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Plant Pathology

Department of Plant Pathology


Emerald Ash Borer

In Search Of Emerald Ash Borer Resistance

An interdisciplinary team of plant pathologists, entomologists, biologists, and ecologists are developing ash trees resistant to the invasive insect pest, Emerald Ash Borer.


The Emerald Ash Borer (EAB) is a wood-boring beetle native to Asia that can infest and kill North American ash trees (Fraxinus spp). EAB was accidentally imported into the U.S. and discovered in Michigan in 2002. Since then, EAB has spread to the northern U.S. and Canada, with the loss of millions of ash trees.  All ash species with a significant presence in North American forests appear highly susceptible to EAB.

The environmental and economic implications are enormous. North American ash trees are dominant species in eastern U.S. forests and, prior to the introduction of EAB, were popular landscape trees.  The economic impact to urban forests alone is projected to reach $10-20 billion over the next 10 years. Ash wood is also well-suited for specialty applications in cabinets and flooring, tool handles and baseball bats. The standing ash timber value in Ohio alone is over $1 billion.


Because EAB is native to Asia, scientists have examined Asian ash to look for species that are resistant to EAB, and to understand how they resist attack. OARDC researchers have identified biochemical and molecular differences in EAB-resistant Manchurian ash compared to susceptible North American ash species. OARDC researchers, in collaboration with USDA Forest Service ecologists and tree geneticists, have also identified individual North American ash trees that appear to have survived in areas of high EAB density, suggesting they may be resistant to this pest.

These trees may provide much need genetic material to select resistant North American ash.


Researchers have made great strides in characterizing the potential mechanisms of EAB resistance and are utilizing this information for applications in breeding, hybridization and selection for EAB resistance in North American ash species.  Candidate genes that may confer resistance to EAB have been identified, and work is progressing to overcome barriers in hybridizing Asian and North America ash tree species.  Key compounds (secondary metabolites and defense proteins) have been identified in the resistant Asian trees that may be important in EAB resistance.  These efforts are important for reforestation and could restore ash as a landscape tree and timber species in the future.  This interdisciplinary effort constitutes a model for the investigation of several plant-pathogen-insect interactions affecting natural and cultivated tree species.

Pierluigi (Enrico) Bonello, Dept of Plant Pathology; DA Herms and O Mittapalli, Dept of Entomology; D Cipollini, Wright State; U.S. Forest Service Northeastern Research Station, Delaware, OH

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