Hemlocks under attack Looper infestation expected to kill many trees

Hemlock looper, a nasty little pest, may soon be coming to a tree near you.

Maine is in the early stages of a looper outbreak that will last up to three years and leave lots of dead hemlock trees in its wake, according to the Maine Forest Service.

Damage from the voracious needle-eating insect is already noticeable around many ponds in the northern and eastern part of the state. The outbreak stretches from Kittery to Houlton, with a lot of damage in southern Aroostook, northeastern Penobscot, western Washington and northern Hancock counties.

Loopers are attracted to hemlock trees, which tend to grow around water bodies and where people build camps. Once there, the larvae will eat many other types of trees, such as white spruce, balsam fir and some hardwoods including maple and wild cherry.

The larvae, which move by forming their light green bodies into a loop before propelling their heads forward – hence the name looper – are wasteful eaters, nibbling on numerous needles rather than finishing one off. Once the cuticle of a needle is broken, it will die and fall off the tree. A heavily infested tree can be defoliated in one summer.

Henry Trial, an entomologist with the Maine Forest Service, is conducting a survey to find out how bad the looper infestation is. The state’s first infestation lasted from 1989 to 1993 and destroyed 250,000 acres of trees.

Trial has found a bad spot along Upper Lead Mountain Pond in northern Hancock County on land owned by International Paper Co. Hemlock trees devoid of needles line a portion of the gravel road along the eastern shore of the pond.

On Tuesday, Trial jumped out of his truck and spread a white canvas sheet over a wooden frame. With a long stick, he tapped a branch on a small hemlock. The canvas was quickly filled with dead and dying needles and a half dozen hemlock loopers. Finding so many of the insects on a single branch is typical in such heavily infested areas, he said as the larvae inched their way across the canvas square.

Two weeks ago, the damage was not visible, he said. On Tuesday, several nearly denuded hemlocks stood between two bright green spruce trees. With 70 percent of their needles gone, the trees are still alive, Trial said. But, if the loopers keep feeding and kill off 90 percent of the needles, the trees will die.

If that’s not bad enough, trees where loopers are munching away are weakened and more susceptible to hemlock borer, an insect that eats the bark, which can also kill the tree.

“Next year, this area will be completely defoliated,” Trial said, standing next to a rustic A-frame camp set among the trees several hundred feet from the pond. “It will look like it was nuked.”

Because the insects congregate around water bodies, the infestation is more of a problem for camp owners than industrial forest land managers, Trial said. As such, it’s hard to put a monetary value on the damage caused by the pests.

“If you lose all the hemlock around your camp, it’s hard to put a dollar figure on it, but it’s quite a loss,” he said.

Most people notice they have a problem when the bugs, which are about an inch long when fully grown, start falling onto their decks and picnic tables. They notice the dying trees later, Trial said.

Hemlock loopers, which hatch in late May or early June, climb upward in search of something to eat. If what they’re climbing isn’t a tree that suits their appetite, they spin a long thread of silk and slide downward. Mazes of silvery silk with light green worms at the bottom hung over the road along the pond.

This has been a great year for defoliating insects, Trial said. That’s probably because we’ve had a series of mild winters that did not kill the insects during their pupal stages. In addition, the recent wet weather has resulted in lush vegetation. In addition to hemlock looper, gypsy moths and yellowheaded spruce sawflies are proliferating this summer.

Loopers are native to Maine but outbreaks are rare. They move from place to place as moths, which are active from late summer through the fall. One moth can lay up to 300 eggs.

“They rely on sheer numbers,” Trial said.

Aerial spraying is effective at killing looper larvae, but pesticide use is controversial and expensive, Trial said. So, in most instances, landowners simply let the loopers run their course. It is believed that a disease kills the pests during the third year of an infestation.

“It will only be around a year or two, but it will kill some trees in that time,” Trial concluded.