HARRISBURG — The Department of Environmental Protection will begin both aerial and backpack spraying on roughly 1,700 stream miles in 35 Pennsylvania counties to control black flies.

The Clarion River in Elk County is one of the areas to be sprayed.

The first aerial spraying, dependent on weather and stream flow, could take place on the Schuylkill River and several of its tributaries within the week. Other waterways will be treated as stream levels drop and weather conditions allow.

“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 can enjoy our natural resources.”