Can this wasp save local ash trees from devastation?
Small insect being used to slow spread of emerald ash borer
Unseen and without a sound, a life-and-death war between two Asian bugs is beginning to play out in Dutchess County.
On one side is the emerald ash borer, a beetle that has been killing ash trees across the nation at a fearsome rate.
Marshaled against the beetles — and vastly outnumbered — are tiny, non-stinging wasps, some so small, they can be mistaken for poppy seeds.
Locally, a front line of this battle is Vassar College. There, scientists from the college are deploying the wasps at the college's ecological preserve to proactively slow the beetle's spread.
While the technique is not new, its presence on the local campus is. It is part of a larger national effort to fight fire with fire — that is, to use biological controls to limit the damage from a runaway biological agent.
Since ash trees are commonly found along municipal streets, the emerald ash borer offers up the possibility of ash trees keeling over onto homes, cars or people. A far more likely impact is the significant expenditure of taxpayer funds to remove standing dead trees.
"It's a pretty brutal pest," said Sharon Lucik, spokeswoman with the U.S. Department of Agriculture.
The story begins in 2002, when wood pallets arriving in Michigan from China included a hitchhiker — a green beetle that lays eggs in ash trees. The beetle's larvae grow under the bark of the trees, leaving serpentine trails called galleries that choke off a tree's nutrient-supply system.
In Asia, ash trees have developed resistance to the beetle. No such resistance exists in the United States, and it can take as few as two years for an infestation to kill a tree.
Scientists acknowledge that right now, there is no way to eradicate the beetle. The goal now is to slow its advance and buy time.
Enter Oobius agrili (pronounced Oh-BEE-us ah-GRILL-eye). The wasp at Vassar is one of three species being deployed across the country. Two of them attack emerald ash borer larvae. The one at Vassar goes after the beetle's eggs.
In all three cases, the result is death before an adult emerald ash borer can emerge.
The wasps, also native to Asia, are reared at a federal facility in Michigan. The first releases came in 2007 in Michigan, after scientists determined the imported bugs would have little impact on anything but the emerald ash borer.
So far, 9 million of the wasps have been released nationwide, according to USDA officials, including about 1 million this year.
"These are very valuable wasps," said Juli Gould, a USDA entomologist. "... It takes a lot of time to rear them, to release them and for the insects to build up in numbers."
Vassar is one of 65 private organizations and public entities that currently have permits from the USDA to receive and release the wasps.
The bug appeared in western New York in 2009 and has been moving east. Infestations were discovered in Dutchess County in and around Rhinecliff in 2012. Since then, infestations in Dutchess have been found as far south as Hyde Park.
The release program at Vassar is being watched, in part, because the college sits on the very edge of the area where the beetles have been found locally.
"This is being proactive about the eventual coming of EAB on our property," said Mary Ellen Czesak, a biology lecturer at the college.
Since the beetle is hard to detect, USDA scientists said they are curious to measure the impact of releasing wasps where the beetle may be present, but has yet to be detected.
Meanwhile, the college is collecting seeds to contribute to a national seed bank, according to Meg Ronsheim, a biology professor.
The goal, Ronsheim said, is "to preserve local groups of plants, providing that overall genetic diversity for the species, if we try to bring the ash back."
John Ferro: 845-437-4816; firstname.lastname@example.org; Twitter: @PoJoEnviro