Residents in New Hampshire say they're worried an invasive beetle that can strip nutrients from ash trees and kill them within a year may be moving into their state.

The concern grows from a discovery by forest officials of a swarm of the extremely destructive emerald ash borers in Salem, Mass., just hundreds of feet away from the New Hampshire state border.

After the discovery they termed "significant," the officials said they were advising homeowners in the adjacent New Hampshire counties of Hllsborough and Rockingham to closely examine their trees.

If the insect is found in New Hampshire, state officials would impose a quarantine on the shipping of ash wood products and of hardwood firewood, state entomologist Piera Siegert said.

The adult beetles, about one-third of an inch long, lay their eggs on the bark of ash tree trunks and major branches.

After hatching, the insect spends its larval stage of life feeding under the bark where it has burrowed. A large infestation can prevent a tree from moving water and nutrients, leading to eventual death, Siegert said.

Because the pest is invisible under the tree's bark, people moving firewood or products containing ash wood from one location to another can unwittingly spread it, she said.

The adult beetles can also fly up to a half-mile.

"So, it spreads rapidly (when there is human assistance), it kills quickly, and it incurs high costs to industries, landowners, and municipalities," she said.

Native to Southeast Asia, the emerald ash borer entered the United States in the mid-1990s in Michigan, possibly in ash wood used in shipping crates.

Since then it has spread to 22 states, as far as Colorado in the West and Georgia in the South, and has also been detected in Canada.

That has led federal officials in both the United States and Canada to quarantine certain areas in an attempt to constrain the spread of the ash borer.

The invasive pest has already decimated ash trees throughout Massachusetts, and the infestation shows every possible sign of moving north into New Hampshire, Seigert said.

Of the approximately 8 billion ash trees in the U.S., around 150 million have died from infestations since the emerald ash borer arrived, experts say.

While some insecticides have proven partially effective in combating emerald ash borers, they are only practical for targeted use on high-value landscape trees, Siegert said, and have limited performance in large or heavily infested trees.