Three waterways in Berks County are targeted by the Pennsylvania Department of Environmental Protection for spraying to reduce those annoying black flies before the peak of the outdoor recreation season.
The Manatawny Creek, Schuylkill River and Tulpehocken Creek are listed among the 48 rivers and streams across more than 1,800 miles of waterways in the state for treatment, officials announced.
“As the weather turns warmer, Pennsylvanians will be spending more time outdoors, and black flies can make that difficult,” DEP Secretary Jessica Shirley said in the DEP announcement. “This program helps reduce those nuisance populations so families can fully enjoy Pennsylvania’s rivers, streams, and outdoor spaces.”
Black flies, often referred to as gnats, are much smaller than the common house fly and closer to the size of a fruit fly, officials said. Black flies do not enter buildings or covered areas in significant numbers. The gnats have the annoying habit of swarming around the heads of people outside on warm days, disrupting outdoor activities. Swatting them is useless as they are quick to return, often flying into people’s eyes and sometimes delivering a painful and itchy bite, officials said.
The program — now in its 41st year — uses Bacillus thuringiensis israelensis (Bti), a naturally occurring soil bacterium that targets black fly larvae in flowing water, officials said. The treatment is applied by helicopter and ground crews in river and stream sections where black fly larvae are present.
Officials said Bti breaks down quickly in the environment and is not harmful to fish, birds, people or other insects.
The treatments focus exclusively on the larval stage of the black fly life cycle and are not conducted on land.
DEP conducts aerial and ground-based applications throughout the spring and early summer, with timing and frequency dependent on weather and stream conditions.
The department notifies county and local emergency management officials before treatments are conducted.
Residents may see helicopters flying low over waterways or crews applying treatments from bridges or in streams.
Spray notifications can be found on DEP’s Vector Management Program website. Treatments are subject to weather and water conditions.
Visit the DEP website for more information about the program. Residents with concerns about black fly activity can report them directly to DEP through the Black Fly Suppression Website.