The brown marmorated stink bug is here in Washington. And it might move in with you this winter. A WSU researcher is breeding tiny samurai wasps in an effort to fight the pests.
It’s already the scourge of the Northeast — an omnivorous, foul-smelling critter from overseas that now threatens this state’s $2.4 billion apple industry, although it’s also partial to peaches, cherries, berries, row crops and cereals.
The brown marmorated stink bug is here in Washington. And it might move in with you this winter.
“Not only do they love the habitat, but where do they like to hang out during the wintertime? Huh! Your home!” said Joshua Milnes, a Washington State University researcher on the front lines of brown marmorated stink bug war in Washington state.
In the 1990s, the brown marmorated stink bug became widespread throughout the Northeastern U.S., starting in Pennsylvania, where it did damage to the apple crop. Brown marmorateds also congregate in massive numbers in buildings over the winter, “simultaneously threatening millions of acres of American farmland and grossing out the occupants of millions of American homes,” as one New Yorker writer put it.
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Milnes, a graduate student in Washington State University’s Department of Entomology, might be called the state’s best defense against the brown marmorated, known to entomologists as BMSBs to distinguish them from native North American stink bugs, most of which don’t cause crop damage.
An enthusiastic bug lover with a spirited sense of humor, Milnes calls the brown marmorated “fascinating and horrifying.” He is breeding and releasing the only known enemy — outside of pesticides — that can vanquish the stink bug: Trissolcus japonicus, otherwise known as the samurai wasp.
The wasp — smaller than a sesame seed — is also an import from Asia. It keeps the brown marmorated stink bug population in check in its native China, South Korea and Japan, said Kim Hoelmer, research leader of the Beneficial Insects Introduction Research Unit of the U.S. Department of Agriculture in Newark, Delaware. Hoelmer is one of the country’s experts on this stink bug.
In 2005, Hoelmer traveled to China to hunt for something to curb the stink bug’s rapid spread.
There, he found the wasp, which lays its own eggs inside the stink bug’s eggs. Samurai wasp larvae devour the developing stink bug nymphs before they can hatch, destroying them. The wasp had been mentioned in recent research in China, but had been misidentified as a different species, he said.
Hoelmer brought the wasp back and put it in quarantine for study. But as luck would have it, the wasp was already here — and in this case, that was a good thing.
Like the brown marmorated stink bug, the wasp had apparently hitched a ride to the U.S., and had made its way into 10 states. In 2015, Milnes discovered a small population of samurai wasps living in a park in Vancouver, Washington, preying on brown marmorated stink bugs.
So while Hoelmer waits for several different regulatory agencies to approve of the wasp release — a process that can take years — Milnes is free to study the wasp in the wild because it’s already taken up residence here.
He began a project to collect the wasps, breed them in the lab, and then ferry them to parts of the state where the stink bug has become a pest — including Walla Walla; Yakima; Prosser, Benton County; White Salmon, Klickitat County; and King County. The work is funded by grants from the USDA and the Washington Tree Fruit Research Commission and overseen by WSU entomology professor Elizabeth Beers, an expert on integrated pest management.
In other states where samurai wasps have been discovered, entomologists are doing similar work.
Milnes’s work is not only keeping the stink bug at bay, it’s also contributing to research to establish whether the samurai wasp is a benign presence in the environment that will only hunt brown marmorated eggs, and won’t wreak havoc with the 400 native species of stink bugs in North America — 51 of which are native to Washington state. Researchers also want to make sure the wasp won’t go after other bugs, livestock or people, Hoelmer said. Milnes “is on the front lines” of controlling the stink bug, he said.
If entomologists can convince the USDA that the wasp is only interested in eating brown marmorated stink bug nymphs, it can be bred in large numbers in laboratories and released into the fields, Hoelmer said.
“We’re not always this quick in response” to a new pest, Milnes said. “Sometimes, it’s too late. But in this case, we’re doing it right.”