Stink bugs are becoming a bigger problem in Oregon

(NOVEMBER 11, 2022) Stink bugs are becoming more than just a smelly problem. They are an invasive insect. And their population in Oregon is increasing. They are a serious threat to Oregon crops and garden plants, according to Oregon State University Extension Service’s orchard crop specialist.

Nik Wiman is an associate professor in the College of Agricultural Sciences. He says that fruit and vegetable crops in the Willamette Valley have been affected.

“It’s unusual for brown marmolated stink bugs to feed on fruit and vegetable crops,” he said. “There has been a lot of damaging populations of BMSB in hazelnuts 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. Like other insects, the population varies from year to year depending on the climate. The extremely wet spring most likely was one reason. However, the increase could also be attributed to a natural cycle.

The stink bugs are native to Asia. They were first introduced on the U.S. East Coast in the late 1990s – probably by ship – and they have spread to almost every state in the country, including Oregon in 2004. The insect feeds on at least 170 plants, particularly vegetables, pears, apples and hazelnuts, but also ornamentals. Its name describes the odor they emit when they’re crushed.

Oregon’s hazelnut industry, valued at $132 million in 2020, is one of the state’s crops hardest hit by the invasive bug, according to the Oregon Department of Agriculture. The state’s problem is similar to the situation in other parts of the world.

One promising biological approach is the samurai wasp (Trissolcus japonicus), an insect native to areas of Asia where it keeps the indigenous BMSB population under control. The wasp hunts for the eggs of the stink bug. The wasp lays its own egg inside each egg in the mass. The wasp develops inside the egg. This kills the stink bug. Then the wasp chews its way out.

In addition to agricultural crops, the stink bug shows up in homes in autumn when they are looking for a warm, dry place for winter.

“We’ve done analysis of reports we get from people,” Wiman said. “We’ve looked at timing and by far and away 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 are coming into homes, 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 stink bug can enter and vacuum up inside infestations. On outdoor buildings, washing them off with a strong shot of water will keep some at bay. If they come back, spray them again.