Fall Cankerworm on the Rise

Feb. 26, 2014

Irene Haske
Urban Forest Management Division
703-324-5821 or 703-324-5500, TTY 711
Fax: 703-803-5955

Fall Cankerworm on the Rise in Fairfax County

Urban Foresters in the Forest Pest Management Branch observed a significant increase in the number of fall cankerworms (Alsophilia pometaria) during their annual survey. The fall cankerworm may defoliate multiple species of trees and has been found in defoliating levels in areas of the Mason, Mount Vernon and Lee districts.

Contrary to its name, the fall cankerworm is destructive only when the caterpillars are active in the early spring.  In normal years, the fall cankerworm causes little to no damage. However, Fairfax County is experiencing a dramatic increase in population levels in residential and forested areas. Defoliation will stress the trees and if the cankerworms are left unchecked, may put hundreds of acres of trees in Fairfax County at risk.  

Due to the increased population levels of the fall cankerworm found in the Mason, Mount Vernon and Lee districts, a voluntary spray program of 2,200 acres in residential areas is planned for late April. Using helicopters and experienced pilots, Fairfax County will spray selected areas of high fall cankerworm populations with Bacillus thuringiensis (Bt). Bt is similar to a naturally occurring bacteria that is often used on organic gardens to combat other caterpillars. After spraying, the fall cankerworm will die within a few days.

For more information about the fall cankerworm, visit www.fairfaxcounty.gov/dpwes/environmental/fallcankerworm.


Fairfax County is committed to nondiscrimination on the basis of disability in all county programs, services and activities. To request this information in an alternate format, or for reasonable ADA accommodations, call the Solid Waste Management Program at 703-324-5500, TTY 711.


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