News

Wasps May Control Borer

The emerald ash borer, an invasive Asian beetle that kills ash trees, was first discovered in Illinois in June of 2006. As a last-resort solution to the growing threat posed by these insects, the U.S. Department of Agriculture (USDA) has suggested that managers of infested areas introduce additional exotic species—namely, three species of Chinese wasps—to control the borer. These parasitic wasps would combat the emerald ash borer by laying their eggs within the eggs and larvae of the borer, preventing them from reaching maturity.

The probability that the wasps will effectively reduce the emerald ash borer in the Chicago area is, statistically, very high. Experiments conducted in China showed that the wasps aided imported North American ash trees to the same extent they helped Chinese-native ash trees. Chicago is home to millions of ash trees.

The USDA has proposed to release the wasps in Michigan first, but no exact dates have been set. According to the agency, landowners in every release area will have to approve any action. While there remain many risks in introducing the wasp in North America, including possible parasitism on native insect species, agency researchers believe that inaction could have much more serious negative consequences. Research is still being conducted on possible chemical insecticides, but at the moment, wasps appear to be the most practical solution.

For more information on the Chinese wasps and the emerald ash borer, e-mail trees@mortonarb.org.

— Katherine DeVries

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State Activates Response to Emerald Ash Borer, CW Fall 2006