The silky caterpillar tree

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

On Monday, May 10, MSU Extension educator Mike Staton sent me the first picture of a mass of caterpillars on a split-rail fence post and asked what they were. The picture was taken in Allegan County, Michigan. My email response to photo 1 was:

“Hi Mike,
I will need some more information to indentify these caterpillars. They look like Euonymus webworm. If so, there should be a defoliated and silk-covered spindle tree (Euonymus europaeus) nearby. Am I right?

The tree may be entirely stripped already. If so, then just wait until next year and be prepared to spray earlier. Any pyrethroid insecticide spray will work well. They have one generation per year. The caterpillars will be pupating soon. Small white moths with black spots will emerge in a few weeks. The moths fold their wings roof-like over their back.”

Mike then sent me photo 2 of the “silky caterpillar tree.” For once, I believe I nailed it. What do you think?

Photo 1. Mass of caterpillars on split-rail
fence post.

silky caterpillar tree
Photo 2. The silky caterpillar tree.

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