**DEPLW0900**

Background **West Nile Virus (WNV) and Eastern Equine Encephalit is (EEE) are growing concerns for many**  **people who want to know more about these diseases, how much of a concern they are in Maine,**  **how they spread, and what they can do to minimize t heir risks of exposure. Entomologists indicate**  **there are at least 44 species of mosquitoes in Main e. Although many are certainly nuisances, it is**  **important to know that less than half of those are biting pests of humans and only a few of them that**  **feed on both humans and birds are actually potentia l vectors or transmitters for WNV and EEE. It**  **also helps that the breeding locations of these spe cies are known. This information will help all of**  **us to determine an appropriate level of concern and to make informed decisions.** 

Breeding Habitat **The few potential WNV vector species primarily bree d in two types of areas: stagnant water and**  **high elevation salt marsh pools. The stagnant wate r areas can be found in artificial containers such**  **as bird baths, used tires left outdoors, buckets, k iddy pools, stormwater and catch basins, drainage**  **ditches, etc. where water may not be regularly exch anged and becomes stagnant. Many of these**  **structures can be easily emptied to eliminate mosqu ito breeding conditions. The high elevation salt**  **marsh pools refer to natural pools that are located above the normal high tide line. These areas are**  **typically only flooded during significant storms or other extremely high tide events, often only once**  **per month. Some of them contain fish that will act as natural predators, keeping the mosquitoes**  **from surviving and breeding. Those pools without f ish, however, provide mosquito breeding**  **habitat. The one potential EEE vector species bree ds in some**  **of Maine’s many red maple and cedar swamps, and these habitats can also contain natural**  **predators.**

**If you are concerned about mosquitoes and WNV, the Department of Environmental Protection**  **(DEP) recommends that you first eliminate or empty any artificial sources of stagnant water. This**  **is a relatively easy step in eliminating breeding h abitat, but is very important and extremely**  **effective. For either WNV or EEE, use personal pro tection, as you would for any mosquitoes.** 

**Information on available and recommended methods ca n be found through the Maine Center for**  **Disease Control (CDC) and the University of Maine’s Cooperative Extension Service.** 

Pesticide Control **Some people ask about the use of pesticides for con trol of mosquitoes that may transmit WNV or**  **EEE. Various chemical and biological agents are ma rketed for control of mosquitoes. In addition**  **to requirements on the use of pesticides from the M aine Department of Agriculture, Food and Rural**  **Resource’s Board of Pesticide Control (BPC), you sh ould be aware that**  any discharge of pollutants, including pesticides, to waters of the State or in such a way that they enter a water of the State, first requires approval from the DEP.

**However, the DEP has determined that some means of non-chemical pesticide treatments can be**  **conducted under specific conditions without DEP app roval. Mosquitoes, black flies, and some non**  **biting midges have physiological differences from o ther species that make them particularly**  **sensitive to the bacterial pesticides** Bacillus thuringiensis **subspecies** israelensis **(Bti) and** B. sphaericus **(Bs). These materials are available in solid and granular formulations that sink to the**  **bottom of waterbodies, will not be released into th e water column, and must be ingested to be** 



# DEP FACT SHEET

Mosquito Control, West Nile Virus, and EEE

Date: **June 2008 Contact:**  Bob Stratton **(207) 287-3901 or**

**Toll Free 1-800-452-1942 June 16, 2008 DEPLW0900** 

**effective. They also have limited persistence in t he environment. Based on these properties, DEP**  **has determined (see DEP guidance DEPLW0704B) that t reatments of solid or granular formulations** 

**of Bti or Bs as larvicides to those artificial cont ainers that can not be emptied, to high elevation**  **(extreme tide) salt marsh pools, constructed ponds, and isolated freshwater wetlands do not require**  **a Maine Waste Discharge License (WDL). In each of these resources, there must be a presence of**  **mosquitoes and an absence of fish or other predator s that can control them. In the salt marsh pools,**  **the Bti or Bs must be placed immediately after pool flooding to enable its dissipation prior to the**  **next flood event. The ponds and isolated wetlands must be contained on one person’s property and** 

**have no connection to other surface waterbodies. D EP emphasizes that people need to inspect**  **breeding areas to make sure that stagnant, breeding conditions exist, that mosquito larvae are**  **present, and that there are no natural predators th at will take care of the mosquitoes for you. It**  **should be noted that spraying for adult mosquitoes with appropriate precautions to avoid contact**  **with surface waters and wetlands, including ground and aerial applications done according to the**  **pesticide label instructions, does not require a pe rmit from DEP.** 

**In addition to the primary breeding areas noted abo ve in which treatment approval is not required,**  **some other natural habitats may at times offer pote ntial breeding conditions for mosquitoes that**  **carry WNV and EEE. There are two regulatory avenue s available to address this. The DEP has**  **developed a General Permit for Aquatic Pesticides f or the Control of Mosquito-Borne Diseases that**  **offers an expedited review for qualified projects. To qualify for the General Permit, there must be**  **preferred breeding habitat for vectors of WNV or EE E, the presence of those mosquito vectors,**  **and/or documentation of infected mosquitoes, birds, or humans within 20 miles. The proposed**  **treatment program must be in conjunction with a wri tten management plan with area-wide control**  **strategies. If these and other conditions can not be met, an applicant can apply for an individual**  **WDL. For either coverage under the General Permit or an individual permit, pursuant to DEP rules**  **Chapter 514,** Regulations Concerning the use of Aquatic Pesticide s **, the applicant must provide adequate protection for non-target species, must de**  **monstrate a significant need to control the target species and that the pesticide offers the only reas**  **onable and effective means, and the application must not result in violations of state water qualit**  **y laws. These conditions require significant attention, as the DEP is very concerned about the g**  **reater environmental effects of aquatic pesticide**

**treatments. It should be noted that Bti and Bs are effective at mosquito control during specific life**  **stages of the mosquito larvae. Thus, it is importa nt that people develop long-term, integrated**  **management strategies and not rely on last minute d ecisions that may not be approvable within the**  **desired timeframe or effective in controlling mosqu ito populations. Physical alterations to any**  **protected natural resource also require approval fr om the DEP under the Natural Resources** 

**Protection Act and the Maine Wetland Protection Rul es. As the U.S. Environmental Protection**  **Agency states in** Wetlands & West Nile Virus **(draft), “** healthy wetlands are not uncontrolled breeding grounds for mosquitoes. These unique ecos ystems sustain numerous species of fish, insects, amphibians and birds that feed on mosquito eggs and larva. Moreover, the mosquito species responsible for West Nile transmission do n ot prefer to reproduce in healthy wetlands. **”**

**It should be noted that all pesticide products must be registered with the BPC and all pesticide**  **applications must be performed in accordance with t he BPC’s regulations. For further information**  **on regulatory requirements, contact the Maine DEP a t (207) 287-3901. For information on**  **mosquitoes, WNV and EEE, methods of personal protec tion, and pesticide regulations, contact: the**  **Maine CDC at (207) 287-3960 (www.maine.gov/dhhs/boh /ddc/_lyme/index.htm**  **), the BPC at (207) 287-2731 (**  **www.maine.gov/agriculture/pesticides/wnv ), or the DEP at**  **(207) 287-3901 (www.maine.gov/dep/blwq/topic/westni le/index.htm**  **).**