A fungus that has long killed oak trees in the Midwest could make its way to New Hampshire, state officials warn.

Oak wilt disease has not been found in the state yet. But several outbreaks in New York in recent years — including in the Albany area — have New Hampshire officials on the lookout for it, said Kyle Lombard, the Forest Health Program coordinator with the N.H. Division of Forests and Lands.

“That opened our eyes,” Lombard said. “… It can definitely travel long distances, and our conditions in the east are just like Albany, N.Y., so there’s no reason it couldn’t get here.”

Oak wilt has been in the central part of the country for decades, but incursions into New York are more recent, he said.

Forestry experts say the fungus can kill a red oak within weeks. White oaks are also susceptible to the disease, though less so, according to the N.H. Division of Forests and Lands.

Lombard said to look for leaves that wilt and fall off during the summer.

“If you notice an oak tree that just all of a sudden decides to drop its leaves in July, there’s nothing else that would cause that,” he said.

The leaves don’t turn brilliant colors before fading to brown and dropping, as they would naturally in the fall. Rather, brown patches creep in, and leaves can fall while half green, according to Lombard.

The N.H. Division of Forests and Lands is asking people to report any oak trees that shed their foliage in July or August.

None of the six New England states has reported any outbreaks of oak wilt.

Red oaks live throughout southwestern New Hampshire, according to Steve Roberge, a forester with the University of New Hampshire Cooperative Extension’s Cheshire County office.

“People who buy oak for timber and things like that come to the Monadnock Region, because we have some of the best oak in its range,” Roberge said.

Oak wilt can spread through conjoined root systems, according to the Division of Forests and Lands. Beetles also carry it from tree to tree.

The disease affects a tree’s vascular system — the mechanism that transports water and nutrients from the roots to the leaves. Infected by the fungus, a tree will shut that system down, Lombard said.

“It basically starves itself to death,” he said. “… The tree just thinks it’s dying of drought.”

While there’s no way to cure an infected oak, the disease spreads relatively slowly, Lombard said. It can be contained by digging a trench around an infected site to sever root connections and removing the diseased trees — though the rocky Granite State soils would make that difficult, he noted.

“Our plan is to use herbicides,” he said. “… We will basically cut the infested tree and treat the stump with an herbicide that kills the roots. And once the roots are dead, nothing can travel through them.”

Oak wilt appeared in New York a little over a decade ago in Glenville, about 30 miles northwest of Albany, and has resurfaced there several times since, according to a management plan published last year by the N.Y. Division of Lands and Forests. The disease has also appeared at sites south of Rochester, N.Y., and on Long Island.

Transporting firewood can spread oak wilt and other pests, like the emerald ash borer, over long distances. New Hampshire forbids bringing in firewood from out of state, unless it’s certified as heat-treated.

Roberge, the county forester, said that if oak wilt comes to New Hampshire it would most likely be through firewood. “So for folks who are picking up their Keene Sentinel who are not from here: ‘Don’t bring your firewood.’ ”

Swift Corwin, a Peterborough-based forester, said that because the disease hasn’t been observed any closer than New York, it’s unlikely to spread to New Hampshire unless someone brings in infected firewood.

Corwin cautioned landowners not to overreact.

“It’s important for people to know they don’t need to go and cut all their oak trees down,” he said.

Harvesting afflicted oak trees for timber is generally safe, provided best practices are followed, Lombard said.

Both he and Roberge encourage people to report any trees they believe are infected.

“As long as we are finding them early and are diligent about taking care of the problem, I think (it) shouldn’t be that big a deal,” Lombard said.

Reports can be made by calling the division’s Forest Health Program at 464-3016 or on the website NHBugs.org.

Paul Cuno-Booth can be reached at 352-1234, extension 1409, or pbooth@keenesentinel.com. Follow him on Twitter at @PCunoBoothKS.