Invasive winter moths making late November appearance

Winter moths, an invasive insect that defoliates trees, could be particularly problematic this spring for drought-stressed trees in New England.

Native to Europe, winter moths have damaged a growing number of trees in the region in recent years. They emerge from Thanksgiving to Christmas when females lay eggs. Caterpillars hatch in the early spring and start chomping. They like maples, oaks and , but they'll feed on a wide variety of hardwood trees.

"Trees can take being defoliated for two years in a row and that third year can kill the tree," said Heather Faubert, who runs the Plant Protection Clinic at the University of Rhode Island. "It can vary by site and tree species, but that's a rule of thumb. In a drought situation, trees just aren't going to be able to survive as well."

The moths were found last year in New York, Connecticut, Rhode Island, Massachusetts, New Hampshire and Maine. They have also been found in Oregon and Washington.

Tawny Simisky, an entomology specialist at the UMass Extension Landscape, Nursery and Urban Forestry Program, describes the moths as "pesky critters."

Some homeowners wrap sticky bands around their trees to trap the moths and stop females from laying eggs in the bark.

It's questionable whether that works. The moths will lay their eggs right below the band and many can make it across the bands, Faubert said. The larvae also blow in the wind and move between .

Horticultural oil spray applied in late winter or early spring can kill the eggs, Faubert added.

Joseph Elkinton, an entomology professor at UMass Amherst, is trying to combat the problem by releasing a parasitic fly that lays eggs on leaves.

Winter moth caterpillars eat the eggs, which hatch inside the caterpillars. The fly larva then eat the caterpillars from the inside out. Elkinton said he has released a few thousand flies annually in 41 locations, starting in 2005.

That has led to a significant decline in winter moths in Wellesley, Massachusetts, he said. The same technique worked in Nova Scotia in the 1950s, he noted.

"It takes time for the flies to catch up with the literally billions of winter moths out there," Elkinton said. "There's no reason it shouldn't work here and the data suggests we're on the verge of doing so."

Each female winter moth lays about 250 and there can be 100,000 per tree, he added.


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