American beech trees are dying in Northeast Ohio and several other states and providences nearby due to beech leaf disease. 

Researchers at Ohio State University are conducting a study of the disease to find out why. 

Enrico Bonello, a professor of plant pathology in Ohio State's College of Food, Agricultural, and Environmental Sciences (CFAES), oversees the study.

"There's no similar forest tree disease that we are aware of anywhere," Bonello said, "It's really a black box."

The disease was first discovered in Lake County in 2012 but has subsequently spread to American beech trees in nine additional counties in Ohio, eight in Pennsylvania, one in New York, and five in Ontario. 

The disease, which young trees appear to be more susceptible to, starts out as dark stripes on the leaves of the trees and then deforms them.

The disease can eventually kill the trees. 

Carrie Ewing, a doctoral graduate student assisting with the study, is comparing the genes of microorganisms present in leaves that have symptoms of beech tree disease and those that do not.

Ewing is hoping to identify the microorganisms that are associated with the disease in order to determine if they are viruses, fungi, bacteria, phytoplasmas or nematodes. 

Phytoplasmas are bacteria without cell walls. Nematodes are microscopic worms.

If Ewing identifies the suspected pathogen causing beech leaf disease, the team can begin using it to inoculate healthy trees in an attempt to prove it is the cause of the disease. Ewing is expecting to have the results of the study by summer. 

"It's like trying to find a needle in a haystack by comparing various haystacks," Bonello said.

The disease first affected American Beech trees in Northeast Ohio, but European beech and Oriental beech trees in nurseries in Lake County have also shown symptoms. 

According to Bonello, this means there is the potential for the disease to spread worldwide in the northern hemisphere.

The U.S. Forest Service and researchers with Lake County's Holden Arboretum in Kirtland are conducting a separate study on potential causes of the disease. 

That study is looking into whether nematodes found two years ago on infected beech leaves were causing the disease or if they were just present on the leaves.