April 23, 2018
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Biologists prepare to attack emerald insect

By Heather Steeves, BDN Staff

CAMDEN, Maine — Insect master Colleen Teerling is hunting for something she doesn’t want to find. She has waged a war against the emerald ash borer — a metallic green beetle that, as far as we know, is not yet in Maine. And although the battle has not yet hit the home front, Teerling and her employer, the Maine Forest Service, are leading the nation in finding new ways of trapping the invasive insect.

Teerling’s weapon is a drawknife. The U-shaped tool has two handles, one on each side of one blade. On Tuesday morning, Teerling drew her knife with both hands and began attacking an ash tree in Camden Hills State Park. It was a necessary sacrifice, she argued.

As Teerling scratched through the silver bark, through the tawny wood, into deeper white wood and finally to a bamboo-yellow core, she was forcing this ill-fated ash to secrete chemicals through its leaves. Emerald ash borers find these chemicals irresistible. Every borer for hundreds of feet — a lot of feet in insect terms — will flock to this distressed tree.

It’s a process called girdling, scraping away the bark all the way around the trunk. It will kill the tree.

“We sacrifice one tree, and it will protect the others,” Teerling said.

Otherwise, if there are emerald ash borers in the forest, they will individually attack many trees — not just one. They use a process similar to Teerling’s, but on a large scale. The insects, which are native to China, will penetrate the bark, slither under it and eat until the bark falls off, which also girdles the tree and kills it.

In the forest, bark fell onto Teerling’s boots as she worked her arms up and down the tree with the knife.

“Oooh, a caterpillar,” she said, bending down to look at what had just fallen with the rubble. “Well. It was a caterpillar.”

A casualty.

In autumn, park ranger Peter Carpenter will cut the tree down. Then Teerling will dice up parts of its trunk to see whether they caught anything.

It will be easy to tell. The emerald ash borer leaves distinct squiggle lines in the tree, underneath the gray diamond-patterned bark. Some of the older larvae burrow an inch or so into the real meat of the tree.

While Teerling scraped the bark, about 25 woodlot-owning volunteers throughout the state were doing the same thing. Because of the Maine Forest Service budget, Teerling can’t girdle many trees. It’s time-consuming and labor-intensive. So they recruited. In autumn, volunteers will fell the girdled trees and hack them to bits looking for insects.

“The emerald ash borer is moving in,” Teerling said. “They will come to Maine at some point. If we find it as a small infestation we can quickly deal with it. If 10 years go by, it will be nearly impossible to get under control.”

Hence the search. Right now the insects are as close as Montreal and New York state.

And when the borer does find its way to Maine, “it will be disastrous,” said Camden Hills State Park ranger Carpenter. Ash make up 15 to 20 percent of all trees in the Camden park.

“These ash trees are beautiful, tall and elegant. And they have a lot of timber value. It’s what baseball bats are made of and what we use for firewood for our camps here. It’s very valuable to our state,” Carpenter said.

In fact, firewood is the main way these evil beetles find their way to new places. That, Teerling said, is why it is illegal to transport out-of-state firewood into Maine.

Carpenter took the knife from Teerling to help strip the tree.

“It’s hard work killing trees. I don’t much like it myself,” he said as he created a bamboo-colored band around the tree, to stress it without killing it. If he killed it, native, “good” insects would attack it too, which would mess up the results.

The difference between good insects and these insects is that the insects native to Maine will wait until a tree is dead to attack it, eat it and live in it. The Chinese beetles won’t wait. They attack healthy ash trees and eat away at them. Chinese trees have natural defenses against the beetles, but Maine trees don’t and are much more vulnerable.

Teerling has seen the devastation of the metallic green beetles elsewhere. This spring she went to New York where emerald ash borer infestations have overtaken some areas.

Entire streets once lined with the trees are now leafless and bare.

In those situations, city folk can inject each ash tree with a pesticide to save it. It’s expensive and they have to do it to every tree every year. In Maine, that’s not an option. Not in a forest.

So Teerling thought up something completely new. She’s gathering troops together in case of an exotic insect invasion. So far, she has rounded up a handful of people to “adopt” a native type of nonstinging wasp. The wasp eats insects just like the borer. And if the borer moves in, she knows the wasps will attack it.

The people who adopt the wasps — which seem to live under baseball diamonds (“they love sandy soil”) — will take a net and try to steal the wasp’s food. When the volunteer sees a victorious wasp, lunch clutched to its body, they will swoop it up in the net. The freaked-out wasp will drop its food. Then the volunteer will see whether its meal was an emerald ash borer.

Teerling and the Maine Forest Service invented this entirely new way of finding the species. Other states are taking Maine’s lead in stealing wasp food.

Also available are relatively ineffective purple nets people can hang from trees that work to catch the borers.

“But all these methods are just drops in the bucket,” Teerling said. “The most effective thing we’ve done is educate people. Forests are important in Maine. It’s an integral part of our identity and tourism and logging. If we lose our trees to these invasive insects, it will change our state for the worse.”

After the breakout of Dutch elm disease in Maine decades ago, “I’m not sure how much more Maine forests can take,” she said.

While the state braces for the potential of the emerald ash borer, there is good news on another front. The Forest Service announced Wednesday that the browntail moth caterpillar infestation in the Brunswick area appears to have been killed off by a fungal disease.

Rainy weather in May seem to have been a catalyst for the fungus which has headed off what experts predicted would be a banner year for the noxious caterpillars. Rains forced them into their web-like tents where their close proximity to one another helped spread the deadly fungus.

For more information visit www.emeraldashborer.info or call 866-322-4512.

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