Motorists may have noticed lately that they’ve been driving through flurries of moths on the region’s roadways — the latest stage of what entomologists are calling the worst gypsy moth infestation since the early 1980s.
Those moths are now laying masses of beige eggs before they die off, leading experts to fear a worse infestation next year.
Hanson and Kingston are among the state’s communities seeing spotty damage from the moths that, in their caterpillar stage, can irritate more than one’s nerves. Tiny hairs on the caterpillars can cause skin irritations for some with allergies.
There may not be much one can do to combat them at this point, however.
“It seems like the consensus is that, because we’ve had two very dry springs in a row, the fungus Entomophiaga Maimaiga … needs a lot of moisture to get going and it has to happen early enough in the season — a nice, wet April and May,” said Tawny Simisky an extension entomologist specializing in woody plant entomology with the UMass, Amherst Center for Agriculture, Food and the Environment. The fungus is a natural enemy of the gypsy moth caterpillar that winters over in the soil and is most effective when it can get into the caterpillar population at an immature stage.
“Although we did see some of the fungus this year and we’ve had more reports recently about the fungus, it didn’t get kicked up into the population soon enough — or early enough — back in April and May,” Simisky said. “We didn’t have enough rain to have the fungus do enough damage to the gypsy moth caterpillars.”
Now the male moths are flying about seeking females with which to mate, as the females do not fly.
“They [caterpillars] were able to eat quite a bit,” Simisky said, noting her office has received a lot of reports about defoliation. “Unfortunately, we do not map it, but I do have some lists of towns [where damage has been reported].”
Besides Hanson and Kingston, there have been reports of spotty damage in, but not limited to, Sturbridge, Monson, Uxbridge, Brimfield, Charlton, Northborough, Westborough, Plymouth, Carver, Wareham, Sharon, Winchendon, Framingham, West Bridgewater, Braintree, Rowley, Georgetown, Ipswich, Newbury, Boxford, Topsfield, Gloucester, and Wrentham have reported continued and elevated caterpillar activity paired with defoliation this spring.
“Defoliation (mostly oaks) was observed by motorists driving in certain areas on Route 3 (Plymouth area), I-495 (Acton, Littleton, and Worcester areas), and the Mass. Turnpike (I-90) near Charlton. However, there have been multiple reports of gypsy moth caterpillars having fed on pines and spruce this season,” according to the Center for Agriculture, Food and the Environment’s periodic Landscape Message. A lot of calls were also received concerning the sound of caterpillar waste — known as frass — falling from the trees.
“It’s psychologically difficult for people to deal with, it seems,” Simisky said.
what to do?
What is a homeowner to do?
Some extension services across the country have suggested soap and water as an acceptable method for removing egg masses within reach. But Simisky said that is not a very effective method, instead recommending horticultural oil applied by a licensed company.
Simisky said each cluster laid by gypsy moths contains 500 or more eggs.
“Where folks are seeing a lot of egg masses being laid right now, that’s a likely sign that next season they’ll have a lot of gypsy moths again, unless we have a wet spring,” she said. “I’ve been advising folks to make their management plans now.”
The horticultural oils suffocate the egg masses, while soap and water requires one to scrape the egg masses into a container of the solution.
“That is really, I think, futile, labor-intensive work,” Simisky said. “You have to be able to reach every single egg mass and getting good coverage with those horticultural oils can be difficult, too.”
That’s where a Massachusetts-licensed pesticide applicator is important in targeting host trees that are covered in egg masses early next spring.
According to UMass entomologist Dr. Joseph Elkinton, Bacillus thuringiensis (B.t.), a low-toxicity pesticide option that only acts on moths and butterflies may be sprayed on susceptible host plants (such as oak) when gypsy moth caterpillars are still small and feeding. The compound is created from a naturally occurring bacterium that is relatively safe for other beneficial insects, but can harm pollinating butterflies.
“It is derived from a bacterium specific to that group of insects and is considered to be safe for people and pets,” Elkinton stated in a recent article. “There is nothing that can be done now to manage the adult moths.”
Wrapping trees in foil — as was the common “remedy” for saving trees from caterpillars in the 1980s infestation — is also considered ineffective today, Simisky said.