HARRISBURG, PA — State officials have begun seasonal treatments across Pennsylvania waterways to reduce black fly populations ahead of peak outdoor recreation months.
What This Means for You
- Black fly treatments are underway across 48 rivers and streams
- Program targets larvae to reduce nuisance insects during warmer months
- Residents may see low-flying helicopters and crews near waterways
The Pennsylvania Department of Environmental Protection has launched its annual Black Fly Suppression Program, covering more than 1,800 miles of rivers and streams statewide.
The effort focuses on reducing black fly populations, which can become a nuisance for residents and visitors during spring and summer outdoor activities.
How the Program Works
The program uses Bacillus thuringiensis israelensis, or Bti — a naturally occurring bacterium that targets black fly larvae in flowing water.
Black flies reproduce in streams and rivers, and treating the larval stage helps reduce the number of adult insects later in the season.
“Black flies can make that difficult,” said DEP Secretary Jessica Shirley, referring to outdoor recreation during warmer months.
Application Methods
DEP applies treatments using both helicopters and ground crews, focusing only on waterways where larvae are present.
Officials said the bacterium breaks down quickly and is not harmful to fish, birds, people, or other insects.
Applications are conducted throughout the spring and early summer, with timing based on weather and water conditions.
What Residents May Notice
Residents may observe helicopters flying at low altitudes over rivers and streams or crews working from bridges and along waterways.
Local emergency management officials are notified before treatments begin.
Next Steps
The treatment schedule may change depending on environmental conditions.
Updated spray notifications and program details are available at https://www.pa.gov/agencies/dep/programs-and-services/bureau-of-labs/vector-management.
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