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Fall Cankerworm

4 photo's from left to right first - Fall Cankerworm caterpillar on leaf caterpillar is black with white stripe, next photo FCW eggs on twig eggs look like round cylinders stacked almost in a hive formation, next photo FCW Female laying eggs on a twig, last photo Oak Leaves with young FCW the young fcw are very small and green in color hard to see against the leaves

Fall cankerworms are forest pests that attack deciduous trees and shrubs. These pests damage trees by causing defoliation that can lead to tree mortality. They feed on a variety of trees including ash, beech, elm, hickory, linden, maples and oak.  If you are unsure of what tree species you have on your property, these sites offer a guide:

Arbor Day Foundation

Virginia Department of Forestry 

Mature fall cankerworm caterpillars measure from 3/4 to over an inch in length and vary in color from green with yellow stripes to green with dark stripes or black with white stripes. Their bodies are smooth and lack hairs. As a member of the inchworm family, they can also be identified by its characteristic movement. The caterpillar movements can be identified by a series of loops and extensions of the body. Adult moths emerge usually after a hard freeze in fall. The very small, dull gray, wingless adult females climb up tree trunks and await the winged males in order to mate. Once the tiny cluster of eggs are laid, they over winter and then hatch in late April to early May. The young caterpillars feed voraciously on tender new spring leaves and by late June to early July, mature caterpillars descend to the ground on threads of silk. Once on the ground, the caterpillars burrow down into the soil, one to four inches, spin a silken cocoon, and then pupate. The pupae remain in the soil until fall and the cycle begins again.

Our field personnel conduct surveys for the fall cankerworm each year starting in December to early March. Surveying for the fall cankerworm involves the use of sticky band traps that are placed around the trunks of the trees. These traps ensnare adult females so that they can be counted to determine population densities. 

Historically, aerial suppression of fall cankerworm infestations have occurred primarily in the Cherry Hill and Bull Run Mountain areas where high populations of this insect pest have been encountered. An EPA-approved insecticide, Bacillus thuringiensis kurstaki is typically used in the aerial spray program when populations warrant treatment for fall cankerworm.

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