Tree-stripping winter moths creep into MetroWest

By Scott O’Connell/Daily News staff
MetroWest Daily News
Posted Dec 04, 2011 @ 09:53 PM
Last update Dec 05, 2011 @ 12:23 PM

They look innocent now, fluttering among the trees and street lamps. But come spring, the winter moths’ green, squirming offspring will be devastating the region’s tree populations.
State and local experts are worriedly watching the invasive species as it spreads from the east into MetroWest, where the moth’s ravenous larvae have already started to thin oaks, maples and cherry trees. Aerial surveillance this past year showed large swaths of bare trees in towns including Wayland, Sudbury and Framingham, said Ken Gooch, Forest Health Program director at the Massachusetts Department of Conservation and Recreation.
“Some of the most defoliated areas (in the state) were those areas,” he said. “The whole MetroWest got hit pretty hard.”
Bill Joseph, an arborist at Lynch Plant Healthcare in Wayland, said he’s seen the pests nearly double in number over the past year.
“I’ve seen them as far west as (Rte.) 85,” he said. “It used to be intermittent – contained to certain neighborhoods. Now I’m seeing them almost everywhere I go.”
In Marlborough, a concentration of the insects along Bolton Street, near Marlborough Hospital, appears to be expanding this fall, said city tree warden Chris White.
“We’ve probably had (the moths) here about three years,” he said. “We’re seeing a pretty good blossom.”
Even in towns where the moths aren’t as widespread, tree wardens are still worried.
“There’s always a concern about them moving in,” said Milford tree warden Charles Reneau. “I’m seeing more than in past years.”
Native to Europe, winter moths, Operophtera brumata, first appeared across the Atlantic in Nova Scotia in the early 1930s, according to the DCR. They were discovered in Massachusetts around 2002, and quickly spread to the coastal and southeastern parts of the state.
Experts’ chief concern is the species’ tiny, inch-worm-like caterpillar, which individually is not as destructive as some other insects but in large numbers can completely strip a tree of leaves. The threat is especially worrisome in Massachusetts, where the moths have flourished with no natural predators to keep them in check.
The swarms of moths that have descended upon the region this fall have begun to alarm homeowners as well, many of whom have started to call tree care services for help.
“We’ve gotten a lot of calls from curious people,” said Nathan Cenis, a consulting arborist at Cedarlawn Tree in Ashland. “They want to know what the moths are – they’re confused.”
Residents do have the option to control small populations of the moth by spraying the larvae in the spring. The DCR advises homeowners to use biological agents such as Bacillus thuringiensis, or “BT,” instead of chemical pesticides, though.
Long-term, experts are banking on a more natural remedy: the gradual introduction of a parasitic fly, Cyzenis albicans, which has helped reduce moth populations in Canada and the Pacific Northwest. The entomology department at UMass-Amherst has received a government grant to release the fly over the past four years, with some success in the past two years in keeping the fly species alive through the winter.
It took scientists nearly a century to execute similar natural controls on another foreign menace, the gypsy moth.
“This is going to be a lot quicker,” Gooch said. “The science is much more advanced.”
But it will still take between 10 to 15 years to fully introduce the fly in the region, he said.
“There’s not enough to control (the moths) right now,” Joseph said.
While a single defoliation is not enough to kill a healthy tree, it requires the plant to divert more of its energy to producing new leaves, making it vulnerable to disease and other predators. If the defoliation continues, most trees will die in three to seven years, Joseph said.
“It’s death by a thousand cuts,” Cenis said. “The tree eventually just runs out of energy.”
That’s why state officials and arborists consider winter moths one of the most imminent threats to tree populations in the area, putting the species beside other tree-killing invaders like the emerald ash borer and Asian longhorned beetle.
Public outreach and education, along with regular communication with arborists, is key to the effort to control the problem, Gooch said, especially considering the rate at which the winter moths are spreading.
“The thing is to get people aware of it,” Joseph said. “Some don’t find out until their trees are bare.”
(Scott O’Connell can be reached at 508-626-4449 or
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