It’s going to be a good year for the brown marmorated stink bug, which means it’s going to be a rough year for farmers and gardeners in Southwest Washington.
The brown marmorated stink bug is a voracious eater of more than 170 ornamental and edible plants. It has no traditional predators locally and few pesticides trouble it. Cold temperatures are one of the few ways to reliably kill the insect, but the same balmy weather that’s hampered the snowpack this year has also proved to be a boon for the bugs.
“The warmer it is, the longer they can continue their eating and mating cycles,” partially because the wet and warm weather also means more foliage for the bugs to eat, said Joshua Milnes, a graduate student at Washington State University who is in Vancouver this summer studying the insect.
Since being discovered in the Portland metro area more than a decade ago, the insect has been in the midst of a destructive invasion through the Pacific Northwest.
“They can easily populate and feed on everything,” Milnes said.
“It’s really a damaging insect to the specialty crops like tree fruit, vegetables and berries” that are grown commercially in Central Washington, said Milnes, who is based at WSU’s tree fruit research center in Wenatchee.
The stink bug has caused millions of dollars in damage to American specialty crops, which the U.S. Department of Agriculture values at about $51 billion per year.
It’s easy to recognize the stink bugs. Adults are about an inch long, with a brown shield-shaped body and white stripes on their antennae. They live in attics, and behind curtains or blinds.
They can be particularly problematic in urban areas, as they escape the cold temperatures by moving into buildings. Brown marmorated stink bugs produce two generations a year. The first adults emerge in early spring and reproduce by late July. Their feces are a wet mess that tends to spread easily, with a smell similar to cilantro.
Most pesticides are ineffective against the bug. Those that have shown to be partially effective aren’t available to the average consumer. Some pest control products are on the market, but because the brown marmorated stink bug is a new pest to the U.S., manufacturers are still trying to perfect them.
The invasive insect was accidentally brought to the United States from Asia. It was first discovered in Pennsylvania in the late 1990s, then discovered in Portland in 2004 and in Vancouver in 2010.
The Pacific Northwest hosts other stink bug varieties, but their populations are kept in check by predators and pathologies that have adapted to them.
Researchers are working on ways to combat the brown marmorated stink bugs before the problem gets too far out of hand.
“People on the East Coast are hauling gallon buckets of stink bugs out of their attics. That’s something that could happen here,” Milnes said.
But another foreign invader may help prevent that from happening. A parasitoid wasp discovered late last summer in the Vancouver area kills brown marmorated stink bugs from the inside, while, so far, ignoring native stink bugs.
The wasp, which is about the size of a comma, lays its eggs inside stink bug eggs. The juvenile wasp then eats its host from the inside before bursting out and restarting the cycle.
“Parasitoids are very host-specific. That’s why we’re hopeful it’ll be one of the solutions to containing the (brown marmorated) stink bugs,” Milnes said. “Scientists all over the world have been rejoicing.”
Still, it’s not a panacea. The wasp kills between 65 and 80 percent of the stink bugs it infests, so some will be left to annoy farmers and urbanites alike.
Now, Milnes’ work will be to see how well the wasp is established in Washington and whether it can be spread to other areas.
Meanwhile, people at least can keep the stink bugs out of their homes, by making sure air conditioners or heating units have screens and the screens on doors and windows are properly sealed.
Dameon Pesanti: 360-735-4541; dameon.pesanti@columbian.com; twitter.com/dameonoemad
