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Cass County Extension

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Protecting Trees from Cankerworms

Cankerworms have a very good appetite when it comes to eating tree leaves. They can be controlled by spraying in the spring, but some of the trees are so large that it's almost impossible for the homeowner to spray with small hand operated equipment. If spraying is not practical, then consider the inexpensive "banding" method of control.

This control should be applied by the middle of September. The female cankerworm is wingless and thus must crawl up the tree trunk to lay their eggs on the branches and twigs. By placing a sticky band around the trunk, she cannot get up the tree. The result, no cankerworm to feed on your trees next spring. The fall cankerworm females lay their eggs in late fall and the spring cankerworms in early spring. All bands should be checked in late March or early April and additional sticky material (tanglefoot) applied if necessary.

The sticky non-drying compound commonly called "tanglefoot" is applied in a continuous band around the tree trunk. A band 3 to 4 inches wide, 1/16 inch thick and 5 to 6 feet from the ground level will do the job. Direct application of tanglefoot to the bark is permissible, however, the outer surface of the bark may be smoothed out with a wood chisel or steel brush. Avoid damaging the live bark underneath. Apply a continuous band of tanglefoot to this smooth surface of scraped bark. A putty knife or old paint will work satisfactorily to apply the paste. There is also an aerosol tanglefoot that is sprayed on tree trunks. Tanglefoot contains no poisonous chemicals. The active ingredients are castor oil, natural gum resins and vegetable wax. Tanglefoot should not be applied to thin barked trees such as apples, flowering crabs or mountain ash trees.

Todd Weinmann, Extension Horticulturist & Master Gardener Coordinator
Phone: (701) 241-5707

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