Kalamazoo MI - Fall webworms beginning to appear

Dave Smitley, MSU Entomologist reports that in the last two to three years, webworms have been abundant throughout southern Michigan in late summer. Silky tents made by webworm caterpillars are beginning to appear now on the branch tips of walnut, hickory, ash, elm, crabapples and other types of trees. The small yellowish-gray webworm caterpillars hide in the webs during the day. Some trees have actually been defoliated from having a tent on nearly every branch. But in most cases, each tree has three or four tents. They look bad, but cause little harm. Tree health is not affected until more than 50 percent of the foliage is consumed, and even then, the trees usually come back just fine the following spring. Pruning-out infested branches is the best strategy if you can reach them. Spraying the foliage around tents with B.t., Sevin, Orthene, or a pyrethroid insecticide will prevent further feeding injury, but the old tent will remain visible for several months. We have many natural parasites and pathogens of fall webworm that will eventually bring infestations under control. Outbreaks usually last two or three years.

To obtain more information about home Horticulture issues, call Linda Whitlock, Consumer Horticulture Coordinator at the Kalamazoo County MSU Extension Office at (269) 383-8815 or email her at whitlo13@msu.edu.

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