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05/10/2019

Winter Moths: Lower concentrations expected after early cold, snow

This spring, tree experts in southern Maine, including the town's tree warden, expect to see fewer of the little green caterpillars that are the offspring of devastating winter moths.

Below-freezing temperatures last fall hampered breading for the moths, whose larvae have been known to defoliate Cape Elizabeth hardwoods to the point of decimation.

"Winter activity was definitely low, mostly because of the early cold and snow," said Tree Warden Todd Robbins. He and other tree experts noted fewer brown male moths in the fall of 2018, and even fewer of the flightless females. "I think they had difficulty getting out of the ground," he said.

The moth larvae descend from hardwoods in the spring where the females had laid their eggs, eating the leaves of the host trees along the way. High concentrations of moth larvae can defoliate the tree, and repeated defolation can mean death.

For the last two years, Robbins has asked residents to help pinpoint areas in Cape Elizabeth where winter moths, and their larvae, are concentrated.

This season he's not expecting high concentrations, but they're still here. "Trees are not going to have perfect leaves," Robbins said. "People are going to have to get used to that."

For residents who have been treating with herbicides, this would be a good season to refrain. "If you are ever looking for a test year to sit out spraying for winter moth, this is the year," Robbins said. With lower larvae concentrations, and as long as trees not defoliated to the point of a second leaf-out, less invasive measures such as banding (placing sticky banks at the base of trees to prevent females from ascending to lay eggs) become more important.

Robbins particularly credited residents in Eastman Meadows for their efforts at banding, and using horticultural oils to kill winter-moth eggs. "I'm very sure those folks saved a bunch of trees," he said.

Residents wishing to report winter moth larvae sightings, or other information about preventive or other winter moth activity, are asked to fill out our online form, and/or contact Robbins directly, 207-756-4113 or todd.robbins@capeelizabeth.org

Emerald Ash Borer

The town continues to focus on protecting municipal trees from winter moth, but Robbins said officials are also on the lookout for the Emerald Ash Borer, something not seen in Cape Elizabeth but has been reported in York County. https://www.maine.gov/dacf/php/caps/EAB/index.shtml

Most ash trees in Cape Elizabeth are on residential rather than town-owned property, but as town tree warden Robbins said he will monitor the situation and report as necessary.