Gypsy moth caterpillar found in Duluth

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DULUTH - Judy Gibbs trains people to look for signs of invading tree pests like gypsy moths, but she hoped she’d never have to use those skills firsthand.

On Thursday in Duluth’s East Hillside neighborhood, Gibbs found Minnesota’s first confirmed gypsy moth caterpillar.

“I happened to look down on a sidewalk and saw it and thought, ‘Please let it be something else,’ ” Gibbs told the News Tribune. “But it was definitely a gypsy moth caterpillar. I saw enough of them growing up back East to know.”

A digital photo of the caterpillar — 2 inches long, furry with blue and red dots — was quickly confirmed by Minnesota Department of Agriculture experts.

Minnesota so far has been spared any gypsy moth damage. But the caterpillar discovery could be a sign that the Duluth area is in for Minnesota’s first-ever infestation of gypsy moth caterpillars — perhaps next year — that would lead to actual deforestation.

However, it would take tens of thousands of the caterpillars to cause much damage and, so far, only one has been found.

Flying male gypsy moths have been found in eastern areas of Minnesota for several years; more than 25,000 were trapped last year alone, including along the North Shore. It was believed that the moths were hatching here and not just blowing in from eastern states, but until now it was never confirmed.

“We’ve had evidence that there was some reproduction (in parts of Minnesota), but we hadn’t found any of the alternate life stages before, either egg masses or caterpillars,’’ said Lucy Hunt, plant health specialist for the Minnesota Department of Agriculture.

“The finding gives us an early warning to go into that area with traps so we can see what kind of numbers are really out there,” Hunt said.

Some moths were trapped two years ago near the caterpillar finding “but, in our traps in Duluth last year, there really was no buildup of moths at all. So I guess now it’s just a waiting game.”

Like the native forest tent caterpillar, gypsy moths spend most of their lives as eggs, then spend several weeks as caterpillars munching leaves. The caterpillars can defoliate vast areas quickly, causing already stressed trees to die and reducing tree growth. In some areas of the eastern U.S., more than 20 percent of trees hit by the moths have died.

Gibbs, an urban forestry specialist for the city of Duluth, a temporary position funded by the federal AmeriCorps program, has been spending the summer counting and cataloging the city’s trees. She’s also training volunteers to look for damaging pests such as emerald ash borers and gypsy moths.

Now Gibbs and others will scour the city looking for gypsy moth egg clusters, another indicator that the invader is here to stay.

The finding wasn’t unexpected and was probably inevitable. The European native moths have colonized the eastern U.S. since 1869 and have marched west en masse, enveloping forests as close as eastern Wisconsin.

Advance populations ahead of that front — riding on trains, trucks, trailers and cars — have been attacked annually by aerial spraying, so far with success. But no one expected to stop the movement entirely.

State and federal resource agencies use two methods to control gypsy moths. The first is a biological or natural insecticide called Btk that kills caterpillars. Another method uses synthetic pheromones to attract male moths so they become confused and can’t find females to mate.

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