PUBLIC NOTICE: Maryland Agencies to Treat Potomac River for Black Fly Control on July 16

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ANNAPOLIS, MD (July 15, 2026) ~ Annapolis, MD - The Maryland Department of Agriculture, in collaboration with the Department of Natural Resources, has announced plans to control black fly populations in the Potomac River near Harpers Ferry, West Virginia. The treatment is set to take place on Thursday, July 16, 2026 between 9:00 a.m. and 11:00 a.m. ET.

A specialized gray Bell 206 Long Ranger helicopter with blue and red stripes will be utilized to apply a Bacillus thuringiensis israelensis (Bti)-based larvicide throughout the targeted area. The helicopter's tail number is N653HA. Bti is a naturally-occurring bacterial insecticide that poses no harm to humans or the environment. It specifically targets midges, black flies, mosquito larvae, and a few other species of aquatic insects.

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While the treatment may temporarily discolor the water, it is completely harmless and will dissipate on its own. There will be no impact on drinking water supplies or any other aquatic organisms outside of the targeted insect groups such as fish and crabs.

The Black Fly Program was established in 2016 after receiving numerous complaints from residents in Washington County. For more information about the program and Bti, interested individuals can visit the Maryland Department of Agriculture's Black Fly Program website.

This targeted treatment aims to alleviate concerns and improve the overall quality of life for residents in the affected area. The Maryland Department of Agriculture remains committed to finding safe and effective solutions for managing black fly populations while also protecting the environment.

Filed Under: Government, State

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