What’s That in the Tree? Fall Webworm

August turns up all kinds of pests and disease in the garden. You may be noticing large webs across the terminal branches of your trees now, similar to stretched pantyhose. Look closely and you will see small caterpillars inside, each marked with parallel rows of black spots on the back. The fall webworm (Hyphantria cunea) is very noticeable now but at this stage, the caterpillars stay in the web and feed inside on the leaves. The web is unsightly but their feeding will not kill the tree. However, this would be a good time to cut the branches and bag the webs, caterpillars and all. Close up the bags tightly and dispose of in the trash. Later, after the last molt, they leave the web and crawl all over the tree. Then they spin cocoons, pupate, and emerge as white moths. If you are not able to bag the web don’t despair, there are many natural enemies of the fall webworm. Another tactic is to spray the first generation in the spring with horticultural oil, Bt (Bacillus thuringiensis), or insecticidal soap before they create the web. Don’t try to burn them out though, it is too dangerous to the tree. For more information on plant pests and diseases, check out the Plant Pests and Diseases tab on pegplant.com.

3 responses to “What’s That in the Tree? Fall Webworm

  1. Thanks for posting this. We’ve been seeing a lot of it in Frederick and Washington counties in Maryland. Along RT. 40 it appears to be concentrated on walnut trees. Seems to be much more noticeable this year – I wonder is this is another result of the “strange” weather we’ve been having all year?

    • Thank you for your comments. I don’t know if it is related to strange weather, could be a question for an entomologist

  2. Yuck! Fortunately, they are rare here. I have not dealt with one directly since I was a kid.

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