01/09/19

Beech Trees are Dying, and Nobody’s Sure Why

A confounding new disease is killing beech trees in Ohio and elsewhere, and plant scientists are sounding an alarm while looking for an explanation.

Beech Trees are threatened by a new disease rapidly killing the species.

In a study published in the journal Forest Pathology, researchers and naturalists from The Ohio State University and metroparks in northeastern Ohio report on the emerging “beech leaf disease” epidemic, calling for speedy work to find a culprit so that work can begin to stop its spread.

Already, the disease has been found in 11 Ohio counties, eight Pennsylvania counties and five counties in Ontario, Canada. It’s characterized by dark-green “bands” that appear between the veins of the trees’ leaves and provide the first hint that the tree is diseased. In later stages, leaves become uniformly darker, shrunken, crinkly and leathery. Affected limbs stop forming buds and, over time, the tree dies. Young trees seem to be particularly vulnerable.

“It’s hard at this point to say where this disease will go, but it has all the hallmarks of something like emerald ash borer or sudden oak death, threats to trees that start slowly and quickly pick up speed. We seem to be in that rapid expansion phase right now,” said senior researcher Pierluigi “Enrico” Bonello, an Ohio State professor of plant pathology.

If just half of American beech trees in Ohio were lost, it would come at environmental costs of approximately $225 million, according to an estimate in the new paper that takes into account various factors, including the trees’ role in removing carbon from the atmosphere, maintaining biodiversity, furnishing habitat for wildlife, aiding in water purification, providing aesthetic and recreational value as well as other ecosystem services.

“The hope is to find a needle in one haystack – the diseased trees – by comparing it with other haystacks, or non-symptomatic trees,” Bonello said. “It’s all about subtracting out all the things they have in common and finding what doesn’t match up.”

In particular, they’re looking for evidence showing whether the disease is bacterial, fungal, viral or possibly caused by a phytoplasma.

That said, some other research has pointed to a microscopic worm, or nematode, as a possible culprit.

In addition to American beech trees, other species in Holden Arboretum in northeastern Ohio have also been infected.

This is worrisome because it appears to mean that the risk of disease extends beyond a single species, putting more trees in more areas of the world under threat, Bonello said.

Until scientists determine what is causing beech leaf disease, there’s little they can offer in the way of specific recommendations to stop its spread. Bonello and Ewing are hopeful their work might produce some answers by this summer.

“Beech trees are a significant food and habitat resource for wildlife. We can’t treat or manage our beech forests effectively if we don’t know what is causing the decline,” Hausman said.

See what researchers plan to do to possibly understand this disease.