The Middletown Press (Middletown, CT)
MUNCH BUNCH
Gypsy moth caterpillars raining down from trees may sound like a horror movie, but state entomologist says there’s a bright side to the bugs
MIDDLETOWN » What sounds like raindrops falling from a canopy of trees over the last couple of weeks as the skies overhead are sunny and bright aren’t sun showers, it turns out.
It’s the contented munching of oak tree leaves by the furry, long-haired gypsy moth caterpillars — or larvae — that look like an unruly eyebrow with raised blue and brick-red spots.
“A big infestation of them is creepy because they are such ravenous eaters that you can hear the crunching, you hear the poop plopping. They’re shredding leaves and they’re excreting pretty much as they go,” said Jane Harris, chairwoman of Middletown’s Urban Forestry Commission. “You could have a real slimy mess if you have a tree that overhangs your deck.
“It’s pretty disgusting,” she said.
In fact, Chris Donnelly, the state’s urban forestry coordinator, said during the worst outbreak in recent memory —
in 1971 — any number of car accidents were attributed to the gypsy moth caterpillar.
“People would skid on their massed numbers in the roadways,” the DEEP website offers in “A brief history of the gypsy moth.”
And the destruction these insects can wreak is legion.
“If you see a fly-over picture of Connecticut during one of the big infestations, you don’t see green,” Harris said. The last time the area was hit badly, she said, the Cockaponset Forest, which stretches throughout Middlesex County, “was really, really bare.”
State Entomologist Kirby C. Stafford III said there was a big outbreak in Connecticut in 1981, after one in the 1970s. Others took place in 2005 and 2006, then 2015 through 2017, he said.
Then, in the late ’80s, a fungus discovered by scientists at the Connecticut Agricultural Experiment Station in New Haven, where Stafford works, offered a potential to kill gypsy moth caterpillars before they got to the pupal stage.
Between mid-June and early July, the pupae go into cocoons and metamorphosize into adult moths.
The fungus, entomophaga maimaiga, is a common disease in gypsy moth populations in its native country of Japan. The fungus was first released into the United States near Boston in 1910 as part of a program to introduce natural enemies of gypsy moth, according to the Midwest Biological Control News.
Stafford said he’s been fielding “widespread but sporadic” reports of fungal activity after taking in several samples from nine towns throughout the state, among them Willington, Windham, Guilford and Durham.
“It’s still a little early to know the extent of what the impact will be,” Stafford said. “We do have a huge population of gypsy moth caterpillars out there. Conditions have been perfect. All the rains we have been getting have been ideal for the fungus.
“Once these caterpillars become infected, it takes a week for them to die,” he said.
When they do, he said, they produce spores that can be spread through air. They, in turn, infect more caterpillars — and on and on.
“It remains to be seen what kind of scale … the fungus will have among the caterpillars out there,” he said.
“We knew we were going to have a large pop this year,” Stafford said. “We had huge outbreak this year, a lot of egg masses laid by female moths, so we knew there would be varying degrees of defoliation just based on the number of caterpillars out there,” he said.
But the wet weather lately has encouraged the spores’ growth, which will go on, Stafford said, “as long as the rains continue. You need rain for germination and for the fungus to infect additional caterpillars.”
These critters prefer feeding on oak trees, Stafford said.
“When you get this many caterpillars, they’re not going be as selective, and after they’re finished defoliating a tree, they’ll move to almost anything else just because they’re hungry and there’s so many of them,” he said.
That even includes sharpneedled ones.
“They don’t particularly care for conifers — spruce, hemlock, pine — but they will hit those, too, if the population is high enough,” Stafford said.
Leaves on at least two of the crab apple trees at the Connecticut Trees of Honor at Veterans Park are completely stripped by tent caterpillars, which can be seen clutching the branches, their legs encircling each one like a person would hug another.
“They’ll just gorge themselves until they drop off,” Harris said.
She’s fielded a “ton of reports” about gypsy moth caterpillars, which turn out to be Eastern tent caterpillars, because to the layman, they look remarkably similar, Harris said.
The misidentification is so common, she said, that a Google image search for “gypsy moth caterpillars” churns out images of tent caterpillars.
“There’s that much confusion about it. The tent is much smaller. Its cocoon is a big, webby mess that hangs on a branch,” Harris said, “which you see in the spring. The spring ones are bad ones: at least as damaging as gypsy moths, but people don’t know what they’re seeing.”
“Gypsy moths start out small and grow quite a bit bigger than tent caterpillars,” she said. “Gypsy moths are large and distinctive looking.”
Further, while tent caterpillars feed on ornamental trees, Harris said, such as cherry and crab apples, gypsy moths “go for really good forest trees and they’ll eat anything, but the first trees they inhabit usually are oaks,” Harris said.
How the pests came to the United States is like a horror movie, she said.
“Someone brought them in thinking they could substitute them for silkworms and start a silkworm industry in the Boston area,” she said.
“The gypsy moth is originally native to Eurasia,” according to the DEEP. By the 1600s, it was already being noted as an insect that causes problems. By the 1800s, it had become a prominent pest in Europe; one that had spread widely and was causing the same sort of damage there as it is now known for on this side of the Atlantic.”
“If they’re falling off the trees now because of the fungus, you could have actual caterpillars raining down, which is also kind of gross,” Harris said.
Harris doesn’t have an infestation in the trees on her property, but said if she did, she’d let them be.
“There’s no good remedy. You cannot spray the forest. There are people that will put traps up and use sticky bands. That helps to a certain extent because the caterpillars do make a lot of trips up and down the trunks of the trees and if they get stuck, obviously they’re going to die there for lack of food.”
Harris said she prefers more of a reactive method of eradicating them.
“I used to do arborist work,” she said. “One of treatments I used to use is to inject pesticides directly into the cambium of the tree (the growing part of the trunk) so I’d be crawling around under a tree on my hands and knees drilling into trees and I wore plastic helmet. I really didn’t want to go home with either caterpillars or caterpillar poop in my hair,” Harris said, with a good-natured laugh.
The fungus, or other controls like a virus that can spread through the gypsy moths, will actually curb next year’s population, Donnelly said.
The fate of trees that are defoliated, however, is less certain.
“Ideally, we’d like to say the trees will recover,” he said, “they can tolerate one or two defoliations — kind of shrug it off — but one of the reasons we’re in this predicament with gypsy moths is it’s been so dry. We’re hopeful that the trees will be able to overcome an even higher obstacle — the defoliation from moths and dehydration from the drought,” Donnelly said.
“It’s not the gypsy moths usually that kills the tree, it’s secondary pathogens that come in and take advantage of a tree that’s been stressed.”