Aerial Spraying for Black Flies

June 27, 2024

The Pennsylvania Department of Environmental Protection (DEP) will conduct an aerial black fly suppression operation on the Delaware River from Trenton, NJ, to Slateford in Bucks and Northampton Counties at 8:30 a.m. on Friday, June 28, 2024.


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 (


Back to Pressroom landing page.