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Environment & Climate Change

Spongy moths are back! Here's what to look for

Female spongy moths laying eggs on a tree in Vermont, 2021. The eggs overwinter on the tree and hatch the following spring.
Jane Lindholm/VPR
Female spongy moths laying eggs on a tree in Vermont, 2021. The eggs overwinter on the tree and hatch the following spring.

The spongy moths are back and once again chewing through leaves across Michigan. Experts say you can expect to see the emergence of the caterpillars throughout April and early May.

The telltale signs of the spongy moth are the munched-on leaves.

The black caterpillars hatch from egg masses together, so there are usually huge groups of them. They prefer oak trees — but may gobble through anything.

The Department of Natural Resources described them as a nuisance.

"They start chewing through you know, lots and lots of leaves, so you would actually be able to sort of almost hear them munching outside," Foreman said. "And you’d also be, if you’re in an area where they are, be pelted by little drops of what we call frass or droppings."

Foreman says that Michiganders should look for the sponge-like egg masses on trees, scrape them off and then place them in soapy water to avoid the moths eating tree leaves.

"It’s rare that trees will actually die from spongy moth defoliation. But such defoliation can exacerbate a tree that’s in poor health and make it decline more rapidly," she said.

If the caterpillars have already hatched, Foreman also suggests spraying tree trunks and branches with soapy water.

The invasive species official name is Lymantria dispar. It was given a new common name in March because it's former name used a derogatory word for the Romani people.

It is now called the spongy moth because of its sponge-like egg masses.

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