Ohio State makes strides in finding resistant ash

Researchers at Ohio State are making good progress toward finding trees resistant to emerald ash borer (EAB). Identifying resistant genotypes is critical for maintaining demand for ash in the nursery industry and for reforestation, said Dan Herms, an entomologist at the Ohio Agricultural Research and Development Center (OARDC).

In the search for an EAB-resistant ash tree, Herms has teamed up with Enrico Bonello, an OARDC and OSU Extension plant pathologist; David Smitley, a Michigan State University entomologist; Donald Cipollini, a biologist at Wright State University; and Jennifer Koch, a biologist with the U.S. Forest Service’s laboratory in Delaware, Ohio.

The team wanted to expose different species of native and Asian ashes to the insect to evaluate their resistance, identify possible mechanisms of resistance, and determine the effects of drought and other stressors on susceptibility to the invasive pest. They’re studying natives such as white ash and green ash; Manchurian ash (an Asian native); and Northern Treasure ash, a hybrid between native black ash and Manchurian ash.

“Our working hypothesis was that the Asian ash would be the most resistant because of natural defenses resulting from co-evolution with the insect over a long period of time, considering that in Asia EAB does not devastate its native hosts,” Herms said. “The native-Asian hybrid was included because it could provide insight into patterns of inheritance of resistance genes and facilitate their identification.”

The hypothesis proved right. While native ashes and even the hybrid succumbed to EAB, most Manchurian ash was much more able to withstand the attack.

Based on preliminary results, Koch and colleagues at the U.S. Forest Service have begun projects to hybridize Asian and North American ashes -- the first step in developing a resistant tree.

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For more: Dan Herms, OARDC, (330) 202-3506; herms.2@osu.edu.

July 2008