How can I reduce or eliminate mosquitoes in and around the waterbodies on or near my property?

Due to concerns regarding West Nile Virus, Wisconsin residents are looking for ways to reduce mosquito populations on or near their property. Although the Department of Natural Resources' (DNR) Bureau of Fisheries Management is not responsible for developing state policy on combatting West Nile Virus, our program is responsible for regulating many of the activities which may first come to mind when attempting to reduce or eliminate mosquito populations, including controlling wetlands, stocking fish or applying pesticides to waterbodies (e.g., lakes, rivers, ponds, etc.).

Background

West Nile Virus (WNV) is a mosquito-borne illness first detected in Wisconsin in 2001. WNV is transmitted to birds and mammals by the bite of an infected mosquito.

Various government agencies have a role to play in helping reduce the risk of WNV in Wisconsin. To learn more about the disease, see the Division of Public Health's Web site on West Nile Virus [exit DNR]. The Division of Public Health and the DNR have a surveillance program for sick crows or birds, including a toll free hotline for reporting sick or dead birds at 800.433.1610. This hotline has been established as surveillance for wild bird morbidity and mortality appears to be the most sensitive early detection system for WNV.

Understandably, Wisconsin residents are looking to reduce mosquitoes populations on or near their property. However, it is important to note that even in areas where WNV has been found, very few mosquitoes (less than 1%) are infected with WNV and less than 1% of people bitten by a WNV-infected mosquito will become sick.

I have a wetland on or near my property. Will draining the wetland help reduce mosquitoes?

No. Healthly wetlands are home to native fish, insects and birds that eat mosquitoes and help keep mosquito populations in balance with predators. Furthermore, several species of mosquitoes are responsible for transmitting WNV. However, the primary species breed prolifically in the stagnant, organically rich, water commonly found in discarded tires, birdbaths and roof gutters. This species of mosquitoes does not prefer wetlands. The stagnant water created -- should a wetland be drained -- may actually produce more mosquitoes than the wetland did! Read more about the importance of wetlands and wetland predators in lowering mosquito populations in our fact sheet West Nile Virus and Wetlands, CE-PUB-453 [PDF 232KB].

Can I stock mosquito fish in my pond to help control mosquito populations?

No. Mosquito fish are non-native predator fish. All fish stockings in waters of the state, which include personal ponds, require a permit from DNR. In addition, stocking a non-native fish, requires an importation permit. Such a permit has never been granted for mosquito fish out of concern for protecting angling and related recreational opportunites and the potential for catastrophic consequences for a delicate food chain. Mosquito fish may eat or harm small or young native fish, young frogs and salamanders, and beneficial aquatic insects. In addition, they may out-compete native species for available food or habitat.

Can I apply chemicals on my lake/pond/river to control mosquitoes?

Chemical control methods can have significant environmental impacts and should be carefully considered before use. In fact, the application of chemicals on waters of the state requires a permit under Section NR 107 of the Wisconsin Administrative Code. Permits for chemical control of mosquitoes will be evaluated for effectiveness of the proposed treatment and monitoring plan, and small scale applications of mosquito control pesticides made by individuals or small groups will generally not be found to be effective. For more information, contact your DNR Aquatic Plant Management Specialist for your county.

What measures can I take to prevent mosquitoes on my property?

There are many simple steps you can take to reduce mosquitoes around your home. The Division of Public Health [exit DNR] maintains a Web site on WNV, which has a number of personal protective measures individuals can take to prevent mosquito bites.

Wisconsin has about 53 different mosquito species, but only one that is the main carrier of WNV. Culex pipiens, more commonly known as the "house mosquito" accounts for about 70 percent of the positive WNV samples. Homeowners can take many simple, effective ways to reduce this mosquito's breeding habitat on their property which do not require a permit such as properly disposing of old tires, cans and other containers which hold water. This is probably the single most effective mosquito control effort one can take to reduce exposure around the home.