From Hills of Menemsha to Oak Bluffs, Hungry Caterpillars Munch Away
Leaves

By IAN FEIN

They're back.

A caterpillar outbreak that left large swaths of trees completely
bare of leaves last summer has returned to feast on Vineyard foliage.

Across the Island this weekend millions of tiny green winter moth
inchworms - which have been munching away on oak, apple and maple
leaves - dangled from branches on silky threads to announce their
uninvited arrival.

Infestations were reported from the hills of Menemsha to the
highlands of East Chop, where one resident said he needed an umbrella to
protect himself from falling frass, a polite name for caterpillar
excrement.

"I was walking in the woods yesterday and you could hear the
frass. It almost sounded like gentle rain," said Sheriff's
Meadow Foundation executive director Dick Johnson. "I think
we're about to see the explosion we've all been afraid
of."

For months Island arborists have been awaiting the return of the
winter moth caterpillars, which some say may be the biggest outbreak of
leaf-eating insects since the gypsy moth of the early 1980s.

Originally from Europe, the non-native winter moth has caused
widespread defoliation along the Massachusetts coast - covering
almost the entire length of Cape Cod and extending as far north as
Gloucester. The pests are now well established in the region, where they
thrive without natural predators.

Winter moth probably arrived in Massachusetts five years ago, but
arborists at first mistook it for the native fall cankerworm. The true
culprit - whose latin name is Operophtera brumata - was not
identified until December 2003, once the outbreak had gotten out of
hand.

A group of University of Massachusetts scientists studying the
winter moth population in southeastern Massachusetts estimate that the
numbers may already be in the trillions, with even more to come in years
ahead.

"It's fair to say that the statewide numbers increased
again this year," said University of Massachusetts entomologist
Robert Childs. "Requests for treatment have gone up about tenfold
in the last year," he added.

In some areas this winter, university researchers counted between
1,000 and 2,000 female moths per tree. Each female lays about 150 eggs,
which translates to roughly a quarter-million eggs per tree.

No one knows how the European pest made its way to coastal
Massachusetts, though it has been eating leaves in eastern Canada since
the 1950s and first appeared in the United States, namely Washington and
Oregon, in the 1970s.

Although it can make summer foliage look as barren as winter, the
moth earned its name because the adults emerge from cocoons to mate in
late November or early December. The moths were as ubiquitous as snow
flakes on the Vineyard this winter, often seen flying around outside
lamps or holiday lights.

"Coming home down Cedar Tree Neck this winter, I would see
dozens and dozens of them," Mr. Johnson recalled. "It looked
like it was snowing. I'd never seen anything like them."

The female moths lay eggs on tree trunks, in branches and beneath
bark scales and loose lichen. The eggs turn orange and then bright red
just before hatching, usually in late April.

The caterpillars then crawl into enclosed leaf buds, where they
begin feeding. Experts say that this may have been a particularly
damaging spring for the Island trees because the cold weather caused the
leaves to bud so late, giving caterpillars extra time at the buffet
table.

This weekend much of the canopy in Menemsha looked like swiss
cheese.

"We'll get a lot more bud damage with the cooler spring
that we had," said arborist Steve Masterson of the Polly Hill
Arboretum. "Normally they'll feed until mid-June. But I
would add ten days onto that."

Winter moth caterpillars continue to feed once the buds have opened,
swinging between branches and trees on silken threads - an act
called ballooning. They eat everything from oaks to maples to fruit
trees, and have even been known to make their way down to rose bushes.

Once a caterpillar has had its fill, it will slide down a thread and
migrate into the soil to spin a cocoon and pupate, only to emerge again
as an adult moth around Thanksgiving.

Walking through the woods during caterpillar ballooning is not a
pleasant experience. It can feel as though you are walking through a
giant spider web, and you may soon find yourself covered in inchworms
and frass.

"The walk to Lambert's Cove Beach is nasty," Karin
Stanley, outreach coordinator at Polly Hill Arboretum, said yesterday.
"They're everywhere. All the leaves were just holes."

Although a summer without leaves does not pose an immediate threat
to a tree, those that are defoliated year after year can die within four
years. Winter moths in parts of Nova Scotia have been blamed for 40 per
cent mortality in the red oak population.

For a defoliated tree, experts recommend watering the entire root
structure at least once a week to help prevent lasting damage.
Consulting with an arborist is also recommended.

Pesticides and insecticides that can help control the infestations
include Bacillus thuringiensis (BT) and spinosad; both are accepted for
use by organic growers.

Joseph Elkinton, a forest entomologist and professor at the
University of Massachusetts, is raising caterpillar-killing flies in a
laboratory at Otis Air Force base in Falmouth. The flies helped control
a winter moth outbreak in Nova Scotia years ago, though some scientists
worry about introducing another non-native species into the region.

At the West Tisbury selectmen's meeting last week, finance
committee member Peter Costas, who also works at Vineyard Gardens, asked
selectmen to explore using certain pesticides to protect town trees from
the caterpillars.

Selectmen said they were eager to help, although the task at hand
appeared more Herculean than the town could afford.

"The problem is," longtime selectman John Early
explained, "the infestation is so widespread, we couldn't
possibly budget enough."