Stink bugs are more than just a nuisance to homeowners when they sneak indoors to escape the cold. They can do major damage to wholesale apple growers’ crops and have impacted past yields at local orchards.

They look like little flying armored bugs, hiding in the folds of blankets and sweaters or plain as day on walls, emitting a foul odor if you try to crush them. Yes, we’re talking about the brown marmorated stink bug.

More than just an ugly, smelly, unwanted pest to homeowners — who, chances are, are seeing more of them right now as the bugs look for a place to stay warm for the winter — stink bugs are highly invasive and can decimate crops. They eat corn, tomatoes, peppers, and fruit, and they’re causing a great deal of trouble for apple growers nationwide and here in the Hudson Valley.

Now, stink bugs are top of mind for apple growers and scientists who are searching for biological solutions to control the apple-loving appetite of a pest that has become an ubiquitous presence in orchards and homes.

Stink bugs were first discovered in the U.S. in 1998, when one found its way to Pennsylvania, likely via a wood shipping pallet from Asia, where it’s from. In places like China, Japan and Korea, the brown marmorated stink bug — just one of many types of stink bugs that exist on earth — has natural predators. But here, those predators are scant, enabling the pest to flourish.

According to the EPA, they’re now in 38 states and the District of Columbia.

In New York, this species of stink bug was first known to have spread here by 2008, when homes in Saratoga and Ulster counties began reporting infestations. The bugs were spotted in orchards, nibbling on one of New York’s key crops: apples.

According to the Cornell University Hudson Valley Research Laboratory, in 2012, more than 20 percent of season fruit blocks in Ulster, Orange, and Duchess counties were impacted by stink bugs.

That spurred a lot of attention, and a lot of research, into a bug that can cost apple growers hundreds of thousands of dollars in damages if they’re not mitigated.

What happens when stink bugs run wild in an apple orchard? They use a straw-like protrusion to sip the juice of the apple itself. This causes damage to the apple that results in dimpling, browning, and, sometimes, a change in the flavor of the fruit.

According to Daniel Donahue, tree fruit specialist for Cornell Cooperative Extension in Ulster County, if an apple orchard is to get an infestation and it isn’t caught early, between 4 and 5 percent of its revenue can be lost for the year.

Donahue says on average, a more popular and, therefore, higher-priced apple like the honey crisp can be worth up to $30,000 per acre. A large operation that grows apples for wholesale distribution can be as large as 800 acres, meaning a 5 percent loss could spell upwards of $1.2 million in evaporated revenue.

Donahue says currently, local growers are encouraged to monitor the possible presence of stink bugs by setting traps at the perimeter of orchards, since the bugs work from the outside in.

Peter Jentsch has been studying ways to mitigate the impact of stink bugs for more than a decade. Previously an entomologist at Cornell University Hudson Valley Research Laboratory in Ulster County, Jentsch is now director of research and entomology for Poma Tech, where he’s exploring the impacts of a fungus called Venerate that works to dispel the stink bug’s appetite.

“It keeps them from feeding,” says Jentsch. “They’ re on the apple and sitting there, a week, two weeks go by and they still haven’ t fed on the apple.”

That Venerate is a biological application that is non-toxic to humans could be a boon for management of the pests. Stink bugs tend to be most problematic toward the end of the growing season, when apples are ripe and ready to be picked — not an ideal time to apply a pesticide, given how close the fruit is to harvest and human consumption. This product, however, doesn’t pose that problem, says Jentsch.

“If you can’ t control them biologically, solely through the use of a biological control, then the use of a biological insecticide would be a great choice because it’ s non-toxic,” he says.

By “biological control,” Jentsch means using nature to control nature.

Shortly after stink bugs’ emergence in the region, a tiny wasp called the Samurai wasp was being studied as a potential control for stink bugs. These wasps are a natural predator — they lay eggs inside the eggs of the stink bug, and when the wasp’s eggs hatch, they effectively kill the host eggs of the stink bug.

Samurai wasps were being studied in a lab, in a controlled laboratory environment, when, in 2016, Jentsch put some brown marmorated stink bug eggs out in the orchard field to study them. He certainly wasn’t expecting to find Samurai wasps in them, and yet: “Lo and behold, the wasp emerges,” says Jentsch.

He says this led to some “hand wringing” — as far as anyone knew, the only Samurai wasps in the United States were in a lab, not yet released into the wild. Jentsch says the wasps were sent to a lab in France where a scientist named Marie-Claude Bon was able to parse out their DNA and find that they were not the same as the quarantined ones in the lab — they’d likely been in the region for a while. So, no lab escapees, but, yes, they were a natural predator to the stink bug.

An explosion of stink bugs significantly damaged orchards and crops in the Mid-Atlantic in 2000. In New York, scientist Peter Jentsch has worked on two possible ways to combat their destruction, through a fungus applied to apples that kills the bugs' appetite, and releasing a known predator, the Samurai wasp, into orchards.

In 2017, Jentsch and his research team reared more Samurai wasps and released them into fruit-tree-heavy regions of New York with stink bug infestations. Whether that effort was a success, Jentsch says, is hard to quantify. Indeed, stink bug populations are down in the region, but he says that could be due to a variety of factors, such as weather and other natural mitigators like fungus. He’s not taking credit for any strides made in current conditions.

“If I said, ‘Oh yeah, the Samurai wasp is working really well, there’ s no stinkbugs out there,’ and all the while, that’s because the fungi are doing their job, why aren’ t I giving credit to these little spores?” posits Jentsch.

Now, Jentsch is turning to local residents for help with his scientific study. He continues to helm a long-running citizen science project whereby people are asked to report any stink bugs they encounter in the home. He says if they’re showing up in high numbers in homes, they’re likely prevalent in nearby orchards as well.

“No one measures in people’ s homes to show success of a biological study,” he says. “Well, that’ s what I’ m doing.”

Donahue likewise emphasizes the importance of citizen science in discovering and tracking all invasive species, including the brown marmorated stink bug. “Having citizens interested in the concept of keeping one eye open for things and reporting it back really helps,” says Donahue.

CORRECTION: This story has been updated to reflect the correct years of Peter Jentsch's research, which are 2016 and 2017, not 2006 and 2007 as originally stated. We regret the error.

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