Attack of the caterpillars, the sequel

Spongy moths are beginning to hatch, repeat damage to trees

By Paul Post

Miles and Kelly Moody’s Clinton County apple orchard was stripped bare of leaves and several 90-foot-tall pines were killed and had to be cut down, at considerable expense.

Their difficulty is one small example of the widespread devastation caused by last year’s massive spongy moth infestation that’s plaguing northern New York again as tiny caterpillars have just started to emerge, devouring everything in sight.

Previously known as gypsy moths, the moths were re-named for their spongy-looking egg masses. Oaks are the voracious insects’ preferred food choice, but they’ll attack both deciduous and coniferous trees while invading forests and residential settings alike.

“At one point we could look out our window and the driveway looked like it was moving because there were so many caterpillars,” said Miles Moody of rural Morrisonville. “They’re perforating leaves again. It’s like a sieve. There are so many holes in leaves you can look right through them.”

“We’ve been here 44 years and we’ve never seen this,” his wife, Kelly, said.

Help on the way

The Moodys are doing their best to combat caterpillars by hand, while awaiting an aerial organic compound application by Lowville-based Duflo Spray Chemical Company, one of several such firms in upstate New York.

Owner Jeff Duflo he’s already received more than 400 calls from parties seeking help from the Thousand Islands to northern Vermont. But the problem is much larger as infestations are anticipated from Michigan to Quebec.

This has created a shortage of spray product he uses, called Btk, which is fermented like beer in large stainless steel vats. “They started production in January,” Duflo said. “It’s a bigger issue than people realize. The spongy moth population is growing. We’re actually on the upswing in this area.”

Aerial spraying, which may cost from $30 to $100 per acre depending on the applicator and location, is quite effective, but also heavily dependent on weather and timing. “The next few weeks are the most critical,” Duflo said. “You need 75-100 percent leaf development and larvae have to be migrating up the tree and starting to feed on leaves. That’s when the spray period begins. Our target date was May 17. I have people in each area sending me photographs with a ruler next to larvae, plus close-up photos of leaves to see what leaf development is taking place.”

When first emerging, tiny caterpillars are comparable in size to thin pencil lead. But they grow quickly and are soon no longer susceptible to spraying, usually by early- to mid-June when they wreak the most havoc.

“Last year it was basically like Godzilla going through Tokyo, destroying everything.”

— Jim Lieberum, Warren County Soil & Water Conservation District manager

Prospect Mountain, overlooking Lake George village, and long sections of the Adirondack Northway from Saratoga Springs to Canada, particularly in Warren and Essex counties, were completely defoliated last summer.

“Then we got a lot of rain. Within two weeks they were gone. That’s exactly what happens,” he said.

Rain activates a fungus in the ground that kills newly-hatched caterpillars before they climb into tree canopies. So officials are hopeful that a heavy storm Monday followed by more precipitation on Thursday this week will have such effects.

The fungus is one two natural enemies of the spongy moth. The other is a virus tends to build up in outbreaks with high populations, which eventually crash.

Spongy moths have been in the U.S. for about 150 years, after being introduced from Europe for silk production. Like many non-native insects, they began spreading and now range from northern Minnesota to North Carolina. Outbreaks typically occur every 10 to 15 years and last two or three years.

This year’s outlook

Most healthy trees grow new leaves, usually in July, in the first year of infestation, although mortality is possible after two years of moderate to severe defoliation, especially during a hot, dry summer. Conifers that lose all their needles will likely die.

Associate Professor Dylan Parry, of the State University of New York College of Environmental Science and Forestry, has done extensive spongy moth research. “The outbreak in Massachusetts, Connecticut and Rhode Island in 2016 to 2018 killed tens of thousands of oaks because it overlapped with drought,” he said. “We got lots of rain here last July and into the fall so the trees should mostly be able to withstand defoliation.”

However, the state Department of Environmental Conservation is spending more than $85,000 to treat about 3,300 acres at some of last year’s hardest hit sites, primarily in Central and Western New York, such as Rome Sand Plains Unique Area and Allegany State Park near the Pennsylvania border.

“Winter egg mass surveys and reports of hatching caterpillars indicate that these areas may be hit again,” DEC forester Robert Cole said. “Spongy moth presence was scattered across most of the state so infestations are possible just about anywhere.”

Last year, Lake George area hiking trails near Bolton Landing were overrun by caterpillars, whose tiny black feces rains down as they munch away on leaves overhead.

“It’s gross,” Lieberum said. “I know some people ended up canceling reservations at RV parks. People coming up to hike, who want to see a lot of nice trees, certainly it’s going to change their minds.”

“No one likes caterpillar poop or millions of hungry caterpillars crawling around.”

— Associate Professor Dylan Parry, SUNY ESF

What homeowners can do

Spraying may not be practical or possible in residential settings. But people can fight back, said Adam Wild, director of Cornell University’s Uihlein Maple Research Forest in Lake Placid.

One way is to wrap a piece of burlap around the trunk of a tree and tie it with string or rope in the middle of the burlap so the top half of the burlap folds down over the string. As the spongy moth caterpillars are climbing back up the trunk of tree they will get caught in the fold of the burlap. Either scrape off caterpillars or remove and submerge the burlap in soapy water.

Some people put sticky-surfaced tape around the trunks of trees and scrape off trapped caterpillars.

In late summer and fall, property owners should look for and destroy egg masses.

At this point there’s no way to predict what type of infestation might occur next year. Officials just hope the problem runs its course sooner rather than later. “This year’s defoliation could be similar to last year,” Cole said. “We started to see virus and fungus activity, along with egg parasitism, late last season so we are hopeful that it will increase. The season has just begun and wet weather over the next few weeks could have a positive impact.”