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Thursday, April 25, 2024

Westerly plans to bio-bomb mosquitos on Monday

Helicopters will spread bacteria that kills mosquito larvae on Chapman Pond

The Rhode Island Department of Environmental Management (DEM) is announcing that the Town of Westerly will conduct an aerial application of mosquito larvicide across 500 acres of Chapman Swamp and nearby swamplands by helicopter on Monday, April 29, weather permitting. 

The application, which consists of pellets that kill mosquito larvae being dropped by a helicopter, will take place between 8 AM and 3 PM. In the event of inclement weather, a rain date will occur on Tuesday, April 30, weather permitting.

Bti, a naturally occurring bacterium applied in granular form to control mosquito breeding in swamps and other breeding habitats, is the treatment that will be applied. It is applied to standing water where developing larvae are found. 

It is an environmentally friendly product whose toxins specifically affect the larvae of only mosquitoes, black flies, and fungus gnats and do not pose a risk to human health. 

Larviciding is recommended as part of the state's action plan to control West Nile Virus and Eastern Equine Encephalitis (EEE) and considered an effective strategy to reduce mosquito populations and related disease risk.

In most communities, the state recommends applying larvicide by hand to roadside catch basins. In the Chapman Swamp area of Westerly, however, aerial application is recommended given the area’s remote location and large footprint. Mosquitoes carrying the EEE virus were found in Chapman Swamp in 1996, 2003, 2019, 2020, 2022. 

Since 1997, the Town has applied Bti annually to help control mosquito breeding. Additional dates for treatment may be scheduled by the Town; the targeted areas include portions of Chapman Swamp and swampland near Hespar Drive.

For additional mosquito prevention tips, videos, and local data from the Rhode Island Department of Health, visit

For more information on DEM programs and initiatives, visit Follow DEM on Facebook, Twitter (@RhodeIslandDEM), or Instagram (@rhodeisland.dem) for timely updates.