A small but feared pest in the Northwest may have an even smaller adversary fighting back, scientists learned after a recent discovery in Vancouver.
A Washington State University research technician this year came across two clusters of a tiny, parasitic wasp known as trissolcus japonicus. Scientists cheered the find because the wasp is known to kill an invasive pest that has caused havoc on area farms: the brown marmorated stink bug.
The wasp had turned up on the East Coast in recent years. But the species had never been confirmed anywhere else in the nation until this year, when it was found in a Vancouver park.
“We never expected to find it 3,000 miles away, in an area that was fairly recently invaded by the brown marmorated stink bug,” said WSU professor of entomology Elizabeth Beers. She added: “This is a 3,000-mile extension of its known range.”
Scientists hope the wasp can help control the fruit-eating brown marmorated stink bug, which continues to spread and cause problems across the United States. Both species hail from Asia, and are not native to this country.
“We’re pretty excited about this find,” Beers said.
It’s unclear how the wasp made its way to Vancouver. The bug likely hitched a ride with cargo shipped from Asia, according to WSU. It may have also traveled with a jet.
The tiny wasp — which measures 1 to 2 millimeters long, or about the size of a typed comma — kills its host in a way WSU likened to the sci-fi movie “Alien.” The female wasps lay eggs inside clusters of stink bug eggs. When a wasp egg hatches, the larva eats the stink bug egg from within, killing it, then bursts out as an adult wasp, according to WSU.
“This is one of the most effective killers of the brown marmorated stink bug,” said Elijah Talamas, a research entomologist with the U.S. Department of Agriculture.
The USDA and other partners have studied the parasitic wasp in quarantined laboratories since 2007. Researchers hope to determine whether it could be released to combat destructive stink bugs and reduce the damage they cause. Those studies continue, even though the wasps have now shown up on their own.
It was WSU field technician Josh Milnes who found the wasp clusters on the leaves of a maple tree in Vancouver this year — first in August, then again in September. Officials didn’t want to say exactly where, fearing they might be disturbed.
The wasps could be elsewhere in the area, Talamas said. But without definitive data, the Vancouver sightings are still “one dot on the map.”
Research so far suggests that the wasps favor the brown marmorated stink bug as hosts, according to WSU. But they’re not as picky as scientists hoped, Beers said. The wasp has also attacked native stink bugs, she said, though lab results aren’t always duplicated in the wild.
Even so, the wasp’s arrival still could be “very good news” in the fight against non-native stink bugs, said Charles Brun, horticulture adviser with WSU’s Clark County Extension. The pests continue to be a problem in the county and elsewhere, and a new foe could give the region a leg up, he said.
“It potentially means that we’ll have some way to keep the population in check to a certain extent,” Brun said.
Even if that happens, don’t expect the bug to disappear entirely.
“It’s not going to wipe out the brown marmorated stink bug by any means,” Beers said. “We’re hoping what it will do is keep down the sort of ambient populations.”