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DELAWARE MOSQUITO CONTROL SECTION 

A Dozen (12) Frequently-Asked Questions (FAQs)

 June, 2008 

Below are 12 FAQs that while relatively simple to ask, are for some a bit 

complicated to answer. As such, over the ensuing 32 pages we’ve devoted some effort to 

provide the detailed answers they deserve. 

1) Why are the mosquitoes so bad around my house, and what can I do or whom 

can I call? 

2) Why do we need mosquito control? What do you do this for? 

 

3) What kinds of insecticides are used, and when do you use them? 

4) Why do you have to use insecticides at all? Aren’t there better ways to achieve 

control? What other approaches do you use? 

5) Are mosquito control insecticides safe to use, and should I be concerned if I’m 

exposed to spraying? 

6) How can I find out when and where mosquito control spraying might be done? 

7) If I don’t want to be exposed to mosquito control spraying, what steps might I 

take? 

8) What personal protection measures can I take to help avoid mosquito bites? 

9) What do I do if I find a sick/dead wild bird that might have West Nile virus? 

10) What are human health problems/symptoms when a mosquito-borne viral 

disease is contracted? And what is the probability of my becoming infected or 

sick? 

11) There are a lot of biting flies around my house or yard that I don’t like (or 

gnats, or ticks, or wasps, etc.). Can’t Mosquito Control do something to get rid 

of them? 

12) Describe the Mosquito Control Section. Where are you housed? How many 

people work for you? Where do you work? What do you do in the winter? 

Who do you work with? Who are your partners? What’s your budget? etc., 

etc., etc. Essentially, just who are you people? 
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Introduction

The performance of mosquito control presents many challenges to its modern-day 

practitioners, and not surprisingly is of much interest to many people. Mosquito control 

in Delaware is done by the Mosquito Control Section, part of the Division of Fish and 

Wildlife in the Department of Natural Resources and Environmental Control. 

As natural resource management professionals charged with mosquito control 

responsibilities, we are asked to perform some complex undertakings. We are tasked to 

somehow reach into the environment to eliminate or nullify a suite of quality-of-life, 

public health, and economic problems of serious concern to many Delawareans. These 

problems are generated by organisms that in their immature stages are found throughout 

the state in almost every type of aquatic habitat imaginable (with exception of the middle 

of fast-running streams), and which if uncontrolled are airborne as adults and capable of 

widespread dispersal and much pestilence. The most practicable modern control tools 

that we have at our disposal are insecticides that we must judiciously spray over or within 

wetlands or other mosquito production habitats to control immature stages, but which we 

also sometimes have to directly apply over or within where people live, work or recreate 

to control adult mosquitoes. We also employ various wetland management techniques 

for larval control that must be carefully installed or implemented in very sensitive, very 

valuable environments. 

It is not unusual for many people to understandably demand even more mosquito 

control than what we can reasonably deliver given environmental constraints and our 

available operational resources. In contrast to these numerous requests for control 

treatments, other folks without a good understanding of what we do and how we have to 

do it are sometimes quite critical of our control methods. Indeed, we do not have an easy 

mission to fulfill. To help the general public (our residents and visitors), elected or 

appointed officials, the media, civic associations, environmental organizations, and other 

interested groups better understand what we do and how we do it, we have compiled a set 

of a dozen (12) Frequently Asked Questions (“FAQ”) below, along with some answers 

that we hope will shed some light on our program. The 12 FAQs are as follows: 

1) Why are the mosquitoes so bad around my house, and what can I do or 

whom can I call? 

2) Why do we need mosquito control? What do you do this for? 

3) What kinds of insecticides are used, and when do you use them? 

4) Why do you have to use insecticides at all? Aren’t there better ways to 

achieve control? What other approaches do you use? 

5) Are mosquito control insecticides safe to use, and should I be concerned if 

I’m exposed to spraying? 

6) How can I find out when and where mosquito control spraying might be 

done? 

7) If I don’t want to be exposed to mosquito control spraying, what steps might 

I take? 
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8) What personal protection measures can I take to help avoid mosquito bites? 

9) What do I do if I find a sick/dead wild bird that might have West Nile virus? 

10) What are human health problems/symptoms when a mosquito-borne viral 

disease is contracted? And what is the probability of my becoming infected 

or sick? 

11) There are a lot of biting flies around my house or yard that I don’t like (or 

gnats, or ticks, or wasps, etc.). Can’t Mosquito Control do something to get 

rid of them? 

12) Describe the Mosquito Control Section. Where are you housed? How many 

people work for you? Where do you work? What do you do in the winter? 

Who do you work with? Who are your partners? What’s your budget? etc., 

etc., etc. Essentially, just who are you people? 

 

1) Why are the mosquitoes so bad around my house, and what can I do or whom can 

I call?

Many adult mosquitoes around the home often come from mosquito-production 

sites within the neighborhood or in close proximity to residential areas. To help 

minimize mosquito annoyances, homeowners should take steps to eliminate or reduce 

standing or stagnant water on or nearby their properties, including attending to 

potential mosquito-production habitats such as clogged rain gutters and downspouts, 

poorly-drained flat roofs, old tires, abandoned inground or aboveground swimming pools 

(including plastic kiddie wading pools), unused bird baths, depressions in boat covertarps, bilge water in boat bottoms, flower pot bottom liners, garbage cans or their 

upturned lids, discarded soda or paint cans, upright wheelbarrows, or any other types of 

structures or containers that can collect and hold water for 4 or more consecutive days. 

[Just imagine the numbers of nooks-and-crannies that might hold rainwater in an auto 

salvage yard or a scrap tire pile!] In addition, any grading of topsoil for grass planting or 

following septic system installation should ensure that rain or sprinkler-system water 

does not become puddled or trapped on the surface for any extended length of time. 
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Ornamental ponds can also breed mosquitoes, and since you obviously want water here, 

other control measures might have to taken – e.g. ensuring good flow or changeover of 

water to avoid stagnant conditions, stocking or raising fishes that eat mosquito larvae, or 

judicious treatment with an appropriate mosquito larvicide. 

Mosquitoes can also breed in roadside ditches, wet woodland pools, or 

stormwater management basins where water is held for 4 or more consecutive days. In 

many situations, a homeowner has limited physical capability or legal ability to eliminate 

these nearby breeding sites, and as such should contact the Mosquito Control Section to 

report such problem areas, which might then lead to the Section helping to physically 

eliminate the breeding habitats, or to our making the reported problem sites part of the 

Section’s surveillance and insecticide treatment program. Frequently, mosquito 

annoyances around the home might not originate from the immediate vicinity at all, since 

some mosquito species have flight ranges of 3-5 miles up to 10-15 miles away from their 

natal sites in order to seek bloodmeals – saltmarsh mosquitoes and some woodland 

species are well known for their long flight distances. A substantial amount of 

Delaware’s saltmarsh mosquito production problems arise from Bombay Hook and Prime 

Hook National Wildlife Refuges, to then potentially affect people in off-Refuge 

locations, and it’s only through good cooperation with the U.S. Fish and Wildlife Service 

that we are able to spare many Delawareans from Refuge-produced mosquitoes. In such 

situations where a private landowner cannot do much to control the mosquitoes that 

eventually make it to his/her property, only the Section’s intervention can help. When 

you have need to contact the Mosquito Control Section about an intolerable nuisance 

situation or a suspected breeding problem, in New Castle County or northwestern Kent 

County please call 836-2555 (our Glasgow operational HQ); and in the remainder of 

Kent County or all of Sussex Counties please call 422-1512 (our Milford operational 

HQ). 

Since our field inspectors and surveillance/monitoring devices cannot be 

everywhere around the State during the time a mosquito brood is in progress, we rely in 

part upon receiving public complaints to help us target where we might best spend our 

limited resources. Your calling one of the two the numbers above is an important, 

valuable way to help us to focus our response actions, and your complaint situation will 

usually be verified as soon as possible through one or more of our field surveillance 

methods discussed in FAQ #3 below. For your getting the most rapid response from our 

control program, and for our most accurately receiving and recording the information you 

want to provide (and that we need to have), we ask that you call us directly, rather 

than your first going through an elected official or third party (i.e. please do not 

immediately call your State Senator, State Representative or a County official) – if for 

some reason you become dissatisfied with our response or service, you could always then 

follow-up by contacting an elected official or third party, but even then we would first 

appreciate your direct callback, to see if we could still try to rectify your problem. 

One exception to your first calling the Mosquito Control Section is that if you 

live in an incorporated municipality and desire to request spraying for relief from 

biting adult mosquitoes, you must first contact your appropriate city or town 
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official, since by our Spray Policy we only provide such spraying services within a 

municipality’s borders only upon official requests from city or town officials. If you 

do not know who your appropriate local officials might be, you can call the Mosquito 

Control Section and we will provide you with their names and phone numbers. 

Additionally, for residential subdivisions in unincorporated areas of New Castle County, 

the Mosquito Control Section prefers to have citizen requests for adult mosquito control 

services to come through local homeowner or civic associations, conveyed by the 

associations to the Section on an annual basis. 

Please understand that during periods of peak mosquito outbreaks, our agency 

often receives dozens of calls per day, and within just several days this can amount to a 

backlog of hundreds of complaints. When such problems pile-up, as they all too 

frequently do, we are then forced to prioritize even further where and when we’ll treat, 

trying to provide the most relief to the most people in the fastest time; as such, depending 

upon your situation from a statewide perspective, you or your neighbors might not always 

get as rapid a response as you might desire. But as always, no matter how you might 

end-up requesting our control services, or where you might end-up in our prioritizations 

for response, we will continue to try to do the best we can with the working resources 

we’ve been provided. 

2) Why do we need mosquito control? What do you do this for?

If you were the caller in FAQ #1 above contacting us about intolerable mosquito 

nuisance problems around your home, then you already know a prime reason for why 

we’re in business. At one time before the advent of modern mosquito control practices in 

Delaware, dating back essentially to the late 1950s and before, many developed areas of 

the First State (e.g. downtown Dover!) would more than occasionally experience severe 

mosquito infestations having landing rate counts of biting adult mosquitoes from 20-50 

per minute up to 100 bites per minute, which through nuisance or annoyance greatly 

diminishes an area’s quality-of-life. A landing rate count of only 1-2 mosquitoes per 

minute in your backyard on some balmy summer evening would translate within a halfhour into 30-60 bites affecting exposed parts of your body, clearly not a desirable 

situation. Imagine how long you’d stay outside in a setting of 20-50 bites per minute, 

with truly ghastly counts of 100 bites per minute having been documented! And as 

more-and-more people move into Delaware, and as they increasingly seem to all want to 

live in areas near coastal wetlands or wet woodlands, demands for our control services 

(and upon our program’s limited resources) only continue to escalate. 

In addition to personal discomfort from such infestation levels, uncontrolled 

mosquito populations can also have significant adverse impacts to local economies

based upon tourism, outdoor recreation, or animal husbandry, along with undesirable 

effects on your neighborhood’s property values. As such, our delivery of mosquito 

control helps to maintain a good quality-of-life and robust economy throughout many 

areas of Delaware – without our continuous, behind-the-scene control efforts, a large 

portion of modern Delaware would not be very livable from April through early 

November. Many visitors coming to our coastal resort areas from Baltimore, 
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Washington, northern Virginia, the New York City area, northern New Jersey, 

Philadelphia, southeastern Pennsylvania, Wilmington, Newark or other urban regions do 

not realize how naturally “buggy” a place they have chosen to visit. It is somewhat 

bemusing when some of these good folks first realize what we have to do to make their 

visit a relatively pest-free (and disease-free) experience – incongruously, they’ll 

sometimes ask: “What do you need mosquito control for?!!! The number of mosquitoes 

flying around here aren’t that bad.” 

Another major reason for controlling mosquitoes is their well-known potential for 

carrying and transmitting pathogens that can cause diseases, not only just to humans, 

but also to our domesticated animals such horses or dogs. In Delaware today, we are 

concerned with encephalitis viruses such as eastern equine encephalitis (EEE), an 

alphavirus, which when either humans or horses contract EEE can often be fatal, with 

special concern for children and elderly. Those who recover from EEE are often left with 

lifelong debilitating symptoms – there is a EEE vaccine for horses, but not for humans. 

Fortunately, the occurrence of EEE is relatively rare, and the Mosquito Control Section 

works hard to keep it this way. West Nile virus (WNV), a flavivirus, is a recentlyintroduced Old World encephalitis virus first coming into the country in 1999 in the New 

York City area, carried by wild birds and mosquitoes that has now spread from coast-tocoast. This virus first appeared in Delaware in 2002, and is now well established 

throughout the state. West Nile Virus is not as virulent as EEE, but nonetheless 

contracting WNV is still quite a medical concern for the elderly or people having 

impaired immune systems. [A more in-depth discussion of the health problems and 

symptoms associate with contracting EEE or WNV is provided in FAQ #10 below.] An 

effective WNV vaccine has now been developed for horses, but if a WNV vaccine is ever 

developed for humans, it’s still several years away. The occurrence of EEE and WNV in 

nature involves complex transmission cycles of several mosquito species and wild birds 

(songbirds play a very prominent role here), with a branching off to humans and horses in 

these cycles as “dead end” hosts for encephalitis viruses. Other encephalitides of much 

more minor concern in Delaware include St. Louis Encephalitis (SLE), another 

flavivirus, which at times has had epidemic outbreaks in the central U.S. and Florida; as 

well as the potential for LaCrosse Encephalitis (LAC), a bunyavirus, which is usually 

associated with the mid-West. Mosquito bites per se, even without pathogen 

transmissions, are also a human health problem, as mothers can readily attest when their 

children are festooned with numerous bites and can’t fall asleep all night long. Excessive 

numbers of mosquito bites per se, sans any pathogen transmission, can cause allergenic 

problems at bite sites (or even systemically) for extremely sensitive individuals, can lead 

to secondary infections from aggressively scratching bites sites (children are most prone 

to doing this), and can cause psychogenic problems from mental anguish/torment. 

Another mosquito-caused problem in Delaware is canine heartworm, a mosquito-borne 

pathogen often fatal to dogs, so dog owners are urged to put their dogs on preventive 

medication to avoid this problem. 

Many Delawareans are probably not aware that so-called “tropical” diseases, such 

as yellow fever (a flavivirus) or malaria (a protozoan parasite, Plasmodium spp.), were 

at one time quite common in the southeastern United States, including areas as far north 
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as Delaware and even into New England. A yellow fever outbreak in Philadelphia in 

1793 killed 10% of the city’s residents and sickened another 20%. Malaria was a serious 

problem for Civil War soldiers throughout the southeast, including Confederate prisoners 

confined to Fort Delaware on Pea Patch Island, and as recently as only a few years ago 

isolated but locally-transmitted cases of malaria surfaced in New Jersey and Maryland. 

Many a colonial estate or antebellum plantation owner along the southeastern seaboard, 

including areas of the mid-Atlantic, knew that come summer it was time to seek refuge 

further inland or up in the mountains for themselves and their privileged families, to 

thereby avoid the “swamp ague” that often somehow caused great sickness for those less 

fortunate who had to remain behind. Dengue (“breakbone”) fever, a flavivirus, is 

currently a mosquito-borne problem throughout the Caribbean and Mexico, with recent 

occurrences in southern Texas, plus potential for this disease in other Gulf Coast states 

too. A serious outbreak of dengue recently occurred in Hawaii -- the hemorrhagic form 

of dengue can often be fatal. Elephantiasis is a mosquito-borne disease caused by 

roundworms, and while primarily occurring in Africa and southeast Asia, there are also 

problem areas in northern South America. It is only through continued vigilance and 

proactive implementation of modern mosquito control practices within the United States, 

combined with good disease screening and follow-up medical care, that these “tropical” 

diseases are no longer major concerns in the lives of most modern Americans, including 

Delawareans. But an example of a mosquito-borne disease that might prove to be the 

next newly emerging infectious disease in the United States is chikungunya, an 

alphavirus causing debilitating febrile illness and incapacitating joint pain, originating 

from Africa that in recent years has caused major disease outbreaks in India; and most 

recently in fairly alarming manner, chikungunya had spread to temperate climes in Italy, 

in concert with how both people and organisms can now rapidly travel around the globe. 

Modern-day mosquito control practices must be vigilantly and aggressively employed if 

we are to avoid or lessen the global spread of these mosquito-borne ills. 

Delaware has about 57 species of mosquitoes that breed in the widest range of 

aquatic habitats, and over a dozen of these species are very problematic for people. 

Problem-causing mosquitoes originate from our coastal marshes, in wet woodlands and 

swamps, and in many urban or suburban locations where they can prolifically breed in 

almost any type of man-made structure or container that collects and holds water for 4 

days or longer. A newly-arrived problem species since the late 1980’s in Delaware (and 

throughout much of the eastern and central United States) is the Asian tiger mosquito, 

which was accidentally imported from the Far East with scrap tires destined for 

recapping, and which is now the #1 urban problem-mosquito from New Orleans to 

Chicago to Baltimore, and in Delaware because of its abundance and aggressive daytime 

biting behavior now causes problems from Wilmington to Dover to Seaford and 

Rehoboth. 

With over 20% of Delaware’s surface area consisting of either tidal marshes or 

wet woodlands, and with the state also having a relatively high human population density 

along with an abundance of domestic breeding sites, there are plenty of opportunities for 

mosquitoes to raise a ruckus, both for our residents statewide and for visitors to our 

coastal resort areas. For the most part, many Delawareans well know why we must 
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perform mosquito control in Delaware, and for over 75 years there has been a strong call 

for organized mosquito control within the First State. Under a clearcut statutory mandate 

from our citizens, the Mosquito Control Section tries our best to provide these desired 

quality-of-life and public health services, doing such in as environmentally-compatible 

manner as practicable to do. 

3) What kinds of insecticides are used, and when do you use them?

A variety of insecticides are needed for performance of modern-day mosquito 

control, and are used only when and where other types of control are not practicable to do 

(see FAQ #4 below for a discussion of alternative control methods to insecticide use). 

The Mosquito Control Section utilizes insecticides as an important component of its 

Integrated Pest Management (IPM) program. Please note that IPM does not mean that 

no insecticides can be used (as sometimes popularly misunderstood), nor that insecticides 

must be only a minor part of an IPM control strategy. Rather IPM refers to making the 

best use of a combination of the most practicable control methods at our disposal to 

deal with real world situations in treating pest problems only when and where they occur, 

doing such in the most efficacious, environmentally-compatible, cost-effective manner 

possible. 

There are two basic types of mosquito control insecticides – larvicides for control 

of larval or immature mosquitoes, selectively applied to wetland areas and other aquatic 

larval habitats; and adulticides for control of flying or resting adults, selectively used 

primarily in upland areas where adults on-wing are causing problems. All insecticides 

that we use are registered by the U.S. Environmental Protection Agency (EPA) for the 

types of applications we perform. Insecticide applications are done only when and 

where we have indications of unacceptable or intolerable numbers of mosquitoes 

undergoing larval development or already on-wing, and these mosquitoes must also be of 

the dozen or so species that are particularly problematic biters of humans or other 

mammals. Indications of when and where spraying is necessary are derived through an 

extensive and intensive field surveillance/monitoring effort, involving a variety of 

detection efforts – e.g. larval sampling in wetlands and other mosquito-production areas 

(“dipper counts”); landing rate counts (i.e. numbers of adult female mosquitoes that land 

on a field inspector per minute); nightly adult light trap collections; detection or 

occurrence of disease viruses or other pathogens within mosquitoes themselves or in 

sentinel organisms; the numbers and patterns of public complaints received; etc. No 

spraying is done unless threshold criteria (involving subjective or objective measures) are 

exceeded for these various indicators, and quite often a combination of indicators is used. 

Spray applications might be aerially done using fixed-wing aircraft or helicopters 

for larvicides or adulticides, or might involve truck-mounted applications of larvicides 

(via “pump truck”) or adulticides (via “foggers”). Larviciding to treat small areas or 

container habitats is often done on-foot, using backpack sprayers or hand-tossed 

formulations. The choice of what type of insecticide to use and its mode of delivery is 

dependent upon the type of species to be controlled, the life stage(s) targeted for control 

during any particular brood, and the type of habitat or location where spraying will occur. 
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Since in almost all cases larviciding involves less direct exposure of people to 

insecticides than adulticiding, whenever we have to spray we usually always prefer to 

try to larvicide first, and turn to adulticiding only as a last resort. 

The timing for when we apply our insecticides, and for how the applications are 

done, is also determined (and quite often complicated) by weather conditions (e.g. air 

temperature, wind speed and direction, humidity, rainfall), all which must be considered 

in our performing appropriate and allowable treatments. All of our public spray 

announcements have the condition of “weather permitting.” When dealing with 

saltmarsh mosquito larval control, we must also take into consideration daily tide stages 

and the monthly lunar tide cycle too. In doing our spring woodland-pool species control, 

we are often racing against the calendar to complete our aerial larviciding before forest 

canopy leaf-out prevents effective spraying of our products. And you can probably 

readily envision the many problems we face when trying to treat urban or congested areas 

– think about all the things you might have to deal with when trying to operate a truckmounted adulticide sprayer as one encounters crowds of people along the streets, traffic 

jams, or detours, during an effort to prescriptively apply uniform amounts or 

concentrations of an insecticide – this is one reason why you might see inner-city ground 

adulticiding being performed 3:00 am in the early morning rather than 5:00 pm in 

afternoon. 

Our frontline larvicides are Bti (e.g. VectoBac, VectoLex, Teknar or Aquabac, 

which are all bacterially-produced insecticides) and methoprene (e.g. Altosid, a juvenile 

growth hormone mimic), both which can be applied in liquid or granular formulations. 

Bti is primarily effective against earlier immature stages, and seems to work better (or at 

least more consistently) for control of freshwater species (e.g. spring woodland-pool 

breeding species) than for saltmarsh mosquitoes of the open marsh. Methoprene is best 

used against later immature stages, and is effective against both freshwater and saltmarsh 

species, but still has to be applied before the larvae pupate. Both Bti and methoprene are 

state-of-art, third-generation pesticides that are classified as “biorational” products. 

Another type of larvicide available to us is temephos (e.g. Abate, an organophosphate 

second-generation insecticide), which we use in liquid formulation for control of 

freshwater mosquitoes in roadside ditches, or in granular form for saltmarsh mosquito 

control in areas of heavy wetlands vegetation – temephos is effective against all larval 

stages. A final type of larvicide that we occasionally use are monomolecular surface 

films (e.g. Agnique or Arosurf) to treat larvae or pupae, usually hand-applied to 

container-breeding or other types of confined freshwater habitats. 

Our frontline aerially-applied adulticide to treat problem mosquitoes on-wing is 

naled (Trumpet or Dibrom, an organophosphate), which is equally effective against 

freshwater or saltmarsh mosquitoes. [Naled is used by many mosquito control programs 

around the country; as is another organophosphate adulticide, malathion (e.g. Fyfanon or 

Atrapa) which the Section currently does not use.] Another category of adulticides that 

we use is synthetic pyrethroids, which seem to be more efficacious when applied by 

truck-mounted sprayers (“foggers”) than by aircraft. The primary synthetic pyrethroid 

that we use for ground “fogging” is permethrin (e.g. Permanone, Biomist, Aqua-Reslin), 
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although alternatives such as resmethrin (e.g. Scourge) or sumithrin (e.g. Anvil) are also 

available and used around the country. Natural pyrethroid derivatives such as pyrethrin 

(e.g. Pyrenone) can also be used. Unfortunately, in comparison to naled, synthetic 

pyrethroids don’t seem to be as efficacious against saltmarsh mosquitoes, nor seemingly 

as good for aerial applications. 

It is important that we have this diversity of mosquito control insecticide products 

to call upon, since we need such versatility in dealing with different target species, 

different brood or life stages, different types of habitats to treat, varying weather 

conditions to work under, special concerns for avoiding certain types of potential nontarget impacts, etc. We must also take steps not to overuse any one of these products 

against our local mosquito populations, in order to avoid or at least postpone the possible 

appearance of insecticide resistance (which undercuts effective control) among our 

target species. Insecticide resistance can arise through overly-aggressively targeting 

certain species or life stages with but a single product, such that the small percentage of 

any species population that might be naturally resistant to whatever insecticide is being 

used then greatly multiplies because of its essentially insecticide “resistant” or immune 

nature, to then dominate future generations of the target species (for which we would 

then have one less control tool that will work). As such, for avoidance of resistance 

problems alone, it’s important to be able to use and rotate a variety of insecticides in our 

control work, and to also adopt new insecticides whenever possible and appropriate. 

4) Why do you have to use insecticides at all? Aren’t there better ways to achieve 

control? What other approaches do you use?

Modern insecticides are but a tool that mosquito control professionals can call 

upon in their IPM programs to help reduce or suppress intolerable numbers of 

mosquitoes. As with all pesticides, there is always the chance in using an insecticide that 

something might go wrong, or that a product’s use might have unintended consequences 

that are not foreseen. However, the development process for modern insecticides, given 

the extensive and intensive product review and registration process that is conducted by 

the U.S. Environmental Protection Agency (EPA), helps to ensure to the extent 

practicable that today’s use and application of modern mosquito control insecticides is 

done as safely as possible, and that any risks from adverse impacts to humans, wildlife or 

environment are extremely minuscule. In fact the EPA has declared that when these 

registered products are used in accordance with all label language requirements and 

conditions, which by federal law they must, then their use “poses no unreasonable risks to 

human health, wildlife or the environment.” In terms of risk-benefits, problems that 

mosquitoes cause for quality-of-life, public health or local economies are far greater 

issues than the deminimus or very small risks that might be associated with infrequent 

exposure to mosquito control spraying. More information about the safety of our 

mosquito control products is provided in FAQ #5 below. 

Having said this, the Mosquito Control Section still prefers wherever 

practicable to use non-insecticide control methods, since the exceedingly small risks 

that might be associated with mosquito control spraying obviously go to zero if or where 
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no spraying is done. The most practicable alternatives to using insecticides are a 

category of control methods collectively called source reduction, which through various 

approaches either eliminate mosquito-producing habitats, or somehow control 

mosquitoes in their pre-emergence larval stages. One example of source reduction was 

mentioned in FAQ #1 above, whereby property owners practicing good water sanitation 

around their homes or businesses can measurably help to reduce mosquito-production 

habitats. Public education and cooperation is the key to this type of domestic water 

sanitation source reduction. 

However, many breeding habitats are too large, or in too remote or inaccessible 

areas, for private citizens to be able to provide much help for source reduction, which is 

where the Mosquito Control Section must then act. Because of the long flight ranges of 

saltmarsh mosquitoes and the remote wetland areas where these mosquitoes are often 

produced, the Mosquito Control Section devotes a lot of its efforts to managing saltmarsh 

habitats for reduction of mosquito production, including using a source reduction 

technique known as Open Marsh Water Management (OMWM). The OMWM 

method selectively excavates small, shallow ponds and ditches in mosquito-production 

areas of the high salt marsh, which in doing helps eliminate or reduces egg-deposition 

habitats for saltmarsh mosquito species (which require moist muds for their egg-laying), 

and which then also provides permanent water habitats for resident native fishes (e.g. 

killifishes, Fundulus) that are voracious predators upon mosquito larvae. All OMWM 

wetland alterations are done under regulatory oversight by the Delaware Mosquito 

Control Advisory Committee (DMCAC), consisting of four federal agencies (Army 

Corps of Engineers, U.S. Environmental Protection, U.S. Fish and Wildlife Service, 

National Marine Fisheries Service), three DNREC agencies (Division of Fish and 

Wildlife, Wetlands and Subaqueous Lands Section, Delaware Coastal Management 

Program), and the State Historic Preservation Office. 

Most OMWM alterations are not directly connected to daily tidal flows, such that 

OMWM ponds and ditches do not typically drain or dewater marsh surfaces of their 

standing water bodies, nor excessively lower the marsh subsurface water table. This 

helps to control saltmarsh mosquitoes without insecticides in a manner that avoids the 

previously detrimental ecological impacts of the old parallel-grid-ditch system, which 

were open tidal ditches geometrically spaced about 150-feet apart, traversing much of 

Delaware’s tidal wetlands (in both mosquito-production and non-production areas), with 

intention to drain or dewater marsh surfaces. The parallel-grid-ditches were constructed 

by the Civilian Conservation Corps in the 1930’s, and these ditches were periodically 

recleaned of accumulated sediments into the 1970’s. The open, tidal parallel-gridditches had adverse impacts on saltmarsh habitats by draining many shallow ponds and 

mudflat areas that were valuable fish and wildlife habitats, and in some areas through 

spoil deposition (from the ditch excavations), or by lowering of the subsurface water 

table by low tide drainage, caused undesirable vegetation changes (e.g. incursions of 

marsh shrubs such as Iva or Baccharis, or the reed grass Phragmites, in ditched areas). 

Furthermore, while the old parallel-grid-ditches helped to reduce mosquito production in 

some areas, these ditches were still not effective enough to achieve the desired level of 
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control needed in many locations, because mosquito-production habitats between the 

parallel-grid-ditches (particularly the small “pothole” depressions) were not drained. 

Today’s modern OMWM technique avoids these problems by using specialized 

excavation machinery that does not cause excessive increases in marsh elevations from 

spoil deposition (e.g. a rotary excavator, which broadcasts excavated spoil as a thin slurry 

over the marsh surface); by OMWM system design and excavated alterations that do not 

lead to excessive lowering of the subsurface water table; and by actually satisfactorily 

controlling almost all mosquito production in areas that are treated. Furthermore, the 

installation of OMWM systems as overlays upon old parallel-grid-ditch networks helps to 

restore standing surface waters to the marsh valuable as fish and wildlife habitats, thereby 

restoring some lost wetland values and functions. Unfortunately, OMWM cannot be used 

everywhere saltmarsh mosquitoes breed, because of factors like not having marsh 

landowner permission or cooperation (for a variety of reasons); by site access 

considerations for heavy machinery; by other environmental considerations (e.g. leaving 

intact the relatively little salt marsh acreage in Delaware, and within the entire Northeast 

too, that still remains undisturbed by any type of alteration, such as what is found at 

Bombay Hook National Wildlife Refuge); or by project size or project scale (it’s not 

usually cost-effective to treat small marsh areas or small amounts of mosquito production 

with OMWM, especially when there are so many larger areas of the State’s coastal 

wetlands still needing OMWM treatment). Wherever there are problematic salt marsh 

habitats that cannot be treated with OMWM, then judicious use of insecticides must be 

employed; and because of the scale of the problems encountered in salt marshes, usually 

treated via aerial spraying by fixed-wing aircraft, or sometimes if more localized treated 

via helicopter. Installing OMWM systems is a labor- and capital-intensive undertaking, 

but in the long-run is usually more cost-effective than continual periodic treatments with 

insecticides. 

Other types of source reduction practiced by the Mosquito Control Section 

include management of tidal flows or exchanges and marsh water levels to discourage 

or control mosquito production in coastal wetlands impoundments, which on federal, 

state and private lands total over 10,000 acres of Delaware’s >90,000 acres of coastal 

wetlands. These impoundments are areas of marsh that are diked-off with levees, whose 

interior waters are then managed by various types of water control structures for multiple 

environmental goals and objectives, including flood prevention, stormwater management, 

waterfowl production and hunting, habitats for wading birds and shorebirds, estuarine 

fish nursery areas, crabbing and fishing, saltmarsh mosquito control, nature study, 

canoeing, etc. Along with our other colleagues in the Division of Fish and Wildlife, the 

Mosquito Control Section plays a major role on State lands in helping to maintain and 

manage these valuable wetland units. 

It is not always possible (nor desirable) to manage tidal exchanges or marsh water 

levels in impoundments for only one purpose, so sometimes it’s not always possible to 

achieve satisfactory mosquito control in impoundments through water management 

alone, which might then necessitate some judicious insecticide spraying (using 

larvicides), usually with a helicopter, but sometimes in more expansive impoundments by 
13

fixed-wing aircraft. Shallow ponds and ditches can also be excavated within 

impoundment interiors to help control mosquito production, but these features are often 

difficult to maintain because of the unconsolidated nature of many impoundment 

bottoms, which then tend to rapidly fill-in any excavations that were made, routinely 

requiring re-excavations. However, where still cost-effective to routinely do this 

periodic re-excavation, and in order to reduce insecticide use or maintain or enhance fish 

and wildlife habitats, the Mosquito Control Section is committed to undertaking this 

impoundment source reduction work. 

Another type of source reduction performed by the Mosquito Control Section 

involves the stocking of mosquitofish (Gambusia) in freshwater mosquito-production 

habitats, such as in stormwater management basins that are often associated with 

subdivision developments or highway projects, or in small natural or ornamental ponds. 

Unfortunately, fish survival cannot always be ensured in many of these locations, because 

of water volume or water quality problems, and often because of too cold overwintering 

temperatures, eliminating the stocked fish. The rearing and distribution of mosquitofish 

is also very labor intensive. Additionally, stocking mosquitofish in some natural areas 

cannot be done because of concerns about adverse impacts to native fishes through 

interspecific competition, or because of concerns about predatory impacts upon 

amphibians of special concern. Unfortunately, there is not a freshwater “OMWMequivalent” method for dealing with non-tidal mosquito production problems found in 

freshwater wetlands or wet woodlands. When source reduction using mosquitofish 

cannot be employed, then these types of habitats must be treated with insecticides 

(primarily larvicides), often done by hand or ground-application equipment. Finally, in 

regard to source reduction approaches for stormwater management basins, there are 

considerations in a basin’s design and construction, and in management of its water 

levels, that will help to reduce mosquito production, all which are encouraged to be 

followed by developers or other agencies. 

Other types of source reduction are possible, but unfortunately their overall 

effectiveness is usually not satisfactory, or is often not up to what one is sometimes led to 

believe will occur. For example, encouraging on your property through nesting 

structures colonies of purple martins (via elevated, multi-chambered “houses”) certainly 

cannot hurt, but scientific studies have shown that when mosquito production is even 

moderately high, and the production problem emanates from expansive nearby areas, that 

these birds are really not very effective at all in reducing mosquito infestations, even for 

achieving the local relief that might be desired. Part of the problem stems from purple 

martins actively flying and feeding only during daytime only, whereas many mosquito 

problems are most pronounced during twilight periods or dark (the birds might have more 

of a beneficial effect here via controlling daytime biting greenhead flies, deer flies, or 

biting gnats). If one is looking to encourage airborne predators to help combat local 

mosquito problems, building bat houses to encourage colonization by nocturnal flying 

bats is probably more effective; but then one has to also tolerate having bats around, 

which aesthetically some people (especially neighbors) might not like, not to mention 

concerns about bats carrying and possibly transmitting rabies. 
14

The electronic “bug zappers” that are so popular in some neighborhoods have 

been scientifically shown to really be of very little value in controlling mosquito 

populations, and have also been documented to have adverse impacts on non-target insect 

species. Commercial mosquito collection/killing traps (e.g. Mosquito Magnet, 

Mosquito Deleto), some which are rather sophisticated with lights, fans and sources of 

carbon dioxide or other attractants (e.g. octenol), might be marginally effective in some 

localized situations. However, because of their relatively high expense (several hundred 

dollars) and limited areal effect (supposedly about 1⁄2-acre), these devices are really not 

very effective for contending with larger-scale problems, and hence not very practicable 

to consider using for large-scale needs or operations. But this is not to say that these 

devices cannot provide some very localized relief in your backyard setting, if not in terms 

of a noticeable drop in the numbers of mosquitoes that are biting you, then perhaps at 

least for psychological relief, in that you’re at least doing something to help kill some 

skeeters. 

Finally, it should be noted that the mosquito control profession is always on the 

lookout for more efficacious, cost-effective control methods that also lessen any nontarget impacts. Various alternatives have been proposed or arisen, and many have been 

tested, such as introduction in the field of irradiated, sterilized adult male mosquitoes or 

genetically manipulated mosquitoes to try to lessen reproductive potential; the 

introduction of fungi, protozoans, nematodes or other microbial pathogens to infect and 

kill mosquito larvae; the introduction of mosquito species that as larvae prey upon other 

mosquito larvae (“cannibal” mosquitoes); etc. However, while these alternatives might 

look good in theory or in the lab, in terms of their performance in the field, or in regard to 

their practicability for large-scale operations, they have so far not been satisfactory. To 

this category might also now be added trying to use ultrasonic sound waves to physically 

kill larvae by rupturing air pockets or bladders within their bodies, which shows some 

promise in smaller or tightly confined aquatic habitats (e.g. Larvasonic for treating storm 

sewer catch-basins), but awaits further research in terms of control efficacy, non-target 

impacts, and practicable utility. In collaboration with academic researchers and product 

manufacturers, we are always seeking “new chemistries” or other improved technologies 

for potential adoption for our control toolbox (e.g. insect growth regulators, 

ovipositioning repellents, algal- or plant-produced toxins, population autoinhibitors, 

molecular or DNA-based insecticides), perhaps leading to yet another generation of 

further improved insecticides. 

More information about the Mosquito Control Section’s options and choices for 

dealing with mosquito production problems can be found on the Section’s Internet 

website at http://www.fw.delaware.gov/Services/Pages/MosquitoSection.aspx. 

5) Are mosquito control insecticides safe to use, and should I be concerned if I’m 

exposed to spraying?

The Mosquito Control Section only uses insecticides that are registered by the 

U.S. Environmental Protection Agency (EPA) for mosquito control purposes. The 

EPA has determined through an inclusive and exhaustive science-based testing and 
15

review process that when these modern insecticides are applied in accordance with all 

EPA-approved product label instructions, which by federal law must be followed, their 

application “poses no unreasonable risks to human health, wildlife or the 

environment.” The EPA’s review process now typically entails that a pesticide 

manufacturer must spend almost 10 years and from $30-$50 million dollars, and 

sometimes up to $100 million, in testing before being allowed to bring a new product to 

market, and also has to invest significant resources in keeping an existing pesticide reregistered for continued use, all which is given careful scrutiny and review by the EPA. 

In part, the types of testing done include exposures and reactions of birds and mammals 

to ingested, inhaled or dermal contacts with a pesticide; as well as examining acutely 

toxic and sub-lethal chronic effects of pesticide exposures to fishes, reptiles and 

amphibians, and terrestrial and aquatic invertebrates (with various types of tests done on 

adults, juveniles, and larval or other immature forms). 

The hazardous warning statements and other safety precautions that appear on 

pesticide product labels are often a source of concern to folks who do not understand 

their context or applicability, and as such sometimes present public relations problems for 

our program. It must be kept in mind that the EPA-approved warning or precautionary 

language on product labels is targeted primarily toward avoiding having a human or other 

type of organism have direct exposure (through ingestion, inhalation or dermal contact) 

to full-strength, undiluted products, as well as what to do if such exposure has occurred. 

The product label language is also of primary utility to the spray applicators themselves, 

who most frequently might routinely or accidentally have such exposures. It must be 

understood that the final application of insecticides during our routine spray operations is 

always done via a mode of delivery approved by the EPA, with applications made at 

concentrations that are either always very diluted or at Ultra-Low Volume (ULV) rates, 

and which are not done very frequently for any given site. As such in real world use, 

these application conditions have allowed the EPA to scientifically conclude that when 

all product label language and instructions are followed as federal law requires, use of 

our mosquito control insecticides “poses no unreasonable risks to human health, 

wildlife or the environment.”

As part of the Delaware Department of Natural Resource and Environmental 

Control (DNREC) within the Division of Fish and Wildlife, the Mosquito Control 

Section is of course very concerned that there are no unacceptable non-target impacts 

(to humans or fish and wildlife) whenever we must conduct our spray operations. The 

first generation of modern insecticides arose in the 1940’s, which included long-lasting 

products like chlorinated hydrocarbons (e.g. DDT), and whose environmental persistence 

unforeseeably might have led to some problems for some higher-order consumers, has 

now been replaced by much shorter-lived second and third generation modern 

insecticides. 

As a sidebar before moving onto a discussion of our more modern second and 

third generation insecticides, it should be noted that the often touted story of adverse 

impacts from DDT’s use, supposedly in part manifested in drastically reduced 

populations of bald eagles, ospreys, falcons or pelicans allegedly occurring via egg-shell 
16

thinning and reproductive failure, actually has only weak scientific underpinnings along 

with some scientific evidence to the contrary, with the historical declines and rebounds 

for these avian populations also being reasonably attributable to several other factors not 

related to pesticide exposures. This may come as a somewhat surprising revelation to 

some folks, in that the DDT/bird decline story has now become so well engrained in 

“popular wisdom” or lore, but this scenario’s perpetuation in unchallenged manner really 

does a disservice to good science. A history over the past 45 years of people 

unknowingly frequently repeating this somewhat dubious set of events and impacts (often 

done with some passion and conviction on the part of the tellers) has taken on a life of its 

own, with this supposed scenario then morphing into “the truth,” which in large measure 

then conforms to what some or even many people want to believe. However, exploring 

this matter in any balanced manner and warranted scientific depth would the subject of a 

whole another review beyond these FAQs. 

Even with the DDT/bird decline story not holding up real well to more objective 

and less impassioned scientific scrutiny, this is not to say that all concerns about the 

potential for yet unknown or poorly-understood non-target impacts, even when products 

are used in strict accordance with all EPA-approved label instructions, have completely 

faded for all modern insecticides – e.g. in the last several years concerns have arisen 

about potential endocrine system effects (“endocrine disrupters”) associated with certain 

types of pesticides (or with their accompanying synergists or other additive ingredients), 

which probably bears objective tracking and further scientific inquiry. However, it is 

fairly safe to say that the benefits of judiciously using modern-day pesticides to help 

meet important societal needs (e.g. mosquito control, rodent control, disease prevention, 

crop production, food storage, timber production, structural building protection, 

landscaping needs, etc.) far outweigh any known risks for EPA-registered products, 

since the EPA’s product registration or re-registration process over the past 35 years has 

taken almost all previously-used “bad actor” pesticides off the market, and has not 

knowingly let any new “bad actor” products into the market. 

As such, in today’s era of heightened environmental concerns, almost all 

remaining potential problems for human health or non-target organism impacts caused by 

mosquito control spraying primarily arise from human mistakes or application errors that 

might be made in the rate of application (e.g. spray equipment calibration errors), the 

timing or place of application (e.g. accidentally repetitively swathing the same area), or 

with other operational aspects of performing spraying (e.g. spraying when too windy or 

not windy enough), all which can be readily avoided when product label instructions are 

scrupulously followed, and applications are made by dedicated, trained professionals. 

Mosquito Control Section staff and our contractual spray applicators are all 

knowledgeable professionals certified by the Delaware Department of Agriculture for 

using insecticides in proper and safe manner. 

In closing our comments about this FAQ, it should be noted that a very small 

segment of the public might be hyper- or chemo-sensitive to the insecticide products 

that we use (as well as perhaps also adversely reactive to other types of chemicals in the 

environment), particularly our adulticides for which people are much more likely to be 
17

exposed in contrast to our larvicides. Such hyper- or chemo-sensitive individuals might 

experience allergic-like reactions to our spraying, perhaps consisting of irritated eyes or 

throat, sneezing, coughing or other mild symptoms. If you experience such discomfort 

during or immediately after a mosquito control spraying, then you’re unfortunately one of 

the very few who might well be concerned about exposures to our treatments. In the 

unusual event that you are experiencing adverse health effects following insecticide 

application, you should consult your personal physician or seek other medical care. You 

will also find information in FAQs #6 and #7 below that should help you (and us) better 

contend with your individual problem, including how to avoid exposures to our spraying. 

More information about the insecticides we use and their safety can be found on 

the Mosquito Control Section’s website at 

http://www.fw.delaware.gov/Services/Pages/MosquitoSection.aspx. The phone number 

to contact the Section’s administrative headquarters in Dover is 302-739-9917. If you 

want information about the State of Delaware’s pesticide oversight/regulatory program, 

you should contact the Department of Agriculture’s Pesticide Compliance Section in 

Dover at 302-698-4500. If you have questions or want more information about any 

possible human health impacts of exposure to our insecticide products, you can call the 

Division of Public Health, Environmental Health Evaluation Branch in Dover at 302-

744-4546. Information about the U.S. Environmental Protection Agency’s (EPA)

positions on mosquito control insecticides can be found on the EPA website at 

http://www.epa.gov/pesticides/health/mosquitoes/. The Mosquito Control Section is also 

a participating affiliate of the American Mosquito Control Association (AMCA), and 

the AMCA in turn participates in the EPA’s Pesticide Environmental Stewardship 

Program (PESP), which encourages safe use and good stewardship of our insecticide 

tools – more information about the AMCA and its PESP partnership with the EPA is 

available on the AMCA’s website at http://www.mosquito.org. Information about nontarget impacts of pesticides can also be found at the EXTOXNET website (a consortium 

of academic research institutions) at http://www.ace.orst.edu/info/extoxnet/. 

6) How can I found out when and where mosquito control spraying might next be 

done?

If you want to know about when a mosquito control spraying might occur in your 

area, for whatever reasons or interest you might have, you can receive our daily spray

announcements automatically on your home or business computer (via e-mail 

notification over the Internet) by subscribing to our Mosquito Control listserver at 

http://www.dnrec.state.de.us/DNREC2000/admin/maillists/maillists.htm. Because of 

many complicating factors in planning, preparing and performing our often daily spray 

operations (such as varying locations or intensities of mosquito problems that often aren’t 

known by our field inspections until the last minute, but which then need rapid response, 

or our having to contend with fluctuating wind or weather conditions), the most advance 

notice that we can routinely give might be up to 24 hours lead time, but sometimes it 

might be as short as only 4 hours notice (this short lead time obviously negates us being 

able to give any effective advance notice of our spray plans in daily newspapers). You 

can also directly electronically access the Mosquito Control Section's updated advance 
18

spray announcements at your convenience, by contacting the Section’s website at 

http://www.dnrec.state.de.us/dnrec2000/Applications/Mosquito/index.asp. 

If you don’t have a computer or lack access to the Internet, or if you prefer not to 

use such electronic approaches, you can listen to one of several radio stations that as 

public service announcements often broadcast Mosquito Control's current plans for 

upcoming sprays. On a daily basis we submit our spray announcements to over 12 radio 

stations around the state, but unfortunately we have no control over if, when or how often 

these stations might run our spray notices. 

We also have a toll-free phone line at 1-800-338-8181 that you can call as often 

as you like, to listen to our taped spray announcements that are updated daily. 

If you live within an incorporated city or town, by our Spray Policy we routinely 

notify designated local officials in advance of almost all of spray operations occurring 

within city or town limits. In many cases it will also be these local city or town officials 

who initially requested our spray services. In turn, municipal officials might then try to 

provide further advance spray notifications to their constituents, so you might want to 

check with your local city or town officers. 

Finally, with the terrorism events of “9-11” (September 11, 2001 in New York 

City and Washington, D.C.) having caused much heightened concern about many 

security issues, it’s important for the public to know that when they observe our lowflying aircraft or “fog trucks” going about our business of spraying mosquitoes, “it’s just 

us” doing what we’re charged to do. In order to help accomplish this awareness for the 

public and other agencies too, we now routinely also inform the Delaware Emergency 

Management Agency (DEMA) about our spraying operations, among several federal, 

state or county agencies for which we routinely provide such information. 

7) If I don’t want to be exposed to mosquito control spraying, what steps might I take?

No matter what the scientific evidence indicates about the safety of the Mosquito 

Control Section’s using modern-day mosquito control insecticides, nor no matter what 

learned professionals might say, there will probably still be people who for whatever 

reasons will still want to avoid having any exposure to our insecticides (and yet 

somewhat ironically, many of these same people will also want mosquito relief, if not 

openly seeking such, at least not objecting to such when it’s achieved). But such desires 

for no spray contact or exposure are by no means insincere or completely unfounded. 

From a medical standpoint, there is a very small segment of the public who might be 

hyper- or chemo-sensitive to exposure to some of our insecticides (particularly for some 

of our adulticides, for which exposure is much more likely than having contact with our 

larvicides), resulting in allergic-like reactions for these people that might involve eye or 

throat irritation, sneezing, coughing or other symptoms – e.g. some people with asthma 

might be more sensitive here. Despite what the EPA has determined regarding the 

overall safety of our mosquito control products for a vast majority of the public, we 

recognize that there are a few individuals who might have mildly adverse physical 
19

reactions to the products we use, and as such we attempt to accommodate these 

individuals the best we can, while still delivering quality-of-life and mosquito-borne 

disease prevention services for the vast majority of the public. 

We also try to accommodate to the extent practicable, in keeping with our best 

serving the needs of the general public, those organic gardeners or produce growers 

who by the conditions of how they want to grow or market their agricultural products try 

to do this in as pesticide-free manner as possible. And through the Delaware 

Department of Agriculture and the Delaware Beekeepers Association, we also have a 

working agreement and notification protocols with commercial beekeepers, whereby 

through some mutually proactive measures they can be kept appraised of our pending 

spray operations, to help avoid any adverse impacts to their beehives or colonies. 

Individuals who for whatever reasons are still concerned about exposure to the 

insecticides applied by the Mosquito Control Section, particularly for adulticides, can 

take some common-sense steps to avoid direct exposure to our spray applications, such as 

temporarily leaving an area about to be sprayed, or by remaining indoors and closing 

doors and windows, plus shutting off window air conditioners, during and immediately 

after insecticide spraying. The general times and locations for knowing about the 

Section’s pending spray operations can be determined through various media devices and 

other means as described in FAQ #6 above. 

The Section will also consider special requests to establish a “No-Spray Zone,”

where mosquito control adulticides (insecticides applied to control adult mosquitoes) are 

not applied to your location. Decisions on granting No-Spray Zone requests are made by 

the Mosquito Control Section in consideration of a citizen’s or resident’s stated purpose

for making such a request; whether such a request can be practicably accommodated by 

our application equipment and within our application operations; and whether not 

spraying your location will unreasonably deny your neighbors or your community of their 

desired mosquito control services. In regard to the last factor, our possibly granting a 

No-Spray Zone will result in no mosquito control treatment either for your 

neighbors or other properties within several hundred feet of a No-Spray Zone’s 

epicenter. This then obviously in some situations could become contentious, and lead to 

some “neighbor problems” not always easy to resolve. 

By our Spray Policy, requests for No-Spray Zones by citizens or residents living 

within an incorporated municipality (city or town), applicable only to use of adulticides, 

must be made to the Mosquito Control Section by a municipal official (on their 

constituent’s behalf), with the municipality then obviously being in concurrence with 

such a request, and with the municipality also providing all the information required for 

the Mosquito Control Section to make its decision. As such, a citizen or resident of a 

municipality wishing to have a No-Spray Zone established around his/her residence or 

property should first contact an appropriate municipal official and obtain the 

municipality’s support or concurrence. Conversely in unincorporated areas, citizens or 

residents wishing to request a No-Spray Zone, again applicable only to use of adulticides, 

may do so by directly contacting the Mosquito Control Section. In all cases for 
20

unincorporated areas, only the actual property owner can make the No-Spray Zone 

request (i.e. not a renter, tenant, vacationer, visitor, etc.). 

Information requested to be provided in a No-Spray Zone request, whether 

coming from a municipal official for a citizen of a city or town, or from property owner 

themselves in unincorporated areas, is pretty straight-forward, involving items such as 

name, address, and phone number of property owner making the request; purpose for 

making the request; description and map showing property’s location; names, addresses 

and telephone numbers of adjacent property owners; whether the request is for aerial 

spraying, ground spraying, or both; etc. It is necessary to complete a No-Spray Zone 

request application each-and-every year that such consideration is desired. This is 

because a property’s ownership might change from year-to-year, or the desire or 

necessity for having a No-Spray Zone might also change from year-to-year, and as such 

there will be no automatic carryover of a previous year’s request for a No-Spray 

Zone. It is the responsibility of the municipality or individual desiring a No-Spray Zone 

designation to provide such notice to the Mosquito Control Section in timely manner on 

an annual basis, which if at all possible should be made by March 1 of each-and-every 

year when such consideration is desired. 

Based upon the information received, the Mosquito Control Section will then 

make an approve/no-approve decision within a few weeks of receiving the completed 

application form. In almost all cases, particularly when a medical case of hyper- or 

chemo-sensitivity is involved, the Section will try its utmost to accommodate the NoSpray Zone request, weighing the good that granting such a request will do for the 

individual making the request, versus what might be lost in the way of quality-of-life or 

public health threats to others nearby (in our not being able to treat adjacent or nearby 

properties). This is by no means always an easy decision to make. And finally, in event 

of a declared human health emergency caused by outbreak of mosquito-borne disease, 

the Section reserves the right to cancel any No-Spray Zone status that it might have 

granted, and to proceed with undertaking whatever spraying might be necessary to 

protect the general public’s health during a disease outbreak. However, the Section will 

attempt to provide advance notice of such cancellation to those people who might now 

have their No-Spray Zone status cancelled or temporarily lifted. 

Additional information on how to request a No-Spray Zone can be obtained by 

contacting the Mosquito Control Section in New Castle County by calling 302-836-

2555, and in Kent and Sussex Counties by calling 302-422-1512. An electronic 

application form for requesting a No-Spray Zone is also available on the Section’s 

website at http://www.dnrec.state.de.us/fw/mcnospray.htm.

8) What personal protection measures can I take to help avoid mosquito bites?

Probably the simplest action whenever possible is to try to avoid areas or times 

where mosquitoes are most active, such as near coastal marshes, wet woodlands or 

other swampy locations. But as was pointed out in FAQ #2 above, many mosquito 

species are long-distance fliers, and as such will often come find you. 
21

If you happen to live in a mosquito-prone area or have occasion to visit such, then 

your next line of defense is try to stay indoors if possible during peak mosquito 

activity, which for many species is near dusk, during the evening or night, and into early 

morning. Using and keeping your door and window screens in good repair is an obvious 

measure. [In many areas, folks who are fortunate enough to have screened-in porches are 

very grateful they do!] Wherever mosquitoes might still be a problem inside a residence, 

the old practice of using mosquito bed-netting could be resurrected. However, some 

particularly troublesome species, such as the common saltmarsh mosquito or the Asian 

tiger mosquito, are also very active daytime biters -- since many people must be outside 

and active during the day, the avoidance measures above don’t have much applicability. 

The type of clothing you wear can also help to reduce mosquito bites. If it’s not 

too hot or uncomfortable, consider wearing long-sleeve shirts and pants when outside. 

Wearing light-colored clothing also helps (in particular, avoid red colors). If the 

mosquito infestation is truly bad and you must remain outside, you might want to 

consider using a fine-mesh head net, or a mesh “shoo-bug jacket” treated or impregnated 

with a repellent. Using yellow light bulbs for outside lighting might also help. 

Avoiding outside activities that require a lot of exertion and hence generate a lot 

of carbon dioxide, a powerful natural mosquito attractant, is also advisable in mosquitoinfested areas. Physical exertion also produces body heat and lactic acid in sweat, 

which are also attractants for mosquitoes. Also do not use strong-smelling perfumes or 

cologne, nor fragrant soaps, shampoos or hairsprays. 

Probably the most common remedy for contending with having to work, live or 

recreate outdoors in mosquito-infested areas is the use of some type of chemical 

repellent. Scientific studies have shown that by far the most effective types of repellents 

are commercially-available, over-the-counter products that contain the chemical DEET 

(e.g. OFF, Cutter, Muskol, Ben’s, 6-12, Sawyer). Other types of repellents are also 

available, including certain brands of cosmetic creams that might have some repellent 

effect (e.g. Avon Skin-So-Soft), or various “natural” oils, spices or other extracts (e.g. 

eucalyptus oil, lemongrass, pennyroyal, allspice, bay, camphor, cinnamon, citronella, 

geranium, lavender, nutmeg, peppermint, pine, thyme). However, most scientific 

evidence shows most of them to be of comparatively little or only marginal effectiveness 

– nonetheless, the bottomline here is to use whatever you think or “know” works best for 

you. 

There is a very small percentage of people who might have some adverse health 

reactions to high concentrations of DEET (e.g. 50-100%), so as a general rule it is 

recommended that adults use repellents containing a DEET concentration of 30% or 

less, and for children the concentration should be 10% or less. Do not use DEET on 

infants under 2 years old. From the standpoint of health precautions, it is better to more 

frequently apply formulations with lower DEET concentrations, versus infrequently 

applying formulations with higher DEET concentrations. Be sure to follow all 

application instructions on a repellent’s label. If you want to avoid using DEET-based 
22

repellents all together, the EPA has recently determined that two other products also 

provide some effective relief – picaridin and oil of lemon eucalyptus. 

Another type of chemical defense is to spray clothing with permethrin, a synthetic 

pyrethroid (e.g. Permanone), which actually functions as both an insecticide and a 

repellent, and is also used to help prevent tick problems. If permethrin is used, it should 

be applied only to clothing and never directly to skin, and all instructions for use must be 

closely followed. 

Finally, there are other measures that you can take around your home or property 

to reduce mosquito bites that were discussed in FAQ #1 above (i.e. practice good water 

sanitation), as well as perhaps taking some measures discussed in FAQ #4 that have 

much lower abatement effects (e.g. purple martin colonies, bat houses, mosquito 

collection/killing traps) -- at the risk of repetition, the true effectiveness of these latter 

methods is quite dubious relative to the level of relief needed or sought. Some people 

also find that burning certain materials (e.g. citronella candles, sticks or coils) to be of 

some limited help in keeping mosquitoes away from their personal airspace. It is known 

that Native Americans tried such smoky approaches (e.g. “smudge pots”) to achieve 

some skeeter relief (if they could stand the smoke and smell), but during seasons of peak 

mosquito activity some tribes were also in the smart habit of relocating their villages to 

less mosquito-prone sites. For most modern Americans this type of ready residential 

movement is no longer an option, which is part of the reason for our Section’s existence 

and mission. 

9) What do I do if I find a sick/dead wild bird that might have West Nile virus? 

As discussed in FAQ #2 above, the recent arrival in Delaware of West Nile virus 

(WNV) is a cause for some concern, and part of the approach to dealing with the problem 

involves an expanded virus surveillance/monitoring program being conducted by the 

Mosquito Control Section. The public can be of great help to us on a statewide basis in 

conducting this expanded effort. If you find a dead or sick bird that you think could 

have been affected by WNV, please follow the protocols discussed below. While WNV 

has now been documented in bats, chipmunks, squirrels, raccoons, skunks, domestic 

rabbits and cats, as an indicator of the virus’ spread and prevalence, the Mosquito Control 

Section still remains interested only in birds as a tracking or diagnostic tool, and only for 

certain species of birds at that. 

First, a determination (to the best of one’s ability) should be made as to what 

species of bird you have. Crows, blue jays, cardinals, robins, and birds-of-prey

(hawks, eagles, falcons or owls) have shown to be quite susceptible species for WNV, 

and are therefore the primary bird species collected. Of these species, crows seem to be 

the most commonly affected and reported. Crows can be identified by their large size 

(approx. 12-16” in total length, or about the size of a football), matted black color (even 

their eyes), large beak (1-2” long), etc. Blue jays are smaller than crows, with mostly 

blue, black and white feathers. Most people know how to recognize a cardinal or robin, 

at least for males of these species. Birds-of-prey can be recognized by their large, sharp 
23

claws and hooked beaks. These are the only bird species (when found singly or in 

numbers less than five) that should be reported to the Mosquito Control Section. 

However, citizens should feel free to report localized occurrences or clusters of 5 or more 

sick or dead specimens of any bird species, which in observing might be associated with 

some type of exposure or problem not related to WNV (e.g. possibly some type of 

pesticide poisoning), which might then be of interest to other agencies, such as DNREC’s 

Wildlife Section or the Delaware Department of Agriculture. 

 

Secondly, it should be determined if the bird has been dead less than 24 hours. 

Current testing techniques require that specimen birds be fresh for accurate virus 

detection. A relative scale such as “the bird was not in your yard when you left for work 

in the morning, but was there when you returned home in the evening” would be fine for 

knowing the bird is probably less than 24 hours old. Dead birds that are infested with 

maggots, or which have deeply sunken eyes or whose feathers are in poor condition, are 

specimens that have probably been dead for too long for any worthwhile analyses. 

 

After the above criteria have been met, the bird should be covered if possible by a 

bucket, box, trash can lid, or other type of covering to protect it from further degradation 

by sunlight, direct heat, flies, scavenging animals, etc. As a general precaution when 

handling any dead animal, it is recommended that you do not have any bare-handed 

contact or otherwise directly handle the bird, even though from what is known about 

WNV you could not contract the disease by doing so. [To date, there has been no 

indication of any animal-to-human transmission of WNV, or person-to-person 

transmission not involving an organ transplant or blood donation.] A call should then be 

placed to the Mosquito Control Section under the following guidelines. If the bird is 

found in New Castle County, call 836-2555 during weekday hours between 8:00 am4:00 pm. The same reporting criteria should be used for birds found in Kent or Sussex 

Counties, but call 422-1512 instead. 

10) What are human health problems/symptoms when a mosquito-borne viral disease 

is contracted? And what is the probability of my becoming infected or sick?

As mentioned in FAQ #2 above, the primary mosquito-borne disease concerns in 

Delaware for humans are now eastern equine encephalitis (EEE) and West Nile virus 

(WNV), with EEE being much more virulent than WNV, but fortunately also less 

common. Insects such as mosquitoes are part of a larger phylum of invertebrates called 

arthropods, and arthropod-borne viruses are known in general as arboviruses. Arboviral 

encephalatides such as EEE and WNV are viruses that in their worst manifestation cause 

encephalitis, which is a swelling of the brain having severe health consequences. [When 

the brain swelling is also associated with inflammation of the brain’s outer lining and 

spinal cord, the condition becomes meningoencephalitis.] 

A large majority of people infected with WNV apparently might never know 

they’ve been infected, in that they feel no adverse effects whatsoever (i.e. they’re 

asymptomatic), or they have only mild overall discomfort that’s not severe enough for 
24

them to seek any medical attention; however, this is relatively benign reaction is rarely 

the case with EEE. 

When symptoms are first felt for either WNV or EEE, early indications of 

infection include headache, mild fever, body aches, malaise, and occasional swollen 

lymph glands, all which are flu-like symptoms (as such, if you live in an area where 

mosquitoes are abundant, you might want to be somewhat suspicious if you or someone 

you know comes down with a “summer flu,” and seek medical care). These early 

symptoms might occur from 7-10 days after receiving an infectious bite, and might come 

on slowly or quite suddenly. [The most probable time of year in Delaware to contract an 

arbovirus is during late summer and early fall, from about the last week in July through 

early October.] A more virulent infection for WNV or EEE can progress to severe 

headache, high fever, neck stiffness, and muscular weakness, and cause behavioral 

changes including stupor, confusion and disorientation. Patients with these more severe 

symptoms are often recognized as neuroinvasive cases, in that nervous system functions 

have become affected or impaired. Progressing to full-blown encephalitis, which 

fortunately is a rare occurrence, can then cause tremors, convulsions, coma and paralysis. 

Death occurs in about 5% of patients with full-blown WNV, with any fatalities most 

common in people >50 years old and those with impaired immune systems. Full-blown 

EEE is more fatal, with death occurring in up to 30% of young adult or middle-aged 

patients, and up to a 70% fatality rate in children or the elderly. For patients who do not 

die from full-blown encephalitis (whether caused by WNV or EEE), after-effects usually 

involve long-term or permanent neurological damage or sequelae, sometimes having 

debilitating consequences. 

 Since arboviral encephalatides are viral diseases, trying to use antibiotics to treat 

WNV or EEE is not effective, and no effective antiviral drugs have yet been discovered. 

For full-blown encephalitis, the best that physicians can do is try to treat the symptoms 

and problems associated with brain swelling, deal with associated complications where 

treatable (e.g. bacterial pneumonia), and hope for the best. No human vaccines yet exist 

for WNV or EEE, although effective vaccines for both viruses are now available for 

horses . 

 Fortunately, transmission of EEE to humans is naturally a relatively rare event, 

and modern mosquito control programs along the East Coast work hard to make such 

events even rarer. A major impetus for the start of modern mosquito control programs in 

the Mid-Atlantic region was the 1959 EEE outbreak in Cape May County, New Jersey 

that occurred around Labor Day, leading to the deaths of over 20 victims and 

hospitalizations of over 100 people (along with some severe economic consequences for 

a tourism-based area). Even with a subsequent expansion and increased effectiveness of 

mosquito control programs in the Mid-Atlantic, localized EEE outbreaks have occurred 

since then, not only in New Jersey but also in eastern Massachusetts, Rhode Island, 

upstate New York, southeastern Virginia, and northeastern North Carolina. Fortunately, 

the numbers of human cases in these EEE outbreaks were relatively low. The most 

recent documented human case of EEE in Delaware occurred in the mid-1980's -- the 

Mosquito Control Section takes considerable pride in our keeping things this way, such 
25

that EEE does not have major impacts on Delawareans, with the chances of you 

contracting EEE exceedingly small. 

 The introduction of WNV into the United States (and really anywhere in the 

Western Hemisphere) occurred in the New York City area during the summer of 1999 

(causing 62 hospitalizations and 7 deaths at that time). Over the span since 1999, the 

virus has spread southward and westward across the country -- WNV human cases have 

now been reported in all lower 48 states with exception of Maine. The total number of 

reported annual WNV human cases and fatalities across the U.S. is shown below from 

1999-2007: 

1999 = 62 cases, 7 deaths 

2000 = 21 cases, 2 deaths 

2001 = 66 cases, 9 deaths 

2002 = 4156 cases, 284 deaths 

2003 = 9862 cases, 264 deaths 

2004 = 2359 cases, 100 deaths 

2005 = 3000 cases, 119 deaths 

2006 = 4269 cases, 177 deaths 

2007 = 3630 cases, 124 deaths 

 Delaware’s first WNV human case occurred in 2002, and Delaware’s peak WNV 

outbreak year for human cases to date happened in 2003, with 17 people reported 

sickened by WNV (involving 13 neuroinvasive cases), leading to 2 deaths. WNV counts 

in Delaware then declined considerably, with no cases in 2004, 2 cases in 2005, no cases 

in 2006, and 1 case in 2007, with no more fatalities. The relatively low numbers of WNV 

human cases in Delaware in terms of total numbers or per capita reflect the results of the 

State having a modern-day, comprehensive mosquito control keeping pathogen-vectoring 

populations of mosquitoes as low as practicable to do, along with a general subsidence of 

WNV in the Northeast starting in 2004 (although WNV has continued to flare-up in other 

areas of the country since then, particularly in California and upper Great Plains states. 

The Mosquito Control Section will continue to work hard to try to keep this disease out 

of our state’s human population for to extent practicable to do. 

People can take some comfort that scientists estimate even in areas where WNV 

has now become established, probably less than 1% of the mosquito populations that can 

carry this virus are infected, and that if you are unlucky to be bitten by one of these <1%, 

there’s then only about a 1% chance that you’ll become severely ill. With the Mosquito 

Control Section aggressively taking measures (as described in FAQs #1, 2, 3, and 4 

above) to reduce the frequency and intensity that you might get bit [note: if there are no 

or only a few bites to start with, then the naturally small chance of your ever 

encountering an infected mosquito goes almost to zero], along with your also taking some 

personal protection measures on your own (as described in FAQ #8 above), the chance of 

your ever contracting WNV is truly exceedingly small. 
26

 Additional information about the human health problems/symptoms of WNV, or 

concerns for its possible contraction, can be obtained by calling the Delaware Division 

of Public Health (Epidemiology Branch) at its office in Dover at 302-744-4541. 

11) There are a lot of biting flies around my house or yard that I don’t like (or gnats, 

or ticks, or wasps, etc.). Can’t Mosquito Control do something to get rid of them? 

While the Mosquito Control Section frequently receives calls for help not related 

to mosquito problems, unfortunately the answer here is NO (even if you get mad at us). 

By our enabling State statute, for pest management purposes we are charged with and only 

allowed to take actions that control mosquitoes. Given the varied and vast amounts of 

mosquito-breeding habitats in Delaware and the long flight ranges of some mosquito 

species, plus the State’s high human population density, coupled with the intolerable 

quality-of-life and human health threats that severe mosquito infestations can cause, our 

just battling mosquitoes gives us plenty to do. Our trying to attend to any other pest 

problems would be beyond our capabilities in terms of time, staffing, budget or other 

resources, and legally not in our authority to do anyhow. But this doesn’t mean that we 

still can’t provide you some advice or guidance, which we do below. 

 There are many species of biting flies in Delaware – greenhead flies in or near 

saltmarshes; deer flies where forested edges or shrubby areas abut marshes or open fields, 

especially along the coast; horse or stable flies around farms; and shore flies that can be 

quite annoying ankle-level biters along our beaches. Biting gnats (punkies or no-seeums) at times can be very annoying, especially in late spring and early summer along 

tidal wetland margins or near other watery/muddy areas. In recent years the public has 

become much more aware of tick-borne problems because of the emergence and 

widespread nature in Delaware of Lyme disease, spread by the very small deer tick, 

which can also transmit human granulocytic ehrlichiosis (HGE); other tick-borne 

concerns in Delaware are associated with the wood or dog tick, as a carrier of Rocky 

Mountain spotted fever, and the lone star tick, capable of transmitting human monocytic 

ehrlichiosis (HME). Calls will also come to us for what to do about problems with bees, 

hornets, wasps, yellow jackets, velvet ants, etc., which can be a special concern to those 

individuals susceptible to anaphylactic shock from their stings. We’ll occasionally get 

questions about chiggers (“red bugs”), or if the spider that somebody saw in their storage 

shed was a black widow. We’ve also taken queries as far afield as gypsy moth spraying, 

or dealing with concerns about rabies transmission. Even calls about bats in the attic, 

skunks under the porch, snakes in the crawlspace, beavers flooding the driveway, or 

moles in the lawn have come our way. Without spending an inordinate amount of time 

trying to explain to the public that we’re not the agency or personnel to call about such 

problems or issues, we still courteously and patiently try to point these often distraught 

callers in the right direction, concerning both what we can and can’t do, and who they 

might want to contact next. 

 

 We recommend that for many non-mosquito pest problems a first point-of-contact 

be the University of Delaware Cooperative Extension Service, with the Extension 

Service having offices in all 3 counties. Expert agents in the Cooperative Extension 
27

Service can give you advice about how to handle that wasp or hornet problem, or how to 

lessen biting fly problems (e.g. they can give you a handout showing you how to 

construct a fly box trap for reducing greenhead fly populations adjacent to saltmarshes). 

If you bring in the tick that you found crawling in your bed or that you pulled off your 

leg, or a specimen of any other type of unknown insect, spider, or invertebrate critter of 

interest that you might have in-hand, they can usually have it identified for you. The 

Extension Service is also the obvious place to call for questions about garden or 

ornamental plant pests, as well as agricultural crop pests. The Extension Service phone 

number to call in New Castle County is 831-2506; for Kent County call 730-4000; for 

Sussex County call 856-7303. 

 

For additional questions related to agricultural, forest or ornamental plant pests, 

including concerns about gypsy moths, one can call the Delaware Department of 

Agriculture offices in Dover at 739-4811. For wildlife-oriented pest problems or rabies, 

we suggest that you start by calling our Division’s Wildlife Section, with offices in 

Dover at 739-9912. In many cases or situations no matter whom you first contact, the 

final solution to your problem will often be you’ll have to try to best handle it by yourself 

(after getting all the good advice and guidance you can); or you might have to call upon 

the professional services of a commercial exterminator or pest control company, who 

in almost all cases will know what to do and how to get it done safely. 

12) Describe the Mosquito Control Section. Where are you housed? How many people 

work for you? Where do you work? What do you do in the winter? Who do you 

work with? Who are your partners? What’s your budget? etc., etc., etc. 

Essentially, just who are you people? 

The Mosquito Control Section is part of DNREC’s Division of Fish and 

Wildlife, and has a staff of 21 people working year-around to deal with Delaware’s 

mosquito problems; additionally, we hire about 15 seasonal employees each year to 

meet our increased seasonal workloads, usually for the period from April into October, 

with peak need from May through September. Our year-around staff of 21 consists of a 

Section administrator, 2 program managers, 3 administrative support professionals, 6 

environmental scientists, a field crew supervisor, 5 heavy equipment operators, an 

automotive/equipment mechanic, and 2 long-term biological aides. Our 15 summer 

seasonals are primarily used as field inspectors, mosquito trap collectors, or members of 

our virus surveillance teams. One of our seasonals works as the Section’s 

taxonomist/counter for sorting and identifying light trap collections, stationed at the 

University of Delaware’s Department of Entomology and Wildlife Ecology on the 

Newark campus. [Sidebar note – during the early days of organized mosquito control in 

Delaware going back to the 1930’s, the Civilian Conservation Corps employed hundreds 

of young men in mosquito control work, to dig by hand and primitive machinery the 

State’s parallel-grid-ditch network, the remnants of which are still quite visible over tens 

of thousands of acres of our tidal wetlands.] 

Aerial spraying of insecticides, whether done by fixed-wing aircraft or helicopter, 

is all contractually performed by private professional aerial applicators, who 
28

throughout our control season are available on short-term standby basis to meet our 

spraying needs. When and where to perform aerial spraying and what products/rates to 

use are solely the calls of our Mosquito Control staff, and as such we do each spraying’s 

technical planning and follow-up for quality control checks, as well as provide general 

oversight throughout each spray operation. While these private aerial applicators are not 

actually part of our Section staff, by the nature of what we must do, we have very close 

working relationships and interactions with our contractors at all times. All truckmounted spraying (ground “fogging”) is directly performed by Mosquito Control staff. 

 The Section has three facilities from which we conduct our statewide program. 

There is an administrative H.Q. office in Dover at DNREC’s headquarters (739-9917); 

a field operations center for New Castle County and northwestern Kent County in 

Glasgow (836-2555); and a field operations center for the remainder Kent County 

and all of Sussex County in Milford (422-1512); 

 Mosquito Control Section personnel have statewide responsibilities for 

controlling mosquitoes wherever they present problems to people, in urban, suburban or 

rural settings. Our staff work up-and-down the state from Wilmington to Odessa to 

Smyrna to Dover to Milford to Georgetown to Selbyville; and across-the-state from New 

Castle to Hockessin, Delaware City to Newark, Port Penn to Middletown, Kitts 

Hummock to Hartly, Bowers Beach to Felton, Slaughter Beach to Harrington, Lewes to 

Greenwood, Rehoboth Beach to Bridgeville, Bethany Beach to Seaford, and Fenwick 

Island to Laurel. Because of the millions of summer vacationers, visitors and tourists 

coming to Delaware’s beach resort communities, coupled with lots of nearby prime salt 

marsh breeding habitats, the coastal strip from Lewes to Fenwick Island and areas 

around the Inland Bays are given special attention, but this doesn’t come at undue 

expense for meeting the statewide control needs of our many other constituents too. 

Special attention is also given to mosquito control on Delaware’s two National Wildlife 

Refuges, with mosquitoes produced from Bombay Hook National Wildlife Refuge

capable of causing problems for people all along the eastern side of the Greater DoverSmyrna area; and mosquitoes produced from Prime Hook National Wildlife Refuge

capable of doing the same for people in the Milford-Milton-Lewes area, including the 

bayfront communities from Slaughter Beach to Broadkill Beach. [Indeed, it is only by 

our having excellent working relationships and cooperation with the U.S. Fish and 

Wildlife Service that the Section is able control Refuge-produced mosquitoes while the 

skeeters are still on-Refuge (at least for the most part), much to the relief of residents and 

visitors up to several miles away from a Refuge’s borders.] Overall, our “Mosquito 

Control District” encompasses about 2000 square miles, providing control services to 

about 850,000 residents and millions of summer visitors. 

 While the Mosquito Control Section’s active field surveillance/monitoring and 

insecticide treatment programs last for about 8 months, from around mid-March into midNovember, the Section continues to work hard year-around doing a variety of tasks. 

For example, source reduction work, such as Open Marsh Water Management (OMWM) 

and coastal impoundment management in particular (as described in FAQ #4 above), 

occurs all year long, weather permitting. Wetland habitat restoration or enhancement 
29

projects, often done in collaboration with our colleagues in the Division’s Wildlife or

Fisheries Sections, also occur throughout the year. The 4 “winter months” from midNovember through mid-March are also the time of year when the Section is able to 

accomplish a lot of tasks that we simply don’t have the luxury to get done during the 

“heat” of our annual “skeeter wars” – e.g. this is time of year for short-term and longterm strategic planning, implementing facilities improvements or upgrades, taking 

inventories, making major machinery repairs, doing routine maintenance to insecticide 

spray gear or scientific equipment, performing research analyses, writing reports, tending 

to personnel matters, preparing permit applications, drafting contracts, attending 

scientific/technical meetings, making budget projections, etc. We often find that our 

spring woodland-pool control program, which kicks-off in mid-March, is all too soon 

upon us once again. There truly is no “downtime” for us throughout the year. 

 In carrying out our mosquito control activities, the Mosquito Control Section 

often comes in contact with, or has the opportunity to work with, many other programs 

within the Delaware Department of Natural Resources and Environmental Control 

(DNREC), not just within our own Division of Fish and Wildlife (DFW), but within all 

the other DNREC Divisions too. For instance, the Mosquito Control Section is the lead 

DNREC agency for the Department’s “Northern Delaware Wetlands Rehabilitation 

Program” (NDWRP), in which the Department has undertaken a long-term commitment 

to try to restore over 10,000 acres of degraded, urbanized coastal wetlands at over 30 

sites along the lower Christina-Delaware River corridor. Besides working with our 

colleagues in the Division and throughout DNREC too in undertaking this NDWRP 

work, for many NDWRP project planning and construction tasks we also work closely 

with the New Castle Conservation District. 

We are close partners with our Division’s Wildlife Section in undertaking 

Phragmites control projects, and with our Wildlife and Fisheries Sections for coastal 

impoundment management. In going about our day-to-day business, we also 

routinely interact with our Division’s Natural Heritage Program and our Non-Game 

and Endangered Species Program, to help ensure that our control activities do not 

adversely impact species or habitats of special concern, and wherever possible in our 

marsh management work that steps are taken to protect or enhance biodiversity. 

 In undertaking our wetlands management work, we interact with DNREC’s 

Division of Air and Waste Management (DAWM) for marsh restoration projects in 

association with the Department’s undertaking Superfund site restoration projects, to 

help the DAWM achieve resource compensation for third party-caused natural resource 

injuries. We also interact with the DAWM in regard to trying to regulate or better 

control problems that are caused by scrap tire piles – tire piles providing prolific 

mosquito-breeding habitat is but one of their several problems. 

We interact with DNREC’s Division of Soil and Water Conservation (DSWC) 

regarding the design and management of stormwater management basins, to try to 

lessen mosquito production problems while still retaining other good attributes of these 

desirable man-made water quality features. Mosquito Control also works collaboratively 
30

within the limit of our discretionary resources with the DSWC’s floodwater 

relief/drainage program, to help the DSWC achieve for site-specific projects its 

floodwater relief/drainage objectives. Such work is often done without primarily or 

directly serving any mosquito control purposes, but rather we assist the DSWC due to the 

availability of our unique heavy marsh equipment and our equipment operator expertise. 

Nothing that we do in collaboration with the DSWC in regard to any floodwater 

relief/drainage projects is done without the DSWC first securing all necessary landowner 

permission/cooperation, plus acquiring any needed wetlands or subaqueous lands 

regulatory permits. We also interact with the DSWC’s Delaware Coastal Management 

Program and its Delaware National Estuarine Research Reserve about a variety of 

coastal zone policy issues and operational practices. 

Mosquito Control works closely with DNREC archaeologists in the Division of 

Parks and Recreation (DPR) to help ensure that our excavation activities don’t 

jeopardize historical or cultural resources, and that anything we might find actually 

adds to our knowledge of this resource base. 

 The Mosquito Control Section also works closely with DNREC’s Division of 

Water Resources (DWR), Wetlands and Subaqueous Lands Section, in regard to 

wetlands permitting needs and a host of associated wetlands regulatory issues 

(including wetlands protection initiatives), and in regard to water quality concerns. 

For purposes of public information and education and media outreach, we work 

closely with DNREC’s Public Affairs Office. 

Besides interacting with our sister agencies within DNREC, we also have 

interactions with several other state agencies. For example, in regard to pesticide use 

and state regulatory issues, we interact with the Delaware Department of 

Agriculture’s Pesticide Compliance Section. To help avoid any problems with our 

spray operations affecting commercial beekeeping operations, the Mosquito Control 

Section has developed a set of procedures and protocols with the Delaware Department 

of Agriculture (State Apiarist) and the Delaware Beekeepers Association, designed to 

prevent or alleviate potential problems. 

As part of the Mosquito Control Section’s virus surveillance/monitoring program, 

the Section contracts and closely works with the Delaware Division of Public Health 

Laboratory for analyses of sentinel chicken blood samples and dead wild bird specimens 

that we collect and submit, plus for analyses of any mosquito collections (“pools”) that 

we might collect and submit. To help the State get a better handle on dealing with West 

Nile virus problems and issues, the Mosquito Control Section is an active partner in the 

State’s tri-Department “West Nile Virus Work Group,” which besides DNREC also 

involves the Department of Health and Social Services (Division of Public Health, 

Epidemiology Branch) and the Department of Agriculture (State Veterinarian). To 

help address concerns about any possible human health or environmental non-target 

impacts of our insecticide use, we work closely with the Division of Public Health’s 

Environmental Health Evaluation Branch. 
31

Concerns about potential impacts to historical or cultural resources in our 

undertaking OMWM or wetlands restoration work also cause us to interface with the 

Division of Historical and Cultural Affairs’ State Historic Preservation Office

(SHPO). 

On the federal side, in addition to our interactions with the U.S. Fish and 

Wildlife Service that we already mentioned above (regarding mosquito control needs on 

our two National Wildlife Refuges), we also interact with the Army Corps of Engineers

regarding mosquito control problems occurring on the Corps’ dredge disposal sites. As 

mentioned in FAQ #4 above, all of our Open Marsh Water Management (OMWM) 

wetland alterations are done under regulatory oversight by the Delaware Mosquito 

Control Advisory Committee (DMCAC), consisting of four federal agencies (Army 

Corps of Engineers, U.S. Environmental Protection, U.S. Fish and Wildlife Service, 

National Marine Fisheries Service), four DNREC agencies (Division of Fish and 

Wildlife’s Natural Heritage Program, Division of Water Resources’ Wetlands and 

Subaqueous Lands Section, Division of Soil and Water Conservation’s Delaware 

Coastal Management Program, Division of Parks and Recreation’s Cultural and 

Historical Resources Section), and the State Historic Preservation Office (SHPO). 

The Mosquito Control Section is a very active participant in the American 

Mosquito Control Association (AMCA), which is a scientific/management organization 

of over 1600 professionals from hundreds of mosquito control programs around the 

country and world (from over 50 countries), academia, government, and industry. 

Through active participation in the AMCA, the Section has the opportunity for input and 

influence regarding national or regional issues with several federal agencies – e.g. U.S. 

Environmental Protection Agency, U.S. Fish and Wildlife Service, Department of 

Health and Human Services (Centers for Disease Control), and Department of 

Agriculture. In regard to legislative issues, our participation in the AMCA also 

provides us with additional avenues of communication with Congress (primarily through 

AMCA-coordinated actions with our two Senators, our Representative, and their 

legislative aides), along with of course the access we have through the Governor’s 

Washington Office. Besides interacting at the national level via the AMCA, the 

Mosquito Control Section is also a member program in the Mid-Atlantic Mosquito 

Control Association (MAMCA), and we also interact with our colleagues in the New 

Jersey Mosquito Control Association (NJMCA). Our professional staff are also 

members of other scientific organizations such as the Society for Vector Ecology, the 

Estuarine Research Federation, and the Society of Wetland Scientists. 

In undertaking our control work, the Mosquito Control Section also has 

considerable interactions with the private sector, in that indeed this is our primary 

constituency (i.e. the public). Our Open Marsh Water Management (OMWM) projects 

are undertaken only after first having the permission and cooperation from the private 

landowners who own much of Delaware’s coastal wetlands. In doing these OMWM 

projects, we have cooperatively worked on lands owned by The Nature Conservancy or 

by Delaware Wildlands, Inc.; and we have partnered with Ducks Unlimited for the 
32

support of other OMWM work and impoundment management projects too. Partnerships 

for some of our private lands restoration work have also been formed through auspices of 

the U.S. Fish and Wildlife Service’s Partners for Wildlife program. 

 

Depending upon available funding, the Mosquito Control Section also helps to 

plan, coordinate and participate in applied mosquito biology or mosquito control research 

projects with faculty or research associates of the University of Delaware’s Department 

of Entomology and Wildlife Ecology. We also interact with faculty or research 

associates of the University of Delaware’s College of Marine and Earth Studies for 

conducting applied research regarding wetlands ecology or management. 

 The Mosquito Control Section operates on an annual General Fund budget of 

about $2.0 million dollars per year. For the past several years, we have also received 

about $100,000 per year in federal funds from the Centers for Disease Control to 

help with WNV surveillance/monitoring, laboratory testing, and applied research. These 

federal funds have come to us via the Division of Public Health’s Epidemiology and 

Laboratory Capacity annual grants that the DPH receives each year from the CDC. In 

comparison to mosquito control programs in many other areas around the country, 

whether the comparison is done on a per capita basis or an areal basis, Delaware’s 

statewide mosquito control program is one of the least expensive, and as such is 

apparently done quite frugally -- we feel that our approach delivers a very good returnon-investment for our citizens, while being accomplished in very effective and 

environmentally-compatible manner. 

 If you have further questions about the Mosquito Control Section, please call our 

administrative headquarters in Dover at 739-9917.