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PADEP begins black fly suppression on both sides of Delaware River


The Pennsylvania Department of Environmental Protection (DEP) began its 2020 Black Fly Suppression Program April 23. The program involves aerial and backpack spraying on roughly 1,700 stream miles in 35 counties of the commonwealth.

Pennsylvania DEP wil sparay both sides of the river in Bucks and Hunterdon counties.

“As warmer weather returns, black flies are a pest that can inundate folks seeking outdoor recreation, especially around rivers and streams,” said DEP Secretary Patrick McDonnell. “Using environmentally compatible methods, this annual initiative reduces this nuisance so that Pennsylvanians and visitors can fully enjoy our natural resources.”

This year, 48 rivers and streams spanning more than 1,700 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 these conditions lower the effectiveness of the treatment as well as significantly increase the cost of the control operations.

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.

Prior to any spraying activity, DEP notifies county and local emergency management officials.

The Pennsylvania DEP is treating areas that cover the entire Hunterdon County border, as a result of financial support from the New Jersey Department of Environmental Protection (NJDEP), Freeholder John E. Lanza, the Hunterdon Board’s Parks liaison, reported.

“The freeholders and our residents are most appreciative that the NJDEP has stepped up and provided to the PADEP the state’s share for the cost of this important public health program that suppresses black flies in the area, after not doing so last year,” Lanza said.

Last July, when the PADEP notified Hunterdon County that spraying along the New Jersey portion of theDelaware River was suspended because New Jersey was not funding its share of the costs, Hunterdon County’s Freeholders provided funding for one spraying along the Hunterdon side of the river in August.

Lanza stated, “Black flies are detrimental to residents, businesses and tourism in the County. The Freeholders believe the black fly suppression along the Delaware River is so important to the quality of life for our residents that county funding was put forward for the program in 2019.