by Katie Bohn, Pennsylvania State University Beech trees affected by beech leaf disease produce leaves with a distinctive banded pattern, according to Penn State researchers. Credit: Mihail Kantor

In the woods of the northeastern U.S., a strange disease is creeping through the canopies. Spreading quickly, it causes leaves and branches to wither and, in many cases, the tree to eventually die.


The arboreal ailment—beech leaf disease—currently has no known treatment or cure, putting large swaths of trees or even entire forests in jeopardy. But researchers in Penn State’s College of Agricultural Sciences are on the case, spearheading ongoing efforts to learn more about the disease and how to combat it.

“This is a big problem for our forests, as well as the trees in our own backyards,” said Cristina Rosa, associate professor of plant virology. “Many species of wildlife depend on beech trees for food and shelter, in addition to the Pennsylvania citizens who value the forests for recreation. It’s vital that we learn more about this disease and how, eventually, to overcome it.”

While beech leaf disease first was observed in Ohio in 2012, it is now particularly widespread in Pennsylvania, with all 67 counties currently affected, said Mihail Kantor, assistant research professor of nematology. Early symptoms of the disease include a dark green banding pattern between the veins of leaves before more severe symptoms spread to the rest of the tree.

While the exact cause and mechanism of the disease is under investigation, Kantor said researchers now know that infection with beech leaf disease is associated with a particular species of nematode—tiny worms that feed on plant cells, bacteria, fungi and other microscopic creatures.

This nematode species, Litylenchus crenatae mccannii, was previously found to be associated with trees suffering from the disease.

“Based on data from a research collaboration with scientists from the U.S. Department of Agriculture’s Agricultural Research Service, we know the nematodes enter the buds and feed on the leaves while they’re still developing within the bud, which can cause morphological changes in the leaf,” Kantor said. “And then, when the buds open, the nematodes can spread among the leaves. But we’re not sure if the nematodes are the only ones causing the disease, or if, for example, they somehow facilitate other pathogens to enter the plant cells and cause the infections.”