Lethal Disease Spreading Rapidly Through PA Trees: How To Spot It

PENNSYLVANIA— Millions of beech trees provide shade to Pennsylvania streets, cover forests, and provide food sources for local wildlife. But an emerging threat that could be even more damaging to the ecosystem than the spotted lanternfly is killing these trees, experts say.

The lethal Beech Leaf Disease (BLD) affects both young and mature American beech trees, and can kill a mature tree in six to 10 years. Younger trees may die quicker than that.

The disease has been rapidly expanding through Pennsylvania, and has been located in 65 of Pennsylvania’s 67 counties as of mid-May, said state forestry officials. Its effect could "drastically change the deciduous forests of the eastern United States," said a researcher with the state Department of Conservation and Natural Resources.

The disease may be caused or carried by a type of nematode (worm) that eats buds and leaves off of the trees. This makes some leaves emerge with leathery, dark green parts that may turn yellow or brown as the season continues, according to Science.org. The damaged leaves fall off and cause the tree to use extra energy growing new ones.

American beech trees are common in eastern U.S. forests, and beech leaf disease has been found in 10 states as well as Ontario. The disease was first detected in northeast Ohio in 2012 and now affects trees from Michigan to Maine. The U.S. Forest Service has been studying the extent of Beech Leaf Disease, and how severe it may be.

BLD is different from the previously-known beech bark disease, which can affect beech trees concurrently with the leaf disease.

How many beech trees are in Pennsylvania?

The beech tree makes up an estimated nine percent of Pennsylvania’s forests, said the Bureau of Forestry. There are upwards of 700 million beech trees in Pennsylvania according to U.S. Forest Service inventory estimates – and that number represents both smaller trees and larger ones.

“A high percentage of (trees) are showing symptoms in the leaves,” said Pennsylvania forest pathologist Jill Rose. Rose added that Beech Leaf Disease is relatively new, so scientists are still studying the exact cause and how to mitigate it.

“In many areas of the state, BLD is co-occurring with beech bark disease (BBD) which is another devastating disease complex,” said Rose.

What does beech leaf disease look like?

The disease can be best seen by looking up into the forest canopy, and symptoms include “darkening and thickening of the tissue” between leaf veins, according to researchers at Penn State.

Natural Resource Specialist Jeffrey Woleslagle added that early symptoms of BLD “include dark stripes between the veins on the leaves” in an article for the Pennsylvania Department of Natural Resources.

And, late spring is a good time to identify trees that may be infected, since their leaves are full and may show signs of disease.

What can people do about beech leaf disease?

Experts are still figuring out how to best manage beech leaf disease. Researchers have “encouraging results” with treating beech saplings with a phosphite product twice a year, according to a study from the University of Rhode Island.

Property owners who spot a beech tree that may have BLD can report it to their local service forester. The Pennsylvania DCNR Bureau of Forestry has assigned foresters for each county.