When the European gypsy moth hatches, it is born as a furry little caterpillar. They emerge from their eggs in the spring and proceed to feed mercilessly on the surrounding foliage. Tree leaves and coniferous needles are the primary target of this tiny scourge, and if you happen to live in the middle of an infestation, you may feel as if the plague has descended on your own home.
This is what’s happening in New England. Caterpillars are everywhere, trees are decimated, and the skyline looks like the middle of winter.
“The tree damage is found in pockets that consist of just a few trees in a yard here and there to several acres completely defoliated,” Phil Burt, a meteorologist in Massachusetts, told The Washington Post. Burt said that, at least in Brewster, Mass., the caterpillars are “probably at their worst since the early to mid-1980s.”
The European gypsy moth was inadvertently brought to the United States near Boston during the late 1800s, according to the U.S. Department of Agriculture. Since then, the moth’s range has expanded to include the entire Northeast south to North Carolina, and as far west as Minnesota and Iowa.
The gypsy moth females lay a mass of eggs on vertical surfaces — usually tree trunks — in the late summer. The eggs ride out the winter and eventually hatch in May. The caterpillars feed on leaves, molt into adult moths, and then start the reproductive cycle all over again.
Usually, this process comes and goes with few complications. But the weather caused this year’s hatching to become more than overwhelming.
The first problem surfaced well before spring. Conditions were very dry in parts of New England in May 2014 and May 2015, which impeded the growth of a certain kind of fungus — entomophaga maimaiga — that serves as a natural “predator” for the gypsy moth caterpillar. Without enough moisture the fungus doesn’t grow, which means it doesn’t help to wipe out part of the caterpillar population.
And you can plainly see the difference between locations that had a spring thunderstorm and those that didn’t. Trees in areas that got May rain will have a smaller caterpillar population and more (uneaten) leaves, and trees that didn’t get enough rain will be more barren.
“This year we experienced rain at the appropriate time, but on the eastern side of the state it was not enough,” said Gale Ridge, an entomologist at theConnecticut Agricultural Experiment Station.
Ridge told The Post that the demarcation is stark. “Within a mile you can literally draw a line,” said Ridge. “It’s completely dependent on how that rain tracks.”
Then the cool spring made the infestation worse.
“When the weather breaks, the caterpillars will hatch, mainly when you get warm days in early May,” said Ridge. “But the caterpillar stage seems to be longer this year, so it must be weather, mainly the cold nights in May. It draws it out longer.”
Ridge says that deciduous trees can usually grow back their leaves, but it takes a lot of energy to do so, which makes them more prone to other insects and pathogens. If an infestation like this occurred two to three years in a row, it could wipe out the trees completely.
Conifers have more trouble with the rebound since they are not able to refoliate. Pine trees will be okay, but spruce cannot bounce back, Ridge said.
The leaf-annihilation should be over by July 4, says Ridge. In the meantime, the silk strands, droppings, leaf remnants and dead moths are a nuisance but are relatively harmless. The only real problem arises from allergies — some people are allergic to the caterpillar hairs.
Oh, and the sound. The sound might get to you.
“It’s actually a bit creepy walking through the woods because you can hear them eating and pooping,” said Burt. “Gross.”