Officials concerned about spread of hemlock-destroying aphid

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HARPSWELL — State entomologists say a woolly adelgid infestation in Cundy’s Harbor means the invasion of the hemlock-destroying aphid is farther north than ever and likely spreading.

Officials with the state Forest Service and the Department of Agriculture say a large infestation of hemlock woolly adelgid was confirmed last week at a property on Cundy’s Harbor Road. Until then the insect, which appears as white, cotton-like balls on the underside of hemlock branches, had only been seen in north coastal York County.

The Harpswell case, which includes several adjacent properties, is about 30 miles from closest known infestation in Saco. The gap in known infestations has officials worried that the invasion is more widespread than previously thought.

“The Harpswell infestation was most unwelcome,” said Allison Kanoti, an entomologist with the Forest Service, adding that officials had anticipated the northward advance, but not so quickly.

The insect, which is native to Japan, first popped up in Maine in the 1990s after being discovered in the western U.S. in 1924. According to Ann Gibbs of the Deparment of Agriculture, the early Maine cases were largely isolated to hemlocks that were brought in from out of state.

It wasn’t until 2003 that the Forest Service discovered the insects appearing naturally, rather than isolated in trees imported from elsewhere.

Gibbs described the Harpswell infestation as the heaviest she has seen.

“I’ve been dealing with (woolly adelgid) since the mid-’90s,” she said. “I’ve never seen it plastered everywhere like that. It was clear that it had been there for a long time, and it was on a native planting.”

Kanoti said the insect can migrate via wind or birds. It tends to stay on the coast, where winters are less likely to reach the sub-freezing temperatures required to kill it.

After a mild winter, Gibbs said officials anticipated that the woolly adelgid would make its way farther north, but not this far and not this fast.

Earlier this month, the Forest Service unleased about 9,000 predatory beetles to fight off the woolly adelgid. According to Kanoti, about 2,500 beetles were deployed last week in Harpswell to combat the latest infestation.

Like the woolly adelgid, the beetles are native to Asia. In that part of the world, hemlocks fight off the adelgid with a host of natural defenders. Maine hemlocks haven’t yet developed those defenses, which means they’re more likely to die or suffer severe thinning of branches and foliage.

“Our goal isn’t to eradicate the adelgid, which would probably be impossible,” Kanoti said. “What the hemlocks need are a suite of controls.”

Until that happens, officials at the Forest Service said they’ll be relying on the public to notify them of additional infestations. Gibbs said they discovered the Harpswell case after being notified by the property owner.

“We don’t have the resources to be everywhere,” she said. “We need to hear from arborists, landscapers and other people who are paying attention to trees. It’s critical.”

Kanoti also advised property owners near suspected infestation areas to take down their bird feeders in the summer months to reduce the adelgid spread.

She said the invasion up the coast is inevitable, but that the Forest Service hopes to control it.

“The adelgid isn’t going anywhere,” she said. “Well, actually it is. That’s the problem.”

Steve Mistler can be reached at 781-3361 ext. 123 or

Sidebar Elements

The hemlock woolly adelgid, shown on the underside of a hemlock branch, is spreading farther and faster than officials at the Forest Service anticipated.

What to do

To report suspected hemlock woolly adelgid infestations, contact the Maine Forest Service at 287-2431, or