CORVALLIS, Ore. — The number of invasive brown marmorated stink bugs in 2022 was the highest Oregon has seen in at least five years, posing a serious threat to crops and garden plants, according to Oregon State University Extension Service’s orchard crop specialist.
It’s unclear why the population exploded this year. The extremely wet spring most likely contributed to it, but the increase could also be part of a natural cycle.
Nik Wiman, an associate professor in Oregon State’s College of Agricultural Sciences, said fruit and vegetable crops in the Willamette Valley have been affected.
Like other insects, the population of the shield-shaped brown marmorated stink bug (BMSB) varies from year to year depending on climate.
“It’s unusual for brown marmorated stink bugs to feed on fruit and vegetable crops,” Wiman said. “There has been a lot of damaging populations of BMSB in hazelnut orchards. Growers use preventative measures, so we’re surprised we’ve seen so many.”
It’s unclear why the population exploded this year, Wiman said. The extremely wet spring most likely contributed to it, but the increase could also be part of a natural cycle.
Native to Asia, BMSB was introduced on the U.S. East Coast in the late 1990s — likely by ship — and has spread to nearly every state, including Oregon in 2004. The insect feeds on at least 170 plants, particularly vegetables, pears, apples and hazelnuts, as well as ornamentals. Its name refers to the odor released when the insects are crushed.
Oregon’s hazelnut industry, valued at $67 million in 2021, is among the crops hardest hit, according to the Oregon Department of Agriculture. The state’s problem mirrors challenges in Turkey, Italy and Georgia, said Wiman, who researches alternative practices for controlling BMSB, including biological control, habitat manipulation, trap crops and barriers.
Samurai wasp shows promise
One promising biological approach is the samurai wasp (Trissolcus japonicus), an insect native to parts of Asia where it helps keep stink bug populations under control. Scientists have discovered the wasp in the United States and in Oregon, where it was initially distributed by Wiman and a team of researchers at Oregon State and elsewhere. The Oregon Department of Agriculture now leads the effort.
The parasitic wasp hunts for stink bug egg masses and lays an egg inside each one. The wasp develops inside, killing the stink bug egg before chewing its way out. Oregon State Extension has a short publication on the wasp and its effect on stink bugs.
Pests move indoors in fall
In addition to damaging crops, stink bugs show up in homes in autumn while seeking warm, dry shelter for winter.
“We’ve done analysis of reports we get from people,” Wiman said. “By far we get the most BMSB reports in the fall. Adults are at peak and are trying to get into houses. Warm fall weather gives more opportunity to get into buildings. They can be very annoying when they come indoors, and they may fly around inside your house all winter. Then they come out in spring.”
Wiman advises homeowners to seal all cracks where the insects can enter and to vacuum up indoor infestations. On outdoor buildings, washing them off with a strong spray of water will keep some at bay. If they return, repeat the process.
Farmers and homeowners can play a key role in samurai wasp research by collecting possible brown marmorated stink bug egg masses and reporting them.
Previously titled Large increase of stink bugs poses serious threat to Oregon crops
