Environment & Climate Change

Gypsy moth boom unlikely to kill many trees, but very likely to gross you out

Michigan Public | By Stateside Staff

Published June 17, 2019 at 4:08 PM EDT

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After three years of drought, some Michigan trees may not have the water they need to fight off insect pests like gypsy moths, Wieferich says. Above, a pair of a male (left) and female (right) gypsy moth.

John H. Ghent, USDA Forest Service, Bugwood.org

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In the 1990s, state officials released a fungus that helps control gypsy moth outbreaks. But Wieferich says that those spores need rain to be released, which means recent drought has reduced its effectiveness. Above, a gypsy moth caterpillar.

Michigan Department of Natural Resources

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Wieferich predicts that Ionia, Barrie, and Washtenaw Counties will experience “heavier defoliation” this year. Although defoliation generally doesn't kill healthy trees, those suffering from disease, old age, or other kinds of damage could be at risk.";s:

USDA Forest Service

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Gypsy moths lay their eggs on everything from trees, to telephone poles, to cars, to concrete slabs, Wieferich says. If you come across gypsy moth egg masses, pictured above, scraping them off can help curb an outbreak.

Milan Zubrik, Forest Research Institute-Slovakia, Bugwood.org

It’s going to be a big summer for the invasive gypsy moth. Three consecutive droughts have created ideal conditions for gypsy moth caterpillars to multiply.

Over the next few weeks, those caterpillars will be doing what they do best: feasting on the leaves of hardwood trees. The Michigan Department of Natural Resources says that could lead to heavy defoliation in outbreak areas.

James Wieferich is forest health specialist with the Michigan Department of Natural Resources.

Gypsy moths did major damage to Michigan trees in the 1980s and 1990s until the state started treating trees with a fungus that killed gypsy moth caterpillars. The fungus has a harder time releasing spores in dry weather, which helped contribute to this year's gypsy moth boom.

Wieferich says that while the increase in gypsy moth caterpillars may lead to unsightly leaf loss, it's unlikely to kill healthy trees these days. They do, however, create a big headache for residents living in areas of an outbreak. Hungry caterpillars release frass — or droppings — onto humans and cars from the trees above, and crushed caterpillars can stain driveways.

Check out the slide show above to find out more about these pests, and what to do if you live in an area with a gypsy moth outbreak.

This post was written by Stateside production assistant Isabella Isaacs-Thomas.

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