Gypsy Moth Feeding Season Nearing Its End

Press release from Michigan DNR:

Gypsy moth caterpillars have been busy this spring in areas across Michigan. As these now large caterpillars near the pupal or cocoon stage, tree defoliation is at its peak.

In highly infested areas, the caterpillars' munching is audible, and round pellets of frass, or waste, rain down throughout the day and night. Oaks, aspens, willows and other host trees may be nearly leafless, or defoliated, by their feeding.

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These suppression efforts have continued to keep gypsy moth populations largely in check since the 1990s, naturalizing gypsy moth infestations into Michigan's forests. Today, gypsy moth outbreaks are cyclical, peaking approximately every seven to 10 years. In these years, the virus and the fungal disease are spread more easily through dense populations, eventually causing a crash.

What to do right now

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The window for effective pesticide application has passed, but if caterpillars remain a nuisance on your property, there are a few inexpensive but effective things you can do to protect individual trees.

• Make a tree trunk trap: Cut a band of burlap 18 inches wide and long enough to go around the tree trunk and overlap a bit. Tie a string around the center of the band to make a two-layered skirt around the trunk. When caterpillars climb trees daily to feed, they will get caught in the band. Scrape them into a bucket of soapy water to kill them.
• Use a safe and easy spray: Soap and water mixed in a garden sprayer can be applied to caterpillars climbing on trunks, decks or siding.
• Gear up: It's best to wear gloves when coming into contact with caterpillars, as their hairs can cause a slight allergic reaction in some people.
• For additional helpful tips, visit Michigan State University's Integrated Pest Management gypsy moth webpage at CANR.MSU.edu.

What's next?

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• Look on trees, buildings, outdoor furniture and playsets - anything that's outside.
• Use a scraper or hard plastic card to scrape egg masses into a container of soapy water.
• Let them soak overnight, then bag and dispose of them.
• Alternately, egg masses can be placed in a fire and burned.
• Note that just scraping them onto the ground will not kill the eggs, and egg masses will still hatch next spring.
• It's important to check for and remove egg masses from cars, equipment and anything that has been outdoors before you pack up for your travels.
• Leave firewood at home - it's a common source for spreading gypsy moth.

To find out more about invasive gypsy moth life stages, identification and management, visit Michigan.gov/Invasives.

Michigan's Invasive Species Program is cooperatively implemented by the Department of Environment, Great Lakes, and Energy, the Department of Natural Resources and the Department of Agriculture and Rural Development.

This press release was produced by the Michigan DNR. The views expressed here are the author’s own.