Those stinking stink bugs are back in Western Pa.

Well, this stinks.

Stink bugs are showing up in homes across Western Pennsylvania. With fall and winter approaching, they’re becoming more prevalent as they seek shelter in homes and buildings.

“I would say anecdotally speaking, there was an increase in stink bugs from last summer. Stink bugs tend to have better populations when you have a long dry summer,” Camila Rivera-Tinsley, director of education at the Pittsburgh Parks Conservancy, said. “When the season is extended, they’re able to get in one more generation, so their population will naturally rise.”

Several types of stink bugs can be found in Pennsylvania. The species most people know is the invasive brown marmorated stink bug or BMSB. That’s the kind of stink bug sneaking into homes during the fall months, according to Michael Skvarla, assistant research professor of arthropod identification at Pennsylvania State University.

Stink bugs are relatively new to the area, Rivera-Tinsley noted. They arrived in Pennsylvania in the 1990s.

These bugs are best known for the unpleasant — but harmless — odor they can emit.

“It’s a defense mechanism,” Rivera-Tinsley said. “When they’re scared or something’s trying to eat them, they’re going to release that scent. A bird or some other creature is not going to like that taste or smell.”

Though their pungent odor can be a nuisance, Rivera-Tinsley said these bugs pose no threat to people or pets. They don’t bite or sting and they don’t carry diseases that can spread to humans.

But Skvarla said they can pose certain problems.

The invasive, shield-shaped insects can cause crop damage, Skvarla explained, citing a study that reported stink bugs caused $37 million in losses to tree fruit producers in the mid-Atlantic in 2010.

“Besides economic damage to commercial crops, BMSB damage fruits and vegetables in home gardens and invade houses and other buildings in the fall when they search for protected places to overwinter,” he said.

Stink bugs can invade home gardens, particularly impacting fruit trees like apples, pears and stone fruits. They tend to target sweet corn, soybeans and tomatoes, Skvarla said.

The issue with stink bugs in home gardens, Rivera-Tinsley said, is they can spread diseases that harm plants. But she noted that stink bugs cause bigger issues with commercial farming than home gardening.

Home gardeners can find ways to deter the bugs.

“In home gardens, the best control is to exclude the stink bugs from high-risk crops like tomatoes with netting. This can be difficult as you have to move the netting to allow bees access to the flowers for pollination and fruit set,” Skvarla said.

Pesticides can kill off stink bugs in a garden, but Skvarla urged caution for anyone who opts for this method.

“All pesticides have a pre-harvest interval (the wait time from pesticide spraying to safe harvest) that can last days to weeks,” he said. He added that pesticides may kill pollinators, too.

Tinsley-Rivera also recommended planting native plants in home gardens to limit the number of invasive insects.

“The best way we can combat invasive bugs is to plant more native species,” she said. “If we have more native species, that’s less food for these invasive insects.”

Plus, right now is the prime time homeowners will start noticing these stink bugs seeking shelter for the fall and winter months.

Stink bugs will enter homes at this time of year and then hibernate through the winter before becoming active again in the spring, Rivera-Tinsley said. Once they become active again, she said, they’ll want to be outdoors.

“The best control in homes is to keep them from entering in the first place, which might include sealing cracks around windows or in siding or injecting expanding foam around pipes and wires where they enter the building,” Skvarla said. “[Once] the bugs are inside, there isn’t much to do about them besides kill individual bugs by hand.”

“You can vacuum them — suck them up and take them outside,” Rivera-Tinsley added.

The good news, Skvarla said, is that people have help fighting off stink bug populations. Samurai wasps — parasitoid wasps that attack BMSB eggs — are here to help. Sumarai wasps are also non-native, but their presence in the U.S. could help combat stink bugs.

“In their native ranges, samurai wasps parasitize 60-90% of BMSB eggs,” Skvarla said. “If samurai wasps become widely established and show similar effectiveness, it’s hoped that they’ll bring BSMB levels to acceptable, non-damaging levels.”

Though people may not love having stink bugs in their homes and gardens, Rivera-Tinsley said there’s really no reason to worry.

“They’re more of a nuisance than they are an actual problem,” she said.

Julia Felton is a Tribune-Review staff writer. You can contact Julia at 724-226-7724, jfelton@triblive.com or via Twitter .

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