By Hiroko Sato
CARLISLE — The tiny green insect sparkles like a metallic jewel in the sun.
It flies into ash trees and feeds on the leaves, then deposits eggs under the bark.
But if left alone, the larvae of this seemingly innocuous beetle called Emerald Ash Borer would eat their way through inner layers of the trees, cutting off the water and nutrient supply.
Since first found in the United States in 2002, in Detroit, this Asian invasive species has killed millions of ash trees throughout the Midwest, according to Nichole Carrier, pest-survey specialist with the U.S. Department of Agriculture. The Emerald Ash Borer raid continues eastward with its newest frontier being the Hudson River in New York, 25 miles west of Massachusetts border.
Early detection is a key to winning the battle against the beetle. Environmentalists are now trying to spot the first sign of the half-inch-long insect in Massachusetts by using its natural enemy: wasps.
The way this particular kind of wasp, called Cerceris fumipennis, catch the beetles is simple. They sting the beetle and carry it back to the nest, Carrier said.
On Thursday, Carrier joined her counterparts from the state Department of Agriculture Resources and Department of Conservation and Recreation in training about a dozen volunteers to become “wasp watchers” at Carlisle’s town-owned Foss Farm.
Look for small holes on the ground that serve as entrances to the wasp nests, Carrier said. Sometimes, the wasps drop their catches near the nests.
It’s all about locating Cerceris fumipennis, because where the wasps are is where there’s a good chance of finding the beetle — and determining if the beetle has already invaded Massachusetts.
The more watchful eyes there are, the more effective the detection. Ron Gemma, a Westford Conservation Trust member who attended the training, plans to call upon fellow townspeople to do their part.
“It’s a matter of getting people excited about it,” Gemma said.
Finding Cerceris fumipennis may not be so difficult, even for those untrained, because of where the wasps live.
Females, which catch the Emerald Ash Borer, choose sandy soil for their nests. They prefer hard-packed soil that keeps the nests from collapsing. Wasps also like having grass to help hide the nests.
This means wasps like nesting under baseball fields and around the goals of soccer fields, according to Carrier.
“A ballfield with compact soil that’s not pristine” would be an ideal nest site, Carrier said.
With the opening typically being the size of a pencil, the first inch of the path to a nest goes vertically into the ground before it bends to a 45-degree angle. A perfectly circular mound of soil around the hole is a telltale sign of a cerceris fumipennis nest.
If the soil is unevenly piled into one direction, that’s not a Cerceris fumipennis nest, said Dennis Souto, retired etymologist for the U.S. Forest Service. The color of the pile soil is also often darker than that of the ground because the wasps bring it up from underground when burrowing their nests, Souto said.
Cerceris fumipennis has a single yellow band around its belly. The adult Cerceris fumipennis isn’t carnivorous, but their larvae are. The larvae clutch onto the shiny beetles left in the nest and eat it.
Experts use Cerceris fumipennis wasp only as a detection tool, not as a biological control, for the Emerald Ash Borer.
Wasps usually catch the beetles within a mile of their nests, which helps narrow the search for infested ash trees, said Melanie Joy, of the DCR’s Forest Health Program. State agencies are also planning to place hundreds of sticky, ash-tree-scented trap boxes across the state, including Middlesex County.
Once beetle-infested trees are found, tree owners have some options to choose from, including injection into the plants to save them or cutting them down, said Jennifer Forman Orth, plant pest survey coordinator for the state DAR.
Experts say an Emerald Ash Borer invasion into Massachusetts is not a matter of if, but when. The region has already seen its share of invasive species, including the Asian Longhorned Beetle, which attacks trees much like the Emerald Ash Borer affects ash trees.
Experts fear the Emerald Ash Borer could devastate the landscapes because ash trees line many streets in New England. Their concern even prompted Massachusetts and federal environmental officials to conduct emergency training on a mock beetle outburst last year, involving all sorts of exercises from media alerts to intensified tree surveys, Joy said. The Wasp Watchers program also models after similar initiatives already launched in Maine and some other states.
The Wasp Watchers program, which is led by Forman Orth, trains volunteers on how to find cerceris fumipennis colonies and how to preserve an EAB if they find one.
Penny Geis, who came all the way from Hatfield to attend Thursday’s Wasp Watchers training, still remembers singing “The Ash Grove” while attending camp as a child decades ago.
“That’s the emotional reason to do this,” she said.
Follow Hiroko Sato at twitter.com/satolowellsun.
For more information about the Wasp Watcher program, visit http://massnrc.org/pests/blog/tag/emerald-ash-borer.
