Leaf disease continues to ravage Pa. beech trees

There’s a disease wreaking havoc on beech trees in Pennsylvania.

Beech leaf disease currently is found in all but two of the state’s 67 counties.

Caused by microscopic nematodes, the disease infects native American beech trees and commonly planted European ones, said Mihail Kantor, an assistant research professor of nematology at Penn State. It is more harmful to younger trees.

About 90% of infected saplings die from the disease, which damages the tree’s leaves and buds, according to the state Department of Conservation and Natural Resources.

There are no preventive or curative treatments available.

“It’s a serious problem,” Kantor said.

Infected beech trees can be spotted by interveinal darkening of the leaves — a “very distinct” feature of the disease compared with other beech diseases, Kantor said.

Researchers believe the invasive nematodes move through the tree via water. Though researchers don’t know how the disease travels from one tree to the next, some theories suggest it could be transmitted by birds, caterpillars or mice, Kantor said.

The disease, which is found in 11 states, doesn’t discriminate between beech trees in forests, residential areas and even nurseries.

First discovered in 2012 in Lake County, Ohio, the disease spread to Pennsylvania’s Erie and Crawford counties in 2016, and has traveled throughout the state since then.

This summer was “particularly bad” for beech trees in the state, according to DCNR forest pathologist Jill Rose.

In June, the disease was detected in 48 counties. By August, that number climbed to 65 counties.

In Allegheny and Westmoreland counties, the disease was detected in 2019 and 2021. Now, parts of Southwestern Pennsylvania are “just smoked” by it, Rose said.

Beech trees are “very important” to Pennsylvania wildlife and diversity, according to DCNR district forester Cecile Stelter, who called beech leaf disease “distressing.”

“Any time we look at our native tree species and see something that could significantly reduce their abundance, it’s concerning,” Stelter said. “The more diverse your forest is, it’s better able to handle insects and diseases that come through.”

Its detection comes as Pennsylvania beech trees also battle beech bark disease, which made its way to the state in 1958.

“Not only do you have (beech bark disease) going on, you’ve got beech leaf disease on top of it,” Rose said.

Rose hopes mature trees build a natural resistance to the disease.

Kantor said state and federal governments should allocate more resources to research the disease and find a way to stop it.

“There are too many unknowns right now,” he said, “and more time and resources need to be allocated to answer those questions.”

Because there are no treatments available, there isn’t much people can do to help infected trees. However, people can try to prevent the disease from spreading by removing infected trees, and pruning and destroying infected material, Kantor said.

Those who think a tree on their property is infected should contact their local service forester.