Foresters all over Southern New Hampshire are on the lookout for a miniscule menace infesting and killing ash trees.
An infestation of emerald ash borers was found two weeks ago by New Hampshire foresters when they accidentally crossed the state line from Salem into Methuen and found an infested tree.
The tree was near Pond Street in Methuen, according to Massachusetts forest health program director Ken Gooch.
The insect is in New Hampshire already, first detected in Concord in March 2013.
The pest originated in China and was first discovered in this country in 2002.
One of the primary ways it spreads is through the transportation of firewood.
In July 2011, New Hampshire banned all imported firewood in an effort to keep the emerald ash borer and equally unwelcome Asian long-horned beetle out of the Granite State.
The adult emerald ash borer is metallic green, with a bullet-shaped body, and is about half an inch long.
The insects destroy tissue under an ash tree’s bark, killing the canopy of the tree. The insects leave exit holes in the bark when they emerge in late spring.
Although ash represents a fairly small percentage of the state’s forest — about 6 percent — nationally, the insect has cost millions in lost revenue. Here, it could cost towns that would have to replace the ash trees that line many streets, firewood dealers who count on the species, and furniture and cabinetmakers who use the lumber.
The infestation seemed to be as many as five years old, which spells trouble for New Hampshire, Gooch said.
“It’s really heavy,” Gooch said. “You’re more than likely infested there, but most of the ash trees we found were on our side of the border.”
Areas threatened include all of Atkinson, Pelham, Plaistow, Salem, Windham and most of Hampstead, UNH Cooperative Extension forester Karen Bennett said.