July 28, 2011

Battle of the bugs

In the war the state expects to wage against the tree-killing emerald ash borer, a native wasp has a prominent role on the front lines.

By Beth Quimby bquimby@pressherald.com
Staff Writer

FREEPORT - A non-stinging wasp that likes to build its nests in baseball diamond dirt is helping Maine entomologists detect an insect that has decimated millions of ash trees in the Midwest.

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The Cerceris fumipennis wasp, which is native to Maine, was found nesting Wednesday at a Freeport baseball field.

Photos by John Ewing/Staff Photographer

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The wasp is the best weapon that researchers have for determining whether the tree-killing emerald ash borer has made it to Maine.

Additional Photos Below



Is native to Maine and many other states.

Is about one-half-inch long.

Has dark, smoky-brown wings, a cream or yellowish band on its second abdominal segment and three large cream or yellowish spots on its face.

Lives in colonies of three to 300.

Does not sting humans.

Digs a nest in the ground.

Stocks the nest with metallic-colored buprestid beetles, including the emerald ash borer.

Builds nests in hard-packed, sandy soil with sparse vegetation and full sunshine within 200 yards of a wooded area.

Prefers baseball diamonds, school playing fields, campsites and trail and road edges.



Is a small, metallic-green beetle about one-half-inch long.

Was first detected in the United States in Michigan in 2002.

Has spread to 20 states and Canada.

Hatches larvae that tunnel under ash tree bark, disrupting the trees’ ability to transport water and nutrients.

Eats foliage in its adult form but does little damage.

Attacks and kills all ash species.


• More information on the Project Canopy wasp-watcher network is available at
www.maine.gov/doc/mfs/fhm/pages/CercerisVolunteers.htm or by contacting Colleen Teerling at the Maine Forest Service Insect and Disease Lab, 168 State House Station, Augusta ME 04333.

The Cerceris fumipennis wasp is the best weapon that researchers have for determining whether the emerald ash borer has made its way to Maine.

Colleen Teerling, an entomologist with the Maine Forest Service, taught volunteers Wednesday how to recognize the wasp, which lives in several colonies in the baseball diamonds at Freeport Middle School. If the emerald ash borer's presence in Maine is detected early, it is much easier to control.

"It has the potential of wiping out every species of ash on the continent," Teerling said.

Since the emerald ash borer was first discovered in Michigan in 2002, it has spread to 20 states and Canada. The beetle is believed to have entered the United States in cargo ships and airplanes from its native Asia.

It has not yet spread to Maine, but is getting close. It has been detected south of Montreal, about 20 miles from the Vermont border and in the Catskill Mountains in New York.

Ash trees make up only 4 percent of Maine's trees. But they are important street species, filling in the niche created when American elm trees were wiped out by a fungus believed to have been imported from Asia.

Maine was one of the first states to set up a bio-surveillance program with Cerceris fumipennis three years ago. Today, about 20 volunteers have adopted some of the 60 known colonies of the wasps in Maine. Researchers are looking for more volunteers to find other wasp colonies and monitor them for the emerald ash borer.

The project has been funded by about $25,000 from the U.S. Forest Service. The Maine Forest Service is working with GrowSmart Maine, a community revitalization group, to widen its network of volunteers, and with Brunswick to develop a response plan for the emerald ash borer. It is expected to arrive in the state by 2015.

Scientists believe the emerald ash borer travels on firewood imported from other infected states. The adult borer feeds on ash foliage but causes little damage. But the larvae feed on the inner bark of ash trees, disrupting the trees' ability to move water and nutrients.

Cerceris fumipennis builds its nest in hard-packed sand with little or no vegetation, which makes baseball diamonds an ideal site for a colony. The female wasp builds the nest with an opening about the size of a pencil eraser. She then hunts metallic-colored buprestid beetles, including the emerald ash borer. She places three to four beetles in the five to 10 chambers in her nest before laying an egg in each of the chambers and sealing them.

The larvae hatch and feed on the beetles, emerging as adult wasps in July and August when the process starts again.

On Wednesday, Teerling showed volunteers how to catch the wasps as they returned to their nests. There is the net method, which involves running after a darting wasp. The trap method, which involves placing a plastic card with a hole too small for the wasp to maneuver her prey through, is easier.

The females hunt on hot, sunny days. After emerging, they circle their nests to orient themselves and then fly off in a search of wood-boring beetles. The hunt can last minutes or up to three hours.

The volunteers are asked to collect 50 prey samples over three to four visits. The samples are stored in a freezer to kill them, then mailed to the Maine Forest Service at the end of the summer.

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Additional Photos

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Colleen Teerling, an entomologist with the Maine Forest Service, shows an example of the damage that an emerald ash borer can do to an ash tree, eventually killing it. The beetle is much easier to control if its presence is detected early. “It has the potential of wiping out every species of ash on the continent,” Teerling said.

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Jan Santerre, director of the emerald ash borer detection project, and volunteer Kathy Bouchard of Scarborough, right, set traps over wasp nests Wednesday on a baseball diamond at Freeport Middle School. The traps are used to collect the prey that the wasps are bringing to the nest. They’ll know the emerald ash borer has arrived in Maine if one shows up in the traps.

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The emerald ash borer

The Associated Press

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