Invasive Species Alert: Michigan’s Spongy Moth Problem Explained

Michigan, meet the spongy moth—formerly the gypsy moth, until 2021 when scientists decided it was time for a rebrand. The Entomological Society of America (ESA) swapped out the old name (goodbye offensive baggage) for something more French-inspired, "spongieuse," because apparently nothing says "tree destroying menace" like a sea sponge?

But let's not get distracted by the name. Whether you call it spongy, gypsy, or "that disgusting hairy caterpillar with spots," this pest has been tormenting Michigan since the 1950s.

How Spongy Moths Damage Michigan Trees

Debu Durlav

Remember the 2021 outbreak when oaks looked like a casting call for Michigan's Charlie Brown Christmas tree? Yeah, that was them, chewing through leaves like it was their last meal.

What happened? Well, the spongy moth caterpillars hatch in April from egg masses that look like fuzzy sponges, then spend the spring and early summer shredding oaks, aspens, and basically anything leafy.

What Is the Spongy Moth?

varbenov

The caterpillars are hairy, with a yellow and black head, with five blue spots, and six red ones. Male moths' wings are brown with wavy patterns and grow to a wingspan of 1.5 inches. Female moths are larger, but don't fly.

When they're not eating your trees bald, they're dropping frass (that's bug poop, and now you know) all over your deck. If it sounds gross, it's because it is.

When Outbreaks Hit Michigan

The good news? Nature fights back. Viruses, fungi, and predators keep outbreaks mostly in check, cycling every 7 to 10 years. The bad news? When spongy moths boom, the BOOM—covering trunks, raining pooh, and making backyards look like an Eli Roth horror movie.

Stop the Spread of Invasive Pests

Evgeniy Romanov

So what should you do if you spot them? Report them using the Midwest Invasive Species Information Network (MISIN) online reporting tool or by using the app.

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And in the interest of keeping Pure Michigan free of invasive pests, don't haul firewood with egg masses attached. That's giving the spongy moth a free Uber ride across the state.

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Source: From Gypsy to Spongy: Michigan’s Most Hated Caterpillar

Filed Under: Michigan Outdoors, Invasive Species