<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/BeechLeafD1.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/BeechLeafD1.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/BeechLeafD1.jpg?v=ap&w=980&h=551 800w" > In later stages of beech leaf disease, after the leaves have developed dark stripes, the leaves shrink and become dry and crinkly. (Ohio Department of Natural Resources Division of Forestry)

At a Glance Beech leaf disease was first found in Ohio in 2012.

Now it has spread to 11 Ohio counties, eight Pennsylvania counties and five counties in Ontario, Canada.

The disease infects at least three species of beech trees: American, European and Oriental.

Scientists are warning that a disease killing American beech trees appears to be spreading more quickly — and they still don't know what's causing it or how to stop it.

Since being discovered in one Ohio county in 2012, “beech leaf disease” can now be found in 11 Ohio counties , eight Pennsylvania counties and five counties in Ontario, Canada, according to a news release from Ohio State University.

A study published in the journal Forest Pathology says the first sign of the disease is dark-green “bands” appearing between the veins of the trees’ leaves.

Later, leaves become uniformly darker and they shrink and get crinkly. Limbs stop forming new buds and eventually the tree dies.

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“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,” senior researcher Pierluigi “Enrico” Bonello, an Ohio State professor of plant pathology, said in the release.

An additional worry is that the disease has been found in European and Oriental beech tree species in nurseries and at the Holden Arboretum in northeastern Ohio. Bonello said that shows the disease can infect more than one species and puts more trees in danger.

John Pogacnik, a naturalist with Lake Metroparks and an author of the new study, first noticed the new disease in 2012. The next summer, he found sick trees across six counties in northeast Ohio , according to the Washington Post.

“I’m glad to have found it, to just put it out there and let people know,” Pogacnik said. “But it’s still not the greatest feeling in the world.”

Pogacnik told the Cleveland Plain Dealer, "I've sent samples to the U.S. Forestry Service and Ohio State, and contacted botanists in Europe and Asia, and no one has ever heard of it. So where did it come from?

"The worst part is that until someone figures out what is causing it, you can't begin to stop it."

Ohio State University researchers suspect a microbe might be to blame. Professor Bonello and graduate student Carrie Ewing, lead author of the new paper on the disease, are working to identify tiny microbial differences between trees with beech leaf disease and those without.

“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.”

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In May, according to the Plain Dealer, Dave McCann, an Ohio Department of Agriculture plant pathologist , announced he had found microscopic worms known as nematodes in infected beech leaves.

He sent the leaves to the U.S. Department of Agriculture's Research Center Maryland where federal scientists determined the nematodes were a new species. The new worms were similar to a nematode in New Zealand that infects trees and causes leaf damage similar to beech leaf disease.

McCann said, "I'm not saying it is [the cause of beech leaf disease], but we're going to continue to conduct research on this possibility... and I plan to share our findings with the U.S. Forest Service."

American beech trees range from Florida to Canada and west to Texas and Wisconsin. Deer, bear and other animals rely on beech nuts for food.

The new paper about beech leaf disease says if only half of Ohio's beech trees were lost, environmental costs would reach $225 million. That figure is based on factors like "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."