Working To I.D. Foes of Emerald Ash Borers
Manual montage image (a technique
pioneered by Klaus Bolte© of Canada)
of a Balcha sp. 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.
The emerald ash borer, a major threat to ash trees, may have met the
enemy. And it's now up to researchers, including those at ARS's
Sytematic Entomology Laboratory (SEL), to figure precisely who that
Among invasive insects, the metallic-green beetle, Agrilus planipennis
Fairmaire, poses one of the greatest threats of becoming a major pest
in the United States. Since its discovery near Detroit in May 2002,
it has devastated ash populations in Michiganwhere it killed about
6 million treesas well as in parts of Ohio and Ontario, Canada.
The beetle has recently been sighted in Indiana, Maryland, and Virginia
but is under close watch in those states to prevent further spread.
Ash is a valuable hardwood that provides habitat for wildlife, ornamentals
for landscapes, and wood for handles, oars, baseball bats, furniture,
The emerald ash borerwhich feeds beneath the bark of green (Fraxinus pennsylvanica), white (F. americana), blue (F. quadrangulata), and black (F. nigra) ash treesprobably originated in eastern Asia. It's likely that it was inadvertently introduced here roughly 6 years ago, hidden in wooden packing material.
Adult emerald ash borers
emerge from an infested
ash tree (Fraxinus pennsylvanica).
"We know of three species of parasitic wasps that are natural
enemies of these beetles," says SEL entomologist Michael Schauff,
who is based in Beltsville, Maryland. He and fellow entomologist Michael
Gates, who works out of SEL's Washington, D.C., facilities, are leading
ARS's taxonomic work against the pest.
"But we can't put a name on these potentially helpful wasps without
first doing research. We do suspect that some of these species have
been unknown to science up to this point."
Researchers with the U.S. Forest Service and Michigan State University
found the potentially beneficial insects in a study plot in Livonia,
Michigan. Unable to identify the wasps, they sent samples to Gates and
Schauff, who determined them to be species of the genus Balcha,
which like to snack on the ash borer's larvae, and the genus Pediobius,
which attack its eggs. But pinpointing the wasps' precise identity will
entail much work. Schauff says the genus Pediobius alone contains
about 215 species worldwide, 32 of which are found in North America.
SEL's work is just one part of ARS's emerald ash borer campaign. Entomologist
Paul W. Schaefer and colleagues at ARS's Beneficial Insects Introduction
Research Unit in Newark, Delaware, hope to analyze the borers' DNA.
They've traveled to South Korea, Japan, and Mongolia in search of the
insect's origin, hoping also to find its natural enemies.
"The biology and behavior of any biological control agents we
find will be intensively investigated, and we'll conduct host-range
studies to ensure that these agents will be suitable for release and
use against the insect," Schaefer says. They'll also explore ways
to trap the borers and perhaps manipulate the behavior of their natural
Pons, Agricultural Research Service Information Staff.
This research is part of Crop Protection and Quarantine, an ARS
National Program (#304) described on the World Wide Web at www.nps.ars.usda.gov.
Michael W. Gates and
Michael E. Schauff are
with the USDA-ARS Systematic
Entomology Laboratory, 10300 Baltimore Ave., Beltsville, MD 20705-2351;
phone (202) 382-8982 [Gates], (301) 504-5097 [Schauff], fax (301) 504-6482.
"Working To I.D. Foes of Emerald Ash Borers" was published in the February 2005 issue of Agricultural Research magazine.