Public Notice: Maryland Agencies to Treat Potomac River for Black Fly Control on September 24

ANNAPOLIS, MD – The Maryland Department of Agriculture—in partnership with the Department of Natural Resources—will treat a targeted area of the Potomac River in Washington County to control black fly populations in the area. Treatment is scheduled for Tuesday, September 24, starting at 8:30 a.m., weather permitting.

The department will apply a Bacillus thuringiensis israelensis (Bti)-based larvicide via helicopter (Bell 206 LongRanger, tail number: N651HA, color: black). Bti is a naturally occurring bacteria found in soils worldwide. It is a bacterial insecticide, not a chemical, and is only harmful to a very limited variety of organisms including midge, black fly, and mosquito larvae, and a few other aquatic Dipteran (flies) insects.

The treatment may cause temporary discoloration of the water, but it is completely nontoxic and is not harmful to humans, fish, crabs, or other aquatic invertebrates. More Information​.

For more information on the department’s black fly program, visit our website.

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