Stink bugs head indoors for winter

By Kym Pokorny

When leaves fall and days get shorter, stink bugs go on the move looking for a warm, dry place for winter. Often that means sharing our homes with these prehistoric-looking insects, whether we know it or not.

This year, it’s difficult not to know. Many homeowners have been inundated as the population of brown marmorated stink bugs (Halyomorpha halys) keeps increasing.

In spring, the shield-shaped insects show up in the garden on foliage and then move on to their preferred fruit, seeds or nuts. Foliage is a last resort because leaves don’t contain enough of the nutrients they need to thrive.

“They’re unmistakable because of the stinky, irritating odor when they’re crushed,” said Vaughn Walton, an entomologist with Oregon State University Extension Service. “They move from wild host plants to our gardens and then in large amounts into our homes. That’s when people get really upset. Bugs inside freak people out.”

Brown marmorated stink bugs don’t bite or do any damage to wood or insulation. In the garden, it’s a different story.  In spring, adults that have snuggled up inside make their way back to the garden and start eating and laying eggs on the underside of leaves. Within a week, the eggs hatch into immature bugs and eventually adults and the process starts again – up to three times a year depending on conditions.

If they’ve found your garden, you’ll find discolored and malformed fruit and vegetables and blank nuts. A large amount of host plants, including blueberries, apples, maples, English holly, tree of heaven and empress tree, are fair game for these voracious and indiscriminate feeders that first showed up in the United States in 1998 on the East Coast, where it’s become a serious agricultural pest. Because scientists had a heads up here, the problem is not as widespread in Oregon.

“It’s a really good hitchhiker,” Walton said. “It’ll attach itself to cars, trucks, RVs, trains, you name it. Generally, the first place you’ll find it is where there’s a lot of human activity. This bug can be found In Portland virtually everywhere in the metropolitan area. But you can go anywhere and find it now, no problem.”

Walton is working with OSU entomologists Nik Wiman and Peter Shearer on control methods. Promising techniques include traps that attract and kill them for the short term and natural predators and parasites for the long term.

“Some gardeners have reported success with home remedies such as horticultural oils or soaps, but none have been proven to work very well,” Walton said. “It’s a difficult bug to manage in the garden. In the house, seal cracks and vacuum up the stink bugs, and you can keep them to a minimum.”

Learn more about brown marmorated stink bugs on the OSU Department of Horticulture website, and learn to tell them from other types of stink bugs in an OSU Extension fact sheet.

Photo by Lynn Ketchum. Brown marmorated stink bugs like the warmth of indoors during winter.

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