Fall Cankerworm

Do you have caterpillars in your trees? Are the leaves eaten off of those trees and other shrubs?

The Hamilton Conservation Authority along with the City of Hamilton recently meet with the Ministry of Natural Resources Forest (MNRF) Health Unit too look at caterpillar outbreak areas in Dundas and Ancaster. Samples of the caterpillars found during the field visit have been sent to a lab for confirmation.Based on similar surveys conducted in Grimsby the MNRF representative indicated that the caterpillars seen in Dundas and Ancaster were likely the same as those confirmed in Grimsby - Fall Cankerworm.

This is a native leaf defoliating caterpillar. Their populations generally peak every 10-15 years and can cause large scale leaf defoliation. This year seems particularly bad. The populations of these caterpillars can peak for one to two years. After that native predators such as birds and small mammals along with diseases in the caterpillars cause the population to decline.

Wide scale spraying programs are not conducted for this native species. Hardwood trees can survive one to two years of defoliation. Once the caterpillars are done feeding by mid-June the trees will re-leaf.

What can you do?

  • Watering the affected trees, especially if it is dry, will help them through this stressful time.
  • In the fall homeowners can apply sticky bands, which are commonly used to protect trees against fall cankerworms. The MNRF recommend that  sticky bands are  applied in the fall when the adults emerge from the soil to crawl up the tree to lay their eggs. Banding should be done before the first frost. It’s important to put a barrier such as broad tape or tar paper on the trunk first so that the sticky compound (Tanglefoot™) doesn’t come into direct contract with the bark. Otherwise the Tanglefoot™ will soften or kill the bark.


Some links for more information on Fall Cankerworm: