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Michigan DNR warns about invasive moth caterpillars

two spongy moths on a tree
John H. Ghent
USDA Forest Service

Michigan's Invasive Species Program within the state Department of Natural Resources is warning residents to look out for a type of caterpillar that could threaten native plant species in the state.

Spongy moth caterpillars are expected to start hatching soon in Michigan’s Lower Peninsula.

The caterpillars are hairy, with a yellow and black head and 5 pairs of blue spots, followed by 6 pairs of red spots.

The insects can eat up all the leaves on trees in a process called defoliation, making plants susceptible to diseases and other pests.

Deborah McCullough is a professor of forest entomology at Michigan State University. She says residents concerned about infestations on their property should watch out for tan, fuzzy egg masses of unhatched moths.

"Lots of egg masses means you’re going to have lots of caterpillars," McCullough said. "You may need to take some kind of management for the trees around your house.”

That could include using the insecticide Btk.

“If you’re going to spray a tree, you spray it before the caterpillars get very large. They’re more susceptible when they’re small, and you’re going to prevent a lot of that defoliation," she said.

The caterpillar eggs can also be scraped into a bucket of soapy water to prevent them from hatching.

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