Aerial Fall Cankerworm Spraying Begins in April

April 2, 2014

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

Aerial Spraying Program to Begin in April

Fairfax County urban foresters will begin aerial spraying to suppress fall cankerworm caterpillars approximately the third week in April.

Experienced helicopter pilots will spray Bacillus thuringiensis,a naturally occurring insecticide, in infested areas in the Lee, Mason and Mount Vernon districts. A detailed map showing these treatment areas is available at public library branches, county government centers located in the Lee, Mason and Mount Vernon districts, and online. Treatment areas are chosen through an annual county survey of the fall cankerworm population. This year the county will treat approximately 2,200 acres.

Because weather conditions are unpredictable, county officials do not know the exact days when spraying will be conducted. Once spraying begins, it may take ten days or more to complete, depending on the weather. Typically, spraying is done in the early morning and at dusk. However, it may continue all day if weather conditions permit.

The county will use a naturally occurring bacterium, Bacillus thuringiensis (Bt), as an insecticide. Extensive research has shown that Bt is not harmful to people, pets, plants or beneficial insects such as honeybees. The spray will not harm painted surfaces, and residues can be removed with soap and water.

Fall cankerworm caterpillars can kill trees by defoliating them. The caterpillars feed on many different types of trees but especially on native hardwoods, such as oak. Because the population level will be high enough to defoliate trees, the fall cankerworm must be suppressed with an insecticide.  

There will be a ‘live’ Ask Fairfaix! chat about fall cankerworms and the 2014 spray program on Wednesday, April 9 at 2 p.m. Joan Allen of the Urban Forest Management Division, will discuss the tree damage that fall cankerworms can cause if left untreated and what the county is doing to address the problem. Submit your questions online now.

For more information about the fall cankerworm, visit or call the Forest Pest Program at 703-324-5304, TTY 711.


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 Forest Pest Division at 703-324-5304, TTY 711.


Contact Fairfax County: Phone, Email or Twitter | Main Address: 12000 Government Center Parkway, Fairfax, VA 22035
Technical Questions: Web Administrator

ADA Accessibility | Website Accessibility
Awards | FOIA | Mobile | Using this Site | Web Disclaimer & Privacy Policy | Get Adobe Reader
Official site of the County of Fairfax, Virginia, © Copyright 2015

Website Feedback Website Feedback    Globe with various flags representing Web site language translations   Language Translations

Return to Graphic Version