DEP Begins Helicopter Spraying To Control Black Flies

The Department of Environmental Protection Monday said it has begun aerial spraying on more than 1,600 stream miles in 36 Pennsylvania counties to control black flies, also referred to as gnats.

The first aerial spraying took place on April 27 along the Schuylkill River. Other waterways will be treated as stream flows and weather conditions allow.

“Black flies are a nuisance, especially when Pennsylvanians are trying to enjoy the outdoors and our many streams and rivers,” Acting DEP Secretary John Quigley said. “This annual initiative reduces the nuisance so that all of us can get out there and enjoy Pennsylvania’s waterways.”

This year, 49 rivers and streams spanning more than 1,600 miles will be monitored and treated as needed. Spraying activities will be performed both by helicopter and ground crews. The frequency will depend upon weather and biological conditions. Treatments cannot occur during periods of heavy rain or when water levels are high as high water conditions lower the effectiveness of the treatment.

DEP uses Bti, a naturally occurring bacterium, to treat the larval stage of four specific human pest black fly species. This bacterium degrades quickly in the environment and does not harm the aquatic ecosystem, birds, or other insects.

DEP notifies county and local emergency management officials prior to any spraying activity. Helicopters seen flying over waterways and ground crews using backpack sprayers off bridges are conducting control operations on behalf of DEP’s black fly program.

Anyone concerned at the sight of a helicopter or ground personnel is encouraged to call their county emergency management office to verify that a black fly treatment is taking place in their area on that day.

A list of the counties in which spraying will occur is available online.

For more information, visit DEP’s Black Fly Program webpage.