BATH — Although the Asian long-horned beetle has not yet been detected in Maine, its tree-destroying presence in New England has put arborists including Tom Hoerth of Bath on alert – particularly since nearly half the city’s public trees happen to be one of the top items on the beetle’s menu.

Hoerth and Nancy Sferra, director of science and stewardship at the Nature Conservancy of Maine, will teach a free one-hour workshop on forest pests on behalf of the Kennebec Estuary Land Trust. The class will be held at the Bath City Hall auditorium from 5:30-6:45 p.m., Thursday, Aug. 6.

The Asian long-horned beetle is a woodboring insect that infests a large variety of hardwoods and was accidentally brought into the United States in wooden pallets from Asia, according to the land trust. Not only would infestation in Maine effect the health of the state’s forests and cohesion of its ecosystems, but it would lead to a loss in forest products, tourism industries and maple sugaring and necessitate an expensive effort to control the spread of the pests.

A large infestation of the beetle was found nearly a year ago in Worcester, Mass., and some speculate that the insect has reached New Hampshire via infested wood products and chips, and specifically recreational firewood. The beetle has also been found in New York and New Jersey, and parts of Canada, Hoerth said.

“It takes a long period of time to go through the process of surveying for it, identifying where it is, doing the remediation, and then doing the follow-up surveys to see if it’s still present or not,” Hoerth said. “You need a certain number of years of negative results to say it’s eradicated.”

Among the beetle’s preferred trees are maples, horsechestnuts, elms, birches, poplars and willows, as well as mountain-ash trees.

“Seventy-five percent of Worcester’s trees are Norway maples,” Hoerth said. “So the bug has a huge population to dine on.”

In Bath, 45 percent of trees on public property are Norway maples, he said.

Ash, apple, oak, cherry and pear trees are questionable host species for the beetle, while hickory, dogwood, beech, honey-locust, walnut and lilac are unknown. Conifers such as spruce, pine and fir are not on the list.

“It’s got a fairly wide appetite,” Hoerth said. “It’s not a fast mover, though, so once it finds a nice spot it kind of hangs out and eats and eats and eats, and it’s a very slow decline of the tree.”

Mitigation techniques include injection of an insecticide into the tree to kill the beetle, as well as an injection into the soil that is taken in by all the surrounding trees. Removal of the host trees around an identified hot spot for the beetle, similar to a fire break in eliminating further spreading, is another technique, as well as total removal of the infested trees.

“The fewer cuts, the better,” Hoerth said, “because the more you cut, the more you run the risk of dislodging an adult, or an egg escaping and surviving.”

The workshop teaches how to identify this beetle, as well as the emerald ash borer, Hemlock woolly adelgid and other pests that are not native to this area but are close by. The information is geared especially toward people who spend significant time in the forest, and citizens have been important in reporting new infestations and outbreaks.

One key message Hoerth wants to get out is for people not to bring firewood into the state, since that is how the beetle can move great distances.

“We’re the most forested state in the Union,” he said. “We’ve got plenty up here that you can burn.”

More information can be found on the U.S. Department of Agriculture Web site at www.na.fs.fed.us/fhp/alb/.

Alex Lear can be reached at 373-9060 ext. 113 or alear@theforecaster.net.

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A male Asian long-horned beetle. (Courtesy Invasive.org/ Michael Bohne/Bugwood.org)