Question: Pest Alert! What are Cankerworms?

Answer: In spring 2012, a cankerworm outbreak occurred in many North Carolina cities. Spring cankerworm (Paleacrita vernata) and fall cankerworm (Alsophila pometaria) are different species but have very similar characteristics. They both feed in the spring on the leaves of many different deciduous trees. Hosts include oak, elm, maple, and others. Willow oak was the tree species most heavily infested in Raleigh, Charlotte, Durham, and other cities. Cankerworms can defoliate trees. A year or two of defoliation may not affect the long-term health of large trees but it causes concern among the public.

Spring and fall cankerworm eggs hatch in early spring and caterpillars feed for five to six weeks. They spend the rest of the summer pupating in mulch and leaf litter beneath trees. In October or November, fall cankerworm adults emerge from pupae and climb up the trunk of nearby trees. They lay clusters of eggs in twigs then die. Spring cankerworms climb up trees in spring to lay eggs.

The female moths of both species climb because they do not have wings. We can use sticky bands to capture them on the way up and prevent them from laying eggs. Sticky bands are made by wrapping duct tape or similar product around trees and covering it with sticky Tangle Foot. Though data is sparse for cankerworm control, these bands have reduced defoliation by other caterpillars such as gypsy moth and winter moth that also have climbing adults or larvae.

Bands need to be installed before fall cankerworms begin climbing up trees in October or November (now! See a video http://youtu.be/DrSniXUaAjE). Steve Frank is monitoring them in Raleigh and will send alerts via Twitter (@OrnaPests) and his website (ecoIPM.com). They are conducting research on cankerworm biology and management. You can see their progress at http://ecoipm.com/research/cankerworm-project/.

Steve Frank is Assistant Professor and Extension Specialist in the Department of Entomology at North Carolina State University. You can receive pest alerts and updates by following @OrnaPests on Twitter and checking his blog ecoipm.com.

This article was written by Steve Frank, NCSU and submitted by Della King, NCCE-Sampson County.

Reminder: A growing program this year is the “Sampson County Friends of Horticulture.” This program offers monthly “How To” Horticultural Seminars. Please call (910) 592-7161 for more information. Please call the Sampson County Cooperative Extension Center at (910) 592-7161 with your horticultural questions and to register for any upcoming events. Be sure to check out the Ask An Expert Widget at sampson.ces.ncsu.edu for any questions you may have.