LAKE GEORGE, N.Y. (NEWS10) – Jim Lieberum remembers the sound he heard last summer on Prospect Mountain. As manager of the Warren County Soil & Water Conservation District, he and staff were at the mountain overlooking Lake George in summer 2021, working on a project for the county, when he heard it.

“I said, ‘What is that noise?’ It was caterpillars chewing.”

The caterpillars in question are the first stage of life of the spongy moth – formerly known as the gypsy moth – which had a big year in the Lake George area in 2021. Originally from Europe, the spongy moth has been in the United states since the 1860s, and called New York home for about 80 years. When they make a major appearance in the North Country, it’s usually been years since the last. A prior outbreak was seen in Lake George in the early 2000s.

The spongy moth lays eggs on trees, which settle in for the winter and hatch in mid-May – meaning Lieberum and his team are on the lookout. When those eggs hatch, it won’t be hard to spot the places where gypsy moth caterpillars have decided to dine. Last year, they found places to live in Glens Falls, the Lake George watershed, Queensbury, West Mountain, and more.

“I live in Thurman, and every year we have some,” Lieberum said. “I have a couple of trees that will see them. My buddy lives in Lake George and has 100 oak trees on two acres – he sees more impact than I ever will.”

What does that impact look like? Spongy moth caterpillars can consume a square foot of leaf matter per day – an amount that adds up when enough eggs hatch. In summer 2021, a drive near Lake George along the Adirondack Northway showed trees along the median between lanes left completely bare, by caterpillars having their fill before cocooning and becoming moths.

Whether or not 2022 is another year heavy on moths and light on leaves depends on the rain. Rainwater stirs up natural viruses and pathogens in soil that kill a large number of moth eggs before they hatch. Often, eggs are laid in lower branches of trees or at their roots, close to the soil.

2021 was a heavy moth season because it was a dry spring. Lieberum said that this spring was looking to go the same way, until earlier this week. Thursday’s steady rainfall is exactly what the region needs to keep the moth population under control.

“You don’t have to have incredibly wet weather,” said New York DEC researcher Robert Cole. “What isn’t helpful is when we go to extreme dryness that’s the problem. As long as we have consistent moisture, a good rainstorm once a week – typical spring weather – that should be fine.”

In a year when the spongy moths do take flight, the trees they target aren’t immediately doomed. Deciduous (leafy) trees can withstand serving as a feast, and re-leaf later in the year, meaning that the oaks and other trees that moths favor are largely safe, unless inundated for several years in a row.

More vulnerable are coniferous (pine) trees. While the spongy moth prefers the leaves of oak trees, it’s far from picky. They can go through pine needles on pine and hemlock trees at a considerably faster rate, due to those needles’ smaller size compared to leaves. Coniferous trees that leave around half their leaves are likely to die.

Cole says that the last outbreak on the scale of 2021’s was during the 1980s. It wasn’t enough to kill off large swaths of pine trees, but the annual overhead photographing the DEC conducts hasn’t been done yet this year, meaning the moths could have left some areas of damage not yet known.

Once they hatch, spongy moth caterpillars can “parachute,” using strands of silk to catch and be carried on the wind. Once fully grown, only the male moths can fly. Females will crawl across the ground, but the limitations of their movement often dictate how far the species will spread in a year.

As eggs are laid in trees, it is possible for them to be carried to new places via the lumber industry. Eggs are also sometimes found laid on the outsides of houses, on lawnmowers, and even boat trailers.

In Warren County, other areas with an especially heavy spongy moth population last year included the Warren County Bikeway, especially in the area around Lake George Expedition Park, and up the west side of Lake George. Cole said that he didn’t get any calls complaining about the size of the moth population last year, but that too many of them flapping around can have a minor impact on human life.

“They’re ballooning on silk now and landing on a lot of people, and we’ve gotten a couple calls about skin irritation,” he said. “The type of caterpillar – the family that it’s in – the hairs are irritating, so we are getting calls about minor rashes, wondering how to deal with that.”

Those who want to keep the spongy moth population out of their yard can start by scraping off any egg clusters they find. Now that many of those eggs are hatching, another method is to use a type of double-sided tape around trees that works similarly to flypaper, catching caterpillars – and other insects – in their tracks. A bacterium called BTK has also been used for several decades. For the industrious, though, Lieberum says that you can’t beat going out and picking.

“Give a 5-year-old that job and it’s a great thing to watch,” he said. “It’s impressive how fast they can catch them.”

The most recent large outbreak of spongy moths elsewhere in New York was on Long Island in 2015. The moth was originally introduced to the U.S. in Massachusetts, by someone hoping to use them in the silk industry. Today, they can be found as far north as Maine, as far south as Pennsylvania, and west into Ohio and Michigan. Cole said their populations are still gradually moving south and west.