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Manual montage image of a Balcha wasp
Manual montage image (a technique pioneered by Klaus Bolte of Canada) of a Balcha wasp, a potentially beneficial insect that attacks the ash borer. To create this image, the wasp specimen was dissected—legs, antennae, wings and other body parts separated—then the parts were digitally captured and reassembled in Photoshop. This technique allows exquisite detail to be shown. Contact Klaus Bolte for high-resolution image.

Work to Identify Possible Foes of Ash-Killing Beetle

By Luis Pons
January 31, 2005

Since its discovery near Detroit in 2002, the emerald ash borer has devastated ash tree populations in Michigan, Ohio and Ontario and has been sighted elsewhere.

Now Agricultural Research Service scientists, including those at the ARS Systematic Entomology Laboratory (SEL) in Washington, D.C., and Beltsville, Md., are working to precisely identify parasitic wasps that seem to be natural enemies of this imported metallic-green beetle, Agrilus planipennis Fairmaire. Thought to have arrived here about six years ago, hidden in wooden packing material, the borer is threatening to become a major U.S. pest.

U.S. Forest Service and Michigan State University researchers found the potentially beneficial wasps in a study plot in Livonia, Mich., and sent them to the SEL for identification. There, entomologists Michael Gates and Michael Schauff identified them as species in the genus Balcha, which like to snack on emerald ash borer larvae, and in the genus Pediobius, which attack the borer's eggs.

According to Schauff, it is suspected that at least one of the wasp species found was unknown to science up to this point. Schauff works at SEL's Beltsville location, while Gates is based at its Washington facilities.

Precisely pinpointing the wasps' identities will entail much work, as the genus Pediobius alone contains about 215 known species worldwide, 32 of which are found in North America. But knowing their exact identities will be key if the wasps are to be used to control the emerald ash borer.

SEL's work is just part of ARS' emerald ash borer campaign. Entomologist Paul W. Schaefer and colleagues in the agency's Beneficial Insects Introduction Research Unit at Newark, Del., hope to analyze the borers' DNA. They've also traveled to South Korea, Japan and Mongolia in search of the insect's origin, hoping to also find its natural enemies.

Ash is a valuable hardwood that provides habitat for wildlife, ornamentals for landscapes, and wood for various products.

Read more about the research in the February 2005 issue of Agricultural Research magazine

ARS is the U.S. Department of Agriculture's chief scientific research agency.