Meg Jones

Milwaukee Journal Sentinel

Nate Beauchaine was dining on the ultimate comfort food — grilled cheese sandwich and bowl of tomato soup — when an uninvited visitor showed up.

A stink bug dived into his tomato soup Friday evening.

"I could see something near the lights and could hear it crashing into the lights. I thought — I'll kill it later," said Beauchaine, who lives in the Dane County community of Oregon. "But then it crashed into my soup and I thought — enough of this. These guys have got to get out of my house."

The stink bug somersaulting into Beauchaine's tomato soup is not a lone wolf. Its malodorous brethren have been confirmed in 30 Wisconsin counties and will likely move into more of the state.

Officially known as the brown marmorated stink bug, the insect is a native of Asia and was first spotted in Wisconsin in 2010. It took the critter a few years to reproduce in enough numbers for many Wisconsinites to notice.

In the fall, they seek places to spend the winter, ranging from rock piles and tree bark to walls, roofs, chimneys and window frames of homes. When temperatures rise to 50 degrees, they wake up, probably figure spring has arrived and start exploring.

With the recent unseasonably warm temperatures, it's likely many stink bugs are awakening from their winter slumber. And that means stink bugs are among the top bug complaints now rolling into the inbox and voicemail of University of Wisconsin Extension entomologist P.J. Liesch.

"From their point of view, they want to hunker down in the winter and leave in the spring," Liesch said in a phone interview Monday afternoon. "It might be 30 outside but if it's a sunny day, it might get warm enough in some spots for them to get active."

The aptly named stink bugs secrete chemicals from glands on the outside of their bodies as a defensive move. The odor has been compared to dirty gym socks or really pungent cilantro or coriander. Folks picking up stink bugs or squishing them in their hands soon learn that even washing their hands doesn't get rid of the smell.

Aside from the nuisance factor, stink bugs are a real threat to gardens and agriculture in Wisconsin. They're not picky eaters. They'll munch on whatever is at hand from dogwood shrubs and ash trees to apples, cherries and peppers. Stink bugs can deform fruits and vegetables and drastically affect the quality of produce.

"It's like a bad science fiction movie, like if someone hybridized a box elder bug with a Japanese beetle. You can imagine the impacts of that," said Liesch.

Stink bugs reproduce in the summer, laying eggs on outdoor plants which hatch in July and August. They become adults in the fall and seek out a place to spend the winter, emerging in the spring. A cold winter generally will not kill them because they're good at finding safe places to hunker down.

Because they're not native to Wisconsin, stink bugs have few predators. They're adept at hitchhiking, most likely catching rides on vehicles and in boxes of produce, said Liesch.

Much of the bottom half of the state has confirmed reports of stink bugs or are suspected of having the creatures. The hot spots are metro Milwaukee, Madison and the Fox Valley.

"If you're in those areas, I've had calls and reports from people who have found hundreds, if not thousands of them in their homes," Liesch said.

If they're already in your home, Liesch said there's probably nothing that can be done. The time to fight a stink bug infestation is in the fall — by closing gaps in homes where the insects can get in or by using insecticide outside homes in the fall.

It's too late for Beauchaine and anyone else who prefers not to share an abode with stink bugs. Beauchaine went to a New Year's Eve party at the home of some friends who discovered dozens of stink bugs on their drapes.

"Both of these guys hate bugs. They took a vacuum to get rid of them. The (stink bugs) crashed the party and didn't even bring booze," joked Beauchaine.