KINGSTON, R.I. – July 29, 2013 – Three University of Rhode Island students are on the trail of an invasive beetle that rapidly kills ash trees, but instead of searching for the beetle itself they are looking for wasps that feed on the beetle.
The new strategy, called biosurveillance, is being implemented in collaboration with the Rhode Island Department of Environmental Management to determine whether populations of the emerald ash borer have arrived in Rhode Island. The exotic beetle from Asia was discovered feeding on ash trees in Michigan in 2002 and has rapidly expanded to the East. It was discovered in Connecticut and Massachusetts in 2012, and New Hampshire in 2013, and it is expected that it may soon be found in Rhode Island.
“Like the name suggests, emerald ash borers bore into ash trees, often girdling them,” said entomologist Lisa Tewksbury, who is leading URI’s effort to find the invasive pest in Rhode Island. “The trees lose much of their canopy in the first year and die within three years.” According to Tewksbury, the larvae of the emerald ash borer spend the late fall and winter eating tunnels through ash trees before emerging from the tree as adult beetles in April or May.
“Ash trees are fairly common forest trees in Rhode Island, and they have also been extensively planted along streets and in landscapes throughout the state, so if we lose our ash trees it will definitely affect our landscapes,” she said.
Because of the difficulty of finding the insect before it becomes abundant, URI and DEM are hoping that a wasp (Cerceris fumipennis or smoky-winged beetle bandit) that feeds on native beetles closely related to the emerald ash borer will help to detect the arrival of the pest insect.
“It’s a solitary wasp that nests in colonies in sandy soil, and they seem to especially like to nest in the infields of baseball fields in parks and schoolyards that are not regularly groomed or irrigated,” explained Tewksbury. “The wasps target beetles in the emerald ash borer family to feed their young. They inject the beetle with paralytic venom and bring it back to their nest.”
As part of their summer intern positions with URI’s Biological Control Lab, Max Ragozzino of Narragansett, Elli Wollenweber of Cranston and Liam Sullivan of Coventry bring insect nets to baseball fields in southern Rhode Island and attempt to capture the wasps as they return to their nests with beetles (Mike Becker and Bruce Payton from RIDEM are undertaking a similar effort in northern Rhode Island). The wasps are released after the beetles are taken from them, and the beetles are taken back to the lab to identify. Over the course of the summer they will collect up to 50 beetles from each site. If none of the beetles collected are emerald ash borer, they can move on to a different site.
“It’s a really cool project surveying for a really bad invasive species, and we’re doing it in a clever way,” said Ragozzino. “We’re using the wasps to find the beetles for us.”
“It’s sort of like treasure hunting,” added Wollenweber. “We have to wait for the ideal time to catch them because the wasps are finicky and aren’t active when it’s too hot or too windy.”
“I’m allergic to bee stings, so I was slightly hesitant to participate in the project at first,” said Sullivan. “But once I realized that they don’t sting people, only beetles, I was fine with it. I am also enjoying the insect collection and identification that comes along with this project.”
So far, no emerald ash borers have been found in Rhode Island, but Tewksbury won’t be surprised if they are. “Generally when a new pest arrives in Connecticut and Massachusetts, it is found in Rhode Island fairly soon.” she said.
Meanwhile, it’s not too early for homeowners and communities to begin preparing for the arrival of this pest. Many of the state’s ash trees are already in decline from a pathogen, and the emerald ash borer will cause widespread mortality of all commonly grown ash species.
Although infested trees can be kept alive through insecticide application, this is costly and requires annual retreatment so planting replacement trees now is an option worth considering. URI has published a list of sustainable trees and shrubs, available on line at:
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