'It's everywhere.' Beech leaf disease is decimating beech trees in Southern Berkshire County — and marching north quickly (2024)

Look up through the leaves of almost any native hardwood forest in Southern Berkshire County today, and you might notice an unhealthy, strange striping to some beech leaves.

Then, on closer examination, you’ll see crinkled leaves, some browning, some buds that never produced leaves, and some buds that are producing a second flush of leaves in a stress response.

Causing this change in the forest landscape is beech leaf disease. It’s on its way to decimating beech trees in Southern Berkshire County— and marching north quickly.

The beech forest in Massachusetts was already under threat from long-entrenched beech bark disease. With this new foe now defoliating trees, one researcher termed the situation a one-two punch.

The long-term impact to the native hardwood forest is uncertain, but there are already noticeable changes.

SPREADING ACROSS MASSACHUSETTS

Discovered in Ohio in 2012, beech leaf disease migrated northeast to Canada and is now seen in at least 13 states.

In Massachusetts, it was first noticed in Plymouth and Bristol counties in 2020. By 2022, it had been found in every county of Massachusetts, with Eastern Massachusetts more heavily affected than Western Massachusetts thus far.

There were 600 reports of beech leaf disease across the state in 2023.

“It’s almost to the point now where I’m looking for beech trees that are not affected by beech leaf disease,” said Tom Ryan, the Southern Berkshire management forester for the Department of Conservation and Recreation.

Ryan’s counterparts in Central and Northern Berkshire County are seeing evidence of the disease as well.

Kris Massini,management forester for DCR's Central Berkshire District, has seen beech leaf disease in all state forests he manages, including the state’s largest, October Mountain, although less widely than in Southern Berkshire. In Northern Berkshire, Kevin Podkowka has noticed beech leaf disease in isolated pockets of Balance Rock and Pittsfield state forests. He expects to find it in Savoy State Forest as well by the end of the season.

WHAT CAUSES IT

After it was first seen in northeast Ohio’s Lake County, researcher David Burke at The Holden Arboretum began studying what was causing the striping and defoliation. It took two years for the disease to migrate the 2 miles from its initial appearance to the arboretum.

Burke initially believed it might have been caused by a fungus or bacteria. He credited plant pathologist David McCann for first noticing the microscopic roundworm, called a nematode, on infected beech leaves.

After McCann’s initial discovery, “We basically demonstrated that if you add the live nematode to beech trees, that it will cause beech leaf disease,” said Burke, who worked on a team to isolate the cause.

“Basically, you can float the leaves or buds in water, and [the nematodes] come out, and then you can collect the live nematode,” Burke said. “We applied them to beech tree buds in the greenhouse. Whenever we added the nematodes to the buds, when those buds opened up in the spring, they had beech leaf disease.”

STUDYING ITS EFFECTS

Nicole Keleher, forest health program director for DCR, has been monitoring the spread of the disease.

As part of a regional effort, the state has 11 plots across the state to monitor beech leaf disease. Every tree (no matter the species) is tagged with a small metal numbered disc in each of these plots.

“It helps us better understand how the disease progresses and know what the timeline looks like,” she said. “It also helps us see how the other trees respond in the plot as you lose beech."

Noting that beech both tolerate and provide shade, "They’re a big part of the canopy," she said. "So once you lose that, you get a lot of sunlight and opening spaces. It can really change how your forest dynamic works.”

Keleher's team measures each mature tree in 37-foot diameter plots, counts seedlings and saplings, measures die-back as well as rates the severity of beech leaf and beech bark disease.

“When we picked our plots, we didn’t think beech leaf disease was so widespread in the state,” Keleher said. The plan was to have two infested and nine uninfested sites.

“The first year we went out, I think six of them had it,” Keleher said. “And then by the next year, all of them had it.”

Walking through one of these plots off the Robert Frost Trail in the Holyoke Range in Amherst, Keleher noted several dead and dying beech trees that were alive when they were tagged in 2021.

“The disease severity has increased dramatically at this specific plot since last year,” Keleher said. “There’s physically more sunlight reaching the ground here because we are losing more of our beech leaves.”

Keleher noted the disease's progression in a single tree.

“The first year we found it, there were like a handful of the leaves with the stripes, but now almost every single beech has very noticeable, pretty severe symptoms,” Keleher said. Viewing a leaf “from the top, you can tell that it’s deformed and blistered, but it’s really when you look from the bottom up that it’s easiest to see.”

She said damaged leaves are not useful to the tree, and the tree will drop them early.

The nematode lives on the leaf during the spring and summer, but in the fall migrates to the bud, where colonies do their damage over the winter.

“As you get more and more nematodes present, what you see on the leaf, it becomes more and more severe,” Keleher said.

Keleher said transmission appears to be driven by wind and birds, rather than humans.

“We know that birds love beech,” Keleher said. “They eat the buds, they eat beech nuts.”

HOW DO YOU STOP IT?

Keleher said the novel aspects of beech leaf disease, including its origin in a nematode, make it more difficult to know how to manage than other threats to trees. In Plymouth, she said, beech trees are starting to die.

“This is so far beyond anything else, that it’s really starting from scratch in a lot of ways,” she said.

There has been some research on pesticide and some success, but that’s an expensive solution and one that can’t readily be applied to forests. Keleher said it’s uncertain what the long-term effectiveness of these are, and “they’re incredibly expensive.”

Keleher said she doesn’t know whether the presence of beech bark disease is adding to the impact of beech leaf disease, or if there may be other variables, such as soil structure, that may be delivering the heavy hit to Massachusetts forests.

European and copperbeech are affected, though Burke said Japanese beech does not appear to be.

In Ohio, Burke is now researching natural resistance. He said he’s finding it among some American beech trees, and has begun grafting to try to both develop and convey that resistance to other trees.

He doesn’t recommend proactively cutting down healthy beech trees, but does recommend what he calls structural pruning, of up to 20 percent of a tree. That will let in light and air, possibly making it more difficult for the nematode to move from the leaf to the bud in the fall.

To prevent spread of beech leaf disease, Burke recommends not moving, or even planting, beech trees.

'IT'S EVERYWHERE'

In Berkshire County, foresters are worried about what the changes to the forest will bring by beech leaf disease.

Ryan pointed out that beech, along with maple and birch, are part of the dominant hardwood mix that has been historic to the Berkshires.

“Last year, I was able to find it, but it took a little bit of effort,” said Ryan, the forester in Southern Berkshire. “This year it seems like it’s everywhere in my travels.”

Podkowka in Northern Berkshire said he's concerned because young, otherwise healthy trees, seem to be particularly susceptible to this novel disease.

Massini in Central Berkshire said beech leaf disease has the potential to dramatically change both the understory and the overstory in Berkshire County.

"It's hard to tell if it's going to be a potential benefit to the forest for other species to have that space," Massini said. "Or if it could have more of a negative effect as well, by losing the beech.I think we're not quite sure which way everything's going to go yet."