Black Fly Suppression Program Re-instated By NJDEP Benefits Hunterdon and Warren Residents


Through a concerted lobbying effort by Hunterdon and Warren County state and county officials, the NJDEP has rejoined the cost sharing partnership with Pennsylvania’s DEP to once again conduct a non-toxic program to suppress Buffalo gnats, more commonly known as black flies, along the Delaware River.

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John King, the Deputy Director of the Hunterdon Freeholder Board who spearheaded the effort, announced at the July 5, 2017 Board meeting, “The residents and visitors in Warren and Hunterdon Counties suffer the most if black fly populations are allowed to go unchecked. The renewed program comes as a great relief to the many residents who wish to enjoy their backyards or the county’s parks, trails, and other outdoor recreational activities.” According to King, “Black flies are not affected by repellents and are extremely painful biters that can cause severe allergic reactions. Livestock, pets, farms, wineries, golf courses, outdoor businesses, events, parks, hiking, gardening, in short, any outdoor commercial or private enterprise is subjected to the effects of these pests.”


New Jersey stopped allocating funding to pay for its share of the cost of the program in the early 2000’s. In 2015, Pennsylvania completely halted black fly treatment on the Delaware due to lack of funding. King added, “We recognized this program as a priority quality of life issue. Our legislative delegation, including Senators Kip Bateman and Mike Doherty and Assemblyman Eric Peterson, along with Hunterdon County’s Health Director Tadhgh Rainery and the Warren County Freeholders, made this a team effort in persuading the state to reinstitute the cost sharing with Pennsylvania for black fly suppression.


There is no cost to Hunterdon County.” The spraying by helicopter of a safe, non-toxic pesticide, takes place on both sides of the Delaware River, including Mercer, Hunterdon and Warren Counties on the New Jersey side. New Jersey’s share of the cost of the program is about $200,000. The first new spraying took place on July 5, 2017. According to the Pennsylvania DEP, the material used 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. This application of B.t.i. is not toxic to fish or other aquatic macroinvertebrates found in the treated waterways. More information can be found at