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Tree warden asks residents to report winter-moth activity

Winter moth infestation has reached epidemic proportion in Cape Elizabeth, and the town tree warden is asking your help in gauging its reach.

Click image to report winter-moth sightings using our online form, or contact Tree Warden Todd Robbins,

In just a few weeks, from November to early January, residents are likely to encounter the mass of brown moths they've seen gathering around outdoor lights and headlights on warm evenings. "This is when the mating process is going on, and hopefully this is when residents will call me, let me know what they're seeing so I'll know where the concentration is in town," Tree Warden Todd Robbins told members of the Town Council at their meeting Sept. 11, 2017. [view video] [download presentation]

Winter moth is a European insect introduced to the United States in the 1970s. It made its way into New England in the 2000s, with the first reports of defoliation in Maine occurring in 2012.

Where there are high concentrations of flying male moths, "some people have claimed it looks like falling snow," Robbins said, there is also likely an equally high concentration of flightless females laying eggs in host trees such as red oak, red maple and other hardwoods common to Cape Elizabeth. Fruit trees are also preferred hosts, Robbins said.

Robbins, tree warden since April 2017, has removed many a tree killed by winter moth in his full-time job as assistant property manager at Ram Island Farm. Signs of infestation are tattered leaves left by hungry winter-moth larvae that crawl up the tree after they hatch in the spring - any time between March and June - when the temperature is about 53 degrees.

If tattered leaves were the only damage, winter moth wouldn't be a problem, Robbins said. "What is causing the problem is when there's a high concentration of winter moth, they completely strip the leaves off of a tree," he said. This forces a second growth of leaves from the tree, eventually depleting its reserves and resulting in death.

Moth Activity Timeline

The good news, in Robbins' opinion, is that as winter moth spreads it also become less concentrated.

"What I've seen around town this year, in my opinion, will not kill a tree," Robbins said. "I've seen minimal second-growth leaves on damaged trees this year. That's a good thing, that's a great thing in my opinion."

But for some trees, it's too late. Town-owned trees that pose a public safety hazard have been removed from Old Ocean House Road as one example, Robbins said. Part of his job as tree warden is to convince owners of remaining trees that are privately owned to remove them if they are hazardous.

For trees still living, Robbins suggests to residents a variety of what he called integrated pest management measures. "Integrated pest management doesn't mean wiping something out, it means managing it ... keeping it a manageable threshold because believe it or not, all insects are needed. You don't want to completely get rid of anything."

Spraying of pesticides can be effective but not recommended. A more favorable measure is applying a sticky band to the bottom of trees to prevent adult moths from climbing them. The town will be banding a lot of public trees around Nov. 15, when the mating activity begins, Robbins said. "I have been telling people Nov. 1 .. (but) I've pushed it ahead to Nov. 15 because last year's hatch was after Thanksgiving," he said.

For the first time Robbins said he has seen some winter-moth damage in Fort Williams Park, so it's helpful to him to get an idea of how the insect may be spreading.

Short-term, long-term action

In 2013 and 2014, the state conducted two separate releases of parasitic flies that feed on winter moth. [news article] Robbins said it will be 7-10 years before the success of the releases will be known, but in his opinion, the infestation has spread enough to warrant another release.

In the long term, the town has adopted a practice of planting trees resistant to winter moth. The subdivision ordinance suggests a variety of preferred and acceptable species for street trees in new developments. The idea is to encourage a mix within the town so that that the loss of any one species would not decimate the town's stand.

In the short term, Robbins' advice to homeowners is to monitor winter-moth activity. "Monitor winter activity so we can understand how concentrated the spring activity may or may not be," he said. Choose an integrated pest-management measure, but also please report your findings to the town. "How's it going? What's the winter activity? Have you banded, are you collecting many female moths? Just kind of give me a heads up," Robbins said.