North Central Research Station

Emerald Ash Borer

North Central Research Station entomologists working in East Lansing, Michigan, provide basic information on the biology and ecology of exotic forest insects so managers can formulate proper management strategies.  Over the years, our work has influenced development of policy and regulations to control various pests on regional, national, and international scales.  We are currently helping combat an outbreak of the emerald ash borer, an exotic pest new to North America.

The emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), was discovered infesting and killing thousands of ash trees (Fraxinus spp.) in southeastern Michigan in July 2002. Evidence suggests that A. planipennis first entered Michigan from China at least 10 years ago, presumably from solid wood packing materials or dunnage used to transport manufactured goods. EAB was subsequently found in Ontario, Canada, Ohio, Indiana, and Illinois. Spread of EAB results from EAB flight and human transport of infested ash firewood, logs, lumber, and nursery stock. For example, EAB-infested nursery stock from Michigan was illegally sold to a nursery in Prince George, Maryland and sold in Maryland and Fairfax County, Virginia in 2003.

To limit human-assisted spread of this pest from areas infested with EAB, states imposed quarantines and regulations on the transport of ash trees and ash wood products. Federal quarantines were imposed by USDA Animal and Plant Health Inspection Service and the Canadian Food Inspection Agency.

Potential Impact

In Michigan, this borer has been observed only on ash trees. It kills black (F. nigra), blue (F. quadrangulata), green (F. pennsylvanica), pumpkin (F. profunda), and white ash (F. americana). The trees die when burrowing larvae girdle the conducting tissues along the main trunk. Many trees seem to lose about 30 to 50% of the canopy after the first year of attack, and the entire tree is often killed after 2-3 years of infestation. Although ash trees stressed by transplantation, drought, soil compaction, and injury contribute to tree vulnerability, healthy ash trees are also susceptible to EAB.

Ash occurs extensively in the natural and urban forests of the Eastern United States. In 2001, ash accounted for more than 149 million cubic feet of timber products nationwide. It is estimated that more than a billion ash trees are growing in the United States, and about 800 million of these occur in Michigan. As of 2005, at least 15 million ash trees have died from EAB in Michigan alone. This loss is especially noticeable in urban areas where ash, once considered a hardy shade tree, was used to replace American elm trees after their demise from Dutch elm disease.