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PSU researchers take on stink bugs

by Alaina Bradley

 The stink bug epidemic has affected farmer’s crops in Centre County and proved a nuisance in college dormitories and houses. Last October, a team of eight Penn State scientists was awarded roughly $900,000 from the U.S. Department of Agriculture’s National Institute of Food and Agriculture to study the life and behavior of the pest and to find a way to control it.


PSU studies stinkbug problem
Photo by Jason Smith.  A brown marmorated stink bug crawls on cut flowers in a State College home in March 2012.

Stink bugs came to America as stowaways on container ships from Southeast Asia. According to the Penn State Department of Entomology website, brown marmorated stink bugs were first seen in Allentown, Pennsylvania in 1998.

Since then, they have become a serious threat to crops across the Mid-Atlantic region. According to the Department of Entomology, stink bugs get under the skin of the crop and suck out the juice, drying out the crop. This causes scarring and distortion, also known as cat-facing.

Unfortunately, this insect resists most pesticides, making it hard to control.

Greg Krawczyk, an entomologist at Penn State’s Fruit Research and Extension Center, is the project director of the stink bug study and is currently conducting research on how farmers can limit crop damage caused by the bugs.

"The brown marmorated stink bugs are big, slow and easy to see in their native habitats, but a lot of our research is done in our laboratory, as we have a fairly big colony of stink bugs in my lab," said Krawczyk.

Although Penn State has not received the $900,000 yet, Krawczyk has been doing research in Biglerville, Pa.

"As much money as it sounds, when you take out the Penn State administrative share from these funds, divide the rest by 3 (years) and again divide by 8 (people), this grant will simply let us work on the problem, but in reality, it will provide very minimal annual support," Krawczyk said in an email.

Krawczyk works very closely with fruit growers, so the majority of his direct work with the stink bugs started when fruit experienced severe damage from the pest.

"Brown marmorated stink bugs are feeding on fruit, vegetables, field crops and many ornamental plants causing cosmetic injury and lowering the economic value of the crop," he said. "I am not sure about their specific preference [of food], but we are looking into this as part of our research effort."

Stink bugs have few natural predators in North America, since they are originally from Asia. The population continues to grow, making it hard to control the bug. As of last fall, the pest was spotted in thirty-three states including California, Vermont and Florida, according to the Maryland Department of Agriculture website.

"If our native predators or parasitoids would be effective, we would not have such a huge stink bug problem right now in the first place," Krawczyk said.

Krawczyk said the goal of the study is to not only find a way to control the pest short-term but also long-term.

"Stink bugs are very easy to kill by insecticides if they are present in the orchard (or any other crop) at the time of application, but since they can move so easily in and out of the orchard, constantly occurring re-infestation is the main challenge," Krawczyk said.

Because the brown marmorated stink bugs are hard to control on the farm, they are damaging crops and ruining the farmer’s harvests.

Barry Moser, a farmer for Moser’s Garden Produce, has been farming in Centre County since 1992. During his most recent season, he experienced problems with stink bugs.

"I saw only a few stink bugs on my farm last year and didn’t notice any crop damage at all," he said. "But, toward the end of this season, I did notice more showing up."

According to the Department of Entomology, in 2010, farmers lost many apple and peach orchards due to stink bugs damaging their crops. The pest was also found eating blackberries, sweet corn, field corn and soybeans.

"I noticed some damage on my apples, but it wasn’t anything too significant," Moser said. "We use 95 percent of our apples to make our famous Apple Cider so we were very fortunate that our apples were not harmed too badly by the stink bugs. I did notice significant damage from stink bugs on my raspberries though. This affected our harvest and we were not able to make much Raspberry Apple Cider because of it."

Moser said he attempted to use a pesticide to keep the stink bugs away on two different occasions.

"After you apply the pesticide, you have to wait 4-5 days before you can pick the fruit," he explained. "The pesticide didn’t really work because the bugs were back within a few days."

Sharon Way, a farmer for Way Fruit Farm for 30 years, said the farm has not suffered from the stink bug infestation.

"I have heard that the stink bugs have been a huge problem on other farms around the area, but they haven’t caused any damage on my farm," she said.

Krawczyk estimated that in 2010, about $37 million were lost in the apple industry due to the invasion of the brown marmorated bugs.

Pennsylvania produces about 440 million pounds of apples every year, making Pennsylvania the fourth largest apple producer in the country, according to In 2010, the apple crop in Pennsylvania and Maryland decreased by approximately ten percent due to the stink bugs, according to

"Until we identify other control options (maybe something to influence or modify the behavior of the insect), we have to help farmers survive," Krawczyk said. "Even though I do not like this statement, at this moment, pesticides are our only effective management tool. [Also], there is only one good long-term strategy: to develop a system in which stink bugs will be controlled, more or less, naturally, without using multiple applications of pesticides."

Penn State researchers are studying other aspects of these pests as well.

"We are still learning and trying to understand the possible effect of weather on the stink bug populations," Krawczyk said. "Unfortunately, this kind of observation cannot be done in the lab, and we need more seasons to get some verifiable information."

Steve Jacobs, a senior extension associate in entomology at Penn State, is also participating in Krawczyk’s project. Jacobs has not started his part of the investigation in State College yet because he has not received money to begin the study.

Jacobs’ role in the investigation is to look at the stimuli that causes the brown marmorated stink bugs to fly to a particular area over the winter.

"My hypothesis is that the stink bugs are attracted to the heat emanating from buildings," Jacobs said. "When the light from the sun hits the building, the stink bugs fly there. The bugs also do this in houses. They fly to the light."

Stink bugs do not produce heat, so they must rely on hot weather to keep warm. This is why they will hibernate in cold seasons, usually somewhere warm, such as a building or wall of a house.

Jacobs said he believes that the climate may have decreased the population of stink bugs last season.

"The cool and wet spring last year may have put the stink bugs reproducing on hold," he said.

Although some believe the number of stink bugs decreased, Krawczyk disagreed.

"Less [stink bugs] survived the fall migration into houses mostly due to more effective control activities, but at locations without adequate control, the number of stink bugs is as huge as it was during the 2010 season," he said. "Just walking around my house during one weekend in September we collected over 400 adults, without even trying to collect some that were out of reach."

Krawczyk said he is hopeful that a way to control stink bugs long term will be discovered within a few years.

"Despite working with laboratory colonies of stink bugs, we can only learn so much when the insect is in the diapausing stage (winter)," said Krawczyk. "We do not know enough about this particular species’ biology to predict how the [mild winter] will affect the survival or abundance during the new season. [For now,] speculations are only speculations."

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