A pesticide spray program to combat an increase in fall cankerworms will begin in mid-to-late April, according to Fairfax County.

The fall cankerworm (Alsophilia pometaria), an insect that destroys trees in North America, is on the rise in the Lee and Mount Vernon Districts. County workers will spray the canopy of trees with Bacillus Thuringiensis (Bt). Once ingested, the worms will stop feeding and die within a week, according to a county announcement.

Urban foresters in the county's Forest Pest Management branch noticed a significant increase in the number of the worms during their annual survey.

The worm begins feeding on trees as a caterpillar in the early spring. According to the county, the caterpillars eat all of the leaves from a variety of trees. This may stress the plants and put them at risk, particularly in urban areas.

The population of fall cankerworm is monitored by urban foresters each year.

Fairfax County residents are encouraged to complete a four-question, online fall cankerworm report form that will assist urban foresters to determine areas where future monitoring may take place.

For more information on the fall cankerworm, visit the county's information page.