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Aerial Spraying for Black Flies

July 09, 2024

WHO: Pennsylvania Department of Environmental Protection


WHAT: Aerial Spraying for Black Flies


WHERE: Delaware River


WHEN: Wednesday, July 10, 2024

The Pennsylvania Department of Environmental Protection (DEP) will conduct an aerial blackfly suppression operation on the Delaware River from Slateford in Northampton County downriver to the area near Trenton, NJ/Yardley, PA, in Bucks County. This operation will begin at approximately 8:00 AM at Braden Air Park tomorrow, July 10th.

The helicopter used for this operation will be a light grey Bell 206L3 with red and blue stripes and tail number N660HA. It is operated by Helicopter Applicators of Gettysburg, PA. DEP personnel will be on site at all landing zones to manage the operation.

Vectobac 12AS is B.t.i. product manufactured by Valent Biosciences. The B.t.i. material is a naturally occurring bacteria (Bacillus thuringiensis israelensis) that kills the immature (larval) form of the black fly when they feed on it in the waterways. It is a bacterial larvicide, not a chemical, and is the only product used in Pennsylvania's waterways for black fly suppression. B.t.i. is not toxic to fish or other aquatic macroinvertebrates found in the treated waterways, degrading quickly in the environment.


Black flies, also known as biting gnats, are considered a pest that can inundate people seeking outdoor recreation in the warmer months, especially around rivers and streams. For more information on the program, please visit the Black Fly Program website: Black Fly (