They eat up farmers’ profits, and if you mess with them, they emit a foul odor.
Those are two good reasons not to let the brown marmorated stink bugs into your home—and your home is where a lot of them are trying to spend the winter in this part of the state.
The insects are native to some East Asian countries. They have invaded Wisconsin over the past 10 years and they have shown up in the southeast quarter of the state most strongly, said P.J. Liesch, an entomologist with the UW Extension.
As temperatures drop in the fall, the bugs start looking for winter shelter, Liesch said, and that’s why they invade houses through the cracks and crevices.
Native stink bugs also exist, but they don’t cause the trouble that these invaders do. Some of the native stink bugs even protect gardens by eating plant-eating larvae and caterpillars.
The brown marmorated stink bug, which appears to have no natural predator, is known to feast on corn, beans, raspberries and tree fruits, among other crops, and ornamental trees and shrubs.
Liesch said he hears few complaints from farmers and gardeners. Homeowners are another story.
Homeowners can keep the stinky ones out by plugging holes with foam insulation or caulk. As an added benefit, this will ward off two other home invaders, boxelder bugs and Asian lady beetles, Liesch said.
Stink bugs are mostly a nuisance inside a house. They don’t bite, sting or otherwise harm anyone. They won’t reproduce indoors. But when disturbed, they will emit an unpleasant smell, a self-defense mechanism. Crushing them produces the same pungent smell.
Catch them by hand and throw them outside, Liesch advises, or use a vacuum cleaner’s hose attachment to attack large numbers.
Another method is to focus a portable light on a pan of soapy water, which encourages the bugs to drown themselves overnight.
The brown marmorateds usually enter new territory quietly, but after they establish themselves, they start reproducing in larger numbers, which might be what’s happening in southern Wisconsin, Liesch said.
These bugs come from parts of Asia in the same latitudes as here, Liesch said, so there’s little hope that a harsh winter will kill them off.
Without any predators or diseases attacking them, these bugs aren’t going away anytime soon.