Maryland state officials have announced plans to chemically treat a designated stretch of the Potomac River near Harpers Ferry, West Virginia in an effort to bring black fly populations under control.
The Maryland Department of Agriculture, working in coordination with the Department of Natural Resources, is scheduled to carry out the treatment on Thursday, July 16, 2026. The operation is expected to run from 9:00 a.m. to 11:00 a.m.
The targeted treatment is aimed at reducing the number of black flies in the area around the Harpers Ferry section of the river.
