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Defoliation from Browntail Moth caterpillars declined over 95% in Maine this year

In a May 2016 photo provided by the Maine Forest Service, a browntail caterpillar feeds on a plant, in Maine. The moth caterpillars have toxic hairs that cause an itchy rash in humans.
AP
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Maine Forest Service ACF via AP
In a May 2016 photo provided by the Maine Forest Service, a browntail caterpillar feeds on a plant, in Maine.

The Maine Forest Service is reporting a steep drop off in damage from Browntail Moth caterpillar infestations this year. But tree experts say now is the time to identify and remove webs.

Last year, aerial surveys found the invasive caterpillars had defoliated 46,726 acres of forest in Maine. This year, the damage was down to an estimated 2,119 acres, a decline of more than 95%.

Brittany Schappach, a Forest Service entomologist, said that's due to a number of factors, including outbreaks of a virus that provided a somewhat gruesome form of population control.

"Their guts explode from the inside out," she said of the infected caterpillars. "So oftentimes these caterpillars look wet."

Schappach said a separate fungal infection also decimated some localized populations, spurred in part by what she called the "Goldilocks effect" of weather conditions.

"The 'just right' of how much rain we need to actually see these pathogens to knock down these populations," she said.

Schappach said locally-driven mitigation efforts also helped tamp down populations across the state.

Still, she said now is the time to identify and remove winter webs, which can contain hundreds of caterpillars.

Even as the Forest Service registered a decline in Browntail Moth, it found another invasive species — the Emerald Ash Borer — is spreading south in Aroostook County.