Wasp used to locate ash borer in Connecticut
PROSPECT, Conn. — An army of citizen scientists and a native species of wasp helped detect the first emerald ash borers to arrive in Connecticut.
The tiny metallic green aliens from Asia have invaded America, and are chomping their way down the East Coast, leaving swaths of dead ash trees in their wake.
The beetles, about as long as a grain of rice, are hard to detect in the treetops where they live.
“It’s a real needle in the haystack trying to find the beetle, especially in low densities,” said Claire E. Rutledge, assistant entomologist at the Connecticut Agricultural Experiment Station.
An area is typically infested between four to six years before scientists find them, Rutledge said.
“The earlier you catch it, the more you can do to slow it down and contain it,” Rutledge said.
Before the emerald ash borer was discovered in Michigan in 2002, not much was known about the bug. Since then, scientists have developed better techniques for detecting it.
On July 16, Mioara Scott, a summer assistant at the Agricultural Experiment Station, caught the first emerald ash borer in Connecticut at Canfield Park in Prospect.
She used a bio surveillance technique to exploit the natural hunting abilities of a native wasp.
The nonstinging solitary wasp, known as the smokey-winged beetle bandit, makes its nest in sand and soft dirt like baseball fields. The female wasp hunts jewel beetles, small iridescent insects — including the emerald ash borer — that mostly feed on dead and dying wood. In its native Asia, the emerald ash borer feeds only on dying ash trees. However, in the United States, healthy ash trees are not as resistant to the bug.
The wasp paralyzes the beetles and brings them back to her tunnel, where they are stored as baby food for the wasp larvae.
“She brings it to us in a more accessible place than the treetops,” Rutledge said.
Groups of volunteer wasp watchers monitor more than 100 wasp colonies in Connecticut, catching beetles as the wasps bring them home.
One of the 55 volunteers this summer caught nine emerald ash borers over three days in Canfield Park beginning July 2, but didn’t report his findings right away because he thought it was one of the many similar-looking beetles the wasp preys on.
Volunteers have collected 50 beetles from each of 20 sites, the number considered representative of the beetle population in the area. Three sites have turned up emerald ash borers: Canfield Park, Fusco Field in Prospect, and Mathies Park in Beacon Falls.
Once scientists found the beetle in Prospect, they started checking area “Barney” traps — purple prisms with dying-ash-scented lures and sticky surfaces — to trap the bugs. Of the 541 traps in Connecticut, the only ones that have caught emerald ash borers so far are in Prospect, Naugatuck, and Bethany.
“They’re not nearly as elegant and efficient as our little girls,” Rutledge said.
Wasps are only active for six to eight weeks in July and August. Most of the adult emerald ash borers have died off by now, Rutledge said, making the infestation more difficult to detect.
Rutledge said scientists are working on the technology to have mobile wasp colonies, similar to honey bee pollinating services, that would bring the smokey-winged wasps to different areas across the state to collect beetles.
Scientists from the Agricultural Experiment Station and the Department of Energy and Environmental Protection are preparing a plan to study ash trees in the area, searching sick trees that may have dead leaves and small shoots in their trunks.
The emerald ash borer makes d-shaped exit holes about one-eighth of an inch long. Scientists can also peel off the bark to look for s-shaped tunnels left by larvae feeding on the tree’s vascular tissue. The larvae girdle the tree, starting at the top and cutting off the flow of nutrients as they make their way down the trunk.
“Once you know where they are, it becomes more worth it to actually go and look at the trees,” Rutledge said.
The study should help scientists understand the limits of the infested area and learn how long the insects have been in Connecticut.
State officials will discuss their ongoing efforts to curtail the insect’s spread at a public hearing at 7 p.m. Wednesday at the Prospect Fire Department.
The Agricultural Experiment Station plans to impose a quarantine on the movement of ash and firewood from New Haven County.
“Buy local, burn local...You never know what’s going to be hitchhiking,” Rutledge said.
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