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Spongy moth outlook is less severe than in years past

2021 saw an outbreak of spongy moths, formerly gypsy moths. This year, populations declined in northern lower Michigan based off DNR surveys.

GRAND RAPIDS, Mich — In 2021, the spongy moths, formerly called gypsy moths, had an outbreak in population. 

This year, the Michigan Department of Natural Resources (DNR) surveys of the egg masses of the moth show population declining in Northern Lower Michigan. 

There could still be some heavier populations in Southern Lower Michigan and some isolated outbreaks as well. 

"If you're seeing those larger egg masses," said Joanne Foreman, the Invasive Species Communications Coordinator for the DNR, EGLE, and MDARD, "and they are that tannish-brown color, likely if you see a lot of them, it suggests that you might still be in the outbreak situation."

The spongy moths are still in their egg mass stage right now. Once the leaves begin to form on trees, the caterpillars will emerge from the eggs. 

The spongy moth caterpillars typically do not do long-term damage to trees. They do eat the leaves and reduce the canopy. For the most part, they are simply a large nuisance to those wanting to spend time outdoors in the summer. 

If there are the egg masses on trees, they can be scraped off into a soapy-water mix to remove them. 

"Because each one [egg mass] can hatch hundreds of caterpillars," said Foreman, "and if you can destroy a couple hundred caterpillars in one easy motion, that's going to be helpful."

There is no statewide mitigation or spray program for spongy months. Some municipalities do their own spray programs, which is done after the caterpillar infestation begins. The spray lands on the leaves, the caterpillars eat the leaves, and are killed. 

The outbreak cycle is also a result of a virus and fungus that targets the moths. The virus kicks into gear when the populations get high, causing the cycle.

"There is also a fungus out there at work that was part of an application program in the '90s that again will continue to bring down these high populations," said Foreman.

During the month of May, Michigan State Extension in Roscommon County is hosting a Moth Busters Egg Mass Hunt. The goal is to work together to responsibly harvest spongy moth egg masses before they hatch. 

You can learn more about spongy moths at michigan.gov/invasives/id-report/insects/spongy-moth.

RELATED VIDEO: 'They're everywhere!': Massive uptick in gypsy moth caterpillars invade properties in the Lower Pen.

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