mosquitoes. 

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(3) Behavior patterns of mosquitoes and martins are such that they tend to not fly at the same height

or at the same time. Thus, contact between the two is minimal. 

(4) There is no evidence that any avian species can effectively control a pest insect upon which it

feeds when the insect is at or near peak abundance. 

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Other Vertebrates

Mosquito control by insectivorous bats was tried in the early part of this century but without success (Kale 

1968, Storer 1926). Bats continue to appear in the popular press as legitimate mosquito-control agents (Wright 

1996) but are not considered worthwhile agents in Common-sense Pest Control (Olkowski et al. 1991), which is

very thorough in its coverage of non-chemical control options, or in mainstream mosquito control (Mitchell 1992). 

c. Invertebrate predators 

Predators of mosquito eggs.

Evidence exists of predation on diapausing flood water mosquito eggs by mites and beetles, and on Culex

egg rafts by fish (Collins & Washino 1985). Nonetheless, egg predation appears to be a relatively minor component 

of natural mosquito mortality and is not being studied for biological control. 

Terrestrial insect and spider predators of mosquito adults

Predation on emerging and indoor resting adult mosquitoes has been readily observed but the impact of this

mortality on populations is extremely difficult to assess. Certain spiders (especially Tetragnatha) and predatory flies 

(mainly Empididae, Anthomyiidae and Dolichopodidae) have been shown by precipitation tests to have consumed 

emerging mosquitoes (Collins & Washino 1985). In one British study, up to 28% of the spiders tested had eaten 

mosquitoes (Service 1973). Certain adult dragonflies reportedly capture mosquitoes on the wing but these 

observations have not been backed up by any controlled field studies. Synanthropic emesine bugs (Reduviidae) 

appears to be potentially important predators of indoor resting mosquitoes in the tropics. In sum, the prospect for 

enhancing or managing invertebrate predators for more effective adult control is not encouraging, especially in 

temperate regions. 

Aquatic insect predators of mosquito larvae & pupae

Aquatic insect predators seldom occur in significant numbers in the temporary floodwaters that produce 

most pest mosquitoes. Studies of predation have therefore largely taken place in permanent ponds or semipermanent habitats such as rice fields, rock pools or vernal woodland pools. The adult stage of most predaceous 

aquatic beetles and true bugs can fly (usually at night) so natural colonization of newly flooded habitats can occur in

a matter of days. Development time for these insects is usually from several weeks to several months. 

Among the beetles, the dytiscids (predaceous diving beetle), which are predaceous both as larvae and 

adults, are the most effective predators of mosquitoes. There is evidence from studies in rice fields that adult 

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dytiscids selectively locate and colonize sites with locally high concentrations of mosquito larvae (Collins & 

Washino 1985). Mass production methods for dytiscids have never been developed. Whirligig beetles (Gyrinidae) 

only feed at the surface where they may prey on concentrations of emerging adult mosquitoes. Hydrophilids are 

only predaceous as larvae and seem to feed mainly on chironomid midges. 

Only two aquatic families of true bugs, the back swimmer (Notonectidae) and pigmy back swimmer 

(Pleidae) have received serious consideration as mosquito control agents. Pleids are generally not abundant enough 

to have significant impact but notonectids can become quite dense in certain habitats. Mass rearing of the latter 

appears to be possible. Water boatmen (Corixidae) are also common and similar in appearance to backswimmers 

but they are mostly detritus feeders. Other predaceous aquatic Hemiptera that have been suggested as mosquito

predators but which normally occur in insufficient densities to have much value as natural control agents include the 

giant water bugs (Belostomatidae), water scorpions (Nepidae), water measuring bugs (Hydrometridae) and the two 

family of surface-feeding, water striders (Gerridae and Veliidae). 

Dragonfly naiads have been marketed commercially for mosquito control and at least one town in

Massachusetts, and others in New Hampshire and Maine, have purchased dragonflies for mosquito control. In 

northern climates these insects require 1-5 years to mature, so they normally occur in permanent waters only. 

Furthermore, many are bottom feeders that seldom if ever come in contact with mosquito species that feed at the 

surface or in the water column. Most bottom-feeding mosquitoes (i.e. Aedes) occur in temporary water containing 

few if any dragonfly naiads. Another factor weighing against the mosquito control efficiency of these aquatic

predators is the fact that they normally occur at low densities. Adults of many species are territorial and this seems 

to spatially limit population densities of naiads as well as adults. In certain habitats such as rice fields, naiads may 

become quite abundant but populations fluctuate greatly and their role in limiting populations of rice field 

mosquitoes is limited at best. No controlled, field studies have been done in which naiads have performed well as 

biological control agents. 

 The trichopteran Limnephilus indivisus may be an important predator of early spring Aedes in woodland 

swamps in Ontario but most caddisflies are omnivorous shredders rather than predators (Collins & Washino 1985, 

Merritt & Cummins 1985). Prospects for mass rearing and manipulating caddisfly larvae are not very bright. Many 

of the aquatic nematoceran relatives of mosquitoes contain groups with predaceous larvae. These include the 

families Chaoboridae, Chiromomidae, Ceratopogonidae, Tipulidae, Anthomyiidae, and others. Most are too small 

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to consume many mosquito larvae. Predation on small, early instars occurs but it is far less efficient in reducing the 

numbers of adults than is predation on late instars and pupae. Mochlonyx (Chaoborid) predation on spring Ae. 

communis populations has been observed in woodland pools in Massachusetts (Edmans, personal communication) 

and in Europe (Chodorowski 1968). The impact of this small but voracious predator is unknown. 

The insect predator with the most promise in mosquito control is another mosquito. Larvae of the nonbiting genus Toxorhychites are large and effective predators of mosquitoes that develop in natural and man-made 

containers such as tires, tree holes, metal cans, and leaf axis (Steffan & Evenhuis 1981). Unfortunately, none of the 

70 some species in this mainly tropical genus can survive the winters as far north as Massachusetts. Their use here 

would therefore require repeated, annual releases of lab-reared females. This is not warranted at the present time 

since container-breeding species generally do not represent the major nuisance or health threat in Massachusetts. 

This situation could change if Ae. albopictus becomes well established in used tires in the Northeast. Focks (1985) 

states that although it is possible to control or reduce certain species of container-breeding mosquitoes with

inoculative or inundative releases of Toxorhynchites, the usefulness of this genus in practical, operational control

programs has yet to be demonstrated. 

Other invertebrate predators of larvae and pupae.

Among the non-insect predators of the immature stages of mosquitoes, only hydra (Cnidaria: Hydrozoa), 

flatworms (Platyhelminthes: Turbellaria) and copopods (Cyclopoida) have been studied in any detail.

Both hydra and flatworms can be easily mass produced and, unlike most predaceous insects, they can be 

maintained at high densities without cannibalism. In the laboratory, they kill far more larvae than they consume. 

Both groups produce semi-dormant eggs so they occur naturally in shallow temporary pools as well as permanent

swamps and ponds. Detrimental effects on young fish have been reported when these predators are at high densities 

(Mulla & Tsai 1978). 

Both of these predators have good potential as control agents in the Northeast but additional long-term

field evaluations are needed. As with mosquito fish, the laboratory production, storage, and field translocation of 

these organisms requires a certain degree of sophistication, which is usually lacking at the local level. Currently, 

there are no commercial sources for the quantities that would be required for mosquito control applications. 

Natural populations of predaceous cyclopoid copepods appear to limit the distribution of container 

breeding mosquitoes in certain tropical settings (Marten 1984). However, they have never been shown to be 

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important predators in temperate regions or in other types of aquatic habitats. Therefore their potential for the 

biological control of pest and vector mosquitoes in Massachusetts appears to be nil.

3. Parasites and Pathogens 

a. mermithid nematode parasites 

Outside of bacteria, parasitic nematodes are the only natural parasites and pathogens that have ever 

achieved operational status in mosquito control. Known parasitic roundworms of mosquitoes now number over 20 

species. The free-living, aquatic, preparasitic stage which hatches from the nematode egg, seeks out and penetrates 

the cuticle of host mosquito larvae. Larvae are usually killed in the last instar. In a few species, the mature worms 

are carried over in the adult mosquito and cause mortality when they exit during attempted pseudo-oviposition. 

 Romanomermis culicivorax (including most references to Reesimermis nfelseni) is the species that has 

been most extensively studied. Methodologies for the mass production and commercial preparation of this species 

have been developed and it was briefly marketed as Skeeter Doom in the late 1970'g. Low sales and problems with

the shipping and shelf-life of viable eggs appear to have been the major factors which led to the marketing failure of 

this agent (Service 1983). Other economic drawbacks include host specificity which limits its effectiveness to only

certain species (e.g., it is ineffective in cold, polluted or brackish water), and the lack of patent protection for 

companies investing in the production and marketing of this product. In addition, applicators need some special 

skill and training to effectively use this biocontrol agent. The tendency of this agent to naturally recycle once it is 

introduced into favorable aquatic habitats is beneficial from a control viewpoint, but it further reduces the long-term

marketability and profit potential for private producers. It remains under study, however, as a recent article ( 

Mijares et al. 1997) discussed the establishment of R. culicivorax in sewage settling ponds and natural ponds in 

Cuba. 

On the biological plus side, mermithids appear to be highly compatible with a wide range of chemical

pesticides and growth regulators. Moreover, they: 1) are non-specific and well suited to the life cycle of their 

mosquito host, 2) produce high levels of infection and mortality, 3) can be easily mass-produced and applied with 

standard spray equipment, and 4) offer no threat to non-target organisms or the environment.

There are species of mermithids which appear to be highly specific to spring snow-pool Aedes and to

saltmarsh Ae. sollicitans (Petersen 1985). However, these worms have not been established and studied in the 

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laboratory. Such species may have greater control potential in northern coastal states like Massachusetts than the 

more tropically adapted R. culicivorax.

Since the technology for using mermithids in mosquito control already exists, and there are numerous field 

trials documenting their control potential, the future availability and use of these biocontrol agents in operational 

programs seems to depend on changing economic and market forces (Petersen 1985). 

 b. Microsporidia

Virtually all mosquito species carefully examined have been found to harbor these parasites. Larvae are 

infected by ingesting the spore stage. Spores, which are produced at the end of the life cycle, have often proven 

difficult to induce and to reinfect larvae in lab cultures. Few microsporidian life cycles are well enough known to

assess biocontrol potential. Life cycles vary from simple to complex and often form the basis for the non-taxonomic

grouping of these protozoan parasites. The simplest forms (Type I) occur mainly in terrestrial insects and even the 

one aquatic species known from mosquitoes (Nosema algerae), does not cause mortality until, the adult stage. For 

this reason N. algerae has limited potential for reducing pest problems but may impact on disease transmission by

reducing survival and fecundity. Wild strains only persist in larval populations for short periods and cause little 

direct mortality. Type II microsporidia have simple, asexual life cycles similar to Type I forms and they also show

little promise in mosquito control (Hazard 1985). Type III forms are dimorphic, have binucleate spores, and kill 

mosquitoes in the larval stage. Only one species (Hazardia milleeri) is known from mosquitoes and it seems to

have low infectivity (Hazard 1985). Type IV microsporidia include many species from mosquitoes and have the 

most control potential. Infected larvae are usually killed but a few females survive and carry the infection via the 

ovary to the next generation. However, transovarial infection ceases after a single generation. Non-ovarian modes 

of transmission must exist but this issue along with the possibility of sexual reproduction and alternate hosts are as 

yet unresolved. Additional basic research is required before any microsporidian can be considered in the biocontrol

of mosquitoes (Hazard 1985). 

Tetrahymena and Lambornella (tetrahymenid ciliates)

The lack of a resistant resting stage and difficulty in culturing these ciliated protozoa has prevented the 

thorough study and evaluation of this group of potential biocontrol agents. Ongoing studies of Lambornella clarki

in California treehole Ae. sierrensis should help to better assess the control value of these parasites in the near future 

(Anderson et al. 1986). 

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Helicosporidium

There is still debate concerning the proper classification of this spore-forming group of parasites; some

believe they are primitive Ascomycetes fungi. There are only 3 reports of natural infections in mosquitoes. They 

appear to infect a wide range of species but also may infect non-target insects as well. High dosages of spores are 

required to infect older instars in the lab. Continuous cultures of these parasites do not exist so the basic research 

needed to evaluate their biocontrol potential is not forthcoming. 

 c. Fungal Pathogens 

Coelomomyces

Many forms of pathogenic fungi have been known from both larval and adult stages of mosquitoes since 

the 1930's. However, it was not until the discovery of the obligate alternate host (i.e., microcrustacea) in the mid70’s that cultures and full-scale laboratory investigations were possible with Coelomomyces (Whisler et al. 1974, 

1975). The rather complex life cycles of some species have recently been described and methods for in vivo 

culturing established. Before wide-scale field application can occur, mass in vitro cultivation of the infective 

biflagellate zygote stage needs to be developed. If Coelomomyces, and perhaps their copepod and ostracod 

intermediate hosts, are introduced into favorable habitats, the potential for natural recycling exists. However, too

little is known about the host ranges and habitat requirement of most Coelomomyces to recommend any such 

introduction at the present time. Moreover, species of Coelomomyces do not routinely provide high and predictable 

levels of mosquito control. It is, premature to critically assess their potential as control agents to be used

independently or as part of an integrated control program (Federici et al. 1985). Studies related to their evaluation 

as operational control agents have only recently been initiated and it is not likely that any Coelomomyces will be

operational within the near future. 

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Lagenidium giganteum. 

This mosquito-specific water mold is a very promising biological control agent, especially in fresh water 

and in warmer climates. This fungal pathogen can be mass produced on artificial media and can recycle in as little 

as 3 hours (McCray 1985). It has a resistant, dormant stage and infects a wide range of mosquito species. 

Unfortunately, it is not effective in polluted, brackish or colt waters. This limits its commercial value and it 

potential usefulness in northern and coastal states like Massachusetts (Service 1983). 

Other Fungi

Fungi are among the commonest pathogens of insects and many other genera besides Coelomomyces and 

Lagenidium have been reported from mosquitoes. Of these, Culicinomyces and Metarhizium have received the most 

attention. Both groups infect a wide range of mosquito species but relatively high concentrations are required to

cause infection. They can tolerate organic pollution and salinity but not high temperatures (i.e. above 30°C). 

These fungi can be grown on inexpensive artificial media but no resistant resting stage has been fount. Difficulty in

achieving long term storage of infective stages and formulation problems remain as barriers to commercial

production. Nonetheless, these fungi are a promising group of biocontrol agents which may provide new mosquito

control tools in the future. 

Erynia aquatica

 Erynia aquatica is an Entomophthorales fungus, and is the only species of the genus known to infect the 

immature aquatic stages of mosquitoes. It was first discovered infecting Ae. canadensis and Cs. moristans larvae in

woodland pools in Hartford County, Connecticut from late May to early June (Anderson & Ringo 1969). It has 

since been recovered in early May from Ae. stimulans in woodland pools near the village of Cambridge, New York 

(Molloy & Wraight 1982) and from Ae. cantator on May 21, 1981 in a shallow salt meadow pool in Milford, 

Connecticut (Andreadis & Magnarelli 1983). Most recently, is was discovered in 1995 and 1996 in a woodland 

pool in Bristol, Rhode Island (Christie 1997). 

Steinkraus and Kramer (1989) collected Ae. fitchii larvae infected with E. aquatica from a semi-permanent

woodland pool in Tompkins County, New York. They used infected pupae to successfully transmit the disease to 

emerging adult Ae. aegypti, on which resting spores of the fungus developed. 

 Erynia aquatica has characteristics which make it attractive as a microbial agent: it is capable of causing 

epizootics, has been found in both freshwater and brackish water mosquitoes and has a resting spore stage that may

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survive well in storage. Operating against it is the fact that it has only been found in cooler, springtime waters. One 

thought is that infected pupae may be removed from the original infestation site and placed in other, nearby pools. 

A fungus that kills in the pupal stage works against its own spread.

 d. Bacterial pathogens 

Bacillus thuringiensis var. israelensis

Bti Serotype H-14 has become an important biological larvicide following its discovery in the Negev desert 

in 1976. Within the last 5 years it has become widely used by the mosquito control projects in Massachusetts. It is

now the larvicide of choice in many situations because of its host specificity, high and rapid mortality to many 

mosquitoes species, and its environmental safety. It is quite distinct from the Bt strains which infect lepidopterous 

insects. Its track record in controlling polluted-water Culex is mixed, apparently because it sinks to the bottom and 

the active moiety rapidly binds to organic particulates. Consequently, higher dosages are required to achieve good 

control in highly organic and deep-water situation. Saltmarsh mosquitoes generally require rates at the high end of 

the labeled application rates for effect control. Liquid, powder, granular and slow-release briquet formulations are 

commercially available. 

 Bti must be ingested to cause toxicity to filter-feeding mosquito larvae; pathology occurs in cells of the 

midgut wall. It is least toxic to 4th instars since they cease feeding at least 12 hours prior to pupation. The 

mosquito toxic ingredient of Bti preparations is the heat labile deltaentotoxin located in the proteinaceous parasporal

crystalline inclusions synthesized concomitantly with the spore during sporogenesis. Once released in the 

environment, it biodegrades rapidly (it is usually only active 1-3 days) and this bacterium (gram negative 

Bacillaceae) does not recycle. This is considered the only major drawback of this highly effective mosquito 

pathogen but it has enhanced its commercialization (Lacey & Undeen 1986). 

The biocidal activity of Bti toxin appears to be limited to larvae of certain families of nematocerous

Diptera. A large number of laboratory and field tests have confirmed that all non-nematocerous, non-target

organisms are virtually unaffected (Lacy 1985). All existing data indicate that the unaltered protoxin of Bti is also 

safe to vertebrates including humans (Lacey 1985). Further improvements in the efficacy and price competitiveness 

of this control agent, brought about by formulation changes and genetic engineering, are likely to occur in the near 

future. In addition, formulation of this agent with other compatible and perhaps synergistic agents such as juvenile 

hormone analogs (e.g. Altosid) is currently underway. Such mixture have two important advantages. They reduce 

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the likelihood of mosquitoes developing resistance to either agent and, secondly, they widen the window for control

since Bti is most effective against early instars and growth regulators against later instars. 

Bacillus sphaericus.

Although only recently available, B. sphaericus may have greater control potential than Bti because of its 

ability to continue to recycle once it is introduced. It has many of the same beneficial attributes of Bti but all strains 

isolated to date are less effective against a wide range of species than is Bti. At the moment it is primarily marketed

against Culex in high-organic waters but research is on-going in expanding its control potential.

 e. Viral Pathogens 

The biological control potential of both non-accluted (iridoviruses and densonucleosis viruses) and 

occludet (baculoviruses, cytoplasmic polyhedrosis viruses and entomopox viruses) viruses pathogenic to

mosquitoes has recently been reviewed by Federicci (1985). It is sufficient here to simply paraphrase from the 

summary of this thorough review as follows:

Analysis of research conducted to date makes it clear that none of the viral pathogens of mosquitoes can 

currently be considered good candidates for mosquito management programs. The two main reasons for this

assessment are that viruses discovered so far possess low infectivity for original or alternate hosts and there is no

readily available method for mass production of virions. This apparent lack of control potential is most obvious 

when one considers that few field trails have been conducted with these agents even though the first one was 

discovered over 15 years ago. While it appears unlikely that viruses will be developed for mosquito control in the 

near future, they may prove to be extremely useful microbial agents in the long term, perhaps in 2 or 3 decades, 

once we learn how to manipulate them effectively. Biotechnology has the greatest potential for engineering new 

more useful biocontrol organisms among the viruses because of their simple molecular structure. 

4. Pest Species Manipulation 

A somewhat different approach to biological control is manipulation of the mosquito genome to either 

1) induce reproductive failure (leading to population elimination) or 2) bring about permanent changes in the 

behavior or physiology of the target population so it no longer vectors disease or bites people. There are numerous 

theoretical mechanisms by which this could be accomplished. Following is a brief discussion of the three 

approaches that have been most commonly discussed and researched. 

a. Sterile Insect Technique 

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The early and continuing success of the sterile male release program in eliminating the screwworm fly 

from the U.S. and Mexico has given rise to many investigations and new ideas for controlling other insects 

(inoculating mosquitoes) through the use of this or some other genetic technique. Except for fruit flies, this method 

has not yet been successfully applied to other insects in operational programs and the technique is not currently

being pursued for mosquito control.

 b. Incompatibility 

Incompatibility resulting from a lack of fertility in sexual unions may occur due to a variety of genomic 

failures or due to the effort of bacteria-like symbionts to control the reproduction of host (Barr 1985). The feasibility 

of suppressing Culex pipiens through cytoplasmic incompatibility was demonstrated in a Burmese Village over 20 

years ago (Laven 1967) but the practicality of this method has not been confirmed by any other field tests. 

Moreover, incompatibility factors have been isolated in only a few mosquito species to date. 

 c. Chromosomal Aberrations 

There are several heritable chromosome rearrangements that can, in theory, be used to inject genetic load

into a mosquito population and/or to effect a permanent change in the genetic makeup of the population. These 

aberrations can be used to 1) increase genetic lethal load (serility is limited to 50-80% because of the low 

chromosome number (three, in most mosquitoes) or 2) replace noxious species with harmless strains if appropriate 

viable homozygous rearrangements are available. The latter is perhaps only applicable in the case of important

disease vectors. Naturally occurring aberrations can be screened for in wild populations but their frequency is

greatly increased through exposure to mutagens. 

Controlling mosquitoes through the use of chromosomal aberrations requires a major basic research effort

and a target species that is easily colonized. This later requirement automatically eliminates many important species 

from consideration. 

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d. Competitive Displacement 

The final, and somewhat abstract, strategy for controlling mosquitoes biologically is the ecologically based 

notion of displacing a noxious species by introducing a benign but more competitive (i.e. better adapted) exotic 

one. This idea has been suggested primarily to control container-breeding species like Ae. aegypti. However, 

benign mosquito species are difficult to find, as most mosquitoes that have become established (Ae. aegypti, Ae. 

albopictus) are as bad or worse than the species with which they compete (container-breeding Culex and Ae. 

triseriatus). 

5. Other Control Approaches 

a. Trap out techniques. All experience to date indicates that while various traps may be 

good sampling devices for adult mosquitoes, they are too inefficient and limited in their range to provide any benefit

in reducing biting annoyances (Nasci et al. 1983). Work is ongoing on attractants (octanol) that would both greatly

increase trap collections of mosquitoes and reduce non-targets trapped, but no products are marketed for this

purpose to date. 

Electrocutor traps (“Bug Zappers”) continue to be a popular item, with an estimated 1.75 million sold in 

the United States each year (Mitchell 1992) but they are extremely non-specific (mosquitoes generally make up less 

than 5% of the catch, and may be harmful to other insect species. They cannot be considered a part of any

mosquito-control program. 

b. Repellents. Personal protection through the use of mosquito repellents is an appropriate

alternative to controlling the mosquito populations before they bite. This is especially true if the periods of 

annoyance are infrequent and brief and where the land areas are too vast and unpopulated to economically consider 

control programs. 

The most commonly used mosquito repellent is DEET (N,N)(diethyl-metatoluamide) which has been 

formulated and sold under a variety of trade names (e.g., Off, Muskol, Cutters), in a variety of concentrations and as 

both aerosol sprays (usually ca 15%) and lotions (up to 100%). Laboratory tests have shown that maximum

repellent duration (ca. 1-2 hours) is obtained with a concentration of ca. 50% so that higher concentrations do not

provide appreciable advantages. The major disadvantage o£ DEET are: 

1) relatively short protection time 

2) somewhat offensive odor 

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3) damage to some fabrics and surfaces at higher concentrations 

4) high cost

5) possible hazards from heavy use 

Small children frequently have skin reactions to DEET. Small children are also most likely to be the 

individuals that develop meurotixicological symptoms from DEET. Thirteen of 14 cases of encephalopathy 

(toxicity of the central nervous system), found in publicly available reports by a recent review (Osimitz and 

Grothaus 1995), were in children 8 years old or younger. Three of these children died, all having used “heavy”

amounts of repellent, even though the repellent in each case had DEET concentrations of 20% or less. Oral 

ingestion may have played a role in some of the cases. Osimitz and Grothaus (1995) concluded that there is no 

evidence that increased DEET concentration has an effect of the severity of symptoms. They also compared reports 

that the Poison Control Center received for DEET (6,724 in children under 6 years old during a five-year period) to 

laundry detergent reports (10,789 in 1989) and household bleach (16,169 in 1989), concluding that accidental 

exposure, while undesirably high, is in line with, or lower than, exposure to other household chemicals. 

There is one unsubstantiated report in the Russian literature of carcinogenic effects in rats at high doses. 

Three other repellent materials are in common use. Dimethyl phthalate (generally sold as 6-12) is not as 

effective as DEET against mosquitoes but still has a share of the market. Citronella-based repellents have long been 

marketed as candles or in oil-burning lamps. Citronella is also available as a repellent to be sprayed in skin and 

clothing (Natrapel). The third material (Avon skin-so-soft) is a popular bath oil that is not marketed as a mosquito

repellent but has, through word of mouth, been recognized for its as yet uncharacterized mosquito repellent affect. 

It is as effective as DEET but it does not persist as long. On the other hand, it is much cheaper, smells better, and 

apparently does not damage any fabrics or surfaces. The active ingredient(s) of skin-so-soft has not been isolated or 

identified to date. It also has not undergone the EPA safety testing that other repellents have because it is marketed 

as a beauty aid rather than a pesticide (Note: repellents are classified as pesticides by EPA). 

Electronic mosquito repellent devices which are periodically marketed in the U.S. (usually by mail order 

houses) are completely ineffective and are not based on any biological rationale (Foster & Lutes 1985, Mitchell

1992, Curtis 1994). 

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C. Physical Control 

1. Types of Habitat Modification 

a. Open marsh water management (OMWM)

Originally developed for New Jersey salt marshes (Ferrigno 1970, Ferrigno & Jobbins 1968, Ferrigno et al. 

 1969), this strategy basically attempts to overcome the limitations of ditching by the incorporation of other water 

management strategies. In particular, champaign pools or reservoirs (which permanently hold water and sustain 

larvivorous fish) are created (by backhoe, dragline or rotary ditcher) in selected tidal pools or large shallow pans 

and are connected via small shallow ditches to surrounding mosquito breeding depressions. If old ditches are redug and used as reservoirs, then plugs must be inserted at the tidal end to prevent drainage. This customized 

approach to marsh management represents the least deleterious and most efficient nonpesticidal method for 

controlling saltmarsh mosquitoes and has been adapted to New England conditions (Boyes and Capotosto 1980, 

Hruby et al. 1985, Christie 1990). A manual outlining this method was developed by the Massachusetts Audubon 

Society (Hruby and Montgomery 1986) and OMWM is currently being practiced by coastal projects in Essex and 

Plymouth Counties in Massachusetts. As of 1996, OMWM had become the accepted technique for new salt-marsh 

water management work, though maintenance work remains dominated by cleaning existing ditching, as opposed to

conversion to OMWM. 

 b. Other Modification Strategies 

Mosquito control efforts in Massachusetts predate modern chemical insecticides. Early control efforts 

consisted of source reduction work, mostly in salt marshes (see “History of Cape Cod Mosquito Control Project, 

1928-1971”). This emphasis was largely abandoned when cheap and seemingly more effective organo-chlorine 

insecticides became available in the early 1950's. Early control programs capitalized on cheap WPA labor but they 

failed to achieve the level of control that the public has come to expect of modern control programs. Nonetheless, 

they serve as a reminder that mosquito control, from its earliest inception, considered and practiced control 

alternatives to synthetic chemical pesticides. 

Except for new OMWM projects in salt marshes, mosquito control source reduction work now consists

primarily of maintenance work on existing culverts, storm sewers and ditches. Very little new ditch construction

has taken place in recent years. Ditch cleaning, which often involves excavating spoil with a backhoe or plow, is an 

activity which has drawn great concern when it takes place in estuarine environments. This is because many of the 

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old grid ditches in the saltmarsh served no real purpose for mosquito control but they must be re-cleaned 

periodically or they themselves become shallow breeding areas for saltmarsh mosquitoes. 

c. Origination of Requests for Physical Control.

The exemption from certain regulations enjoyed by mosquito control is a two-edged sword. On the one 

hand, it enables mosquito control projects to more quickly respond to drainage problems. On the other hand, it

makes the heading “Mosquito Control” particularly desirable for drainage projects in which mosquito control is, at

best, a marginal goal. This pressure can come from property owners, public officials, or from within control

projects themselves. The pressure to conduct drainage work that does not have a mosquito-control component must

be resisted. 

The best interests of mosquito control programs are served by conservative application of the definition of 

mosquito control, as over-use of the wetlands exemptions may result in the loss of those exemptions. To this end, 

mosquito control programs, in conjunction with state and federal wetlands protection agencies, must develop a 

strong set of guidelines for alterations exempt from Wetlands Protection Act. 

2. Ecosystem changes of non-target biota as a result of physical controls. 

 a. Salt Marsh . 

New England coastal wetlands have been heavily impacted by man (Shisler 1990). However, evidence 

concerning the negative impact of saltmarsh ditch maintenance activity is mixed. The principal concern is with

disposal of the spoil on the marsh and the invasion of upland plants that can occur with even slight elevation 

increases (i.e. 1-2 inches) (Miller and Egler 1950, Buchsbaum 1994). Ditching also permits Spartina alterniflora to

invade the upper marsh (dominated by Spartina patens and Distichlis spicata) along the edges of the newly created 

ditches. There is evidence to support the claim that this increases marsh productivity (Buchsbaum 1994). 

In 1979, staff biologists from the New England Division of the U.S. Army Corps of Engineers (DeSista & 

Newling 1979) carried out preliminary investigation in several Massachusetts salt marshes to explore the issue of 

spoil deposition and upland plant invasion. In many instances they found little plant invasion despite evidence of 

previous spoil deposition of 2 inches or more in depth on the marsh. In a few locations with minimal tidal 

influence, some invasion by species such as common ragweed (Ambrosia artemisifulia), march elder (Iva 

frutescens), and seaside goldenrod (Solidago semprevirens) had occurred over time. However, they concluded that

it was not obviously correlated with the spoil itself but was perhaps caused by some other factor associated with the 

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disturbance to the marsh. They recommended the sort of long-term monitoring studies which have as yet not been 

carried out in Massachusetts salt marshes. 

Clarke et al. (1984) studied the effect of ditching and vegetation changes on the use of the saltmarsh by

birds in Rowley, Massachusetts. They concluded that bird use of the marsh was negatively impacted by mosquito

control ditching. This is in contrast to the studies of Shisler & Jobbins (1977) in New Jersey marshes where 

increase productivity was observed in ditched marshes. Daiber (1986) noted that, where ditches drain pannes, birds 

that need a constant water supply (American bittern, pied-billed grebe and American coot) may decline. Also noted 

was a case where spoil ridges invade by Baccharis and Iva caused gulls to seek less brushy areas for nesting. 

Scheirer (1994) encouraged mosquito control programs to develop water management partnerships with the U. S. 

Fish and Wildlife Service, especially for OMWM-type marsh restorations designed to improve migrant waterfowl

habitat. 

In a series of investigative reports by staff biologists from the National Park Service, the environmental 

impact of ditching and diking of salt marshes in the Herring River basin of Cape Cod National Seashore were 

investigated (Soukup & Portnoy 1983, Portnoy 1984a, 1984b). These reports held that Cape Cod marsh 

management practices were responsible for the freshening, stagnation, acidification and high sulfate and aluminum

concentration in diked marshes. These authors suggest that the destruction of a thriving eel and herring fishery in

Wellfleet was the direct result of these marsh disruptions. However, the main dike across the mouth of the Herring 

River (from Griffin Island to the Mainland) was constructed in 1909 with the main objective of providing for 

agricultural use of the basin. These structures are not typical of early mosquito marsh management practices in

other coastal regions in Massachusetts. The impact may be largely reversible if dikes are removed and normal tidal

flow is allowed to return to these areas. OMWM tailored to the unique characteristics of these small estuaries 

should be explored as a way to manage the Ae. sollicitans populations which are likely to replace the present Ae. 

cantator populations if tidal flow and normal vegetation and salinity are restored in these marshes. 

Perhaps the most damaging assessment of ditching in salt marshes was the report of Bourn and Cottam

(1950) in which they blamed open ditching for converting up to 90% of the Spartina alterniflora marsh along the 

Mispillion River in Delaware to Baccharis. However, Provost (1977) reported that the area had returned to Sp. 

alterniflora after navigational dredging of the river had ceased and concluded that it was the dredging of the main 

channel, not the marsh ditching, which had permitted Baccharis to invade the marsh (see Daiber 1986 and 

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Buchsbaum 1994 for reviews of this debate). Arguing against significant water-table lowering in salt marshes is the 

strong affinity for water exhibited by salt marsh soils. Because permeability is so low, the water table may be 

lowered only within a meter or so of the ditch itself (Balling and Resh 1982). 

Grid ditching, even if not the marsh destroyer some claim it to be, still reduces standing water on the marsh

and creates an unnatural and aesthetically unpleasing view. Open marsh water management was designed to more 

closely approximate the diversity of the natural marsh while eliminating the shallow pannes in which mosquitoes 

breed. 

Wolfe (1996) reviewed the effects of OMWM on numerous tidal marsh resources. OMWM systems 

tended to enhance tidal exchange and salinity in marshes that were converted from grid ditching. Except where 

spoil piles were left (improperly) on the marsh, vegetation change was slight and favored salt-marsh species such as 

Spartina patens and Distichlis spicata. Small changes in elevation due to spoil deposition sometimes result in

invasion by Iva, Baccharis, and Phragmites. Salt-marsh snails (Melampus bidentatus) have declined in some

OMWM sites but not in others. Similar mixed observations have been made for marsh periwinkle (Littorina

irrorata) and fiddler crabs (Uca species). Marsh fish populations are, by design, enhanced by OMWM. However, 

changes in species composition may occur where existing pools are deepened. Mummichogs (Fundulus 

heteroclitus)and spotfin killifish (Fundulus luciae) should decrease while sheepshead minnows (Cyprinodon 

variegatus), inland silversides (Menidia menidia) and rainwater killifish (Lucania parva) should increase (Talbot et

al. 1986). The small reservoirs are not particularly attractive to birds and the minor changes in hydrology, flora and 

invertebrate fauna caused by OMWM do not cause significant changes in bird use on OMWM sites. Effects on 

mammals are not well documented. OMWM has had no long-term detrimental effects on water quality. As a result, 

Wolf concludes that, “Open Marsh Water Management is an environmentally focused management tool that is

designed to be compatible with nature rather than compete with it.” Of course, the technique is new enough that

long-term monitoring is required to ensure that altered sites remain functional salt marshes. 

b. Freshwater Wetlands (exclusive of Vernal Pools). Palustrine wetlands, including 

emergent, scrub-shrub and forested wetlands, are the dominant system in which Massachusetts freshwater physical 

control take place. In the vast majority of cases, this work consists of maintaining existing ditching designed to 

remove standing water from the wetland, thereby reducing mosquito-breeding habitat. For most MCPs, this type of

work (source reduction) makes up a large percentage of their control effort. Though reducing standing water 

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certainly reduces mosquito breeding, there has been little research concerning the overall effects of these alterations

on the modified wetland. Ditch systems can become problems in their own right, producing mosquitoes if left

unmaintained. Most of these systems were never designed specifically for mosquito control and their other, primary

function, such as removing runoff from large parking lots, may cause considerable damage to the ecosystem, 

leaving the MCP to clean up, or at least deal with, someone else’s mess. 

The majority of drainage systems currently maintained by MCPs were not initially constructed by MCPs 

and the effort of MCPs today is almost entirely restricted to removing blockages to existing flows, rather than 

enlarging or straightening channels to increase flow. Most freshwater drainage is an inherited problem which 

requires intervention not because of mosquito-control activities but because of the activities of others. Road sand 

and yard waster represent two of the most common obstructions MCPs are called upon to remove from existing 

streams and drainage networks. New developments also can cause dramatic changes in the sediment load in

streams, despite regulations designed to prevent such problems. Road sand, yard waste and increased sediment load 

from development can all have impacts on a stream that are as greater or greater than regular ditch maintenance. 

Because MCPs are often involved in removing manmade sediments from streams, a system under 

appropriate ditch maintenance may function more closely to a natural system than one in which manmade wastes 

are allowed to accumulate unabated. The appropriate response by the MCP in such cases is not obvious because, 

although the problem, and its cause, may not be mosquito related, the mosquito control program may be the 

organization best equipped, both from and equipment and a training perspective, to rectify the situation. 

Since mosquito control projects came into being in Massachusetts, the perceived values of wetlands have 

changed. Once shunned as disease-bearing waste lands, best suited for dumping, draining or filling, wetlands are 

now viewed in a much more positive way. They are important wildlife habitats, perform a myriad of water quality 

maintenance functions, and serve as flood control, erosion, ground-water recharge and water supply regulators 

(Tiner 1989). Mosquito control programs have been slow in adapting to the increased value accorded wetlands. On 

the one hand, long-residual and/or broad-spectrum pesticides are no longer used in wetlands in Massachusetts. On 

the other hand, there is real resistance to halting maintenance work in drainage networks that may be seriously

damaging wetland habitat.

There has not been a great deal of work done specifically on the effects of physical control for mosquitoes 

on non-target organisms. Therefore the following discussion is based on the general effects that can be expected 

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when wetland alterations are made. Care should be taken in extending these general concerns to mosquito control

in Massachusetts. For example, channelization (straightening) of natural streams is not permitted in Masachusetts, 

where programs are required to follow the natural meanders of the stream. The three broad categories of wetlands 

alteration are outright loss, changes in the abiotic system and changes in the biotic community. Filling and/or

draining wetlands to convert them to upland is a mosquito-control practice that has been all but eliminated in

Massachusetts. There is no indication that MCPs are intentionally reducing wetland acreage in order to control

mosquitoes. However, the fact that the wetlands boundary remains essentially unmoved by a mosquito-control

alteration does not mean that profound alterations have not occurred. 

Changes in the abiotic system and biotic community are deeply intertwined, though physical control most

often causes abiotic changes which then cause biotic changes. For channels changes in flow rates, microhabitats, 

sediment load, sedimentation, and groundwater interactions can all occur. For wetlands (outside of channels) 

changes can include lost water-storage capacity, increased sedimentation and pollutant load, changes in water depth, 

and changes in groundwater hydrology. 

When a stream is altered to improve water flow for the purpose of removing standing water, either within

the stream or from adjacent wetlands, a number of changes may take place. By definition, improving water flow 

increases runoff. This, in turn, may decrease the surface-water storage capacity of the wetland system and decrease 

the capability of the wetland to retain load (suspended solids). This may increase the load of the water moving

through the stream (Brown 1988). Increasing runoff into a given stream tends also to increase erosion, which 

further increases load (Williams & Feltmantle 1992). Not only is total flow increased, but alteration tends to 

increase peak flow, which is associated with reductions in faunal diversity (Hynes 1972). 

The effects of increased flow and loading are many. At its most obvious, higher peak flows increase 

scouring of the stream bed by gravel and sand being transported by the water. Bottom dwelling animals are either 

affected on-site or swept downstream, leaving an impoverished community as flows return to normal (Hynes 1972). 

 Increased flows can also remove organic matter, leaving a sandy bottom on which macrofauna is reduced (Ward 

1992). As stated earlier, higher peak flows also encourage erosion, a process that can increase stream load long 

after sediment controls put in place during the actual drainage work are removed. 

High levels of suspended solids alter the stream habitat by: 

1. reducing light penetration 

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2. reducing primary production 

3. altering the trophic structure 

4. altering nutrient dynamics 

5. changing thermal conditions 

6. reducing oxygen levels (Ward 1992). 

These effects can, in turn can have the following impacts on the stream fauna: 

1. abrating respiratory epithelia 

2. clogging respiratory structures 

3. reducing feeding rates 

4. reducing feeding efficiency

5. increasing exposure to toxins 

 6. reducing vision 

7. inducing organisms to drift.

All of these effects can alter behavior patterns, change predator/prey interactions and change the outcome of inter 

and intra-specific competition (Ward 1992). 

Maintenance for the purpose of reducing mosquito breeding also includes removing obstructions within

streams. Tree branches and fallen trees are a particularly important part of the stream environment, providing food, 

living space, concealment from predators, protection from abiotic conditions and emergence sites (Ward 1992). 

They also provide varied microhabitats by deepening and slowing flow on the upstream side and often creating 

deeper pools on the downstream side. Removing these obstructions diminishes the variability of the stream

ecosystem. 

At the other end of the flow-rate spectrum, increasing peak flow may lead to faster drying in intermittent

streams. The insect fauna (and biotic community in general) of intermittent streams does not overlap to a great 

extent with that of permanent streams (Ward 1992). As a general rule, this is because intermittent stream dwellers 

have evolved to deal with the drying down stream. Survival mechanisms include leaving the stream (swimming 

down stream or emerging as land-living forms), surviving in crayfish burrows or remaining pools of water, burying 

either at shallow depths or quite deeply into the substrate or hiding under rocks or leaflitter within or along the 

stream course (Ward 1992). Streams the dry more quickly, and stay drier longer, may disrupt all of these techniques 

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as insects that emerge as adults may not have enough time to complete development (the primary example being 

mosquitoes themselves), remaining pools may decrease in size and number and shallow burrows and hiding sites 

under rocks and leaf litter may become too dry to support the fauna hiding there. 

The effect of rapid drying brings up the aspect of the hyporheic zone. This is the interstitial space between 

the substrate particles in a stream bed. Within the hyporheic zone the macrofauna can find shelter from floods, 

drought and extreme temperatures, can find suitable and predictable conditions for immotile stages such as eggs, 

pupae and diapausing nymphs and larvae and, particularly for early instars, protection from predation. Gravel beds 

provide the best hyporheic zones and animals can often be found many feet down (Ward 1992). This hyporheic

zone fauna can be an important source of recolonizing organisms after a stream bed is denuded (Williams & 

Feltmantle 1992). Excessive drying can reduce the viability of the hyporheic zone. 

Sedimentation, both within stream beds and in wetlands into which streams flow, is a problem because it 

can alter the stream bed composition, thereby altering the fauna, and can clog interstitial spaces, thereby reducing 

the hyporheic zone and/or reducing groundwater recharge. Sediments can also increase exposure to pollutants as 

they provide additional sites for pollutant binding while suspended, and then carry the pollutants to the benthic 

fauna. 

MCPs routinely conduct maintenance to remove sediments. Therefore, there is good reason to expect the 

overall effect of maintenance may be to reduce the negative impacts of sedimentation within the stream. In such 

cases, it would be preferential to develop systems designed to prevent the deposition of road sand into drainage 

systems, rather than to prevent the removal of that sand, once it has entered the system. Removing the dense, 

rotting masses of grass clippings that are dumped into streams by property owners should also improve overall

stream quality. 

Up to this point the discussion has focused on the stream itself, but freshwater wetland alterations are 

typically designed to change standing-water wetlands to soil-saturated wetlands (New Jersey DEP 1997). The 

obvious problem is that any organism that requires standing water for periods other than peak flooding, the wetland 

may become unusable. Mosquitoes fit this definition perfectly, but so do many other organisms. Many species of 

amphibians use temporary standing water for breeding and are becoming scarce as these habitats are eliminated. 

Increased drainage also may have an effect on groundwater. Precipitation and inflow determine the 

amount of water initially available to a wetland for ground water recharge (Todd 1972). Increasing the amount of 

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water removed from the wetland prior to percolation downwards can decrease the capacity of the wetland to

recharge groundwater supplies. Not only can groundwater recharge within the wetland lowered, it can be lowered 

with the outflowing stream as well. During peak flows, water moves from the stream into the substrate and raises 

the water table (increases groundwater). As the flow declines, groundwater percolates back into the stream (if it

does not, the stream dries out). By eliminating upstream reservoirs (wetlands), more water flows out of the system

initially, leaving less water within the system. As water levels fall, groundwater discharge occurs sooner than might 

otherwise be the case. If nothing else, stream depth is liable to vary more widely after adjacent wetlands are 

reduced to soil saturation.

What is most needed is a comprehensive understanding of the true ecological costs of physical alterations 

for mosquito control. This is particularly important because, although the environmental effects of pesticides 

receive the lion’s share of concern, it is possible that the long-term effects of physical controls may have a greater 

effect on the environment than does pesticide use (Buchsbaum 1994). This may be especially true today with the 

switch from broad-spectrum, more-persistent pesticides to methoprene and Bti.

New Jersey has recently updated it’s Best Management Practices for Mosquito Control and Freshwater 

Wetlands Management and Massachusetts should look to such guidelines to establish a protocol for physical control

in freshwater wetlands. At a minimum the common-sense requirements that all alterations be planned (not random), 

necessary, and desirable should be rigorously applied to all MCP water management projects regardless of whether 

they are defined as new or maintenance work. The North East Massachusetts MCP Standards for Ditch 

Maintenance (Appendix F) can be viewed as a starting point for a statewide protocol, though it fails to mention the 

need for sediment controls during maintenance work and leaves the MCP superintendent with wide latitude for 

determining the necessity of a given project. A response from the Massachusetts Audubon Society (also Appendix 

F) to these Standards provides additional comments which deserve consideration when a protocol is established. 

c. Vernal Pools. Vernal pools form in contained depressions in which water stands for a 

period of several months, generally from mid- to late winter through the spring. Water either comes in the form of 

snow melt or spring precipitation or can be a result of a rising water table. Some pools dry down within two or 

three months, others may only dry when the water table is lower than normal, resulting in a pool that is semipermanent. Regardless, a key feature of vernal pools is that they undergo periods of dry down. Vernal pools may

have permanent inlets but do not have permanent outlets (Kenney 1995). 

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There are numerous obligate species for vernal pools, the most visible of which include fairy shrimp, the 

wood frog (Rana sylvatica) and several species of salamander (Ambystoma spp.). 

The Massachusetts Division of Fisheries and Wildlife (Publication #15498-10-600-6-1-88C.R) has created 

guidelines for certifying vernal pool habitat on the grounds that many vernal pool species cannot successfully 

survive without vernal pools and that vernal pools are under pressure from continued development within the state. 

The certification program is coordinated by the Natural Heritage and Endangered Species Program (NHESP - see 

next section). “Automatic” protection is given to vernal pools only if they 

1. occur either (a) within the 100 year inland flood plain or (b) on “isolated land subject to

flooding” (as defined in the regulations at 310 CMR 10.57 (2)(b)); and 

2. its existence and location has been certified by the Massachusetts Division of Fisheries 

and Wildlife. 

Curiously, upland vernal pools are not granted the same protection but may be certified as vernal pools. The 

NHESP does not seek out pools to certify; it certifies submissions from the public. A guidebook for vernal pool

certification (Wicked Big Puddles) is available to help those who wish to submit a vernal pool site for certification 

(Kenney 1995). 

 Mosquitoes, particularly Ae. canadensis, also use vernal pools for breeding. From a control perspective, 

vernal pools are important because, due to increasing protection, vernal pool habitat is often left undeveloped while 

the land adjacent to the pool is built up. As a result, many new developments surround known breeding sites. 

Regardless of the wisdom of developing so close to vernal pools, mosquito-control personnel are charged with

controlling the mosquitoes coming from the pool. 

d. Rare and Endangered Species. Hynes (1972) states three axioms of running water 

biotic communities: 

1. The greater the diversity of the abiotic system, the greater the number of species within the 

system. 

2. The more conditions deviate from the normal, the fewer species will be present, but those 

remaining will be present in greater numbers. 

3. The longer a system is left undisturbed, the richer and more stable is the biotic community. 

Operating under the assumption that it is rare and endangered species which are most likely to be lost from the 

system first, the above statements would suggest that reductions in habitat diversity, alterations from the natural

state, and frequent disturbances will all work against these species. Channelization of streams reduces diversity by

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removing obstructions, straightening the channel and increasing flood levels. Wetlands changed from standingwater to saturated-soil regimes have been drastically changed from their natural state. Maintenance is ongoing, as is

the disturbance it causes. 

The key question is, however, to what extent does mosquito control contribute to the above 

problems. First, Massachusetts MCPs do not channelize streams, as their certification manual calls for following 

the existing meanders. Second, MCPs work neither in historically undisturbed, nor currently undisturbed streams. 

There is every reason to argue that there is no specific “natural” state that can be assigned a ditch dug by man and 

intermittently filled with road sand and grass clippings. Even with natural streams, the “natural” habitat in which

they flow has long been altered and continues to be altered. 

The Natural Heritage and Endangered Species Program (NHESP) was created in order to conserve and 

protect those plants and animals not hunted, fished, trapped or commercially harvested in the state. The program’s 

highest priority is to inventory rare and endangered species and to develop conservation plans through research, 

management and habitat protection for those species. One such program that directly impacts mosquito control is

the vernal pool certification program mentioned above. 

The NHESP also reviews proposed alterations to wetlands habitats under the Wetlands Protection Act

(M.G.L. c. 131, s. 40 and regulations 310 CMR 10.00). NHESP has produced a series of estimated habitat maps for 

rare and endangered species (Massachusetts Natural Heritage Atlas) which proponents of a given alteration are 

required to check. Should a project fall within an estimated habitat, NHESP will then determine if the area to be 

altered is actual wetland habitat for a state-listed species. The results of the NHESP determination are given to the 

inquiring MCP. 

The Massachusetts Endangered Species Act (M.G.L. c. 131A and regulations 321 CMR 10.00) prohibits

the “taking” of rare plants or animals. From a mosquito-control perspective, the most important definition of 

“taking” is disrupting nesting, breeding or feeding sites of animals or killing or cutting a plant. Aside from directly 

protecting rare or endangered species, this Act also allows areas to be designated “significant habitats.” Alterations 

in “significant habitats” require a permit from the Division of Fisheries & Wildlife. 

In Massachusetts, the species that have caused modifications in mosquito control practices are the Bluespotted salamander (Ambystoma laterale), Mystic Valley amphipod (Crangonyx aberrans), and banded bog 

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skimmer (Williamsonia lintneri). In addition, ditch maintenance in vernal pond areas has been curtailed to protect

this type of habitat. Other animals for which concerns have been raised are the yellow-spotted turtle and osprey. 

The presence of a threatened species need not prevent water management, however. In the East Volusia 

Mosquito Control District in Daytona Beach, Florida, OMWM was carried out in a salt marsh that contained the 

Atlantic salt marsh snake (Nerodia clarkii taeniata). An observer walked in front of the ditching machinery and 

work was halted until observed snakes left the area. In practice the snakes were difficult to spot and several were 

seen in the freshly cut ditches behind the ditcher. Two dead snakes were found, and assumed killed by the work. 

The dead snakes were handled as “incidental take” and placed on ice for delivery to the Florida Game and Fresh 

Water Fish Commission (Goode 1996). With an increased understanding of the ecosystems in which mosquito

control takes place, mosquito control projects should improve their ability to work in areas containing endangered 

species with minimal impact to those species. 

Under the current system mosquito-control maintenance activities are exempt from the Massachusetts 

Wetland Protection Act, leaving only the federal 401 Water Quality Certification Act and both the Massachusetts 

and federal Endangered Species Act as methods for regulating maintenance. Unfortunately, water quality, while 

important, does not address the issue of changing habitat and the presence or absence of a rare and endangered 

species has little to do with the merits of a given project. 

Rare and endangered species will probably increase in their impact for several reasons. First, as data is 

collected on these species, additional species and additional habitats will most likely come under protection. 

Second, residential areas are creeping closer to wetlands areas. The net effect is that the clash between economic

development and environmental protection will likely increase, with mosquito control being one component of an 

intense debate. Again, a more comprehensive understanding of the true ecological effects of mosquito control is

required to better determine the cost/benefit ratio for different types of mosquito control. 

D. Food Web Effects of Mosquito Control. 

Throughout their life cycle mosquitoes are a part of the food web, both as consumer s and prey. As larvae 

most species feed on algae, protozoa, and organic debris (Pennak 1953). As adults they drink nectar and the 

females of most species take blood meals from a wide variety of animals. Larval mosquitoes are eaten by an 

impressive array of animals (Bates 1949) while adult mosquitoes are taken by spiders, predatory flies, odonates, 

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bats and birds (Collins and Washino 1985). Given that mosquitoes are so thoroughly embedded in the food web, 

the question arises as to the effect of removing a large percentage of the mosquitoes from that food web. 

At first glance, the effect would appear to be large, particularly in habitats with dense larval populations. 

However, mosquitoes are r-strategists, in that they produce large numbers of eggs that develop quickly (when 

immersed in water) to adulthood. Most pest species seek out temporary and spatially disconnected habitats for 

breeding and can complete a breeding cycle long before an adequate predator complex can develop. Mosquitoes 

are, therefore, a highly unpredictable food source for predators, and predation rates must be equally unpredictable 

(this section will focus on predation, as parasites and pathogens are not widespread control agents in 

Massachusetts). This is borne out by the fact that mosquito predators are generalists which can readily switch to

other prey when mosquitoes become scarce (Collins and Washino 1985). In a study in Florida, immature 

mosquitoes made up over 50% of the diet of several species of saltmarsh fish (Fundulus confluentus, Lucania 

parva, Gambusia a. holbrooki). But each of these species fed on other items as well, including copepods, shrimp, 

other fish and even some plant material (Harrington and Harrington 1961). 

One important point regarding predation and larval broods is that the concepts of handling time and 

satiation come in to play (Varley et al. 1973). A predator must spend a certain amount of time with each prey. 

Hydrophilid larvae took several minutes to feed on larvae and pupae taken in a panne in Tiverton, Rhode Island 

(Christie, pers. observation). Not only does it take time to catch and eat the prey, but invertebrate predators are 

typically not much larger than the mosquito larvae they are attacking. Satiation must play a role in limiting predator

take, particularly when mosquito numbers are high. 

Predators can play an important role in regulating mosquito numbers in some situations. That mosquitoes 

are absent from waters with fish populations is well known. Less well known is the influence of chaoborid larvae, 

which can severely reduce mosquito populations in vernal pools (Morrison and Andreadis 1990). In this case the 

larvae are present in snow-melt pools for approximately two months, so predation has time to operate as a 

regulating mechanism.

Although adult mosquitoes are eaten by numerous predators, it is rare that they make up an appreciable

proportion of the diet of any one predator. One exception is the spider Tetragnatha montana for which, in Poland,

mosquitoes made up 74% in June and 62% in July of all prey captured (Collins and Washino 1985). Bats and 

purple martins are not effective mosquito predators nor do mosquitoes form a significant part of their diet. 

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From a mosquito-control perspective, the mosquitoes to be controlled are, for the most part, those which 

have escaped predation to become predators in their own right. In the absence of scientific data supporting the 

necessity of mosquitoes in the diets of specific animals, removing mosquitoes from the food web by chemical, 

biological or physical control remains an easily justifiable activity. Even so, control personnel should take care to

avoid chemical applications where mosquito larvae are not present or are present in very small numbers, should use 

control measures that do not harm existing predator complexes, and should limit control to areas where control is

necessary, allowing natural cycles to continue in areas where human activity and the risk of disease transmission is

slight. One argument made in favor of Altosid is that it does not kill the young larvae, leaving them available as 

food for the existing predator complex. 

Up to this point, the discussion has focused on the effect of chemical control (including Bacillus products

and IGRs) of mosquito populations on other species. Within the context of biological control, one of the primary

reasons Gambusia are not being used in Massachusetts is the fear that they might displace native species of fish, 

thus altering the natural biota, not by predation but by competition for the same resource. 

Physical control by water management may increase predation, as in OMWM, or may eliminate predator 

and prey as when wetlands are drained to soil saturation. Mosquito breeding must be thoroughly documented before 

new work is done. Because disturbances may displace some species, and because predator species tend to rebound 

more slowly than their prey, maintenance work should be conducted only when necessary. 

E. No Program

Another alternative strategy to current mosquito control practice is no control. Many communities in

Massachusetts have chosen this option. These town are usually outside of the enzootic EEE zone so the risk of 

human diseases transmitted by mosquitoes is viewed as practically nil by these communities. In addition, they are 

not located near salt marshes and their attendant pest mosquito problems. The mid-section of Massachusetts, where 

most no-control communities occur, also has a more rural character, less wetland , lower human populations, and a 

lower mean family income than most eastern areas with organized mosquito control programs. In general, the view 

of these communities is that the anticipated benefits from mosquito control do not outweigh the anticipated costs 

and perceived risks. 

A more precise way of polling the public and confirming this opinion would be through establishing the 

Human Annoyance Threshold (HAT) for the town. Communities in which the HAT is below the actual annoyance 

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level should be persuaded to choose the no control option since justification for control is lacking unless a 

documented disease threat exists. 

In some communities, biting annoyance is created by a combination of biting insects (i.e. mosquitoes, 

black flies, biting midges and tabanids) which require completely different control approaches. Many people do not

recognize the difference between these insects, especially in dim evening light. It is critical to accurately identify 

the biting insects actually responsible for the human annoyance. In general, black flies and tabanids only cause 

annoyance during the daytime while mosquitoes and biting midges are most annoying from 6-10 PM. The HAT 

level for tabanids and biting midges is likely to be less than for mosquitoes because of their more painful bites. 

Perhaps part of the reason why Berkshire County communities have supported a MC program while other 

Western Massachusetts communities have not, lies in the fact that this region supports many summertime outdoor 

activities (e.g. camps, resorts, golf courses, Tanglewood, etc.). In addition, this more mountainous region has a 

significant black fly annoyance problem superimposed on top of the mosquito problem. Vacationers are likely to 

have a lower HAT than permanent residents since they are spending more time and money on outdoor recreational

activities. 

In addition to risk-benefit considerations, other criteria for weighing the control/no control option are 1) 

the feasibility of successfully reducing annoyance below the HAT level, and 2) the adequacy of community 

resources for reducing annoyance to acceptable levels. 

Towns with large areas of mosquito-producing freshwater wetland should recognize that effective 

mosquito control in these habitats is difficult at best and often impossible. As indicated earlier in this report, 

permanent wetlands do not usually produce large numbers of pest mosquitoes but in situations where they do, the 

public needs to be aware that these wetlands are a valuable resource that must be protected from significant

perturbation and that options for mosquito control are therefore few. Community planning boards and zoning laws 

can and should be used to restrict residential development and other human activities from such wetland areas. 

Towns with annoyance problems but with large land areas and thinly, scattered populations must

understand that the same level of mosquito control achieved in more populated communities will cost them

significantly more per capita. In many such cases, the economic status of the population means that insufficient tax 

dollars can be generated to adequately deal with the problem. 

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Nantucket provides an interesting case study. Mosquito control had lapsed in the early eighties. However, 

by 1989 saltmarsh mosquitoes were becoming a significant problem in the west and north areas of the island. The 

town began applying Altosid (including aerial applications of pellets in 1992) to control the mosquitoes while. 

getting the requisite permits for OMWM in several west-end marshes (Madaket, Warren’s Landing Eel Point). The 

OMWM systems were dug in January 1993 (Christie 1993). It was hoped that the OMWM alone would be 

sufficient to control mosquitoes but large-scale breeding continued in the north end (Pocomo) and the low tidal

range has hindered the effectiveness of the OMWM as dug. As a result, some lariviciding continues. The 

conclusion on Nantucket is that mosquito control against saltmarsh mosquitoes must be continued at some level in

order to provide residents with the summer environment they want. However, Nantucket does not target freshwater 

mosquitoes at all and does no adulticiding. Nantucket and Cape Cod together indicate that adulticiding is not a 

requirement even in high-tourist areas. 

It is difficult to measure the impact of choosing the no control option. The example of towns that have left, 

and left and later rejoined MC projects is perhaps the only available basis for estimating public opinion concerning 

such impact. No documentation of annoyance levels, cases of disease, recreational dollars spent, etc., was ever 

attempted in these towns when they had mosquito control versus when they did not. Thus, public complaints were 

apparently the main indication of the impact of the no control option that was used in guiding town decision 

making. 

In the 1986 questionnaire, only about 10% of the towns in organized projects indicated that there had been 

controversy relative to leaving, joining, or rejoining a project. Those that had experienced controversy indicated 

that 4 factors were about equally involved. These were: 1) monetary constraints, 2) concern over the effectiveness 

of project control programs, 3) concern over the safety of the methods used by the project, and 4) concern over the 

environmental impact of the control procedures. Paradoxically, 86% of these towns indicated they were unwilling 

to spend more money (if legally possible) to obtain more effective control and 67% indicated unwillingness to 

spend more money to support less hazardous control methods. However, the bias of the people filling out the 

questionnaire sent to each town may have influenced these responses; no town in Massachusetts has actually polled 

their citizens on these questions. In fact, some towns within projects have taken advantage of new provisions which 

allow towns to collect additional money for MC activities which projects can then only spend in these towns. 

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Among towns that actually withdrew from MC programs, monetary constraints played a role in 73% of 

these decisions, followed by environmental concerns in 32% and concern over effectiveness in 27% of these cases. 

Towns that contemplated withdrawing but did not do so, indicated that monetary and effectiveness considerations 

dominated their concern. 

The number of towns in MCPs declined in the late eighties. Economic factors, not environmental

concerns, were the dominant reason given for withdrawal. This trend has reversed itself significantly in the last 

several years. The 1990 EEE problem is probably one reason, coupled with the fact that several coastal programs 

tried the no-control option and found mosquito numbers rose quickly. 

Many towns in the Berkshire County and South Shore projects withdrew in 1981 mainly in response to

Proposition 2-1/2 monetary constraints. The remaining 8 towns in Berkshire County subsequently chose to 

continue as a multi-town Project (Note: the town of Lanesborough rejoined in 1986, the city of Pittsfield rejoined in 

1988, and other towns are contemplating reentry). South Shore actually disbanded as a project but by 1988 most

towns had joined neighboring MC projects in Norfolk and Plymouth Counties. These actions suggest that these 

communities were not content with the no control option that resulted from the disbanding of their former project. 

Towns that voluntarily withdrew from MC projects but then later rejoined a project, did so for a variety of reasons. 

These were in order of their importance: increased public support for MC, increased mosquito annoyance, 

alleviation of monetary constraints, threat of EEE, improved methods and effectiveness of the project. 

The Environmental Impact Statement (Sjogren 1977) prepared for the Metropolitan Mosquito Control 

District in Minnesota attempted to quantify the no control option for their community. Any attempt to develop

similar estimates for Massachusetts would be meaningless given the lack of appropriate baseline data. 

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B. Biological Control.

1. Introduction 

Biological control includes attacks on the pest species by other species and manipulation of the pest species 

itself. The former includes the traditional biological control agents, predators, pathogens and parasites, whereas the 

later includes such techniques as sterile-male release and genetic manipulations. 

Biological control agents are grouped into three categories: predators, parasites and pathogens. Predators 

include both vertebrates and invertebrates and may attack both adult and immature stages of mosquitoes. Helminth, 

protozoan and fungal parasites and microbial pathogens generally only invade immature stages, though mortality 

may not occur until the early adult stage. Parasitic water mites are an exception in that they attach to certain adults 

as they emerge from the pupal stage and apparently reduce adult survivorship if they are abundant (Lanciani & 

Boyett 1980) In general, biological control is much more feasible in managing permanent water mosquitoes than 

temporary water forms. 

There are three basic strategies for utilizing all biological control agents: (1) increasing existing natural 

enemy populations by habitat alteration, (2) one-time introduction of sustainable exotic agents from other regions or 

habitats, and (3) augmentation of natural or exotic enemy populations by repeatedly releasing non-sustainable, labreared (or field collected) organisms. To date only the first, increasing fish habitat through OMWM, has been used 

in Massachusetts. Bti is sometimes classified as a biological control agent but its application technique and mode of 

action as a stomach poison more closely resemble a pesticide than a biological control agent per se. Bacillus 

sphaericus may more closely fit the model of repeatedly releasing non-sustainable lab-reared organisms as there is

evidence to suggest that it recycles within the environment.

No other biological control agent is currently available for general field use, though experiments continue 

with may different organisms (see below). There are important reasons why biocontrol is not more widely used 

against mosquitoes. First, the differences in biology of the various species of mosquitoes make it unlikely that any

one control agent will operate across a wide range of species. Second, mosquito breeding is wide spread, making it 

difficult for a biological control agent to find, or be placed in, all breeding areas. Third, predators such as bats and 

purple martins, may eat mosquitoes but prefer to eat other, larger insects. Further, even when abundant, they do not

drive mosquito populations below levels that people generally find intolerable. Finally, there is a high cost

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associated with sustained releases of a biological control agent and there are not, at this time, control agents 

available that require a single, or a few, releases to become established. 

Because of the limited application of biological control to mosquitoes in Massachusetts, the following 

discussion will focus primarily on the feasibility of control agents currently being studied for mosquito control. An

important point to make regarding biological control is that the mosquito control have limited research capabilities. 

While conducting field evaluations of new control techniques is a desirable practice for any mosquito control

program, the projects should not be expected to find and bring forward biological control agents without substantial

help from research institutions such as the state university. 

2. Predators 

 a. Introduction 

In order for any predator to independently be an effective control agent, it must meet two important

criteria: (1) its size and abundance in relation to the target species must be sufficient for it to kill or consume a high 

percentage of the prey population within a relatively short time period, and (2) its feeding behavior should be 

selective toward the prey species when it is present but allow it to utilize other food items when the target species is 

absent. These criteria are rarely met in full. Predators that are sufficiently large and/or abundant to have a major 

impact, usually lack feeding specificity. Conversely, those with feeding specificity are usually less abundant

because their populations are regulated by a more restricted food supply. Vertebrate predators of insects have a 

clear size advantage but invertebrate predators tend to exist in much greater numbers. 

Because of the limitations of predators as biocontrol agents, it is normally essential to continuously raise 

and release the predator to achieve field densities high enough to cause real reductions in the prey species. 

However, in some cases, manipulation of the environment to the advantage of natural predator populations can 

provide an adequate augmentation effect. 

 b. Vertebrate predators 

Fish

Larvivorous fish are the oldest and perhaps most effective traditional biological control agent used against

mosquitoes. In certain habitats they may, by themselves, provide adequate larval control throughout the breeding 

season. If not, pesticides such as BTI or methoprene which are non-toxic to vertebrates can be used in an integrated 

fashion with fish. 

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As already mentioned, the main reason open saltmarsh management strategies effectively control many

saltmarsh Aedes in the Northeast is because this method provides access for the abundant estuarine populations of 

larvivorous killifish (Fundulus spp.) into the mosquito breeding pools in the high saltmarsh (Hruby & Montgomery

1986). 

 The mosquitofish Gambusia affinis is distributed widely throughout the warmer parts of the world and is

the species most often reared and introduced into fresh water habitats for mosquito control. The biology and use of 

this fish in mosquito control was reviewed by Meisch (1985). It is an opportunistic feeder and avidly eats pupae 

and late-instar larvae of culicines and chironomids. It is most effective against Culex in unvegetated, permanent

ponds but has been widely used in California and the Gulf States against ricefield Aedes and Psorophora. 

 Because Gambusia is so aggressive and fecund, it may replace important commercial or rare native fish 

species. This has raised environmental concern over the introduction of this fish into natural waters where it does 

not already occur. A recent article by Rupp (1996) has renewed this debate, both emphasizing real successes and 

real concerns over Gambusia use (see “Comments on ‘adverse Assessments of Gambusia affinis’” (JAMCA 1996) 

and Boklund 1997, Eliason 1997, and Rupp 1997). Because it is not a native species of Massachusetts it may not be 

imported and released in state waters. 

Outside of the mosquitofish, the common guppy (Poecilia reticulata) has received the most attention for 

mosquito control (Bay 1985). Comparative studies indicate that it is a less effective predator than Gambusia but it

is more tolerant of polluted waters. Many other native fish have been explored for their mosquito control potential

(Bay 1985). Studies in North Africa (Allo et al. 1985) suggest that malaria may be controlled through the annual

introduction of native fish from streams into the manmade water storage tanks which produce the vector Anopheles

in this region.

Birds

Many birds depend on insects as food and those which capture insects on the wing (e.g., the swallows), 

have been credited with consumption of significant numbers of mosquitoes. Purple martins specifically have been

promoted on the basis of the claim that they often consume 10-12 thousand mosquitoes per day but Kale (1968) 

concluded on the basis of existing evidence that all claims of martins significantly reducing mosquito populations 

were unsubstantiated and, because of several biological facts, were unlikely to ever be demonstrated. The facts on 

which these conclusions were drawn are as follows: 

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(1) Mosquitoes were a negligible item in the diet of martins in the only two published studies in

which the contents of martin gizzards were examined. 

(2) None of the published statements appearing in the popular ornithological literature which 

attributes a mosquito-eating habit to martins is based on factual study or scientific reference. In

fact, there is evidence that martins feed more on larger insects including species of dragonflies 

which may be predators of adult mosquitoes. 

(3) Behavior patterns of mosquitoes and martins are such that they tend to not fly at the same height

or at the same time. Thus, contact between the two is minimal. 

(4) There is no evidence that any avian species can effectively control a pest insect upon which it

feeds when the insect is at or near peak abundance. 

Other Vertebrates

Mosquito control by insectivorous bats was tried in the early part of this century but without success (Kale 

1968, Storer 1926). Bats continue to appear in the popular press as legitimate mosquito-control agents (Wright 

1996) but are not considered worthwhile agents in Common-sense Pest Control (Olkowski et al. 1991), which is

very thorough in its coverage of non-chemical control options, or in mainstream mosquito control (Mitchell 1992). 

c. Invertebrate predators 

Predators of mosquito eggs.

Evidence exists of predation on diapausing flood water mosquito eggs by mites and beetles, and on Culex

egg rafts by fish (Collins & Washino 1985). Nonetheless, egg predation appears to be a relatively minor component 

of natural mosquito mortality and is not being studied for biological control. 

Terrestrial insect and spider predators of mosquito adults

Predation on emerging and indoor resting adult mosquitoes has been readily observed but the impact of this

mortality on populations is extremely difficult to assess. Certain spiders (especially Tetragnatha) and predatory flies 

(mainly Empididae, Anthomyiidae and Dolichopodidae) have been shown by precipitation tests to have consumed 

emerging mosquitoes (Collins & Washino 1985). In one British study, up to 28% of the spiders tested had eaten 

mosquitoes (Service 1973). Certain adult dragonflies reportedly capture mosquitoes on the wing but these 

observations have not been backed up by any controlled field studies. Synanthropic emesine bugs (Reduviidae) 

appears to be potentially important predators of indoor resting mosquitoes in the tropics. In sum, the prospect for 

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enhancing or managing invertebrate predators for more effective adult control is not encouraging, especially in 

temperate regions. 

Aquatic insect predators of mosquito larvae & pupae

Aquatic insect predators seldom occur in significant numbers in the temporary floodwaters that produce 

most pest mosquitoes. Studies of predation have therefore largely taken place in permanent ponds or semipermanent habitats such as rice fields, rock pools or vernal woodland pools. The adult stage of most predaceous 

aquatic beetles and true bugs can fly (usually at night) so natural colonization of newly flooded habitats can occur in

a matter of days. Development time for these insects is usually from several weeks to several months. 

Among the beetles, the dytiscids (predaceous diving beetle), which are predaceous both as larvae and 

adults, are the most effective predators of mosquitoes. There is evidence from studies in rice fields that adult 

dytiscids selectively locate and colonize sites with locally high concentrations of mosquito larvae (Collins & 

Washino 1985). Mass production methods for dytiscids have never been developed. Whirligig beetles (Gyrinidae) 

only feed at the surface where they may prey on concentrations of emerging adult mosquitoes. Hydrophilids are 

only predaceous as larvae and seem to feed mainly on chironomid midges. 

Only two aquatic families of true bugs, the back swimmer (Notonectidae) and pigmy back swimmer 

(Pleidae) have received serious consideration as mosquito control agents. Pleids are generally not abundant enough 

to have significant impact but notonectids can become quite dense in certain habitats. Mass rearing of the latter 

appears to be possible. Water boatmen (Corixidae) are also common and similar in appearance to backswimmers 

but they are mostly detritus feeders. Other predaceous aquatic Hemiptera that have been suggested as mosquito

predators but which normally occur in insufficient densities to have much value as natural control agents include the 

giant water bugs (Belostomatidae), water scorpions (Nepidae), water measuring bugs (Hydrometridae) and the two 

family of surface-feeding, water striders (Gerridae and Veliidae). 

Dragonfly naiads have been marketed commercially for mosquito control and at least one town in

Massachusetts, and others in New Hampshire and Maine, have purchased dragonflies for mosquito control. In 

northern climates these insects require 1-5 years to mature, so they normally occur in permanent waters only. 

Furthermore, many are bottom feeders that seldom if ever come in contact with mosquito species that feed at the 

surface or in the water column. Most bottom-feeding mosquitoes (i.e. Aedes) occur in temporary water containing 

few if any dragonfly naiads. Another factor weighing against the mosquito control efficiency of these aquatic

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predators is the fact that they normally occur at low densities. Adults of many species are territorial and this seems 

to spatially limit population densities of naiads as well as adults. In certain habitats such as rice fields, naiads may 

become quite abundant but populations fluctuate greatly and their role in limiting populations of rice field 

mosquitoes is limited at best. No controlled, field studies have been done in which naiads have performed well as 

biological control agents. 

 The trichopteran Limnephilus indivisus may be an important predator of early spring Aedes in woodland 

swamps in Ontario but most caddisflies are omnivorous shredders rather than predators (Collins & Washino 1985, 

Merritt & Cummins 1985). Prospects for mass rearing and manipulating caddisfly larvae are not very bright. Many 

of the aquatic nematoceran relatives of mosquitoes contain groups with predaceous larvae. These include the 

families Chaoboridae, Chiromomidae, Ceratopogonidae, Tipulidae, Anthomyiidae, and others. Most are too small 

to consume many mosquito larvae. Predation on small, early instars occurs but it is far less efficient in reducing the 

numbers of adults than is predation on late instars and pupae. Mochlonyx (Chaoborid) predation on spring Ae. 

communis populations has been observed in woodland pools in Massachusetts (Edmans, personal communication) 

and in Europe (Chodorowski 1968). The impact of this small but voracious predator is unknown. 

The insect predator with the most promise in mosquito control is another mosquito. Larvae of the nonbiting genus Toxorhychites are large and effective predators of mosquitoes that develop in natural and man-made 

containers such as tires, tree holes, metal cans, and leaf axis (Steffan & Evenhuis 1981). Unfortunately, none of the 

70 some species in this mainly tropical genus can survive the winters as far north as Massachusetts. Their use here 

would therefore require repeated, annual releases of lab-reared females. This is not warranted at the present time 

since container-breeding species generally do not represent the major nuisance or health threat in Massachusetts. 

This situation could change if Ae. albopictus becomes well established in used tires in the Northeast. Focks (1985) 

states that although it is possible to control or reduce certain species of container-breeding mosquitoes with

inoculative or inundative releases of Toxorhynchites, the usefulness of this genus in practical, operational control

programs has yet to be demonstrated. 

Other invertebrate predators of larvae and pupae.

Among the non-insect predators of the immature stages of mosquitoes, only hydra (Cnidaria: Hydrozoa), 

flatworms (Platyhelminthes: Turbellaria) and copopods (Cyclopoida) have been studied in any detail.

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Both hydra and flatworms can be easily mass produced and, unlike most predaceous insects, they can be 

maintained at high densities without cannibalism. In the laboratory, they kill far more larvae than they consume. 

Both groups produce semi-dormant eggs so they occur naturally in shallow temporary pools as well as permanent

swamps and ponds. Detrimental effects on young fish have been reported when these predators are at high densities 

(Mulla & Tsai 1978). 

Both of these predators have good potential as control agents in the Northeast but additional long-term

field evaluations are needed. As with mosquito fish, the laboratory production, storage, and field translocation of 

these organisms requires a certain degree of sophistication, which is usually lacking at the local level. Currently, 

there are no commercial sources for the quantities that would be required for mosquito control applications. 

Natural populations of predaceous cyclopoid copepods appear to limit the distribution of container 

breeding mosquitoes in certain tropical settings (Marten 1984). However, they have never been shown to be 

important predators in temperate regions or in other types of aquatic habitats. Therefore their potential for the 

biological control of pest and vector mosquitoes in Massachusetts appears to be nil.

3. Parasites and Pathogens 

a. mermithid nematode parasites 

Outside of bacteria, parasitic nematodes are the only natural parasites and pathogens that have ever 

achieved operational status in mosquito control. Known parasitic roundworms of mosquitoes now number over 20 

species. The free-living, aquatic, preparasitic stage which hatches from the nematode egg, seeks out and penetrates 

the cuticle of host mosquito larvae. Larvae are usually killed in the last instar. In a few species, the mature worms 

are carried over in the adult mosquito and cause mortality when they exit during attempted pseudo-oviposition. 

 Romanomermis culicivorax (including most references to Reesimermis nfelseni) is the species that has 

been most extensively studied. Methodologies for the mass production and commercial preparation of this species 

have been developed and it was briefly marketed as Skeeter Doom in the late 1970'g. Low sales and problems with

the shipping and shelf-life of viable eggs appear to have been the major factors which led to the marketing failure of 

this agent (Service 1983). Other economic drawbacks include host specificity which limits its effectiveness to only

certain species (e.g., it is ineffective in cold, polluted or brackish water), and the lack of patent protection for 

companies investing in the production and marketing of this product. In addition, applicators need some special 

skill and training to effectively use this biocontrol agent. The tendency of this agent to naturally recycle once it is 

 194
introduced into favorable aquatic habitats is beneficial from a control viewpoint, but it further reduces the long-term

marketability and profit potential for private producers. It remains under study, however, as a recent article ( 

Mijares et al. 1997) discussed the establishment of R. culicivorax in sewage settling ponds and natural ponds in 

Cuba. 

On the biological plus side, mermithids appear to be highly compatible with a wide range of chemical

pesticides and growth regulators. Moreover, they: 1) are non-specific and well suited to the life cycle of their 

mosquito host, 2) produce high levels of infection and mortality, 3) can be easily mass-produced and applied with 

standard spray equipment, and 4) offer no threat to non-target organisms or the environment.

There are species of mermithids which appear to be highly specific to spring snow-pool Aedes and to

saltmarsh Ae. sollicitans (Petersen 1985). However, these worms have not been established and studied in the 

laboratory. Such species may have greater control potential in northern coastal states like Massachusetts than the 

more tropically adapted R. culicivorax.

Since the technology for using mermithids in mosquito control already exists, and there are numerous field 

trials documenting their control potential, the future availability and use of these biocontrol agents in operational 

programs seems to depend on changing economic and market forces (Petersen 1985). 

 protozoan parasites 

 b. Microsporidia

Virtually all mosquito species carefully examined have been found to harbor these parasites. Larvae are 

infected by ingesting the spore stage. Spores, which are produced at the end of the life cycle, have often proven 

difficult to induce and to reinfect larvae in lab cultures. Few microsporidian life cycles are well enough known to

assess biocontrol potential. Life cycles vary from simple to complex and often form the basis for the non-taxonomic

grouping of these protozoan parasites. The simplest forms (Type I) occur mainly in terrestrial insects and even the 

one aquatic species known from mosquitoes (Nosema algerae), does not cause mortality until, the adult stage. For 

this reason N. algerae has limited potential for reducing pest problems but may impact on disease transmission by

reducing survival and fecundity. Wild strains only persist in larval populations for short periods and cause little 

direct mortality. Type II microsporidia have simple, asexual life cycles similar to Type I forms and they also show

little promise in mosquito control (Hazard 1985). Type III forms are dimorphic, have binucleate spores, and kill 

mosquitoes in the larval stage. Only one species (Hazardia milleeri) is known from mosquitoes and it seems to

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have low infectivity (Hazard 1985). Type IV microsporidia include many species from mosquitoes and have the 

most control potential. Infected larvae are usually killed but a few females survive and carry the infection via the 

ovary to the next generation. However, transovarial infection ceases after a single generation. Non-ovarian modes 

of transmission must exist but this issue along with the possibility of sexual reproduction and alternate hosts are as 

yet unresolved. Additional basic research is required before any microsporidian can be considered in the biocontrol

of mosquitoes (Hazard 1985). 

Tetrahymena and Lambornella (tetrahymenid ciliates)

The lack of a resistant resting stage and difficulty in culturing these ciliated protozoa has prevented the 

thorough study and evaluation of this group of potential biocontrol agents. Ongoing studies of Lambornella clarki

in California treehole Ae. sierrensis should help to better assess the control value of these parasites in the near future 

(Anderson et al. 1986). 

Helicosporidium

There is still debate concerning the proper classification of this spore-forming group of parasites; some

believe they are primitive Ascomycetes fungi. There are only 3 reports of natural infections in mosquitoes. They 

appear to infect a wide range of species but also may infect non-target insects as well. High dosages of spores are 

required to infect older instars in the lab. Continuous cultures of these parasites do not exist so the basic research 

needed to evaluate their biocontrol potential is not forthcoming. 

 c. Fungal Pathogens 

Coelomomyces

Many forms of pathogenic fungi have been known from both larval and adult stages of mosquitoes since 

the 1930's. However, it was not until the discovery of the obligate alternate host (i.e., microcrustacea) in the mid70’s that cultures and full-scale laboratory investigations were possible with Coelomomyces (Whisler et al. 1974, 

1975). The rather complex life cycles of some species have recently been described and methods for in vivo 

culturing established. Before wide-scale field application can occur, mass in vitro cultivation of the infective 

biflagellate zygote stage needs to be developed. If Coelomomyces, and perhaps their copepod and ostracod 

intermediate hosts, are introduced into favorable habitats, the potential for natural recycling exists. However, too

little is known about the host ranges and habitat requirement of most Coelomomyces to recommend any such 

introduction at the present time. Moreover, species of Coelomomyces do not routinely provide high and predictable 

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levels of mosquito control. It is, premature to critically assess their potential as control agents to be used

independently or as part of an integrated control program (Federici et al. 1985). Studies related to their evaluation 

as operational control agents have only recently been initiated and it is not likely that any Coelomomyces will be

operational within the near future. 

Lagenidium giganteum. 

This mosquito-specific water mold is a very promising biological control agent, especially in fresh water 

and in warmer climates. This fungal pathogen can be mass produced on artificial media and can recycle in as little 

as 3 hours (McCray 1985). It has a resistant, dormant stage and infects a wide range of mosquito species. 

Unfortunately, it is not effective in polluted, brackish or colt waters. This limits its commercial value and it 

potential usefulness in northern and coastal states like Massachusetts (Service 1983). 

Other Fungi

Fungi are among the commonest pathogens of insects and many other genera besides Coelomomyces and 

Lagenidium have been reported from mosquitoes. Of these, Culicinomyces and Metarhizium have received the most 

attention. Both groups infect a wide range of mosquito species but relatively high concentrations are required to

cause infection. They can tolerate organic pollution and salinity but not high temperatures (i.e. above 30°C). 

These fungi can be grown on inexpensive artificial media but no resistant resting stage has been fount. Difficulty in

achieving long term storage of infective stages and formulation problems remain as barriers to commercial

production. Nonetheless, these fungi are a promising group of biocontrol agents which may provide new mosquito

control tools in the future. 

Erynia aquatica

 Erynia aquatica is an Entomophthorales fungus, and is the only species of the genus known to infect the 

immature aquatic stages of mosquitoes. It was first discovered infecting Ae. canadensis and Cs. moristans larvae in

woodland pools in Hartford County, Connecticut from late May to early June (Anderson & Ringo 1969). It has 

since been recovered in early May from Ae. stimulans in woodland pools near the village of Cambridge, New York 

(Molloy & Wraight 1982) and from Ae. cantator on May 21, 1981 in a shallow salt meadow pool in Milford, 

Connecticut (Andreadis & Magnarelli 1983). Most recently, is was discovered in 1995 and 1996 in a woodland 

pool in Bristol, Rhode Island (Christie 1997). 

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Steinkraus and Kramer (1989) collected Ae. fitchii larvae infected with E. aquatica from a semi-permanent

woodland pool in Tompkins County, New York. They used infected pupae to successfully transmit the disease to 

emerging adult Ae. aegypti, on which resting spores of the fungus developed. 

 Erynia aquatica has characteristics which make it attractive as a microbial agent: it is capable of causing 

epizootics, has been found in both freshwater and brackish water mosquitoes and has a resting spore stage that may

survive well in storage. Operating against it is the fact that it has only been found in cooler, springtime waters. One 

thought is that infected pupae may be removed from the original infestation site and placed in other, nearby pools. 

A fungus that kills in the pupal stage works against its own spread.

 d. Bacterial pathogens 

Bacillus thuringiensis var. israelensis

Bti Serotype H-14 has become an important biological larvicide following its discovery in the Negev desert 

in 1976. Within the last 5 years it has become widely used by the mosquito control projects in Massachusetts. It is

now the larvicide of choice in many situations because of its host specificity, high and rapid mortality to many 

mosquitoes species, and its environmental safety. It is quite distinct from the Bt strains which infect lepidopterous 

insects. Its track record in controlling polluted-water Culex is mixed, apparently because it sinks to the bottom and 

the active moiety rapidly binds to organic particulates. Consequently, higher dosages are required to achieve good 

control in highly organic and deep-water situation. Saltmarsh mosquitoes generally require rates at the high end of 

the labeled application rates for effect control. Liquid, powder, granular and slow-release briquet formulations are 

commercially available. 

 Bti must be ingested to cause toxicity to filter-feeding mosquito larvae; pathology occurs in cells of the 

midgut wall. It is least toxic to 4th instars since they cease feeding at least 12 hours prior to pupation. The 

mosquito toxic ingredient of Bti preparations is the heat labile deltaentotoxin located in the proteinaceous parasporal

crystalline inclusions synthesized concomitantly with the spore during sporogenesis. Once released in the 

environment, it biodegrades rapidly (it is usually only active 1-3 days) and this bacterium (gram negative 

Bacillaceae) does not recycle. This is considered the only major drawback of this highly effective mosquito 

pathogen but it has enhanced its commercialization (Lacey & Undeen 1986). 

The biocidal activity of Bti toxin appears to be limited to larvae of certain families of nematocerous

Diptera. A large number of laboratory and field tests have confirmed that all non-nematocerous, non-target

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organisms are virtually unaffected (Lacy 1985). All existing data indicate that the unaltered protoxin of Bti is also 

safe to vertebrates including humans (Lacey 1985). Further improvements in the efficacy and price competitiveness 

of this control agent, brought about by formulation changes and genetic engineering, are likely to occur in the near 

future. In addition, formulation of this agent with other compatible and perhaps synergistic agents such as juvenile 

hormone analogs (e.g. Altosid) is currently underway. Such mixture have two important advantages. They reduce 

the likelihood of mosquitoes developing resistance to either agent and, secondly, they widen the window for control

since Bti is most effective against early instars and growth regulators against later instars. 

Bacillus sphaericus.

Although only recently available, B. sphaericus may have greater control potential than Bti because of its 

ability to continue to recycle once it is introduced. It has many of the same beneficial attributes of Bti but all strains 

isolated to date are less effective against a wide range of species than is Bti. At the moment it is primarily marketed

against Culex in high-organic waters but research is on-going in expanding its control potential.

 e. Viral Pathogens 

The biological control potential of both non-accluted (iridoviruses and densonucleosis viruses) and 

occludet (baculoviruses, cytoplasmic polyhedrosis viruses and entomopox viruses) viruses pathogenic to

mosquitoes has recently been reviewed by Federicci (1985). It is sufficient here to simply paraphrase from the 

summary of this thorough review as follows:

Analysis of research conducted to date makes it clear that none of the viral pathogens of mosquitoes can 

currently be considered good candidates for mosquito management programs. The two main reasons for this

assessment are that viruses discovered so far possess low infectivity for original or alternate hosts and there is no

readily available method for mass production of virions. This apparent lack of control potential is most obvious 

when one considers that few field trails have been conducted with these agents even though the first one was 

discovered over 15 years ago. While it appears unlikely that viruses will be developed for mosquito control in the 

near future, they may prove to be extremely useful microbial agents in the long term, perhaps in 2 or 3 decades, 

once we learn how to manipulate them effectively. Biotechnology has the greatest potential for engineering new 

more useful biocontrol organisms among the viruses because of their simple molecular structure. 

4. Pest Species Manipulation 

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A somewhat different approach to biological control is manipulation of the mosquito genome to either 

1) induce reproductive failure (leading to population elimination) or 2) bring about permanent changes in the 

behavior or physiology of the target population so it no longer vectors disease or bites people. There are numerous 

theoretical mechanisms by which this could be accomplished. Following is a brief discussion of the three 

approaches that have been most commonly discussed and researched. 

a. Sterile Insect Technique 

The early and continuing success of the sterile male release program in eliminating the screwworm fly 

from the U.S. and Mexico has given rise to many investigations and new ideas for controlling other insects 

(inoculating mosquitoes) through the use of this or some other genetic technique. Except for fruit flies, this method 

has not yet been successfully applied to other insects in operational programs and the technique is not currently

being pursued for mosquito control.

 b. Incompatibility 

Incompatibility resulting from a lack of fertility in sexual unions may occur due to a variety of genomic 

failures or due to the effort of bacteria-like symbionts to control the reproduction of host (Barr 1985). The feasibility 

of suppressing Culex pipiens through cytoplasmic incompatibility was demonstrated in a Burmese Village over 20 

years ago (Laven 1967) but the practicality of this method has not been confirmed by any other field tests. 

Moreover, incompatibility factors have been isolated in only a few mosquito species to date. 

 c. Chromosomal Aberrations 

There are several heritable chromosome rearrangements that can, in theory, be used to inject genetic load

into a mosquito population and/or to effect a permanent change in the genetic makeup of the population. These 

aberrations can be used to 1) increase genetic lethal load (serility is limited to 50-80% because of the low 

chromosome number (three, in most mosquitoes) or 2) replace noxious species with harmless strains if appropriate 

viable homozygous rearrangements are available. The latter is perhaps only applicable in the case of important

disease vectors. Naturally occurring aberrations can be screened for in wild populations but their frequency is

greatly increased through exposure to mutagens. 

Controlling mosquitoes through the use of chromosomal aberrations requires a major basic research effort

and a target species that is easily colonized. This later requirement automatically eliminates many important species 

from consideration. 

 200
d. Competitive Displacement 

The final, and somewhat abstract, strategy for controlling mosquitoes biologically is the ecologically based 

notion of displacing a noxious species by introducing a benign but more competitive (i.e. better adapted) exotic 

one. This idea has been suggested primarily to control container-breeding species like Ae. aegypti. However, 

benign mosquito species are difficult to find, as most mosquitoes that have become established (Ae. aegypti, Ae. 

albopictus) are as bad or worse than the species with which they compete (container-breeding Culex and Ae. 

triseriatus). 

5. Other Control Approaches 

a. Trap out techniques. All experience to date indicates that while various traps may be 

good sampling devices for adult mosquitoes, they are too inefficient and limited in their range to provide any benefit

in reducing biting annoyances (Nasci et al. 1983). Work is ongoing on attractants (octanol) that would both greatly

increase trap collections of mosquitoes and reduce non-targets trapped, but no products are marketed for this

purpose to date. 

Electrocutor traps (“Bug Zappers”) continue to be a popular item, with an estimated 1.75 million sold in 

the United States each year (Mitchell 1992) but they are extremely non-specific (mosquitoes generally make up less 

than 5% of the catch, and may be harmful to other insect species. They cannot be considered a part of any

mosquito-control program. 

b. Repellents. Personal protection through the use of mosquito repellents is an appropriate

alternative to controlling the mosquito populations before they bite. This is especially true if the periods of 

annoyance are infrequent and brief and where the land areas are too vast and unpopulated to economically consider 

control programs. 

The most commonly used mosquito repellent is DEET (N,N)(diethyl-metatoluamide) which has been 

formulated and sold under a variety of trade names (e.g., Off, Muskol, Cutters), in a variety of concentrations and as 

both aerosol sprays (usually ca 15%) and lotions (up to 100%). Laboratory tests have shown that maximum

repellent duration (ca. 1-2 hours) is obtained with a concentration of ca. 50% so that higher concentrations do not

provide appreciable advantages. The major disadvantage o£ DEET are: 

1) relatively short protection time 

2) somewhat offensive odor 

 201
3) damage to some fabrics and surfaces at higher concentrations 

4) high cost

5) possible hazards from heavy use 

Small children frequently have skin reactions to DEET. Small children are also most likely to be the 

individuals that develop meurotixicological symptoms from DEET. Thirteen of 14 cases of encephalopathy 

(toxicity of the central nervous system), found in publicly available reports by a recent review (Osimitz and 

Grothaus 1995), were in children 8 years old or younger. Three of these children died, all having used “heavy”

amounts of repellent, even though the repellent in each case had DEET concentrations of 20% or less. Oral 

ingestion may have played a role in some of the cases. Osimitz and Grothaus (1995) concluded that there is no 

evidence that increased DEET concentration has an effect of the severity of symptoms. They also compared reports 

that the Poison Control Center received for DEET (6,724 in children under 6 years old during a five-year period) to 

laundry detergent reports (10,789 in 1989) and household bleach (16,169 in 1989), concluding that accidental 

exposure, while undesirably high, is in line with, or lower than, exposure to other household chemicals. 

There is one unsubstantiated report in the Russian literature of carcinogenic effects in rats at high doses. 

Three other repellent materials are in common use. Dimethyl phthalate (generally sold as 6-12) is not as 

effective as DEET against mosquitoes but still has a share of the market. Citronella-based repellents have long been 

marketed as candles or in oil-burning lamps. Citronella is also available as a repellent to be sprayed in skin and 

clothing (Natrapel). The third material (Avon skin-so-soft) is a popular bath oil that is not marketed as a mosquito

repellent but has, through word of mouth, been recognized for its as yet uncharacterized mosquito repellent affect. 

It is as effective as DEET but it does not persist as long. On the other hand, it is much cheaper, smells better, and 

apparently does not damage any fabrics or surfaces. The active ingredient(s) of skin-so-soft has not been isolated or 

identified to date. It also has not undergone the EPA safety testing that other repellents have because it is marketed 

as a beauty aid rather than a pesticide (Note: repellents are classified as pesticides by EPA). 

Electronic mosquito repellent devices which are periodically marketed in the U.S. (usually by mail order 

houses) are completely ineffective and are not based on any biological rationale (Foster & Lutes 1985, Mitchell

1992, Curtis 1994). 

C. Physical Control 

1. Types of Habitat Modification 

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a. Open marsh water management (OMWM)

Originally developed for New Jersey salt marshes (Ferrigno 1970, Ferrigno & Jobbins 1968, Ferrigno et al. 

 1969), this strategy basically attempts to overcome the limitations of ditching by the incorporation of other water 

management strategies. In particular, champaign pools or reservoirs (which permanently hold water and sustain 

larvivorous fish) are created (by backhoe, dragline or rotary ditcher) in selected tidal pools or large shallow pans 

and are connected via small shallow ditches to surrounding mosquito breeding depressions. If old ditches are redug and used as reservoirs, then plugs must be inserted at the tidal end to prevent drainage. This customized 

approach to marsh management represents the least deleterious and most efficient nonpesticidal method for 

controlling saltmarsh mosquitoes and has been adapted to New England conditions (Boyes and Capotosto 1980, 

Hruby et al. 1985, Christie 1990). A manual outlining this method was developed by the Massachusetts Audubon 

Society (Hruby and Montgomery 1986) and OMWM is currently being practiced by coastal projects in Essex and 

Plymouth Counties in Massachusetts. As of 1996, OMWM had become the accepted technique for new salt-marsh 

water management work, though maintenance work remains dominated by cleaning existing ditching, as opposed to

conversion to OMWM. 

 b. Other Modification Strategies 

Mosquito control efforts in Massachusetts predate modern chemical insecticides. Early control efforts 

consisted of source reduction work, mostly in salt marshes (see “History of Cape Cod Mosquito Control Project, 

1928-1971”). This emphasis was largely abandoned when cheap and seemingly more effective organo-chlorine 

insecticides became available in the early 1950's. Early control programs capitalized on cheap WPA labor but they 

failed to achieve the level of control that the public has come to expect of modern control programs. Nonetheless, 

they serve as a reminder that mosquito control, from its earliest inception, considered and practiced control 

alternatives to synthetic chemical pesticides. 

Except for new OMWM projects in salt marshes, mosquito control source reduction work now consists

primarily of maintenance work on existing culverts, storm sewers and ditches. Very little new ditch construction

has taken place in recent years. Ditch cleaning, which often involves excavating spoil with a backhoe or plow, is an 

activity which has drawn great concern when it takes place in estuarine environments. This is because many of the 

old grid ditches in the saltmarsh served no real purpose for mosquito control but they must be re-cleaned 

periodically or they themselves become shallow breeding areas for saltmarsh mosquitoes. 

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c. Origination of Requests for Physical Control.

The exemption from certain regulations enjoyed by mosquito control is a two-edged sword. On the one 

hand, it enables mosquito control projects to more quickly respond to drainage problems. On the other hand, it

makes the heading “Mosquito Control” particularly desirable for drainage projects in which mosquito control is, at

best, a marginal goal. This pressure can come from property owners, public officials, or from within control

projects themselves. The pressure to conduct drainage work that does not have a mosquito-control component must

be resisted. 

The best interests of mosquito control programs are served by conservative application of the definition of 

mosquito control, as over-use of the wetlands exemptions may result in the loss of those exemptions. To this end, 

mosquito control programs, in conjunction with state and federal wetlands protection agencies, must develop a 

strong set of guidelines for alterations exempt from Wetlands Protection Act. 

2. Ecosystem changes of non-target biota as a result of physical controls. 

 a. Salt Marsh . 

New England coastal wetlands have been heavily impacted by man (Shisler 1990). However, evidence 

concerning the negative impact of saltmarsh ditch maintenance activity is mixed. The principal concern is with

disposal of the spoil on the marsh and the invasion of upland plants that can occur with even slight elevation 

increases (i.e. 1-2 inches) (Miller and Egler 1950, Buchsbaum 1994). Ditching also permits Spartina alterniflora to

invade the upper marsh (dominated by Spartina patens and Distichlis spicata) along the edges of the newly created 

ditches. There is evidence to support the claim that this increases marsh productivity (Buchsbaum 1994). 

In 1979, staff biologists from the New England Division of the U.S. Army Corps of Engineers (DeSista & 

Newling 1979) carried out preliminary investigation in several Massachusetts salt marshes to explore the issue of 

spoil deposition and upland plant invasion. In many instances they found little plant invasion despite evidence of 

previous spoil deposition of 2 inches or more in depth on the marsh. In a few locations with minimal tidal 

influence, some invasion by species such as common ragweed (Ambrosia artemisifulia), march elder (Iva 

frutescens), and seaside goldenrod (Solidago semprevirens) had occurred over time. However, they concluded that

it was not obviously correlated with the spoil itself but was perhaps caused by some other factor associated with the 

disturbance to the marsh. They recommended the sort of long-term monitoring studies which have as yet not been 

carried out in Massachusetts salt marshes. 

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Clarke et al. (1984) studied the effect of ditching and vegetation changes on the use of the saltmarsh by

birds in Rowley, Massachusetts. They concluded that bird use of the marsh was negatively impacted by mosquito

control ditching. This is in contrast to the studies of Shisler & Jobbins (1977) in New Jersey marshes where 

increase productivity was observed in ditched marshes. Daiber (1986) noted that, where ditches drain pannes, birds 

that need a constant water supply (American bittern, pied-billed grebe and American coot) may decline. Also noted 

was a case where spoil ridges invade by Baccharis and Iva caused gulls to seek less brushy areas for nesting. 

Scheirer (1994) encouraged mosquito control programs to develop water management partnerships with the U. S. 

Fish and Wildlife Service, especially for OMWM-type marsh restorations designed to improve migrant waterfowl

habitat. 

In a series of investigative reports by staff biologists from the National Park Service, the environmental 

impact of ditching and diking of salt marshes in the Herring River basin of Cape Cod National Seashore were 

investigated (Soukup & Portnoy 1983, Portnoy 1984a, 1984b). These reports held that Cape Cod marsh 

management practices were responsible for the freshening, stagnation, acidification and high sulfate and aluminum

concentration in diked marshes. These authors suggest that the destruction of a thriving eel and herring fishery in

Wellfleet was the direct result of these marsh disruptions. However, the main dike across the mouth of the Herring 

River (from Griffin Island to the Mainland) was constructed in 1909 with the main objective of providing for 

agricultural use of the basin. These structures are not typical of early mosquito marsh management practices in

other coastal regions in Massachusetts. The impact may be largely reversible if dikes are removed and normal tidal

flow is allowed to return to these areas. OMWM tailored to the unique characteristics of these small estuaries 

should be explored as a way to manage the Ae. sollicitans populations which are likely to replace the present Ae. 

cantator populations if tidal flow and normal vegetation and salinity are restored in these marshes. 

Perhaps the most damaging assessment of ditching in salt marshes was the report of Bourn and Cottam

(1950) in which they blamed open ditching for converting up to 90% of the Spartina alterniflora marsh along the 

Mispillion River in Delaware to Baccharis. However, Provost (1977) reported that the area had returned to Sp. 

alterniflora after navigational dredging of the river had ceased and concluded that it was the dredging of the main 

channel, not the marsh ditching, which had permitted Baccharis to invade the marsh (see Daiber 1986 and 

Buchsbaum 1994 for reviews of this debate). Arguing against significant water-table lowering in salt marshes is the 

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strong affinity for water exhibited by salt marsh soils. Because permeability is so low, the water table may be 

lowered only within a meter or so of the ditch itself (Balling and Resh 1982). 

Grid ditching, even if not the marsh destroyer some claim it to be, still reduces standing water on the marsh

and creates an unnatural and aesthetically unpleasing view. Open marsh water management was designed to more 

closely approximate the diversity of the natural marsh while eliminating the shallow pannes in which mosquitoes 

breed. 

Wolfe (1996) reviewed the effects of OMWM on numerous tidal marsh resources. OMWM systems 

tended to enhance tidal exchange and salinity in marshes that were converted from grid ditching. Except where 

spoil piles were left (improperly) on the marsh, vegetation change was slight and favored salt-marsh species such as 

Spartina patens and Distichlis spicata. Small changes in elevation due to spoil deposition sometimes result in

invasion by Iva, Baccharis, and Phragmites. Salt-marsh snails (Melampus bidentatus) have declined in some

OMWM sites but not in others. Similar mixed observations have been made for marsh periwinkle (Littorina

irrorata) and fiddler crabs (Uca species). Marsh fish populations are, by design, enhanced by OMWM. However, 

changes in species composition may occur where existing pools are deepened. Mummichogs (Fundulus 

heteroclitus)and spotfin killifish (Fundulus luciae) should decrease while sheepshead minnows (Cyprinodon 

variegatus), inland silversides (Menidia menidia) and rainwater killifish (Lucania parva) should increase (Talbot et

al. 1986). The small reservoirs are not particularly attractive to birds and the minor changes in hydrology, flora and 

invertebrate fauna caused by OMWM do not cause significant changes in bird use on OMWM sites. Effects on 

mammals are not well documented. OMWM has had no long-term detrimental effects on water quality. As a result, 

Wolf concludes that, “Open Marsh Water Management is an environmentally focused management tool that is

designed to be compatible with nature rather than compete with it.” Of course, the technique is new enough that

long-term monitoring is required to ensure that altered sites remain functional salt marshes. 

b. Freshwater Wetlands (exclusive of Vernal Pools). Palustrine wetlands, including 

emergent, scrub-shrub and forested wetlands, are the dominant system in which Massachusetts freshwater physical 

control take place. In the vast majority of cases, this work consists of maintaining existing ditching designed to 

remove standing water from the wetland, thereby reducing mosquito-breeding habitat. For most MCPs, this type of

work (source reduction) makes up a large percentage of their control effort. Though reducing standing water 

certainly reduces mosquito breeding, there has been little research concerning the overall effects of these alterations

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on the modified wetland. Ditch systems can become problems in their own right, producing mosquitoes if left

unmaintained. Most of these systems were never designed specifically for mosquito control and their other, primary

function, such as removing runoff from large parking lots, may cause considerable damage to the ecosystem, 

leaving the MCP to clean up, or at least deal with, someone else’s mess. 

The majority of drainage systems currently maintained by MCPs were not initially constructed by MCPs 

and the effort of MCPs today is almost entirely restricted to removing blockages to existing flows, rather than 

enlarging or straightening channels to increase flow. Most freshwater drainage is an inherited problem which 

requires intervention not because of mosquito-control activities but because of the activities of others. Road sand 

and yard waster represent two of the most common obstructions MCPs are called upon to remove from existing 

streams and drainage networks. New developments also can cause dramatic changes in the sediment load in

streams, despite regulations designed to prevent such problems. Road sand, yard waste and increased sediment load 

from development can all have impacts on a stream that are as greater or greater than regular ditch maintenance. 

Because MCPs are often involved in removing manmade sediments from streams, a system under 

appropriate ditch maintenance may function more closely to a natural system than one in which manmade wastes 

are allowed to accumulate unabated. The appropriate response by the MCP in such cases is not obvious because, 

although the problem, and its cause, may not be mosquito related, the mosquito control program may be the 

organization best equipped, both from and equipment and a training perspective, to rectify the situation. 

Since mosquito control projects came into being in Massachusetts, the perceived values of wetlands have 

changed. Once shunned as disease-bearing waste lands, best suited for dumping, draining or filling, wetlands are 

now viewed in a much more positive way. They are important wildlife habitats, perform a myriad of water quality 

maintenance functions, and serve as flood control, erosion, ground-water recharge and water supply regulators 

(Tiner 1989). Mosquito control programs have been slow in adapting to the increased value accorded wetlands. On 

the one hand, long-residual and/or broad-spectrum pesticides are no longer used in wetlands in Massachusetts. On 

the other hand, there is real resistance to halting maintenance work in drainage networks that may be seriously

damaging wetland habitat.

There has not been a great deal of work done specifically on the effects of physical control for mosquitoes 

on non-target organisms. Therefore the following discussion is based on the general effects that can be expected 

when wetland alterations are made. Care should be taken in extending these general concerns to mosquito control

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in Massachusetts. For example, channelization (straightening) of natural streams is not permitted in Masachusetts, 

where programs are required to follow the natural meanders of the stream. The three broad categories of wetlands 

alteration are outright loss, changes in the abiotic system and changes in the biotic community. Filling and/or

draining wetlands to convert them to upland is a mosquito-control practice that has been all but eliminated in

Massachusetts. There is no indication that MCPs are intentionally reducing wetland acreage in order to control

mosquitoes. However, the fact that the wetlands boundary remains essentially unmoved by a mosquito-control

alteration does not mean that profound alterations have not occurred. 

Changes in the abiotic system and biotic community are deeply intertwined, though physical control most

often causes abiotic changes which then cause biotic changes. For channels changes in flow rates, microhabitats, 

sediment load, sedimentation, and groundwater interactions can all occur. For wetlands (outside of channels) 

changes can include lost water-storage capacity, increased sedimentation and pollutant load, changes in water depth, 

and changes in groundwater hydrology. 

When a stream is altered to improve water flow for the purpose of removing standing water, either within

the stream or from adjacent wetlands, a number of changes may take place. By definition, improving water flow 

increases runoff. This, in turn, may decrease the surface-water storage capacity of the wetland system and decrease 

the capability of the wetland to retain load (suspended solids). This may increase the load of the water moving

through the stream (Brown 1988). Increasing runoff into a given stream tends also to increase erosion, which 

further increases load (Williams & Feltmantle 1992). Not only is total flow increased, but alteration tends to 

increase peak flow, which is associated with reductions in faunal diversity (Hynes 1972). 

The effects of increased flow and loading are many. At its most obvious, higher peak flows increase 

scouring of the stream bed by gravel and sand being transported by the water. Bottom dwelling animals are either 

affected on-site or swept downstream, leaving an impoverished community as flows return to normal (Hynes 1972). 

 Increased flows can also remove organic matter, leaving a sandy bottom on which macrofauna is reduced (Ward 

1992). As stated earlier, higher peak flows also encourage erosion, a process that can increase stream load long 

after sediment controls put in place during the actual drainage work are removed. 

High levels of suspended solids alter the stream habitat by: 

1. reducing light penetration 

2. reducing primary production 

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3. altering the trophic structure 

4. altering nutrient dynamics 

5. changing thermal conditions 

6. reducing oxygen levels (Ward 1992). 

These effects can, in turn can have the following impacts on the stream fauna: 

1. abrating respiratory epithelia 

2. clogging respiratory structures 

3. reducing feeding rates 

4. reducing feeding efficiency

5. increasing exposure to toxins 

 6. reducing vision 

7. inducing organisms to drift.

All of these effects can alter behavior patterns, change predator/prey interactions and change the outcome of inter 

and intra-specific competition (Ward 1992). 

Maintenance for the purpose of reducing mosquito breeding also includes removing obstructions within

streams. Tree branches and fallen trees are a particularly important part of the stream environment, providing food, 

living space, concealment from predators, protection from abiotic conditions and emergence sites (Ward 1992). 

They also provide varied microhabitats by deepening and slowing flow on the upstream side and often creating 

deeper pools on the downstream side. Removing these obstructions diminishes the variability of the stream

ecosystem. 

At the other end of the flow-rate spectrum, increasing peak flow may lead to faster drying in intermittent

streams. The insect fauna (and biotic community in general) of intermittent streams does not overlap to a great 

extent with that of permanent streams (Ward 1992). As a general rule, this is because intermittent stream dwellers 

have evolved to deal with the drying down stream. Survival mechanisms include leaving the stream (swimming 

down stream or emerging as land-living forms), surviving in crayfish burrows or remaining pools of water, burying 

either at shallow depths or quite deeply into the substrate or hiding under rocks or leaflitter within or along the 

stream course (Ward 1992). Streams the dry more quickly, and stay drier longer, may disrupt all of these techniques 

as insects that emerge as adults may not have enough time to complete development (the primary example being 

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mosquitoes themselves), remaining pools may decrease in size and number and shallow burrows and hiding sites 

under rocks and leaf litter may become too dry to support the fauna hiding there. 

The effect of rapid drying brings up the aspect of the hyporheic zone. This is the interstitial space between 

the substrate particles in a stream bed. Within the hyporheic zone the macrofauna can find shelter from floods, 

drought and extreme temperatures, can find suitable and predictable conditions for immotile stages such as eggs, 

pupae and diapausing nymphs and larvae and, particularly for early instars, protection from predation. Gravel beds 

provide the best hyporheic zones and animals can often be found many feet down (Ward 1992). This hyporheic

zone fauna can be an important source of recolonizing organisms after a stream bed is denuded (Williams & 

Feltmantle 1992). Excessive drying can reduce the viability of the hyporheic zone. 

Sedimentation, both within stream beds and in wetlands into which streams flow, is a problem because it 

can alter the stream bed composition, thereby altering the fauna, and can clog interstitial spaces, thereby reducing 

the hyporheic zone and/or reducing groundwater recharge. Sediments can also increase exposure to pollutants as 

they provide additional sites for pollutant binding while suspended, and then carry the pollutants to the benthic 

fauna. 

MCPs routinely conduct maintenance to remove sediments. Therefore, there is good reason to expect the 

overall effect of maintenance may be to reduce the negative impacts of sedimentation within the stream. In such 

cases, it would be preferential to develop systems designed to prevent the deposition of road sand into drainage 

systems, rather than to prevent the removal of that sand, once it has entered the system. Removing the dense, 

rotting masses of grass clippings that are dumped into streams by property owners should also improve overall

stream quality. 

Up to this point the discussion has focused on the stream itself, but freshwater wetland alterations are 

typically designed to change standing-water wetlands to soil-saturated wetlands (New Jersey DEP 1997). The 

obvious problem is that any organism that requires standing water for periods other than peak flooding, the wetland 

may become unusable. Mosquitoes fit this definition perfectly, but so do many other organisms. Many species of 

amphibians use temporary standing water for breeding and are becoming scarce as these habitats are eliminated. 

Increased drainage also may have an effect on groundwater. Precipitation and inflow determine the 

amount of water initially available to a wetland for ground water recharge (Todd 1972). Increasing the amount of 

water removed from the wetland prior to percolation downwards can decrease the capacity of the wetland to

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recharge groundwater supplies. Not only can groundwater recharge within the wetland lowered, it can be lowered 

with the outflowing stream as well. During peak flows, water moves from the stream into the substrate and raises 

the water table (increases groundwater). As the flow declines, groundwater percolates back into the stream (if it

does not, the stream dries out). By eliminating upstream reservoirs (wetlands), more water flows out of the system

initially, leaving less water within the system. As water levels fall, groundwater discharge occurs sooner than might 

otherwise be the case. If nothing else, stream depth is liable to vary more widely after adjacent wetlands are 

reduced to soil saturation.

What is most needed is a comprehensive understanding of the true ecological costs of physical alterations 

for mosquito control. This is particularly important because, although the environmental effects of pesticides 

receive the lion’s share of concern, it is possible that the long-term effects of physical controls may have a greater 

effect on the environment than does pesticide use (Buchsbaum 1994). This may be especially true today with the 

switch from broad-spectrum, more-persistent pesticides to methoprene and Bti.

New Jersey has recently updated it’s Best Management Practices for Mosquito Control and Freshwater 

Wetlands Management and Massachusetts should look to such guidelines to establish a protocol for physical control

in freshwater wetlands. At a minimum the common-sense requirements that all alterations be planned (not random), 

necessary, and desirable should be rigorously applied to all MCP water management projects regardless of whether 

they are defined as new or maintenance work. The North East Massachusetts MCP Standards for Ditch 

Maintenance (Appendix F) can be viewed as a starting point for a statewide protocol, though it fails to mention the 

need for sediment controls during maintenance work and leaves the MCP superintendent with wide latitude for 

determining the necessity of a given project. A response from the Massachusetts Audubon Society (also Appendix 

F) to these Standards provides additional comments which deserve consideration when a protocol is established. 

c. Vernal Pools. Vernal pools form in contained depressions in which water stands for a 

period of several months, generally from mid- to late winter through the spring. Water either comes in the form of 

snow melt or spring precipitation or can be a result of a rising water table. Some pools dry down within two or 

three months, others may only dry when the water table is lower than normal, resulting in a pool that is semipermanent. Regardless, a key feature of vernal pools is that they undergo periods of dry down. Vernal pools may

have permanent inlets but do not have permanent outlets (Kenney 1995). 

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There are numerous obligate species for vernal pools, the most visible of which include fairy shrimp, the 

wood frog (Rana sylvatica) and several species of salamander (Ambystoma spp.). 

The Massachusetts Division of Fisheries and Wildlife (Publication #15498-10-600-6-1-88C.R) has created 

guidelines for certifying vernal pool habitat on the grounds that many vernal pool species cannot successfully 

survive without vernal pools and that vernal pools are under pressure from continued development within the state. 

The certification program is coordinated by the Natural Heritage and Endangered Species Program (NHESP - see 

next section). “Automatic” protection is given to vernal pools only if they 

1. occur either (a) within the 100 year inland flood plain or (b) on “isolated land subject to

flooding” (as defined in the regulations at 310 CMR 10.57 (2)(b)); and 

2. its existence and location has been certified by the Massachusetts Division of Fisheries 

and Wildlife. 

Curiously, upland vernal pools are not granted the same protection but may be certified as vernal pools. The 

NHESP does not seek out pools to certify; it certifies submissions from the public. A guidebook for vernal pool

certification (Wicked Big Puddles) is available to help those who wish to submit a vernal pool site for certification 

(Kenney 1995). 

 Mosquitoes, particularly Ae. canadensis, also use vernal pools for breeding. From a control perspective, 

vernal pools are important because, due to increasing protection, vernal pool habitat is often left undeveloped while 

the land adjacent to the pool is built up. As a result, many new developments surround known breeding sites. 

Regardless of the wisdom of developing so close to vernal pools, mosquito-control personnel are charged with

controlling the mosquitoes coming from the pool. 

d. Rare and Endangered Species. Hynes (1972) states three axioms of running water 

biotic communities: 

1. The greater the diversity of the abiotic system, the greater the number of species within the 

system. 

2. The more conditions deviate from the normal, the fewer species will be present, but those 

remaining will be present in greater numbers. 

3. The longer a system is left undisturbed, the richer and more stable is the biotic community. 

Operating under the assumption that it is rare and endangered species which are most likely to be lost from the 

system first, the above statements would suggest that reductions in habitat diversity, alterations from the natural

state, and frequent disturbances will all work against these species. Channelization of streams reduces diversity by

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removing obstructions, straightening the channel and increasing flood levels. Wetlands changed from standingwater to saturated-soil regimes have been drastically changed from their natural state. Maintenance is ongoing, as is

the disturbance it causes. 

The key question is, however, to what extent does mosquito control contribute to the above 

problems. First, Massachusetts MCPs do not channelize streams, as their certification manual calls for following 

the existing meanders. Second, MCPs work neither in historically undisturbed, nor currently undisturbed streams. 

There is every reason to argue that there is no specific “natural” state that can be assigned a ditch dug by man and 

intermittently filled with road sand and grass clippings. Even with natural streams, the “natural” habitat in which

they flow has long been altered and continues to be altered. 

The Natural Heritage and Endangered Species Program (NHESP) was created in order to conserve and 

protect those plants and animals not hunted, fished, trapped or commercially harvested in the state. The program’s 

highest priority is to inventory rare and endangered species and to develop conservation plans through research, 

management and habitat protection for those species. One such program that directly impacts mosquito control is

the vernal pool certification program mentioned above. 

The NHESP also reviews proposed alterations to wetlands habitats under the Wetlands Protection Act

(M.G.L. c. 131, s. 40 and regulations 310 CMR 10.00). NHESP has produced a series of estimated habitat maps for 

rare and endangered species (Massachusetts Natural Heritage Atlas) which proponents of a given alteration are 

required to check. Should a project fall within an estimated habitat, NHESP will then determine if the area to be 

altered is actual wetland habitat for a state-listed species. The results of the NHESP determination are given to the 

inquiring MCP. 

The Massachusetts Endangered Species Act (M.G.L. c. 131A and regulations 321 CMR 10.00) prohibits

the “taking” of rare plants or animals. From a mosquito-control perspective, the most important definition of 

“taking” is disrupting nesting, breeding or feeding sites of animals or killing or cutting a plant. Aside from directly 

protecting rare or endangered species, this Act also allows areas to be designated “significant habitats.” Alterations 

in “significant habitats” require a permit from the Division of Fisheries & Wildlife. 

In Massachusetts, the species that have caused modifications in mosquito control practices are the Bluespotted salamander (Ambystoma laterale), Mystic Valley amphipod (Crangonyx aberrans), and banded bog 

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skimmer (Williamsonia lintneri). In addition, ditch maintenance in vernal pond areas has been curtailed to protect

this type of habitat. Other animals for which concerns have been raised are the yellow-spotted turtle and osprey. 

The presence of a threatened species need not prevent water management, however. In the East Volusia 

Mosquito Control District in Daytona Beach, Florida, OMWM was carried out in a salt marsh that contained the 

Atlantic salt marsh snake (Nerodia clarkii taeniata). An observer walked in front of the ditching machinery and 

work was halted until observed snakes left the area. In practice the snakes were difficult to spot and several were 

seen in the freshly cut ditches behind the ditcher. Two dead snakes were found, and assumed killed by the work. 

The dead snakes were handled as “incidental take” and placed on ice for delivery to the Florida Game and Fresh 

Water Fish Commission (Goode 1996). With an increased understanding of the ecosystems in which mosquito

control takes place, mosquito control projects should improve their ability to work in areas containing endangered 

species with minimal impact to those species. 

Under the current system mosquito-control maintenance activities are exempt from the Massachusetts 

Wetland Protection Act, leaving only the federal 401 Water Quality Certification Act and both the Massachusetts 

and federal Endangered Species Act as methods for regulating maintenance. Unfortunately, water quality, while 

important, does not address the issue of changing habitat and the presence or absence of a rare and endangered 

species has little to do with the merits of a given project. 

Rare and endangered species will probably increase in their impact for several reasons. First, as data is 

collected on these species, additional species and additional habitats will most likely come under protection. 

Second, residential areas are creeping closer to wetlands areas. The net effect is that the clash between economic

development and environmental protection will likely increase, with mosquito control being one component of an 

intense debate. Again, a more comprehensive understanding of the true ecological effects of mosquito control is

required to better determine the cost/benefit ratio for different types of mosquito control. 

D. Food Web Effects of Mosquito Control. 

Throughout their life cycle mosquitoes are a part of the food web, both as consumer s and prey. As larvae 

most species feed on algae, protozoa, and organic debris (Pennak 1953). As adults they drink nectar and the 

females of most species take blood meals from a wide variety of animals. Larval mosquitoes are eaten by an 

impressive array of animals (Bates 1949) while adult mosquitoes are taken by spiders, predatory flies, odonates, 

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bats and birds (Collins and Washino 1985). Given that mosquitoes are so thoroughly embedded in the food web, 

the question arises as to the effect of removing a large percentage of the mosquitoes from that food web. 

At first glance, the effect would appear to be large, particularly in habitats with dense larval populations. 

However, mosquitoes are r-strategists, in that they produce large numbers of eggs that develop quickly (when 

immersed in water) to adulthood. Most pest species seek out temporary and spatially disconnected habitats for 

breeding and can complete a breeding cycle long before an adequate predator complex can develop. Mosquitoes 

are, therefore, a highly unpredictable food source for predators, and predation rates must be equally unpredictable 

(this section will focus on predation, as parasites and pathogens are not widespread control agents in 

Massachusetts). This is borne out by the fact that mosquito predators are generalists which can readily switch to

other prey when mosquitoes become scarce (Collins and Washino 1985). In a study in Florida, immature 

mosquitoes made up over 50% of the diet of several species of saltmarsh fish (Fundulus confluentus, Lucania 

parva, Gambusia a. holbrooki). But each of these species fed on other items as well, including copepods, shrimp, 

other fish and even some plant material (Harrington and Harrington 1961). 

One important point regarding predation and larval broods is that the concepts of handling time and 

satiation come in to play (Varley et al. 1973). A predator must spend a certain amount of time with each prey. 

Hydrophilid larvae took several minutes to feed on larvae and pupae taken in a panne in Tiverton, Rhode Island 

(Christie, pers. observation). Not only does it take time to catch and eat the prey, but invertebrate predators are 

typically not much larger than the mosquito larvae they are attacking. Satiation must play a role in limiting predator

take, particularly when mosquito numbers are high. 

Predators can play an important role in regulating mosquito numbers in some situations. That mosquitoes 

are absent from waters with fish populations is well known. Less well known is the influence of chaoborid larvae, 

which can severely reduce mosquito populations in vernal pools (Morrison and Andreadis 1990). In this case the 

larvae are present in snow-melt pools for approximately two months, so predation has time to operate as a 

regulating mechanism.

Although adult mosquitoes are eaten by numerous predators, it is rare that they make up an appreciable

proportion of the diet of any one predator. One exception is the spider Tetragnatha montana for which, in Poland,

mosquitoes made up 74% in June and 62% in July of all prey captured (Collins and Washino 1985). Bats and 

purple martins are not effective mosquito predators nor do mosquitoes form a significant part of their diet. 

 215
From a mosquito-control perspective, the mosquitoes to be controlled are, for the most part, those which 

have escaped predation to become predators in their own right. In the absence of scientific data supporting the 

necessity of mosquitoes in the diets of specific animals, removing mosquitoes from the food web by chemical, 

biological or physical control remains an easily justifiable activity. Even so, control personnel should take care to

avoid chemical applications where mosquito larvae are not present or are present in very small numbers, should use 

control measures that do not harm existing predator complexes, and should limit control to areas where control is

necessary, allowing natural cycles to continue in areas where human activity and the risk of disease transmission is

slight. One argument made in favor of Altosid is that it does not kill the young larvae, leaving them available as 

food for the existing predator complex. 

Up to this point, the discussion has focused on the effect of chemical control (including Bacillus products

and IGRs) of mosquito populations on other species. Within the context of biological control, one of the primary

reasons Gambusia are not being used in Massachusetts is the fear that they might displace native species of fish, 

thus altering the natural biota, not by predation but by competition for the same resource. 

Physical control by water management may increase predation, as in OMWM, or may eliminate predator 

and prey as when wetlands are drained to soil saturation. Mosquito breeding must be thoroughly documented before 

new work is done. Because disturbances may displace some species, and because predator species tend to rebound 

more slowly than their prey, maintenance work should be conducted only when necessary. 

E. No Program

Another alternative strategy to current mosquito control practice is no control. Many communities in

Massachusetts have chosen this option. These town are usually outside of the enzootic EEE zone so the risk of 

human diseases transmitted by mosquitoes is viewed as practically nil by these communities. In addition, they are 

not located near salt marshes and their attendant pest mosquito problems. The mid-section of Massachusetts, where 

most no-control communities occur, also has a more rural character, less wetland , lower human populations, and a 

lower mean family income than most eastern areas with organized mosquito control programs. In general, the view 

of these communities is that the anticipated benefits from mosquito control do not outweigh the anticipated costs 

and perceived risks. 

A more precise way of polling the public and confirming this opinion would be through establishing the 

Human Annoyance Threshold (HAT) for the town. Communities in which the HAT is below the actual annoyance 

 216
level should be persuaded to choose the no control option since justification for control is lacking unless a 

documented disease threat exists. 

In some communities, biting annoyance is created by a combination of biting insects (i.e. mosquitoes, 

black flies, biting midges and tabanids) which require completely different control approaches. Many people do not

recognize the difference between these insects, especially in dim evening light. It is critical to accurately identify 

the biting insects actually responsible for the human annoyance. In general, black flies and tabanids only cause 

annoyance during the daytime while mosquitoes and biting midges are most annoying from 6-10 PM. The HAT 

level for tabanids and biting midges is likely to be less than for mosquitoes because of their more painful bites. 

Perhaps part of the reason why Berkshire County communities have supported a MC program while other 

Western Massachusetts communities have not, lies in the fact that this region supports many summertime outdoor 

activities (e.g. camps, resorts, golf courses, Tanglewood, etc.). In addition, this more mountainous region has a 

significant black fly annoyance problem superimposed on top of the mosquito problem. Vacationers are likely to 

have a lower HAT than permanent residents since they are spending more time and money on outdoor recreational

activities. 

In addition to risk-benefit considerations, other criteria for weighing the control/no control option are 1) 

the feasibility of successfully reducing annoyance below the HAT level, and 2) the adequacy of community 

resources for reducing annoyance to acceptable levels. 

Towns with large areas of mosquito-producing freshwater wetland should recognize that effective 

mosquito control in these habitats is difficult at best and often impossible. As indicated earlier in this report, 

permanent wetlands do not usually produce large numbers of pest mosquitoes but in situations where they do, the 

public needs to be aware that these wetlands are a valuable resource that must be protected from significant

perturbation and that options for mosquito control are therefore few. Community planning boards and zoning laws 

can and should be used to restrict residential development and other human activities from such wetland areas. 

Towns with annoyance problems but with large land areas and thinly, scattered populations must

understand that the same level of mosquito control achieved in more populated communities will cost them

significantly more per capita. In many such cases, the economic status of the population means that insufficient tax 

dollars can be generated to adequately deal with the problem. 

 217
Nantucket provides an interesting case study. Mosquito control had lapsed in the early eighties. However, 

by 1989 saltmarsh mosquitoes were becoming a significant problem in the west and north areas of the island. The 

town began applying Altosid (including aerial applications of pellets in 1992) to control the mosquitoes while. 

getting the requisite permits for OMWM in several west-end marshes (Madaket, Warren’s Landing Eel Point). The 

OMWM systems were dug in January 1993 (Christie 1993). It was hoped that the OMWM alone would be 

sufficient to control mosquitoes but large-scale breeding continued in the north end (Pocomo) and the low tidal

range has hindered the effectiveness of the OMWM as dug. As a result, some lariviciding continues. The 

conclusion on Nantucket is that mosquito control against saltmarsh mosquitoes must be continued at some level in

order to provide residents with the summer environment they want. However, Nantucket does not target freshwater 

mosquitoes at all and does no adulticiding. Nantucket and Cape Cod together indicate that adulticiding is not a 

requirement even in high-tourist areas. 

It is difficult to measure the impact of choosing the no control option. The example of towns that have left, 

and left and later rejoined MC projects is perhaps the only available basis for estimating public opinion concerning 

such impact. No documentation of annoyance levels, cases of disease, recreational dollars spent, etc., was ever 

attempted in these towns when they had mosquito control versus when they did not. Thus, public complaints were 

apparently the main indication of the impact of the no control option that was used in guiding town decision 

making. 

In the 1986 questionnaire, only about 10% of the towns in organized projects indicated that there had been 

controversy relative to leaving, joining, or rejoining a project. Those that had experienced controversy indicated 

that 4 factors were about equally involved. These were: 1) monetary constraints, 2) concern over the effectiveness 

of project control programs, 3) concern over the safety of the methods used by the project, and 4) concern over the 

environmental impact of the control procedures. Paradoxically, 86% of these towns indicated they were unwilling 

to spend more money (if legally possible) to obtain more effective control and 67% indicated unwillingness to 

spend more money to support less hazardous control methods. However, the bias of the people filling out the 

questionnaire sent to each town may have influenced these responses; no town in Massachusetts has actually polled 

their citizens on these questions. In fact, some towns within projects have taken advantage of new provisions which 

allow towns to collect additional money for MC activities which projects can then only spend in these towns. 

 218
Among towns that actually withdrew from MC programs, monetary constraints played a role in 73% of 

these decisions, followed by environmental concerns in 32% and concern over effectiveness in 27% of these cases. 

Towns that contemplated withdrawing but did not do so, indicated that monetary and effectiveness considerations 

dominated their concern. 

The number of towns in MCPs declined in the late eighties. Economic factors, not environmental

concerns, were the dominant reason given for withdrawal. This trend has reversed itself significantly in the last 

several years. The 1990 EEE problem is probably one reason, coupled with the fact that several coastal programs 

tried the no-control option and found mosquito numbers rose quickly. 

Many towns in the Berkshire County and South Shore projects withdrew in 1981 mainly in response to

Proposition 2-1/2 monetary constraints. The remaining 8 towns in Berkshire County subsequently chose to 

continue as a multi-town Project (Note: the town of Lanesborough rejoined in 1986, the city of Pittsfield rejoined in 

1988, and other towns are contemplating reentry). South Shore actually disbanded as a project but by 1988 most

towns had joined neighboring MC projects in Norfolk and Plymouth Counties. These actions suggest that these 

communities were not content with the no control option that resulted from the disbanding of their former project. 

Towns that voluntarily withdrew from MC projects but then later rejoined a project, did so for a variety of reasons. 

These were in order of their importance: increased public support for MC, increased mosquito annoyance, 

alleviation of monetary constraints, threat of EEE, improved methods and effectiveness of the project. 

The Environmental Impact Statement (Sjogren 1977) prepared for the Metropolitan Mosquito Control 

District in Minnesota attempted to quantify the no control option for their community. Any attempt to develop

similar estimates for Massachusetts would be meaningless given the lack of appropriate baseline data. 

 219
VI. MOSQUITO CONTROL INTEGRATED PEST MANAGEMENT 

A. Definition of IPM as it Relates to Mosquito Control. 

1. Overview of IPM. Few ideas stir more debate in pest control than “Integrated Pest

Management” (IPM). Everyone agrees it’s a good idea, but there agreement ends. For some it means, “No 

pesticides.” For others it means, “Extensive research followed by careful implementation.” For others it

means, “Don’t spray when they aren’t there and use several different chemicals when you do spray.” What 

makes agreement so difficult is that all three definitions are, at least in part, correct. 

For the purposes of this report, however, a simpler statement of IPM is in order. At its most basic IPM

is: 

A system designed to reduce the negative impact of a pest species to an acceptable level while 

avoiding unnecessary additional problems (Virginia Cooperative Extension Service 1987). 

For mosquito control the negative impacts of mosquitoes are reduction in outdoor use, particularly

recreational, and disease transmission. Problems that have developed in the past are loss/degradation of 

valuable habitat, exposure of non-target organisms to pesticides, creation of new, sometimes worse, breeding 

habitat, and resistance of mosquitoes to pesticides in use. Of course, determining which of these problems is

unnecessary is the crux of much debate over mosquito control.

IPM was originated as a pest control strategy for agricultural systems. It has been modified for urban 

systems under the name Urban Pest Management (UPM). UPM varies from IPM (modified from Olkowski et

al. 1978, Horn 1992, and Christie 1994) in that:

1. UPM systems are generally more complex, particularly with regard to determining thresholds

 for control. 

2. UPM takes place close to large numbers of people. 

3. Control decisions are often made for aesthetic, not economic reasons. 

4. Pests of human health require control even at small numbers. 

Mosquito control falls between the classic agriculture-based IPM program and current UPM systems. 

Control of numerous species over a wide range of habitats is more complex than most agricultural systems 

(modification 1) and control work often takes place adjacent to (in the case of larviciding retention basins) or 

on (in the case of adulticiding) human populations (modification 2). In addition, mosquitoes, even when 

220
controlled for nuisance purposes, would be classified as pests of human health (modification 4). However, 

mosquito control decisions are not made for aesthetic purposes (modification 3) in a manner similar to tent

caterpillars in a city park. 

The important point here is not what to call mosquito control IPM or UPM or something entirely

different (the term integrated mosquito management has been proposed (Anonymous 1995) but rather to make 

it clear that one cannot pick up bodily a system designed for agricultural systems and transplant it into mosquito

control without accepting that modifications have to be made. That being said, the second important point is 

that the difficulty in arriving at a scientifically based, economically and environmentally sound control program

should not be used as an excuse to avoid implementing mosquito integrated pest management. 

2. Integrated Pest Management for Mosquitoes. Before an IPM program can be put in place, a 

strong organization must be in place. There is a huge difference between tossing some pesticide at possible 

breeding sites and conducting a full-fledged IPM program. The organization must be adequately funded, 

adequately trained and provided with the materials to do the job correctly. At a minimum expertise in mosquito

biology, wetlands ecology, and program administration are required. 

Adequate staffing and resources are only the first steps in creating an IPM program. The main step is 

in creating the analytical process whereby control decisions are made, evaluated and modified. This process 

can be divided into four steps: 1) Surveillance and Monitoring, 2) Establishing Thresholds for Action, 3)

Prevention and Control and 4) Evaluation. 

a. Surveillance and Monitoring (including identification). The initial step in IPM is to

survey the existing pest population and monitor its occurrence over time. For mosquitoes, adult populations are 

monitored for their direct impact on people whereas larval populations are monitored for their potential impact

after they emerge as adults. For adult populations, monitoring is used to determine if adulticiding is required 

and to identify the species of mosquito in a given area so that future larval control efforts can be directed at the 

appropriate breeding sites. Larval populations are monitored to determine if larviciding is required and/or if

physical or biological controls are working. Larval counts also aid in determining what areas are candidates for 

water management. Monitoring should also take place post-control, in order to evaluate efficacy of various 

control measures. 

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Mosquitoes collected during monitoring must be identified, to the extent possible, to species. For 

adult mosquitoes, the species of adult will give a clue as to where larval monitoring should be focused. For 

larvae, enough non-pest species exist that field staff should be able to sight identify most of the common 

species to genera, primarily to avoid larviciding a non-pest species. 

The habitats in which breeding occurs or in which the adult mosquitoes are most numerous must also 

be identified. Wetlands should be mapped. With the recent rise in the number of drainage basins in new 

developments, an important aspect of mosquito control is to maintain an up-to-date list of all such basins and

work with local building officials to discourage constructing mosquito-breeding basins. 

A third component of monitoring is to classify the area in which control is to take place by human 

usage. Unless funding is not a constraint, the goal of surveillance and monitoring should be to produce a site 

list prioritized by the level of mosquito breeding and its proximity to humans. 

b. Establishing Thresholds for Action. The goal of IPM is to keep pest levels below 

the Economic Injury Level (EIL). This is the level where the economic loss from pest damage exceeds the cost 

of control. In mosquito control, this is the Human Annoyance (or Disease) Threshold (HAT) and represents

the highest biting density (or Disease Incidence) that most citizens in a community find tolerable. Intolerance 

is usually exemplified by people moving indoors, putting on repellent, leaving a campground etc.. HAT is 

generally the biting level above which most people prefer to pay to have the level reduced than put up with the 

annoyance. This level will vary from community to community and may be influenced by the species biting 

(Sjogren 1977), the time of day when annoyance occurs, and the duration of the period when HAT is exceeded. 

In agricultural IPM programs, a 2nd pest density, the Economic Threshold (ET) is established and 

monitored by frequent and systematic sampling of the pest population. This is the so-called action level. It is

the pest density that, if left unchecked, will result in the Economic Injury Level (EIL) being reached. It is a 

computer-assisted predictive level, (lower than the EIL) and is based on previous experience, populations of 

beneficials, time of year, etc. It is difficult to translate this management concept into mosquito control practice 

because the populations responsible for biting annoyance (adult females) differ from those that need to be 

monitored and controlled (larvae). Biting is not restricted to areas with the larval habitats and it is difficult to

assess the future biting impact of any given larval population. 

222
During the surveillance and monitoring phase, workers need to establish thresholds for the various

control options they have. Thresholds may be established based on those found in the literature but will 

generally require local modification. Standard thresholds for adulticiding are generally given as complaint calls 

for a given area, landing counts (mosquitoes landing on an observer per minute) or light trap counts (number of 

human-biting mosquitoes collected per night). Standard thresholds for larviciding and/or water management

are based on dip counts. 

Thresholds need not be expressed in terms of existing mosquito populations. In the case of existing 

programs, the threshold for drainage maintenance will most likely be based on some variation from the existing

cross-section of the system or some measure of water flow as compared to a previously established norm. 

Prevention cannot be based on existing mosquito populations but must be based on the potential for populations 

to develop. 

Thresholds for action are influenced by economic factors. Only programs with sufficient operating 

funds can fully exploit the flexible control strategies generally found in a full IPM program. Programs strapped 

for funds may have no, or very high, thresholds for open marsh water management, because the high initial 

cost cannot be borne by the program. 

Political realities also influence thresholds. Local populations vary widely in their acceptance of 

various control measures. In Massachusetts there are projects that adulticide on the basis of a single request 

and there is one project (Cape Cod) that does not adulticide at all. Human population density and behavior 

patterns also influence thresholds for action. Where budgets are limiting, funds will be earmarked for areas in 

which the most people will benefit. Seashore communities dependent on summer tourists will generally 

demand higher levels of control, hence, lower thresholds for action, than will thinly populated rural areas. 

Finally, environmental factors are also included in establishing thresholds. Control measures that have 

little impact on non-target organisms can be conducted at lower thresholds than can control measures that have 

large impacts on non-targets. In addition, thresholds for action will be influenced by the sensitivity of the 

location in which control is to be conducted. An on-going example in Massachusetts is the use of Altosid 

(methoprene) in endangered-species areas. In Suffolk County Bti use is permitted, methoprene is not. Should 

Bti become significantly more costly than methoprene, the threshold (larvae per dip) for larviciding in the 

affected areas will most likely be raised. 

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In summation, the choice of control measures to use, and the extent to which a given control measure 

is used, is determined by the pest species and population, the environment in which the pest population is

located, and human factors expressed in political and economic terms. Determining which control options are 

available and how much funding will be allocated to each, coupled with an understanding of the pest 

population, should allow action thresholds to be created. 

c. Prevention and Control. As a general rule, prevention refers to maintaining a pest

population below an action threshold for control, whereas control refers to bringing a pest population back 

down under the threshold for control. The line between the two, however, is blurred enough that there is little 

conceptual reason to separate them. Clearing a blocked ditch so that larvae are flushed out is a short-term

control measure with long-term preventative effects. 

Source reduction is the primary prevention technique for mosquito control. Maintaining water flow 

through drainage networks is the primary freshwater mosquito control technique while ditching (previously) 

and open marsh water management (currently) are designed to eliminate the isolated, shallow pannes in which

salt-marsh mosquitoes breed. Programs that do not stress source reduction cannot make long-term reductions 

in mosquito populations. 

That being said, there are cases where source reduction is not possible. The most obvious are areas 

where source reduction would impact an endangered species or where the type of source reduction necessary

would severely impact the wetland resource. In Massachusetts any alteration in such an area must undergo 

NHESP review. Less obvious but equally real are cases where property owners deny permission for source 

reduction projects or where the breeding area is simply too large for source reduction to be economically

feasible. 

Public education is a second vital component of prevention. An educated public should be more 

willing to cooperate in eliminating man-made breeding habitats, should better understand the trade-offs 

between the various available control techniques, and should be more willing to fund more expensive 

approaches if the expense can be justified by a better long-term benefit. A side benefit from public education is

that lines of communication are usually strengthened, so that the economic and political aspects of mosquito 

control, areas often controlled by non-mosquito-control personnel, bear a stronger relationship to the realities of 

mosquito control.

224
Control, in the strict sense of killing mosquitoes, is dominated by chemical use. For adult mosquitoes, 

no current control alternative to pesticides exists. However, options exist for larval control. Biological control 

using mosquitofish is possible. 

Expanding on the concept of control to understand that what is being controlled is the negative impact

of mosquitoes, rather than mosquitoes themselves, then all efforts designed to reduce human exposure to

mosquitoes constitute control. Public awareness becomes a vital component. This does not mean teaching 

people to live with mosquito bites. It does mean teaching people how to make informed decisions about 

mosquito control.

Thresholds are vital to the control process because only through thresholds can a rational response be 

made to unusual circumstances. A quality IPM program cannot “fail” in the strict sense because it has control 

techniques available for each step in pest population increase (or, in the case of a disease threat, each increase 

in the risk of contracting the disease). Source reduction is adequate when mosquito breeding is absent or low. 

Larviciding is triggered by increasing larval numbers. Localized adulticiding is triggered when adult 

populations pass a given threshold. Finally, aerial adulticiding is available when populations explode and/or 

the disease threat is high. 

d. Evaluation. Each control step is evaluated for efficacy and future actions modified 

to improve control or reduce negative impacts. Field evaluation will generally use the same monitoring

techniques described above and the important criteria will be changes in the mosquito population and/or 

environment. Over time, a steady state should develop where realistic thresholds trigger effective responses.

B. Aspects of IPM currently in place in Massachusetts mosquito control programs. 

1. IPM Questionnaire. 

Along with the general questionnaire sent to the projects in 1996, a separate page concerning IPM was 

included. In it, projects were requested to provide a definition of IPM and then either agree or disagree with a 

series of statements about IPM (Tables 15 and 16). 

225
Table 15. Project responses to IPM Questionnaire as given. 

 No 

 Agree Disagree 

Response 

14. Mosquito breeding outside the Program has an impact on adult mosquito 7 1 

populations within the Program. 

1. The Program already practices IPM. 6 1 1 

4. Quantifying human annoyance is difficult 6 2 

2. The wide range of breeding habitats to be monitored makes implementing 2 6 

 IPM difficult. 

3. The wide range of areas in which adult mosquitoes are a problem makes 3 4 1 

implementing IPM difficult.

5. Control techniques and options are more often determined by a vocal 5 3 

minority rather than the community average. 

6. Light trap catches are influenced by too many factors unrelated to mosquito 2 6 

population densities to be used as a reliable indicator of actual problems. 

7. Current funding provides a rough measure of a community’s perceived need 3 5 

for mosquito control. 

8. Personnel shortages prevent collection of data required for IPM decisions. 4 4 

9. Knowledge gaps prevent implementation of IPM. 2 6 

10. The wide range of species of mosquitoes to be controlled makes 3 5 

implementing IPM difficult.

12. Predicting adult mosquito populations from larval monitoring is not 4 4 

 sufficiently accurate. 

13. Waiting until adult mosquitoes are biting is too late to initiate control. 4 4

11. IPM is not possible in mosquito control. 0 8 

The most encouraging aspect of the answers is that none of the eight projects responding felt that IPM was 

not possible in mosquito control (Statement 11) and six of the eight felt they were already practicing some form

of IPM (S1). On a less optimistic note, there was strong feeling that quantifying human annoyance is difficult

(S4). Of the two (Cape Cod and East Middlesex) that did not think quantifying human annoyance is difficult,

Cape Cod is dominated by the summer tourist season and is probably is not very hard to figure out whether or 

not mosquitoes should be controlled, the answer being, “Yes!” An additional concern when attempting to 

establish HATs is that most of the projects felt that vocal minorities have more say in mosquito control than

does the community average (S5). There is little question that the HAT concept, while theoretically of value, 

may be based on incorrect assumptions about the driving forces behind control decisions. 

Equally troubling from a control perspective is that most projects felt that mosquito breeding outside their 

Table 16. Project responses to IPM Questionnaire sorted from highest number of “agree” responses to lowest. 

 No 

 Agree Disagree 

Response 

226
14. Mosquito breeding outside the Program has an impact on adult mosquito 7 1 

populations within the Program. 

1. The Program already practices IPM. 6 1 1 

4. Quantifying human annoyance is difficult 6 2 

5. Control techniques and options are more often determined by a vocal 5 3 

minority rather than the community average. 

 

8. Personnel shortages prevent collection of data required for IPM decisions. 4 4 

12. Predicting adult mosquito populations from larval monitoring is not 4 4 

 sufficiently accurate. 

13. Waiting until adult mosquitoes are biting is too late to initiate control. 4 4

3. The wide range of areas in which adult mosquitoes are a problem makes 3 4 1 

implementing IPM difficult.

7. Current funding provides a rough measure of a community’s perceived need 3 5 

for mosquito control. 

10. The wide range of species of mosquitoes to be controlled makes 3 5 

implementing IPM difficult.

2. The wide range of breeding habitats to be monitored makes implementing 2 6 

 IPM difficult. 

6. Light trap catches are influenced by too many factors unrelated to mosquito 2 6 

population densities to be used as a reliable indicator of actual problems. 

9. Knowledge gaps prevent implementation of IPM. 2 6 

11. IPM is not possible in mosquito control. 0 8 

district has an impact on adult mosquito populations within their district (S14). The only project that did not

was Cape Cod, which is more isolated than are the other projects. IPM programs that stress water management

of larval populations must be flexible enough to allow projects to control adults mosquitoes coming in from

other areas. 

Looking at some specifics by project, Norfolk and Essex both agree with the three statements (S2, S3, 

and S10) relating to the wide range of mosquito habitats. Though these programs have both salt-marsh and 

freshwater components, their distribution of effort is not markedly different from Plymouth or Suffolk

Counties, which disagreed with all three statements. Norfolk and Essex also were the two projects that agreed 

with the statement that, “Knowledge gaps prevent implementation of IPM” (S9). As both Norfolk and Essex 

MCPs are active in pushing for stronger, more ecologically sound mosquito control, their responses may be less 

an indication of their dissatisfaction with IPM and mosquito control and more an indication of their desire to

see mosquito control IPM improved. 

2. Mosquito Control IPM as practiced in Massachusetts today.

227
The strategy of IPM as developed for agricultural ecosystems is an ecologically-based concept (Axtell 

1979). It has yet to be fully applied to mosquito management programs. IPM is a strategy for managing insect

populations not a method for controlling them. It is more than integrated control which is simply the 

combining of several control methods. Mosquito control has a long history of integrating different control

methods. 

The general feeling among most MC practitioners is that any significant larval population within flight 

range of residential areas will probably result in some human annoyance and therefore should be controlled. 

Few MC programs in the U.S.A. have developed annoyance threshold levels for their communities. No Project 

in Massachusetts has undertaken such an effort. In the Metropolitan MC District in Minneapolis/St. Paul, it 

was found that the HAT was 2 bites/5 minutes between 7-9 PM on typical summer evening. Thus, the 

minimum goal of this District is to keep the human biting rate at or below 1 bite/5 minutes. This number is so 

low, however, that few projects are likely reach it consistently throughout their district. Therefore, whether or 

not a given breeding site is larvicided is more a function of economics than of absolute mosquito numbers. 

Although many MC programs regularly monitor adult population levels (with light traps and landing 

counts) they do it to evaluate larval control effectiveness and the need for adulticiding; not to determine when 

immediate larval control is needed as in the case of agricultural IPM programs. However, light trap counts, 

landing rates and complaint calls are used to create a general picture of the need for mosquito control and 

projects with long-term experience develop larviciding plans based on this historical data. 

It would be beneficial if techniques for predicting future adult biting annoyance from larval counts 

could be developed. One way this could be accomplished by marking different larval populations (for example 

with Geimsa stain) and then assessing the subsequent contribution of marked females to the population biting 

humans in neighboring areas (Fish & Joslyn 1984, Joslyn et al. 1985). A simpler technique is to mark adults

with a fluorescent dust, release them at the breeding site, and attempt to recover them in adjacent biting areas 

(Morris, et al. 1991). This can show which areas are being affected by which breeding areas. The drawback to

these types of is the need to do it for each species in question and, due to the large number of site-specific 

variables, for many breeding sites. Regardless, studies like this would require a research element not present in

the current Massachusetts system. 

228
Assessment of the cost/benefits resulting from outdoor recreational activities have been dealt with 

extensively in the literature (Pierce & Napier 1977, Beardsley 1971, Moeller et al. 1976). The theoretical basis 

for most of these analyses is found in general welfare theory (Pierce 1971, Prest & Turvey 1965, Walsh & 

Williams 1969). When applied to the assessment of economic benefits, these analyses represent attempts to 

establish the consumer surplus" (Blaug 1968). This surplus represents the consumers willingness to pay" 

(WIP) for a specific service or facility e.g., a mosquito-free campground or park. Once determined, the WIP is 

used as a proxy for benefits emanating from the service (Mishan 1976). John et al. (1987) established the WIP 

for a Texas community to be $22.44 per household ($18.96 per renter household). Once the benefits and costs 

of mosquito control are assessed, it is possible to establish Economic Thresholds (e.g., the mosquito density at

which the cost of control is equal to the value (estimated benefits) forthcoming from the controls (Edens & 

Cooper 1974, Edens 1977). 

A major concern in all of these cost/benefit analyses is that they compare dollar costs of various 

control techniques or discuss consumer willingness to pay but they do not address ecological costs associated 

with mosquito control. Due to the lower and more specific toxicities of newer pesticides, water management

may not always be less ecologically damaging than pesticide application. 

There is no study to date of the costs and benefits of Massachusetts mosquito control programs. There 

is good reason to believe, even if such studies were done, that the results would reflect local, current thought, as 

opposed to some underlying “true” cost/benefit for mosquito control. Variables that would affect perceived 

cost/benefit include relative economic strength of the local community and of the state, recent weather patterns 

and their influence on mosquito breeding, the rate and direction of development within the community, and the 

techniques available for mosquito control. Regardless of the underlying variability of any cost/benefit analysis, 

working towards an understanding of the costs and benefits of mosquito control is desirable. The following 

information would aid in such work:

1) Establish human annoyance thresholds (HAT) 

2) Document how human activity patterns relate to HAT and economic factors 

3) Determine cost/benefit analysis of control (willingness to pay) 

4) Correlate HAT with a standard non-biting sampling method (e.g. light trap) 

5) Correlate densities of immatures with future levels of biting annoyance 

229
6) Establish the ecological costs of various control techniques. 

The cost/benefit of various control options (e.g., permanent vs. temporary control) also has been 

evaluated in recent papers (Ofiara & Allison 1986a, 1986b) but this should not be confused with the 

cost/benefit of control programs. 

3. Improving Physical Control.

Reducing pesticide use is not a primary goal of IPM (Robinson 1996). Reducing unnecessary 

pesticide applications and improving the effectiveness of pesticide applications are goals, and improving our 

knowledge of how a system works often results in pesticide-use reduction, but there is nothing in the concept of 

IPM that mandates reducing pesticide use. Indeed, at Essex County, when they established a landing count rate

of 1 per five minutes for adulticiding, they found that the total area that qualified for adulticiding jumped 

dramatically (Walter Montgomery, personal communication). That being said, pesticide use remains an issue 

and improving non-chemical controls is a desirable goal.

Most organized MC projects in Massachusetts engage in source reduction activity. Current sourcereduction efforts generally consist of cleaning and repairing ditches and other water control structures built 

previously rather than with the construction of new structures. New construction is limited by State and Federal

wetland protection laws and regulations. Also, the economics of source reduction programs is an important

consideration. The higher initial cost of this semi-permanent control strategy must be amortized over the multiple 

years of anticipated benefit. It cannot be implemented at all when limited annual budgets prevent MCPs from

acquiring the large up-front capitol sums that are needed for major source reduction projects. Another shortcoming 

of the current regulations, as they apply to mosquito control, is they fail to adequately differentiate between natural 

and manmade wetlands. 

One major advance already underway is vastly improved mapping through Geographic Information 

Systems (GIS). GIS wetlands mapping can both aid mosquito control agencies in determining control priorities 

but can be used by mosquito control agencies to integrate their work with other land-use agencies (Guthe 1993). 

Very detailed maps can also be made when planning water management projects (Gettman 1995). 

a. Saltmarsh management

There are two major strategies for managing tidal waters to achieve control of saltmarsh mosquitoes: (1) 

long-term flooding or impoundment of the high marsh to prevent mosquito egg laying and encourage larvivorous 

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fish, or (2) drainage of the high marsh to prevent water from standing for the 6+ days required for the completion 

of mosquito larval development. Some combination or modification of these two might be considered as a third 

strategy. Permanent or seasonal impounding of the entire high marsh is not a viable option in New England's 

grassy salt marshes with wide tidal fluctuation (Provost 1969). 

Early source reduction work in grassy salt marshes consisted of grid ditches, initially dug by hand. 

.Everyone concerned now seems to agree that such a blanket approach to saltmarsh ditching is overly destructive 

and less effective than more customized designs though the actual impacts have been debated (Bourn & Cottam

1950, Lesser et al. 1976, Provost 1977, Daiber 1986, Buchsbaum 1994). This approach is no longer practiced or 

recommended, but many of these old, square-bottomed ditches still criss-cross Massachusetts salt marshes. Many

have become silted-in shallow depressions in which mosquitoes breed. To avoid this, some MC projects continue

to clean and maintain at least some of the old grid ditches. 

Contour ditching grew out of the realization that grid ditches often fail to flush with the tides and 

therefore, unless continuously maintained, they eventually silt in and form breeding. Contour ditches are more 

strategically placed and follow the natural topography of the marsh. Contour ditching schemes are essentially 

integrated extensions of natural tidal creeks and they better take into account the hydrodynamics of tidal marshes. 

Although they are a more intelligent approach to ditch design, they are still ineffective in preventing mosquito 

breeding in many shallow pans and isolated, irregular depressions which characterize the upper part of many

Massachusetts salt marshes. 

An obvious alternative to maintaining grid or contour ditching would be to upgrade the grid-ditch systems 

to OMWM systems. In a Rhode Island salt marsh such a conversion consisted of creating a reservoir within an 

existing ditch, cleaning out those sections of ditch that functioned as connectors from the reservoir to breeding 

pannes, and using the spoil to fill in ditching that was not serving a mosquito-control function. As a result, 

breeding densities of hundreds per dip were reduced to virtually none and larviciding practically eliminated 

(Christie, personal communication). This type of work is occurring in Massachusetts but could probably be 

increased. 

b. Fresh water management

Natural Wetlands. Over the past decade there has grown up a tremendous force for the preservation of all 

wetlands, the “no-net-loss” policy. This policy is based on three assumptions: 

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1) each and every wetland is of infinite value 

2) that all wetlands are of equal value 

3) that any actions or other properties sacrificed to maintain a wetland must have less value than the 

wetland itself. (Gates 1995). 

The challenge for mosquito control programs is to ensure that a more balanced set of assumptions comes to the 

fore as our understanding of wetlands, mosquitoes, and vector control increases. No IPM program for mosquito

control can be adequately developed if the areas in which control takes place are off limits to manipulation. Just as 

mosquito-control personnel must become more aware of the ecological costs of mosquito control, so too must

advocates of wetlands preservation become more aware of the benefits of mosquito control.

Most permanent wetlands offer few options for water management. Draining or filling natural wetlands

are no longer considered acceptable practices. Extensive existing drainage networks are currently maintained by 

the Mosquito Control Projects but new ditching is rarely permitted. Most existing systems were not originally dug 

with mosquito control in mind. Unfortunately, a ditch system, once in place, almost invariably breeds mosquitoes 

if it is not maintained. A primary goal for mosquito-control programs and state agencies should develop criteria 

for continued drainage maintenance, using the New Jersey guidelines (New Jersey DEP 1997) and the North East

Massachusetts Mosquito Control and Wetlands Management District “Standards for Ditch Maintenance” as 

starting points. 

The prospect for source reduction activity in the thousands of acres of wooded swamps common 

throughout the eastern third of Massachusetts is slim. The primary vector mosquito, Cs. melanura, produced in

these swamps is essentially an after dark, passerine bird feeder, and is unlikely to transmit EEE to humans and 

horses (Nasci & Edman 1981a, Morris et al. 1980). Therefore, any effort to control this mosquito is perhaps 

misplaced, though some success has been had with aerial applications of Altosid pellets (Henley 1992). If the 

vector(s) of EEE virus to mammals were known, control efforts directed against this mosquito would be a more 

logical and efficient way to interrupt disease transmission during threatened epidemics. The most likely candidates 

for such attention are Cq. perturbans, Ae. vexans, and Ae. canadensis. 

Vernal pools are both a valuable resource and a reliable source of mosquitoes. Their size makes them

more amenable to habitat modification but their value as nurseries for amphibians and other semi-aquatic animals 

makes their preservation important. In rare cases, however, ditching (when possible) or filling small woodland 

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pools in close proximity to human populations may provide sufficient benefits to outweigh the loss of some of 

these temporary aquatic habitats. Vernal-pool certification by NHESP will, over time, bring under protection of 

the Division of Fisheries and Wildlife those vernal pools which should be left undisturbed. Most vernal pools 

slowly fill in naturally while new ones are constantly being created in the root cavities created by blown over trees. 

Massachusetts forests are currently maturing so 'blowdowns' and new vernal pools may be increasing. 

Populations of tree-hole Ae. triseriatus seldom reach serious densities in Massachusetts at present but this 

could change. Because this species is a daytime biter, adapts readily to discarded tires, and is a potential vector of 

La Crosse encephalitis, it bears careful monitoring. The city of La Crosse in Wisconsin has mounted an effective 

campaign to nearly eliminate human cases of LAC encephalitis by simply removing old tires and other small 

water-holding containers and filling in tree holes near residential areas (Parry 1983). This model for source 

reduction of tree-hole mosquitoes is undoubtedly the most effective way to presently deal with Ae. triseriatus in

areas where it becomes a localized problem species. 

Reservoirs and dug ponds. The majority of small permanent ponds and lakes in Massachusetts are man-made. 

They were created by dredging natural seepage areas or by damming streams. Many Massachusetts reservoirs are 

old, having been built to provide power and water for adjacent factories built between the middle of the 19th 

century and the depression years of this century. Some have become badly silted and eutrophic. Nearly all of 

these bodies of water create some mosquito habitat, at least along vegetated shorelines and in shallow upper 

reaches distal to the dam. Anopheles and Culex are the principal mosquitoes associated with these wetlands and, 

when cattail or water willow invade along the shoreline, Cq. perturbans become established as well. Also, small 

permanent ponds or reservoirs within wooded habitats often hatch large broods of univoltine Aedes along 

leaf-packed borders during spring flooding. 

Older dams seldom have flexible water level control structures. Thus, well-established principles for 

managing mosquitoes in impounded waters (Edman 1964) can not be applied in most Massachusetts reservoirs. 

All new and rebuilt structures should include adequate control capabilities so that water level management can 

become a mosquito control option in all impoundments in the future. The main features of water level control

plans are: (1) maximum pool levels when flood-water Aedes are laying eggs, (2) gradual summer drawdown with

weekly surcharges to strand floating debris and keep water out of the shoreline vegetation that protects Culex and 

Anopheles larvae from wave action and predators, and (3) during the spring egg hatch period, keep pool levels

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from rising above the levels maintained during the previous year's univoltine Aedes egg-laying period. 

Grass and scrub marshes created by drainage disruption. Most serious pest/vector problems associated with these 

habitats are created in situations where vegetation favorable to the cattail mosquito, Cq. perturbans has invaded the 

marsh. This mosquito is difficult to control by conventional larvicides, is an aggressive biter of humans and 

domestic animals, and may play a role in EEE epidemics. Spring Aedes, and summer Anopheles and Cx. 

salinarius problems may be associated with these marsh habitats as well. Also, a univoltine bird feeder, Cs. 

moristans, which may play a role in enzootic cycles of EEE virus (Morris and Zimmerman 1981), breed 

principally in this category of wetland.

There are two potential habitat management strategies for eliminating breeding associated with these 

wetlands and neither is popularly practiced. One involves removing the vegetation which supports breeding (e.g., 

cattails). This can be done with a dragline provided the vegetation is still restricted to the pond border. 

Alternatively, selective herbiciding or hand removal when invasive plants like cattails first become established

along the shore may be effective in some situations. A second management strategy is to correct the drainage 

disruption which created the wetland situation in the first place. This may be as simple as installing or lowering a 

culvert. In contrast, it may be so complex and expensive that it is not a viable option. When feasible, restoring 

natural drainage will permanently eliminate the wetland. This may be considered unacceptable despite the fact that 

these wetlands are man-made and of limited life expectancy. The builders of roads, railroads, and power or pipe 

lines are responsible for the majority of these wetlands. Expecting contractors to retroactively address, at great

expense, the public health and nuisance problems that they have created is perhaps unrealistic. However, all new 

construction which involves significant changes in topography and natural drainage should be reviewed by an 

agency such as the SRMCB to assess impact on water flow and creation of new wetlands which may produce 

pest/vector mosquitoes. 

Roadside ditches and tire ruts. A major source of reflood Aedes are ditches that fail to completely drain because of 

a lack of culverts or culverts that are located above the level of the ditch bottom. Heavy equipment and tractor tires 

leave permanent ruts in soft turf which is another major source of reflood breeding sites associated with ditches 

and low-lying fields. Both of these categories of man-made wetlands can be prevented by proper engineering, 

construction, and maintenance practices. Where these breeding sites already exist, they can be permanently 

eliminated by appropriate lowering of culverts and regrading work. Tapered cement aprons at both ends of 

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culverts and cement linings in the bottom of roadside ditches in residential areas with poor drainage characteristics 

can also assist in preventing the creation of these breeding sites. Municipal and state road crews should be 

cautioned against mowing when the sod is too soft to fully support mowing equipment without creating depression 

in the ditch bottom.

Storm catch detention and retention basins, ornamental pools, tires, and other man-made containers. Good sanitary

practices promoted through homeowner education can eliminate most of the water-holding vessels which support

container-breeding mosquitoes. The policy of many landfills to charge extra for accepting used rubber tires and 

appliances has created undesirable stockpiles in many backyards or illegal dumping along isolated roadsides. Tires 

can be eliminated as breeding sources by cutting 3-4 large holes on either side, but those most likely to dump tires 

illegally are least likely to care about creating breeding habitat. Tire dumps create a special problem that can best 

be dealt with through recycling plants which are now being built in many areas. Retreading operations frequently 

stockpile large numbers of used tires that are awaiting processing. If tires are stored in open sunlit area, they will 

not be colonized by Ae. triseriatus. Culex pipiens, which will colonize sunlit containers and underground catch 

basins are not a major pest or vector problem in Massachusetts. Culex salinarius is the only Culex frequently taken 

in mid to late summer human biting collections in the Northeast and it does not normally breed in catch basins or 

other containers. The urban autogenous form of Cx. pipiens (i.e. molestus) reportedly bites humans (Spielman 

1973) but outdoor pest populations of this form are not well documented in the Northeast. In any event, well

designed and regularly cleaned catch basins should not retain runoff water. Cities in Massachusetts with old sewer 

systems still contain many catch basins which produce Culex. The actual pest status of mosquitoes produced in

catch basins should be well established by each community prior to control considerations. New detention and 

retention basins are frequently built around new malls and similar large construction site to manage rainwater and 

protect nearby wetlands from runoff pollution and siltation. In many cases these basins are becoming a mosquito

problem (Culex, Anopheles, Aedes, and even Coquillettidia). Better design and maintenance could help to alleviate 

this growing problem. 

About 12 years ago the Asian tiger mosquito, Ae. albopictus, was accidentally introduced into Texas, 

presumably via used tires from northern Asia (Moore 1986). Since its introduction, this day-active, man-biting 

pest and potential vector species has spread into 17 states including several in the North. It has been found in

Maryland and may appear in Massachusetts. Biting densities of 30 per minute already have been reported in

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Texas, Louisiana and Illinois. This species is most common in tires but will occupy a variety of man-made

containers. Its control is likely to become an important priority in the Northeast within a few years. 

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VII. STANDARDS FOR MOSQUITO CONTROL 

A. Standards for Monitoring and Control: Pesticide applications in an IPM program require monitoring 

insect populations and comparing data with pre-established thresholds for treatment. In addition, post-treatment 

evaluation is required to ensure the treatment worked as planned and did not have unintended side-effects. 

1. Larval Populations: The primary technique for larval population counts is the dip count. It is

hard to standardize dipping technique but, for the purposes of this document, it is assumed that dips are taken in

undisturbed pools (the field person is aware that disturbing the water and/or casting a shadow over the water will 

cause mosquitoes to dive, thereby lowering counts) known by the field personnel to be typical of the breeding area 

being monitored. For large-scale work, dipping will be done at permanent, marked (or easily located) dip stations. 

For small sites such as drainage basins and woodland pools, dips will be taken at random throughout the site. Up to 

twenty dips per site will be taken unless the count for treatment and/or water management is exceeded with a 

smaller number of dips. Specifics for various types of work are given in Table 17. 

 a. Larval Identification. Field identification of larvae to genus is desirable. The 

following genera should be recognizable most of the time: Aedes, Anopheles, Coquillettidea, Culex, Culiseta, 

Psorophora, and Uranetaenia. Programs should rear out sufficient numbers of larvae (or identify larvae to species) 

to allow correlation between adult mosquito species and larval populations. Because there may be situations where 

treatment will depend on the species (as opposed to the genus) present, programs are encouraged to have a staff 

member trained in larval (4th instar) identification

b. Pre-control Larval Monitoring. Larval populations are monitored to determine whether or 

not control is required and, if so, whether short-term or long-term control is preferred. Criteria for water management

in salt marshes are given in more detail in Appendix D. Projects should develop their own criteria for freshwater water 

management work, though some guidelines are given below under standards for physical control.

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Table 17. Specifics for monitoring larval (& pupal) populations of mosquitoes for determining control.

No Treatment Pesticide Water management # Sites for large-scale work

 Application 

Salt Marsh <1 per 10 dips 1+ per 10 dips 5+ per dipa 1 dip station per 250 acres 

 

Freshwater 

 Ground <1 per 5 dips 1+ per 5 dips Variable Not applicable

 Aerial <1 per 10 dips 1+ per 10 dips Not applicable 1 dip station per 250 acres 

a

Numerous additional factors go into determining water management options for OMWM. 

c. Post-control or post-alteration monitoring will be conducted as follows: 

Treatment Technique Evaluation Sites Time Period Number of Dips 

Aerial applications each dip station within two business days. Ten dips 

Ground applications one of every ten sites within two business days Ten dips 

Water management each dip station for two years post-alteration Three dips 

d. Additional Water Management Requirements. Projects have an obligation to ensure that

all alterations function as intended without adverse effects on the environment. Post-alteration work for water 

management (Appendix 4 for OMWM) will also monitor vegetative re-growth, changes in fauna and notes on

whether or not the hydrology of the site is as intended. 

e. Pre-hatch Work. On occasion, pre-hatch treatment is desirable. In such cases, the 

project should have historical data that establishes a pattern of breeding at a given site. Pre-treatment work is

limited to Category IV larvicides. 

2. Adult Populations. No adulticiding program will be conducted on a routine, pre-scheduled basis 

(i.e. once per week, regardless). 

 a. Monitoring for Adulticiding

Monitoring Mechanism Rate to trigger adulticiding

Light traps Human-biting mosquito counts exceed five per night 

Landing counts Landing count rates exceed one per minute 

Complaint calls When complaint calls exceed two per geographical area 

(this area will vary but assume approximately one square mile) 

b. Considerations for adulticiding. Adulticide applications for mosquito control require 

particular care as they are generally made with rather broad-spectrum pesticides (for example, resmethrin is of 

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concern near fish waters) in areas of high human use. Pesticide aerosols, while an effective technique for using 

small amounts of pesticide to impact large numbers of mosquitoes, also increase concerns over drift into non-target

areas such as apiaries and organic farms. As is always the case, reading and following the pesticide label is 

essential. Also, adulticide operators should have a map of no-treatment zones with them on their routes and they 

should be aware of variations in weather conditions (high wind) that would affect, or even cancel, a treatment. 

c. Further notes on complaint calls. Because different people complain at different 

mosquito population levels, program personnel will conduct landing counts and/or place light traps within adulticide 

zones at intervals throughout the season to determine what mosquito population levels are triggering what levels of 

complaint calls. Chronic complaint callers should be checked by conducting landing counts and/or hanging light

traps at the location of the complainer. 

d. Adult Identification. Light trap mosquitoes should be sorted and up to 100 individuals

(randomly selected from the larger pool) should be identified, where possible, to species. If trap counts are being 

used to monitor water management work, species identification (particularly of Aedes) is more critical than if traps 

are being used for adulticide monitoring. 

At least ten mosquitoes from each landing count should be identified to species. 

Complaint callers should be asked the time of day at which biting occurs. 

e. Post-Adulticide Monitoring. Although determining the exact effect of a given adulticide 

application is difficult, projects should increase their efforts to understand the impact of adulticiding on mosquitoes. 

Projects should cross-reference complaint calls with adulticide applications and record the number of calls coming 

in the week before an application and in the following week (this work may be done during the winter for the 

previous season). In addition, projects should conduct before and after landing counts and/or light-trap counts for 

ten percent of their adulticide applications. Landing counts should be taken within 48 hours pre- and postapplication at the same location both times. Light trap samples should be from the same trap and for the same time 

period before and after treatment. Where possible, non-treated areas similar to the treated area should be checked to

determine population trends outside the spray zone. 

Projects should keep a log of complaint calls received post-treatment Such complaints may be of nontarget effects such as fish or bird kills, or of human exposure to the treatment. While establishing a link between an 

adulticide application and a specific problem is very difficult, such complaints may provide insight into the efficacy 

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of the application or may alert control projects to problems with spray equipment, treatment timing and/or treatment

area. 

C. Standards for Physical Control. Altering or eliminating mosquito breeding sites range from proper 

disposal of tires through analyzing drainage systems to creating entire new open marsh water management systems. 

All mosquito control programs should create a map of their area of responsibility on which they have 

roughly demarcated endangered species estimated habitats and significant habitats as listed in the Natural Heritage

Atlas. This should be referred to before any maintenance or new work is done and specific maps within the Atlas 

checked when work is taking place near such an area. Any work with such an area, must go through NHESP. 

For this section Physical Control refers specifically to alterations to breeding habitat to prevent mosquitoes 

from maturing to adulthood. Physical Control is divided further into three types:

Source Elimination: Completely eliminating the breeding site not just the mosquito breeding. Source 

elimination is generally limited to breeding habitats created by humans in non-wetland areas. 

Source Maintenance: Maintaining potential breeding sources in such a way that mosquitoes cannot become

a problem. 

Source Reduction: Reducing the ability of an area to breed mosquitoes. It differs from source 

maintenance in that the existing habitat is breeding mosquitoes whereas, if a maintenance program

is running as designed, mosquito breeding should not occur. Once a source reduction project is

completed, it will, in most cases, require at least some source maintenance in order not to return to

being a mosquito-breeding habitat.

Although the three types of Physical Control blend into one another, there is value in recognizing the 

difference, particularly between maintenance and reduction. Here the critical issue is the need to document 

mosquito breeding. While unwarranted ditching is not desirable, neither is it desirable to prevent maintenance of

existing ditching to the point where mosquito breeding begins in an area that has been mosquito free in the past. It

is important to stress that no mosquito-control activity that would result in the permanent loss of true wetland (as 

opposed to temporarily flooded areas resulting from human mismanagement) can be accepted as a standard practice. 

1. Source Elimination. 

a. Tires. All mosquito-control programs should have a system in place for contacting 

departments of public works within the project so that the tires can be removed. Where tires are being intentionally

stored, projects should attempt to contact the property owner and explain the breeding potential of the tire dump. 

Projects are not responsible for ensuring compliance with tire-disposal regulations; their sole responsibility is 

education of property owners and notification of appropriate local authorities. 

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b. Blocked drainage. In this situation, the assumptions are that the stagnant water would 

not be present if not for the blockage and that the drainage in question has not been part of an on-going maintenance 

program (see source maintenance below). In this case, mosquito breeding must be documented within the blocked 

ditching for mosquito control programs to re-open the ditch (without mosquito breeding the ditch may be re-opened 

by Highway or Public Works Departments for drainage reasons). 

c. Residential problems. Such situations would include pools, refuse dumps, tire tracks, 

and other localized, man-made problems. As is the case with tire removal, projects can only advise property owners 

of the breeding potential and/or notify the appropriate authorities of a problem. 

d. Drainage basin design. A primary tenet of IPM is to avoid creating pest problems 

through good planning. Projects are strongly recommended to make available to local agencies the specifications 

for drainage basin design located in Appendix 5. Projects should evaluate various basin designs for breeding 

potential and should educate local officials about the problems basins can cause. 

 2. Source Maintenance 

a. Stormwater runoff and ditch maintenance. A primary goal of any mosquito control

program is to monitor existing drainage to ensure that it is working as designed. Within existing drainage, any

blockage may be removed regardless of mosquito breeding. As an example of the type of guidelines projects should 

use for this type of work, the standards for the North East Massachusetts Mosquito and Marsh Restoration Project

are given in Appendix F. 

Record keeping for maintenance purposes should be improved. Projects should maintain at their 

headquarters a list of all drainage that is monitored and maintained. This list should include location and 

approximate cross-section and length. Projects should also maintain a record of when and where maintenance was 

done. In instances where ditching has not been maintained, and no historical documentation of maintenance exists, 

the projects should request a review of the proposed work by DEP’s Water Quality Certification program to ensure 

compliance. 

In the long run, projects should develop priority lists for ditch maintenance based on the potential for 

mosquito breeding, the proximity of human activity, the ecological cost in reduced wetland benefits from the area 

being drained, and the relative value or scarcity of the wetlands resource affected. Maintenance should be based on 

breeding potential and ecological factors. 

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Drainage basin maintenance is also included within this area. Some basins that do not produce mosquitoes 

when maintained properly, will become breeding sources if left unmaintained. Projects should conduct yearly 

checks of drainage basins to ensure that pooling within the basin is not increasing to a point where breeding may

occur. In deeper basins, invasion by cattail or emergent grasses might also create breeding habitat.

Basin ownership and maintenance responsibility are often difficult to determine. Mosquito Control 

Programs need to remind the appropriate authorities that basin maintenance is an important issue and should be 

monitored by the Building Inspector’s office or other responsible agency. 

b. Salt-marsh Ditching. It is generally not recommended that the open ditch systems be 

maintained as is. however, projects will self-determine the need for maintenance of existing ditching versus

conversion to OMWM, understanding that conversion is preferred. 

c. Waste Disposal. Projects are not responsible for waste disposal but they can and should 

monitor areas known for problems with either tire dumping and/or improper general waste disposal, particularly

where it blocks drainage. The purpose of this work is not to get projects involved in policing dump sites, but rather 

to get them to move from a passive strategy of treating known tire piles to an active strategy of eliminating such 

areas and preventing their return. 

 3. Source Reduction. 

a. Open Marsh Water Management. Open Marsh Water Management (OMWM) is the 

preferred technique for salt-marsh source reduction. When done properly, OMWM can result in virtual elimination 

of breeding without any loss of wetland. Although each project with salt marsh will develop its own standards, the 

standards of the North East Massachusetts Mosquito Control and Wetlands Management District are included as 

Appendix 4 as guidelines for establishing an OMWM system that will comply with all state and federal regulations. 

New open tidal ditch systems are not recommended except as an integral part of an OMWM system. 

b. Freshwater wetlands. Source reduction in freshwater systems, exclusive of existing 

drainage networks, does not have an equivalent to OMWM in salt marshes. At this time there can be no standards 

for water management within freshwater systems except that any such work must be evaluated by the appropriate 

authorities on a case-by-case basis. 

An additional consideration is wetlands replication, the process by which existing wetlands may be altered 

and new wetlands created. While mosquito control projects should not be the authors of such work, they will be 

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involved in monitoring such areas. Further, reclassifying some areas as wetlands replication sites may well alter the 

extent to which water management work and/or larviciding can or should be done. For this reason, projects should 

be made aware of all wetlands replication projects. As with drainage basin design, projects should likewise develop 

a working relationship with town Zoning Boards and Building Inspectors so that mosquito control programs are 

included in the review process for wetlands restoration, replication or creation projects. 

c. Cattail control. In order to prevent increases in Coquillettidea perturbans, projects should 

discourage the creation of deep-water (two feet plus) cattail marshes (Drainage basins) in residential areas. Failing

in that, projects should request that such marshes be designed so that water may be drained from the marsh for a 

period of several weeks in late summer. 

D. Standards for Biological Control.

1. Larvivorous fish. OMWM is dependent on native fish immigrating into the newly created ditch 

and reservoir system. Projects should explore the idea of stocking native fish species in deep-water drainage basins. 

2. Other biological control agents. Exclusive of the Bti and Bacillus sphaericus products (listed 

here under pesticides), there are no current biological control agents available for use for mosquito control in

Massachusetts other than larvivorous fish. Mosquito control programs in Massachusetts are not research institutions

and cannot be expected to develop biological control agents without extensive research support. Should research 

uncover possible control agents, projects are encouraged to experiment with them. 

E. Standards for public notification, public awareness and education. 

1. Public Notification.

 Projects must comply with regulations for aerial applications of pesticides. 

For truck-mounted adulticiding, projects should notify the public through the print media, between March 

1st and May 1st of each year, as to the areas that may be treated, the pesticide to be used and a number to contact for 

more information or to request exclusion from treatment. 

All projects should maintain, either at their headquarters or at a designated public library, a copy of this

GEIR and copies of the labels and MSDSs of all the pesticides they use. it is further recommended that they include

copies of any educational materials they have put out. 

2. Public Awareness and Education. As education is a primary aspect of an IPM program, projects 

are encouraged to develop educational flyers covering such aspects of their work as pesticide use, water 

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management, and property-owner mosquito control. Flyers may either be developed in-house or be obtained from

the state or other agencies. Examples of educational materials may be found in Appendix 7. 

3. Staff Development. Aside from the pesticide applicator recertification requirements, programs are 

urged to provide opportunities for staff to increase their knowledge about mosquitoes, wetland, and mosquito 

control. Membership in professional organizations, accessing information through university Libraries or the 

Internet, and developing good working relationships with federal, state and local officials whose tasks overlap that

of mosquito control are all good ways to improve the knowledge and performance of staff. 

F. Standards for EEE monitoring and DPH liaison. 

1. Role of Programs in EEE Surveillance. 

The MA DPH in cooperation with the Executive office of Environmental Affairs (EOEA) and the regional

mosquito control districts of eastern Massachusetts developed the “Vector Control Plan to Prevent Eastern Equine 

Encephalitis (1991, currently being revised). This plan outlines and defines policy for vector control of mosquitoes 

that transmit the EEE virus and provides guidance for the coordination of state, regional, and local efforts during 

EEE outbreaks, This plan requires the active cooperation of MCDs in the EEE Risk Area. At clearly defined levels 

of EEE risk, based upon surveillance data collected by DPH, MCDs are asked to assist DPH in assessing vector 

species abundance levels and control options in their communities. The cooperative efforts of the MCDs working 

with DPH helps effect targeted, species-specific vector control when warranted. At the Level of EEE Public Health 

Emergency (see Appendix B), the MCDs work in conjunction with DPH to carry out all phases of the control effort. 

2. Standard Operating Procedures during EEE problem. 

When surveillance data points to increasing levels of EEE risk, DPH notifies the SRMCB and regional 

MCD superintendents. The EEE Surveillance Program informs MCD superintendents of isolations of EEE in their 

districts and the districts, in turn, provide feedback to DPH regarding population and life stage indices for critical 

mosquito species. At certain defined interim levels of risk as outlined in the “Vector Control Plan,” MCDs may be

asked to increase their ground control larvicide and/or adulticide applications in response to increased EEE virus 

activity. The SRMCB is responsible for contracting with appropriate mosquito control applicators in the event that

aerial EEE vector control is recommended by DPH. 

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VIII. SUMMARY AND RECOMMENDATIONS 

A. Legal, Organizational and Fiscal Aspects of Massachusetts Mosquito Control

The organizational structure and funding for Massachusetts mosquito control programs, be they regional or 

town based, rests predominately at the level of town government, although the state legislative bodies have a direct

influences over eight of the nine MCPs’ annual budgets (only East Middlesex is not so affected). In contrast, the 

overseer of mosquito-control activity in Massachusetts is the State Reclamation and Mosquito Control Board. This 

is a loose arrangement for delivering a public service that is best applied at a regional level. Lack of control effort

in one town can greatly effect the efficiency of control efforts in neighboring towns. 

Enabling legislation has been written in a patchwork manner so that there is currently little consistency 

from project to project. For example, towns in Barnstable County (and formerly in Berkshire) are all members of 

their respective regional MC project and no individual community may withdraw from the program without

changing the legislation as did Chap. 119 of the Acts of 1982 in the case of Berkshire County. This provides an 

assurance of fiscal and organizational stability that is lacking in other programs. For example, the Essex County 

and Central Massachusetts projects both went through considerable upheavals in membership between 1988 and 

1993. Fortunately, the other projects have remained remarkably stable over the past decade. Maintaining and 

improving stability, both in membership and funding, is a desirable goal. 

This uncertain fiscal picture is further compounded by the fact that all MC projects in Massachusetts are 

seriously under-funded. In other states, with progressive MC programs, the per capita expenditure varies from $2 

upward. In Massachusetts, it averages about $0.50 (based on $2 per household of 4 people). In addition, many 

other states provide supplemental state funds to encourage non-chemical control efforts and for supportive research 

and educational activities. No such state support exists in Massachusetts. When supplemental state support has 

come, it has been for chemical adulticiding in the wake of EEE threats. 

To a large extent, funding dictates the control approaches that can be pursued. IPM, source reduction, 

1arval control, and adult control represent the four major options in their order of decreasing cost and efficiency. 

Thus, poorly funded programs are forced into more reliance on less efficient and more controversial techniques. 

Larger, better-funded, and stable regional projects can invest in better paid and trained employees, better 

surveillance and public education programs, and expensive equipment such as helicopters which can broaden the 

 245
options for safer and more efficient larval control (e.g., granular larviciding with Bti and methoprene). 

Given the fact that several different state agencies are concerned with mosquito control activities, the 

current system of interagency responsibility for overseeing MC activities (i.e., State Reclamation and Mosquito 

Control Board representing 3 different state agencies) is perhaps the best compromise arrangement. On the other 

hand, the level of general support services that projects and towns receive from this Board seems to be inadequate. 

Recommendations

That new and comprehensive enabling legislation be drafted, reviewed, appropriately revised, and passed 

into law, which will bring all MC control activity in Massachusetts under the same organizational, fiscal and 

operational guidelines. This legislation should provide for the following:

1. The State Reclamation and Mosquito Control should have the following personnel:

a. An Executive Director @ approximately $45,000 per year 

b. An Engineer @ approximately $35,000 per year 

c. An Entomologist @ approximately $35,000 per year 

Not only would this staffing permit the state to conduct research into mosquito control, it would 

provide a team for rapid response to EEE threats in communities that are not members of 

established MCPs. This staff would also provide services such as incorporating DEP stormwater 

management guidelines into Massachusetts MCP Upland Water management operational

procedures. 

2. An operations budget, above and beyond the normal needs of the SRCMB, for research and 

development. A minimum of $50,000 per year is suggested. 

3. A competitive grant fund (funded by the state, administered by the Executive Director of SRMCB 

and advised by an ad hoc panel of outside experts) to support IPM related research and delivery

programs within the state mosquito control enterprise. This should provide support for studies 

such as: cost/benefit analysis of mosquito-control programs; development of human annoyance 

thresholds (HAT); improved methods for monitoring and predicting mosquito population levels;

development, evaluation, and implementation o£ new, non-chemical mosquito management

techniques (e.g., open marsh management and biological control); management of pesticide 

resistance, drift and other use exposures; impact of MC activities on surface and ground water, 

 246
and on non-target organisms; and the biology and role of selected species in disease transmission. 

4. The SRMCB should establish a committee to work with their staff to develop best management 

practices (BMPs) for all aspects of mosquito control, the results of their work being used to

update the GEIR on a regular basis. The committee should include four mosquito-control 

superintendents, four representatives of environmental agencies (federal, state or private) and one 

at-large member to serve as chairperson. Their first order of business should be to develop a set

of BMPs for freshwater drainage maintenance for mosquito control. These BMPs should 

establish strict definitions for projects in which the mosquito control exemption from the 

Wetlands Protection Act may be applied. 

5. MCPs must have the authority to deny requests for maintenance work that does not have a 

mosquito-control component. Because these requests are often made by the same persons or 

municipalities which provide funding to the MCPs, the SRMCB must be willing to act as an 

appeals board, to which a request for work may be sent by an applicant in the event the mosquito

control program denies the request. 

6. Limit mosquito control activity to regionally based regional mosquito control programs which can 

be organized by the appropriate public vote. The SRMCB should organize the regional based 

mosquito control programs and appoint project or district commissioners. The SRMCB should 

select Commissioners from candidates proposed by authorized Boards/individuals from the cities 

and towns of the mosquito control projects or districts. 

7. A flexible and appropriate system of tax assessment which allows for budgets that are adequate to

provide for the implementation of the most contemporary and least risky strategies for controlling 

mosquitoes. 

8. A legal system whereby all major zoning and construction plans in the Commonwealth are 

reviewed by the executive director of SRMCB and the appropriate county MC director for their 

potential impact on mosquito populations and human health. 

B. Operational Aspects of Massachusetts Mosquito Control

 Operational programs in Massachusetts could legally be using chemicals (approved by EPA and the 

Massachusetts Pesticide Board) that are significantly more hazardous than those used in current practice. This 

 247
suggests that knowledge and sensitivity for the environment and human safety are generally being considered by the 

existing control programs. As already indicated, funding levels seldom allow projects to follow the optimum

operational course. Despite these fiscal constraints, projects have significantly changed their operational methods in

recent years toward more source reduction work such as the Open Marsh Water Management projects in Essex, 

Norfolk and Plymouth Counties. Most projects also use more selective and environmentally compatible larvicides 

such as Bti and methoprene. 

The operational recommendations that follow are predicated on additional and adequate funding being 

available for implementation. 

Recommendations

1. All MC Projects should build their programs around the IPM strategy of keeping human 

annoyance below threshold levels as given in the Standards of this GEIR. 

2. Control methodology should be source reduction whenever possible and larvicidal control when it

is not. Projects should work closely with the DEP water quality certification program and the 

Natural Heritage Endangered Species Program to minimize negative impacts of source reduction 

to wetland habitat and/or rare or endangered species. The most target-selective and 

environmentally compatible larvicides (e.g., Bti, methoprene) should be used whenever possible 

regardless of cost considerations. 

3. Saltmarsh mosquito control efforts should emphasize OMWM. All OMWM proposals should 

include plans for filling many of the old grid ditches in Massachusetts salt marshes which do not

function in a productive way and which must regularly be cleaned in order to prevent breeding in

the ditches themselves. This will gradually eliminate the controversy over the continuing need to

clean these ditches and the problem of what to do with the resulting spoil that is created. 

4. Document location, length, and cross-section(s) of all drainage systems maintained by the project

and have that information available in an easily understood format for public inspection. 

Exemption from the permitting process extents only to those drainage systems for which adequate 

historical records of maintenance work exist. 

5. The SRMCB should create a list of pesticides approved for mosquito control in Massachusetts. 

Adulticides should be from Categories III and IV and larvicides should be from Category IV. 

 248
6. Adulticiding should only be carried out in emergency situations involving disease threats or pest 

densities which consistently exceed the human annoyance threshold. 

7. For large-scale adulticiding, only ULV-cold fogging should be used. For spot treatment around 

recreation areas or other areas where public events are to be held, portable mistblowers using 

permethrin as a residual pesticide can be used. 

8. Aerial applications should be restricted to granular formulations in areas where drift could be a 

significant problem. Sometimes some drift is desirable so as to reduce the chance of gaps 

between application swathes. In such cases a liquid formulation may be a better choice. At this

time liquid formulations are also significantly cheaper, making larger applications, and more 

effective control, easier. Increased use of helicopters for aerial larviciding in coordination with

the use of drift-suppression agents and technologies should be encouraged (particularly for 

enhanced larval control in inaccessible habitats such as salt marshes, wooded swamps, vernal 

pools, etc.). 

9. Projects should file a post-treatment report for aerial applications with the Pesticide Bureau which 

gives location and acreage actually treated. The pre-application forms do not always accurately 

represent what actually happened. 

10. Chemical-use reporting needs to be monitored to ensure uniformity and accuracy in reporting. 

Previous reports contained such problems as no units are given on the 1993 through 1995 Cape 

Cod report for Bactimos (BTI), two different EPA registration numbers for Bactimos are given in

the 1993 Cape Cod and Central Massachusetts MCPs reports, and briquets are variously reported 

in terms of number of briquets, pounds of briquets or pounds of active ingredient. The Pesticide 

Bureau should insist that yearly chemical-use reports be filled out according to standardized 

procedures. Reports should be checked as they come in to ensure that standardized reporting 

procedures are followed. 

11. All pesticide storage areas should be equipped with smoke, fire and security systems. A standard 

procedure should be developed for the disposal of all insecticidal materials used in Massachusetts

for mosquito control. The State Pesticide Board should encourage manufacturers of such products

to market reusable containers. A standard procedure should be developed for the clean-up of 

 249
accidental spills of insecticides. Proper use of absorbent materials and the disposal of such 

materials are necessary. Proper attire during formulation and application of insecticides should be 

made mandatory for all individuals involved in these processes. 

C. Research Needs 

There is a need in the mosquito control process in Massachusetts for a strong, operationally focused, 

research effort in freshwater wetlands, exclusive of chemical application techniques. This is not to condemn current

research efforts, for we know more about EEE mosquitoes than ever before, have improved saltmarsh mosquito 

control dramatically, and have made improvements in both chemicals used and methods of chemical use over the 

past decade. But there is a need for research to assess the environmental impacts and efficacy of the current MCP 

programs relative to the freshwater environment. 

Additional research on topics such as long-term effects of OMWM, economically viable control of Cq. 

perturbans, and mosquito control in endangered species habitats also require attention.

Recommendations

1. For water management practices, monitor impacts on animals on a case-by-case basis, depending 

on the site and establish vegetation transects to document changes in wetland vegetation. 

2. Develop a unified data base that documents mosquito populations on an ongoing basis from

regular monitoring sites. Establish state standards for monitoring mosquitoes and provide training 

to mosquito control project staff in data collection and management. 

3. Conduct comparative studies with different management approaches (e.g. pesticide applications 

vs. water management). 

4. Develop a Geographic Information System (GIS) with known breeding sites and areas of 

historical water management activities. 

5. Qualify sites on the basis of need for control, based on breeding (potential or actual), mosquito

species, proximity to human activity, level and type of human activity, and type of wetland habitat

affected. 

6. Create an ongoing research partnership with NHESP to document wetland types, etc.. Mosquito

Control Projects have knowledge and expertise about wetlands that could be invaluable to

NHESP. 

 250
IX. WRITTEN COMMENTS ON GEIR 

NOTE: CONTACT THE STATE RECLAMATION AND MOSQUITO CONTROL BOARD TO OBTAIN 

COPIES OF THESE DOCUMENTS 

A. Comments on Notice of Project Change (1996). 

B. Comments on Spring 1997, Rough Draft.

C. Comments on Final Rough Draft (1997-98). 

196 251
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 260
APPENDIX A 

GENERAL ENVIRONMENTAL IMPACT REPORT 

1996 QUESTIONNAIRE 

MASSACHUSETTS MOSQUITO CONTROL PROGRAMS 

NOTE: CONTACT THE STATE RECLAMATION AND MOSQUITO CONTROL 

BOARD TO OBTAIN COPIES OF THIS DOCUMENT.

261
APPENDIX B 

DPH EEE RISK ASSESSMENT, RISK CATEGORIES, STRATEGY FOR VECTOR CONTROL 

(from the Vector Control Plan to Prevent EEE) 

VI. RISK ASSESSMENT 

 The potential risk for EEE disease in humans is categorized into one of four levels according to an 

assessment of EEE surveillance data from the current and previous year. The risk levels are (1)Low (2)Moderate 

(3)High and (4)Public Health Emergency. Under Risk Levels 2, 3 and 4, the characterization of risk includes a 

definition of areas of concern. The concept of "area of concern" is important in defining the magnitude of the EEE 

risk and selecting appropriate intervention options. There are three components within the conceptual construct of 

area of concern: study area, risk area and treatment area. 

(1) The study area is the geographical area where most human and equine EEE cases in 

Massachusetts have occurred. This area is shown in Figure 3 and includes Plymouth, Norfolk, 

Suffolk, Bristol, Middlesex and Essex Counties. Personal protection measures are emphasized in 

this area through a public information campaign that intensifies at each level of risk. 

(2) The risk area is the geographical area where most of the human EEE cases have occurred. This 

area is shown in Figure 4 and includes Plymouth, Bristol and Norfolk Counties, and parts of 

Middlesex and Suffolk Counties. Vector control efforts may be implemented by state agencies or 

Regional Mosquito Control Districts within this area. Vector control efforts may be extended 

outside of this area, if surveillance data indicate the probability of multiple human EEE cases 

occurring outside the area of historical disease prevalence. 

(3) Treatment areas are defined by EEE surveillance data and are used to guide vector control efforts. 

 The basic cell is defined by a mosquito trap site and is approximately 100,000 acres. These 

treatment cells are calculated to be the set of "best-fit" polygons that represent the areas around 

trap sites. The area for treatment will be defined by the GIS polygon inclusive of all towns with 

more than 20% of their area within the unit. Vector control intervention will be dependent upon 

viral isolation from mosquito pools trapped at the DPH site. The treatment area for a positive 

EEE virus isolation from a horse or human is defined by a circle approximately 2 miles in radius 

around the case. Within a treatment area, larviciding is recommended in areas where significant 

262
levels of vector species larvae are present, and treatment would be expected to reduce adult 

emergences in proximity to large numbers of people. Adulticiding of a treatment cell is 

recommended if predetermined risk indices are met and significant numbers of vector species 

adults are present. 

 At a Moderate or High level of EEE risk, vector control is considered within an area following 

identification of EEE virus in the environment. Following a positive finding supplemental surveillance is done to 

assess the need for a vector control intervention. Additional trapping will be implemented in the treatment area to 

determine the age structures and population abundance of vector species. Larval surveys may also be initiated after 

significant rainfall events. 

 EEE occurs disproportionately by area within eastern Massachusetts. The human cases of EEE by county 

have been 25 in Plymouth, 19 in Norfolk, 13 in Middlesex, 9 in Suffolk, 5 in Bristol, 1 in Essex, 1 in Barnstable, 

and 1 in Hampden. A disease prevention strategy must respond to this disproportionate distribution of risk by 

providing supplemental mosquito control funding (and/or state or federal assistance delivered through independent 

contractors) for high risk areas and by coordinating efforts among Mosquito Control Districts that share common 

risk areas. The epicenter of EEE appears to be the contiguous area where Plymouth, Norfolk and Bristol Counties 

join. This area should be the primary target of coordinated mosquito control efforts under the direction of a state 

office. In the event that fiscal, staff, and equipment resources available to regional mosquito control districts are 

insufficient, the state must be prepared to assist in the effective control of mosquitoes to help prevent or minimize 

human EEE cases. 

263
RISK CATEGORIES 

(1) LOW - A LOW LEVEL OF EEE RISK exists if all of the following conditions are met: 

Current Season 

 1. EEE virus isolates in Cs.melanura <10 

 2. Population of Cs. melanura below long-term mean 

 Previous Season 

 1. No human or horse cases 

 2. Cs. melanura below long-term mean 

 3. EEE virus isolates <20 

 At this level surveillance activities are routine and supplemental control efforts are not recommended. 

Mosquito control efforts should be standard in accordance with established plans for integrated pest management 

(IPM). IPM is an ecologically based strategy for managing insect populations with the goal of keeping pest levels 

below predetermined threshold levels. Mosquito Control District (MCD) IPM programs may include source 

reduction, ground or truck spray adulticide, larvicide, and other control activities in response to human annoyance 

thresholds (HATs) as determined by the MCDs operating under the State Reclamation and Mosquito Control Board. 

(2) MODERATE - A MODERATE LEVEL OF EEE RISK exists if any of the following conditions exist: 

Current Season 

 1. EEE virus isolates from Cs. melanura >10 

 2. Cs. melanura populations approaching long-term mean 

 3. 1-2 presumptive or confirmed horse cases 

Previous Season 

 1. 1-2 human cases or 2-4 horse cases 

 2. Cs.melanura population above the long-term mean 

 3. EEE virus isolates from Cs. melanura >20 

 At this level, mosquito control interventions should be directed only against those species suspected as 

epidemic vectors (capable of EEE virus transmission to humans). Regional mosquito control efforts should be 

intensified only in EEE virus positive treatment areas. These efforts may include larviciding and ground or truck 

spray adulticiding based upon surveillance data that indicates significant larval and/or adult populations of bridge 

vector species. 

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(3) HIGH - A HIGH LEVEL OF EEE RISK exists if any of the following conditions exist: 

 Current Season 

 1. Confirmation of 1 human case 

 2. 3 or more presumptive or confirmed horse cases 

 3. Cs. melanura population above the long term mean and MIR in Cs.melanura >1 

 4. EEE virus isolate from bridge vector species 

 Previous Season 

 1. 2 or more confirmed human cases or 5 or more presumptive or confirmed horse cases. 

 These indices trigger intensive surveillance of bridge vector species and recommendations for state-funded 

vector control interventions which may include ground or targeted aerial larviciding and/or adulticiding. 

Treatments would be undertaken only in EEE virus positive treatment areas, defined by EEE virus isolates and 

horse or human cases, as surveillance of bridge vector populations indicate. 

(4) PUBLIC HEALTH EMERGENCY - DPH will forward a recommendation immediately to the Governor’s 

Office to declare a PUBLIC HEALTH EMERGENCY in the event that any of the following conditions exist: 

Current Season 

 1. 2 human cases are confirmed 

 2. More than 10 horse cases are confirmed 

 Surveillance data indicating that multiple human cases of EEE will occur without intervention 

 These criteria will be considered sufficient for a recommendation that an emergency be declared, if they 

occur at a time when seasonal and biological conditions present a continuing high risk of EEE human disease. The 

declaration of an Emergency may trigger state supported mosquito control efforts using wide area aerial application 

of mosquito larvicide or adulticide. A recommendation for a wide area aerial adulticide application will be made 

only if surveillance data indicate a risk of multiple human cases and biological conditions are favorable for 

continuing risk. When such control strategies are recommended, treatment areas will be defined by DPH 

surveillance data. Areas targeted for aerial pesticide application will immediately be notified and all media sources 

utilized to alert residents to the timing and scope of the application. Environmental monitoring will be done before 

and after treatment and rare and endangered species habitat excluded from the spray zone in affected areas. In 

addition a 500-1000 foot setback will be observed when spraying around water bodies. The objective of this option 

is to cause a significant reduction in all species capable of EEE transmission. This intervention is successful if the 

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target species are temporarily reduced thereby interrupting the amplification of the virus within its avian reservoir. 

The timing of this late season option is critical and is intended to be a one-time intervention. 

VII. STRATEGY FOR VECTOR CONTROL 

 A vector control plan must be safe, economical, minimize environmental effects, and minimize the risk of 

human EEE disease. To achieve these ends, the plan must be, to the maximum extent possible, geographically and 

vector species specific. Vector control measures are chosen according to species, seasonal and climatic conditions, 

and vector life stage indices. 

 Three options will be available for vector control: larviciding; targeted small scale adulticiding; and widearea aerial adulticiding; with specific activities chosen by analysis of surveillance data. Treatment areas will be 

defined by mosquito trap sites and/or human/equine case locations. Within a treatment area, the use of larviciding 

or adulticiding interventions will be guided by additional field information and surveillance data to limit the area of 

intervention to the extent possible, taking into account the uncertainty of risk data. All state supplemented vector 

control interventions will be done under the authority of Regulation 304-CMR. Section 50.08 (3)(a). 

 The number of mosquito species that potentially could serve as epizootic vectors of EEE is extensive; 

however the three species most often thought to be responsible for human and equine infection are Coquillettidia 

perturbans, Aedes vexans and Aedes sollicitans (Tsai 1991). Recent studies suggest that Anopheles species and 

Culex salinarius should also be considered as epidemic EEE vectors (Edman et al 1993, Vaidyanathan et al. 1997). 

An historical analysis of the epidemidology of EEE in Massachusetts and mosquito abundance and isolation data 

indicate that Ae. vexans, Ae. canadensis and Cq. perturbans are likely vectors involved in human disease 

transmission in Massachusetts. Ae. sollicitans may also be a vector for cases located closer to the coast, and may be 

targeted in areas where known human and/or equine cases have occurred. 

Cq. perturbans, a permanent water species, breeds in cattail marsh areas, common in the disturbed sections 

of wetlands. This species has one generation per year, emerging by mid June and reaching peak populations by 

early to mid July. An aggressive human biter, Cq. perturbans presents a difficult control problem because its larvae 

develop attached to the roots of emergent vegetation in permanent marsh areas. The insect growth regulator 

methoprene in the form of slow release Altosid formulations has proven to provide effective larval control of this 

mosquito (Sjogren et al. 1986). This chemical is relatively nonpersistent in the environment and exhibits 

266
morphological rather than direct toxic action by interfering with larval development. 

 Aedes vexans, Aedes sollicitans, and Aedes canadensis, are reflood mosquitoes whose abundance levels are 

directly related to rainfall and floodwater or moon tide events sufficient to flood intermittently flooded oviposition 

areas. All of these species may exhibit peak populations mid to late summer concurrent with peak EEE virus 

activity in birds and may be treated at the larval stage using the biological control product, Bacillus thuringiensis

var. israelensis (Bti). The success of such applications, may be hampered, however, by the small treatment window 

available due to rapid larval development and by the difficulty of application through the dense canopy and thick 

underbrush of late summer. Bti is a natural microbial agent toxic to most mosquito and blackfly larvae. It is nontoxic to bees but some mortality to other Diptera has occurred at mosquito-control application rates. In all EEE 

vector interventions standardized larval surveys will be conducted pre and post application. 

 Aedes vexans is the most predominant summer reflood mosquito in Massachusetts. The appearance of this 

species is dependent on the frequency and spacing of major rains. Broods have been observed from the latter part of 

June throughout the summer and into the fall. Although the window for effective larval treatment is narrow due to 

the rapid development of this species, Bti applications have been used successfully for control. 

 Aedes sollicitans breeds in the high salt marsh that is normally only flooded by moon tides at the full and 

new moon. Aedes sollicitans is an aggressive biter know to travel great distances from its breeding habitat. This 

species can be effectively controlled with Bti and treatment is made easier by the predictability of its life cycles. 

Aedes canadensis is primarily a univoltine species that appears from late spring through mid summer. A second 

brood can develop in early fall if rainfall is sufficient. These mosquitoes develop in temporarily flooded woodland 

depressions and vernal pools that are often inaccessible, particularly late in the summer, due to heavy underbrush 

making ground control difficult if not impossible to accomplish. Due to the heavy tree canopy and dense 

underbrush of this habitat, aerial larval control of Aedes canadensis is also very difficult. 

 Anopheles mosquitoes inhabit permanent water, and may be found along the edges of slow moving 

streams. In the latter part of the summer they may also be found in temporary pools and puddles caused by summer 

rainfall. Culex salinarius is classified as a permanent water species. This species is multivoltine with peak 

populations occurring late in summer. Cx. salinarius is an active human biter and although mammalophagic, it is 

more likely than other potential epidemic species to feed on birds thus increasing its chances of a playing a role in 

EEE virus transmission (Vaidyanathan et al 1997). The larvicide Bacillus sphaericus has been found to be effective 

267
against Culex species. Bacillus sphaericus is a naturally occurring bacterium with the same mode of action as Bti 

but with an even more narrow toxicity range. This larvicide is more effective than Bti in the highly organic water 

favored by Culex species. The spores of this bacterium are slowly removed from the water column and B. 

sphaericus may undergo limited recycling in certain environments thereby increasing its availability to target 

organisms. Granular formulations of B. sphaericus have been found to work effectively against Anopheles species 

(Arrendondo et al. 1990). Altosid formulations have also been used successfully as larval control agents. 

 Small-area, targeted, ground or aerial adulticiding with ULV malathion or resmethrin may also be utilized 

if specific risk conditions are met. This effort will be aimed at all potential vector species in the target area where 

population and life stage studies indicate treatment is required. Wide-scale aerial adulticiding may only be 

employed during a public health emergency if it is determined that use of such treatment is needed to prevent further 

human disease transmission. 

 An effective adulticide provides a sufficient reduction in vector species such that there is insufficient time 

for reinfection of a subsequent brood of vector species before the end of the mosquito season. Late season risk 

following a wide area intervention is usually limited by lack of virus availability in avian species, the low 

probability of significant numbers of infectious human biting mosquitoes surviving, and cooler weather that limits 

the activity of mosquitoes. 

 All state supplemented aerial adulticide treatments will use ULV malathion. A comprehensive review of 

aerial applications of insecticide for mosquito control concludes that ULV applications are efficacious, cost 

effective and can be used effectively over dense foliage or open housing (Mount et al. 1996). Malathion has been 

chosen because of its effectiveness against adult mosquitoes and its relative safety for humans and other vertebrates 

(Edman and Clark 1990). The efficacy of all adulticiding treatments will be determined by a comparison of pre and 

post-spray DPH trap site mosquito abundance levels. 

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Literature Cited 

Arrendondo-Jimenez J.I., T. Lopez, M.H. Rodriguez, and D.N. Bown. 1990. Small scale field trials of Bacillus

spaericus (strain 2362) against Anopheline and Culicine mosquito larvae in southern Mexico. J. Am. 

Mosq. Control Assoc. 6(2):300-305. 

Edman J.D. and J.M. Clark 1990. Draft generic environmental impact report on mosquito control in Massachusetts 

Edman J.D., R. Timperi, and B. Werner. 1993. Epidemiology of Eastern Equine Encephalitis in Massachusetts. J. 

Florida. Mosq. Control Assoc. 64: 84-96. 

Komar, N. 1997. Reservoir capacity of communally roosting passerine birds for eastern equine encephalitis (EEE) 

virus. Ph.D. diss., Department of Tropical Public Health, Harvard School of Public Health. 

Mount, G.A., T.L. Biery and D.G. Haile. 1996. A review of ultralow-volume aerial sprays of insecticide for 

mosquito control. J.Am. Mosq.Control Assoc. 12(4):601-618. 

Sjogren, R.D., D.P. Batzer and M.A. Juenemann. 1986. Evaluation of methoprene, temephos, and Bacillus

thuringiensis var. israelensis against Coquillettidia perturbans larvae in Minnesota. J. Am. Mosq. Control 

Assoc. 2(3):276-279. 

Tsai, T.F. 1991. Arboviral infections in the United States. Infectious Disease Clinics of North America. 5: 73- 101. 

Vaidyanathan, R., J.D. Edman, L.A. Cooper, and T.W. Scott. 1997. Vector competence of mosquitoes 

(Diptera:Culicidae) from Massachusetts for a sympatric isolate of eastern equine encephalomyelitis virus. 

J. Med. Entomol. 34:346-352. 

Villari, P., A. Spielman, N. Komar, M. McDowell, and R.J. Timperi. 1995. The economic burden imposed by a 

residual case of eastern encephalitis. Am J. Trop. Med. Hyg. 52: 8-13. 

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APPENDIX C 

GENERAL ENVIRONMENTAL IMPACT REPORT 

PESTICIDE LABELS AND MSDS 

MASSACHUSETTS MOSQUITO CONTROL PROGRAMS 

NOTE: CONTACT THE STATE RECLAMATION AND MOSQUITO CONTROL 

BOARD TO OBTAIN COPIES OF THIS DOCUMENT.

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APPENDIX D 

GENERAL ENVIRONMENTAL IMPACT REPORT 

NORTHEAST MASSACHUSETTS MCP STANDARDS FOR OPEN MARSH WATER 

MANAGEMENT 

NOTE: CONTACT THE NORTHEAST MASSACHUSETTS MOSQUITO CONTROL 

AND WETLANDS MANGAMENT DISTRICT TO OBTAIN COPIES OF THIS 

DOCUMENT.

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APPENDIX E 

STORMWATER MANAGEMENT 

 

 The following is a brief summary of information relevant to mosquito control found in the three state 

publications: 

Stormwater Management. Volume One: Stormwater Policy Handbook. (March 1997) 

Stormwater Management. Volume Two: Stormwater Technical Handbook. (March 1997) 

Both prepared by the Massachusetts Department of Environmental Protection and the Office of Coastal 

Zone Management. 

Massachusetts Erosion and Sediment Control Guidelines for Urban and Suburban Areas. 

Prepared by the Franklin, Hampden and Hampshire Conservation Districts and available through the 

Department of Environmental Protection. 

These documents should be referenced directly for more detailed information. 

 The two concerns addressed by these publications are water quality (pollutants) and water quantity (flood 

control). They are primarily concerned with preventing pollutants from flowing into waterways and wetland 

systems, and with controlling runoff from developed sites. For mosquito control, therefore, the regulations are 

generally not directly applicable (except in rare cases of new construction) but come into play when MCPs are 

asked to conduct mosquito control within these constructed systems. This results in the odd situation where Best 

Management Practices for stormwater management are not evaluated for their mosquito-breeding potential. 

However, failing to address mosquito control in the design phase may result in a larger-than-necessary number of 

stormwater management systems that contribute to mosquito problems. In endemic eastern equine encephalitis 

areas, creating additional breeding habitat for bridge (bird-to-human) vectors such as Cq. perturbans or Ae. vexans

is unwise. Wet (Retention) Basins and Constructed [Stormwater] Wetlands may do precisely that. 

 A significant limitation of the handbooks for mosquito control is that they discuss new construction of 

manmade systems only. Maintenance of existing and/or natural systems is not discussed. The Erosion and 

Sediment Control Guidelines should be referred to for information about working in and around existing drainage 

though even here the issue of maintenance within the existing channel is not discussed. 

 Four issues regarding stormwater management exist for MCPs and are addressed in order of importance 

(most important first).

272
 1. The expectation that MCPs will maintain drainage systems even when MCP actions did not cause 

the problem (road sand into a stream). 

 Standard #9 of the “Stormwater Management Form” (page 1-11 of the Policy Handbook), relates to the 

Operation/maintenance plan for control designs. Although this particular form is optional, the requirement for a 

maintenance plan should not be. Where MCPs will be expected to monitor for mosquito breeding, they should have 

access to the maintenance plan for the stormwater system in question and should be able to request maintenance onsite where mosquito breeding is caused by a breakdown in the system’s operation. Suggested maintenance 

requirements for each BMP are given in the Technical Handbook. MCPs should also be able to request system 

alterations in the event a system is continually breeding mosquitoes. 

 Where maintenance responsibility is clear-cut, maintenance work should be done by the responsible party. 

Unfortunately, the vast majority of drainage channels have no official maintenance plan and MCPs have routinely 

assumed or been assigned responsibility for maintenance. In these cases, MCPs should, wherever possible, adhere 

to the maintenance requirements as given for the BMP that most closely describes the system in question. In most 

cases this will be the Drainage Channel. 

 2. The erosion and sediment control standards relating to (exempted) maintenance work done by 

MCPs. 

 Despite the fact that MCP maintenance work is exempted from the Wetlands Protection Act, the best 

interests of the MCPs are served by minimizing disruption during maintenance work. Temporary erosion and 

sediment controls should be used when necessary. Vegetation bordering the channels should be left as undisturbed 

as possible. Again BMPs for maintenance in existing systems should be developed. 

 3. System design and the extent to which mosquito breeding is considered prior to construction. 

 BMPs for stormwater management in urban and suburban areas must include some consideration of 

mosquito-breeding potential. That the current publication does not is an indication of the need to improve 

communication between mosquito control and other agencies involved in stormwater management. The best place 

to practice mosquito control in manmade drainage systems is in the design phase. Clearly there is cause for concern 

over the BMP Constructed [Stormwater] Wetlands, where pools ranging from 6 to 18 inches deep are desired.

273
 4. New construction by MCPs. 

 New drainage construction is not exempted from the Wetlands Protection Act and MCPs should refer to 

the policy and technical handbooks when designing any new work. 

 

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APPENDIX F 

GENERAL ENVIRONMENTAL IMPACT REPORT 

NORTHEAST MASSACHUSETTS MCP STANDARDS FOR DITCH 

MANAGEMENT 

NOTE: CONTACT THE NORTHEAST MASSACHUSETTS MOSQUITO CONTROL 

AND WETLANDS MANGAMENT DISTRICT TO OBTAIN COPIES OF THIS 

DOCUMENT.

275
APPENDIX G 

GENERAL ENVIRONMENTAL IMPACT REPORT 

EDUCATIONAL FLYERS REGARDING MASSACHUSETTS MOSQUITO 

CONTROL PROGRAMS 

NOTE: CONTACT THE STATE RECLAMATION AND MOSQUITO CONTROL 

BOARD TO OBTAIN COPIES OF THIS DOCUMENT.

276
APPENDIX H 

Preparer Qualifications: George D. Christie 

CHRISTIE MOSQUITO CONTROL 

36 Ewing Road 

North Kingstown, RI 02852-2020 

Tel. (401) 885-7055 

FAX: (401) 885-0877 

E-Mail: chripest@ids.net 

EDUCATION: MS, Entomology, U. of California, Riverside, CA June 1984 

 BS, Entomology, Cornell University, Ithaca, NY Jan. 1981 

 Continuing Education: 

 Courses in Environmental Planning and Community 

 Development, Dept. of Community Planning, URI 1987-88 

 

EXPERIENCE: Director of the Portsmouth Vector Control Program (14 

years), and of mosquito control programs for Tiverton (13 years), 

Warren (11 years), Bristol (9 years), Lincoln (8 years), and 

Westerly (5 years). Currently assisting Warwick Mosquito 

Control Program (12 years). 

 

Mosquito Control Consultant for Nantucket, MA 1990 - 1993, 

1996 - 1998. 

Have designed and marketed elementary-school-level classes in 

Entomology. 

 Assisting Warwick in implementation of city-wide integrated pest 

management program 1993-1995. 

MEMBER: American Mosquito Control Association 13 Years 

 Northeastern Mosquito Control Association 13 Years 

 Member, Board of Directors: 1994-1997 

 Entomological Society of America 7 Years 

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EDITORIAL 

EXPERIENCE: Editor: Northeaster. The newsletter of the Northeastern 

 Mosquito Control Association. 

SELECTED

PUBLICATIONS: Christie, G. D. 1995. Guidelines for the use of pesticides on cityowned property. Warwick, RI. 54 pp. 

Christie, G. D. 1993. Business and political skills in mosquito control. Wing 

Beats. 4(3): 17-18. 

Christie, G. D. 1992. Non-toxic bait trapping for yellow jackets. Pest Control

60(5): 30-32. 

Christie, G. D. and R. A. LeBrun. 1991. Culiseta minnesotae and further notes 

 on Aedes aegypti in Rhode Island. J. Am. Mosq. Control Assoc. 6: 742. 

Christie, G. D. 1990. Salt marsh mosquito control in Portsmouth, Rhode 

 Island. J. Am. Mosq. Control Assoc. 6: 144-147. 

MOSQUITO CONTROL TALKS (all talks at the Annual Meeting of 

 the Northeastern Mosquito Control Association unless otherwise noted) 

1996 Information on a Fungal pathogen of Aedes canadensis in Vernal Pools. 

 Mosquito Control through Marsh Restoration in Portsmouth, RI 

1995 Killer Pathogen, Probably Fungus, appears in Bristol, Rhode Island 

1994 Community-level Application of IPM for Medically Important Arthropods 

 65th Annual meeting, Eastern Branch, Entomological Society of America 

1993 When the Edge Meets the Middle: Mosquito Breeding during Intermittent Tides 

 Open Marsh Water Management on Nantucket 

1992 Reaching out for Resource Tools and Development 

 Altosid Pellets in Nantucket 

1991 Report on Mosquito Control in Rhode Island 

 Monitoring Mosquito Populations for Eastern Equine Encephalitis in 1991 

 in Rhode Island 

1990 Encephalitis in Tiverton, Rhode Island 

1989 Open Marsh Water Management in Portsmouth, RI 

 55th Annual Meeting, American Mosquito Control Association 

1987 Private [business] Mosquito Control Endeavors 

1986 Overview of Mosquito Control in Portsmouth, RI. 

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