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What to do about eastern tent caterpillars

If you have a flowering fruit tree, like apple, chokecherry, crabapple, plum, and cherry, check it for silken tents in the forks of the branches. This is the work of eastern tent caterpillars.

These caterpillars are bluish black with a yellow and white stripe running down the top of their body. They are mostly smooth but do have hairs sticking out along the sides of their bodies. They are two inches long when fully grown.
Eastern tent caterpillars on a small tree.
Photo: Jeff Hahn, UMN Extension

Are they harmful?

Healthy, well-established trees can tolerate eastern tent caterpillar feeding. Their feeding, as well as the presence of their webs, is usually a cosmetic problem, affecting just the trees’ appearance.

However, young trees, as well as unhealthy, stressed trees, are more susceptible to feeding damage and may need to be protected.

Can I manage these caterpillars without a chemical?

A great method to deal with eastern tent caterpillars without pesticides is to wait until they have retreated into their tents at the end of the day or when it is raining. Then pull out the webbing, along with the caterpillars. Then dispose of them by burying or bagging them (only burn them if it is permitted where you live).

You can also ignore the caterpillars and do nothing. The goal is to protect your trees; if spraying does not help, then it is best just to leave them alone. This is a good option if the trees are large and healthy and are not at risk and/or the caterpillars are large (close to two inches long) and finishing their feeding.

What are the best pesticides to use?

If your tree is susceptible to damage, and spraying can help protect it (i.e. the caterpillars one inch or smaller), then consider an insecticide. There are different residual insecticides that are effective against caterpillars. Consider using a product that has a low impact on the environment, such as Bacillus thuringiensis, spinosad, or insecticidal soap.

Bacillus thuringiensis is a particularly good product if the tree is flowering since it will not harm visiting honey bees and other pollinators. If you use insecticidal soap, the product needs to directly contact the insects. There is no residual activity so you may need to repeat the treatment. Both of these products are most effective against small caterpillars.

For information about eastern tent caterpillars and other caterpillars, see Caterpillars on ornamental plants.

Author:  Jeffrey Hahn, Extension Entomologist
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