Where have all the stink bugs gone?
Yes, stink bugs remain unwelcome guests in our Rappahannock homes and orchards, but the days when millions of the invasive insects raised havoc in our lives appears to be waning.
The question, posed with great pleasure, is why?
Doug Pfeiffer, a renowned Virginia Tech entomologist who works with the Virginia Cooperative Extension Office, suspects there are several reasons for the fetid bugs to be on the decline.
‘There are fewer these past few years, and a definite decline since 2010. That was the big year’
There’s been progress through classic biological control, pest management with safe insecticides, and just maybe disease is helping to kill off the pungent Asian buggers that first arrived in Pennsylvania in 1996 and invaded Virginia in 2004.
“There are fewer these past few years, and a definite decline since 2010. That was the big year,” Pfeiffer tells the Rappahannock News in a telephone interview from Blacksburg. “Orchards looked like a hail storm had come through. They’ve still been a problem, but it’s not as big.”
As for the biological warfare Pfeiffer refers to, Rappahannock residents may have heard about the wasps discovered to be parasitizing stink bug eggs across the border in Maryland.
“Samurai wasps,” Pfeiffer identifies them, educating that researchers from the U.S. Department of Agriculture had traveled several years ago to Asia to learn about the brown marmorated stink bugs’ natural enemies. The thought was to introduce a biocontrol species or two in North America, where hundreds of millions of dollars in crop damage was occurring annually, including in Virginia’s apple orchards.
While some of the socalled samurai wasps (Trissolcus japonicus) were eventually brought to America to study in the lab environment, to everybody’s surprise they were recently discovered to already be living here. Identified by Maryland researchers, these tiny wasps had immigrated to the mid-Atlantic states on their own, so small in size (no bigger than a sesame seed) they were hardly noticed. Not to mention they can’t sting.
“Often when we search for natural enemies we go back to the homeland to look for the pest . . . find what works well in the home country,” Pfeiffer explains. “Of course these ‘enemies’ have to undergo testing” to prevent any adverse effects on the local environment, “to make sure they’re predatory instead of plant feeding.”
“Nobody knows how it got here,” the entomologist says of the U.S. samurai discovered first in Delaware, although researchers are convinced they didn’t escape their scientific quarantine. Now, as we speak, additional wasps are being released in fields and orchards up and down the east coast.
“It’s unclear how much of an impact the wasp is having,” says Pfeiffer, but everybody is hoping for some progress.
The Tech professor says there may be other “natural enemies” to stink bugs that increase its mortality, including disease. Plus, he says, fruit growers “are more aware of how to handle” the invasive pests, from safe insecticides to traps placed on trees.
Pfeiffer also pointed to research conducted in his own lab for short term pest control, where for instance “on the night before a grape harvest an organic insecticide blasts the bugs out of the clusters.
“The issue is less with grape growers, but we do provide another tool,” he says.
Stink bugs feed on numerous fruits and vegetables, from apples and peaches to tomatoes and sweet corn. For orchard growers and farmers a plentiful army of stink bugs can wipe out an entire season’s harvest.
For homeowners, they are a nuisance pest as they look for places to over-winter. Hopefully this winter of 2018-19 there won’t be as many swimming in our soup.