Beech trees, one of the most abundant and crucial hardwood trees in New Hampshire, are getting pummeled by beech leaf disease this season.
“The trees actually look quite terrible,” said Jeff Garnas, an associate professor of forest ecosystem health at the University of New Hampshire. Many across the Seacoast and southern tier are crumpled and browning, instead of bright green.
While initially spreading rapidly across southern New Hampshire after it was first discovered in the state in 2022, this year it spread slower than expected. Experts are not sure why.
“It really has not gone as far north as we thought it was going to,” said Kyle Lombard, a forest entomologist with the Division of Forest Lands. He said this year, new cases were found primarily along the southern border of the White Mountains, failing to penetrate northern Coos or Grafton counties.
The disease, which has been found in 15 states, occurs when microscopic roundworms called nematodes burrow into the buds of the trees’ leaves. According to Garnas, they then block photosynthesis, resulting in leaves and buds falling off and trees growing bare. Younger beech trees are susceptible to beech leaf disease, and eventually, it can kill trees after a few years.
Lombard said much of the disease is still mysterious for scientists, and there is not yet a clear approach to halting its spread.
“There's no bio controls that we're aware of. Pesticides are not really a thing for ecosystem wide control,” he said. “At this point, it's just moving through the beech forests, not just in New Hampshire, but all across the Northeast.”
The trees are also contending with beech bark disease, which has been around for decades. But Garnas, the UNH professor, said beech trees have been able to hold up to the bark disease because it doesn’t target young saplings and seedlings.
Garnas said the statewide drought isn’t helping beech trees either.
“Drought, plus beech bark disease plus beech leaf disease can really be a bad combination,” Garnas said.
There has been little tree mortality caused by beech leaf disease since its arrival in the state, but Garnas said he expects that will happen in the near future.
“[The trees are] surviving, but they're suffering,” he said.
Both Garnas and Lombard underscored the vital roles beech trees play in New Hampshire forests.
“Ecologically, it's very important to wildlife, to bears, to many mammals, to birds, to insects,” Garnas said. “It would really be a huge loss if it were to decline.”