Cankerworm & Gypsy Moth Fall 2017 Update

From: Mississauga Parks & Forestry

What’s the problem?

Fall cankerworms, also called loopers or inchworms, have been found in areas throughout the City in varying degrees of infestation.

As part of their natural cycle, these yellow, green or brown caterpillars feed on the leaves of hardwood trees including maple, oak, cherry and apple.

Tell me about cankerworms:

Cankerworm populations go through 10-year cycles which often peak for two to three years. Many will be eaten by birds and other predators. The remaining cankerworms will feed until mid-June and then will crawl into the ground to pupate. In October, they will begin to re-emerge as moths.

Will they damage my trees?

The defoliation of trees by insects occurs naturally and will not kill healthy trees. These trees will grow new leaves by the end of June after the caterpillars have gone underground. Trees already in marginal health may eventually decline should repeated defoliation occur.

What can be done?

There are several options:One is to do nothing except wait for the caterpillars to go underground and for the trees to grow new leaves.

In the fall, individual trees can also be protected by placing a plastic band with a sticky substance such as Tanglefoot around the truck. This prevents the wingless female moths from climbing the trunk to lay eggs.

Ensure that your trees get enough water through the summer and fall.

Do not use a high nitrogen fertilizer on a lawn near a defoliated tree. It causes the tree to use up its starch reserves. Wait until fall and use a complete granular fertilizer.