Hope for Ash Trees? For the First Time, Scientists Successfully Use Wasps to Locate a New Infestation of Destructive Beetles


Photo: Michael Bohne US FS

Scientists employing a technique called biosurveillance, which uses one species to find another, recently discovered an invasive beetle called the emerald ash borer in Connecticut, where it was previously undocumented. Although the discovery was unsurprising – there is a known infestation in neighboring New York State – it marks the first time that biosurveillance has detected the beetle in a new state.

The emerald ash borer probably arrived on this continent as a boat stowaway from Eastern Asia. It destroys ash trees during its larval stage by feeding on their cambium and phloem—the layers directly under the bark where nutrients are transported — effectively girdling the tree. Ten years ago, the first of these destructive beetles was found in Michigan and it has since spread to 17 other states and two Canadian provinces, leaving more than 50 million dead ash trees in its wake.

Photo: Sandy Ingellis

Smaller than a penny, the emerald ash borer is extremely difficult to locate because infected ash trees’ symptoms are similar to those that are exhibited by trees suffering from other diseases. In order to find the beetle before it wreaks havoc, researchers have turned to a wasp for help. During the months of July and August, members of the native, non-stinging wasp species Cerceris fumipennis fly up to the forest canopy and hunt beetles to bring back to their underground nests for their young. Armed with nets, scientists and volunteers catch the wasps and take their beetles for identification.

Using this method, a team including Dr. Claire Rutledge of the Connecticut Agricultural Experiment Station, Mioara Scott, and this author, captured an emerald ash borer from a wasp on July 16, 2012 in Prospect, CT, a town in New Haven County. Since then, there have been finds in three other towns in New Haven County as well as a find in Massachusetts using the wasp and other surveying methods.

Now that the emerald ash borer has been discovered in Connecticut, the next step is “to limit the spread” of the pest, says Scott, the scientist who caught the first of these green insects. There is a quarantine on ash materials and firewood for New Haven County. Individual trees can be protected or even rescued in the early stages of infestation by insecticides. Heavily infested trees will need to be taken down.

So how can you help to slow the spread of emerald ash borer? According to Rutledge, “The most important way to slow the spread of EAB is to not move firewood. Buy local, burn local.”

Photo: Katherine Dugas CAES

For more information on the emerald ash borer (Agrilus planipennis) visit emeraldashborer.info

For more information on Cerceris fumipennis visit Cerceris.info

For information on the current quarantine in New Haven County Connecticut visit www.ct.gov/caes

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