The move comes after tests showed that adult mosquitos in samples taken by the Department of Environmental Protection carried the West Nile virus.
Certain mosquito species carry the West Nile, which if it is transmitted to humans, can cause encephalitis, a swelling of the brain. That can lead to paralysis and other life-threatening problems.
There has been one confirmed human case of West Nile virus this year.
Crews from the Pennsylvania DEP will spray in Conshohocken, in an area bounded by North Lane, Hallowell Street, Elm Street and Interstate 476. Montgomery County health department teams will spray areas of Plymouth and Whitemarsh Townships between North Lane, Butler and Germantown Pikes, and Joshua Road.
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