Growing Magazine - December, 2012

NORTH FEATURES

Entomologists Work to Combat the Mighty Stinkbug

By Wendy Komancheck

The brown marmorated stinkbug (BMSB) made its Pennsylvania debut in 1998, but 2010 is the year that the BMSB population exploded and terrorized Pennsylvania fruit and vegetable crops.


A close-up of an adult brown marmorated stinkbug.
Photos courtesy of Penn State University unless otherwise noted.

Now, growers and entomologists alike believe they're moving in the right direction, but they're still in the starter phase of controlling BMSB outbreaks.

The history of BMSB in Pennsylvania

Entomologists think BMSB (Halyomorpha halys) entered Pennsylvania before 1998, when it was first collected in Allentown. Beginning in 2010, BMSB spread to 37 Pennsylvania counties, as well as 22 states in the U.S.A Penn State Extension BMSB update report (http://extension.psu.edu/lackawan na/programs/master-gardener/news/2012/brown-marmorated-stink-bug-update) stated that in 2010 the pest caused serious damage to peach and apple crops, with some growers in southeastern Pennsylvania losing up to 60 percent of their crops. According to a Penn State Extension fact sheet (http://ento.psu.edu/extension/factsheets/brown-marmorated-stink-bug), the BMSB is also an agricultural pest in Asia, its native home.

Cherry Hill Orchards (www.cherryhillorchards.com), located in Lancaster County, Pa., was hit particularly hard by the 2010 BMSB invasion. When the insects feed on apples and peaches, they leave a "cat face" mark, which makes the fruit unsalable.

"This particular farm experienced tremendous losses during the 2010 season, caused by the brown marmorated stinkbug, aka Asian stinkbug," said Dr. Greg Krawczyk, senior entomology research associate at the Fruit Research & Extension Center (http://agsci.psu.edu/frec) in Biglerville, Pa.

Krawczyk noted that in 2010, "some peach blocks lost close to 50 percent of marketable crop, while some apple blocks had over 50 percent injured fruit. While the affected stone fruit - peaches and nectarines - were lost completely (not marketable crop), the apple crop loss was reflected mainly in the lower value of fruit. While fresh apples can be sold for anywhere between $20 to $40 per bushel, the fruit affected by BMSB can only be sold for processing, mainly [as] juice or cider, with an estimated value of about $4 per bushel."


Here is an example of BMSB damage on apples. In 2010, some Pennsylvania orchards suffered economic loss due to an explosion of BMSB on apple and peach crops.

Cherry Hill Orchards has 50 acres in peaches, 50 acres in apples, 23 acres in cherries, and a few acres in plums and apricots.

"During the 2010 growing season, the [BMSB] population exploded, and we were not prepared because we were blaming the damage on frost events and nutritional deficiencies. By the time we figured out what was going on, extensive damage had occurred on peaches and apples," explained Tom Haas, owner of Cherry Hill Orchards.

Stop BMSB

Fifty researchers from 10 American institutions have banded together to combine research on BMSB. The group has a Stop BMSB website, www.stopbmsb.org, and is funded with a grant from the USDA's Specialty Crop Research Initiative. Krawczyk, who is involved in the program, said that as a group, they're still learning how to control the pest's population.


Crates filled with Cherry Hill Orchards' peaches. The orchard's peach crop was hard-hit by BMSB in 2010.
Photo courtesy of Cherry Hill Orchards.

"Until some new, local, biological or cultural control tactics can be implemented, BMSB has an upper hand on our management activities," Krawczyk said. "Due to [its] wide host range, BMSB can develop everywhere, utilizing so many wild and cultivated hosts that controlling it in agricultural settings actually impacts only a very small portion of the population. With insecticides, killing BMSB is relatively easy, but what about populations that will never come to ag commodities, but will still develop outside [in] woods, gardens, parks, etc., and still invade houses?"

Unfortunately, stinkbugs overwinter in homes and other outbuildings, only to re-emerge in the spring. Pennsylvania's early warm-up in spring 2012 created an ideal environment for BMSB.

"Since the survival of BMSB adults is not dependent on the winter weather - most BMSB overwinter inside some dwellings - the warm winter did not affect their survival. Early spring, on the other hand, provided emerging adults with plenty of available food to support their reproduction and [increase] in numbers," Krawczyk said.

Control options

Krawczyk couldn't give a specific monetary value for crops lost due to BMSB damage and insecticide costs. He said that the money going toward insecticides includes the chain reaction on secondary pests as well. Studies on BMSB predators are still in their infancy because of their possible impact on the natural environment and beneficial insects.

Krawczyk said that some parasitic wasps are still being evaluated under quarantine by the USDA. Whether or not they could ever be released in large numbers would depend on their off-target impact, such as on native insect species.

Krawczyk noted that there are 25 types of stinkbugs native to the mid-Atlantic region, and the predatory wasps, which would kill BMSB, may also decimate beneficial stinkbug species.

"Without full understanding of the possible side effects of new species on our native fauna, nothing can be released. Additionally, there are thousands of questions how this kind of release will even work, who will pay for it, where it should be targeted, and so on," Krawczyk said.


Four BMSB nymphs on a soybean leaf.

The good news, according to Krawczyk, is that the BMSB is sensitive to various classes of insecticides: pyrethroids, carbamates and neonicotinoids. However, the insecticides are not a permanent solution - they only work for 24 hours, and there are some definite drawbacks to this temporary answer.

"With so many alternative hosts around, and basically unrestricted BMSB movement ability, reinfestation can occur at any point, and new damage can occur. An insecticide can control only what is there at the time of application, but can't stop new individuals from coming and causing new damage to a crop. And each single feeding or even probing is actually new damage and is causing a loss in yield and/or crop value," Krawczyk said.

On the flip side, the insecticides, which work on BMSB elimination, threaten beneficial insects. This results in a decrease of beneficial insects, and researchers are noticing an increase in the reappearance of some secondary pests, such as scale insects and woolly apple aphids.

"Since the normal biological control agents are being removed from the system, this reappearance of pests also needs to be controlled," Krawczyk said.

Grower challenges


A close-up of an adult brown marmorated stinkbug.
Photo courtesy of Cherry Hill Orchards.
Haas said there's no shortage of challenges for orchard growers, but the BMSB explosion has upped the ante.

"We have had to suspend our whole-farm mating disruption program due to additional costs associated with BMSB control," Haas said. "We are seeing the detrimental effects of spray treatments on the beneficial population of predator insects that we have come to rely on over the years."

Haas doesn't have specific numbers on this year's BMSB-damaged crops at his operation, but he advised other growers to continue to scout crops and be prepared to invest in BMSB control measures to keep the population from exploding in their orchards.

A ray of hope

Haas noted that Krawczyk's research on BMSB has been a tremendous help in expediting preventative measures since 2010. Haas added that he and Krawczyk discovered that the whole-farm mating disruption wasn't working to control BMSB in his orchard. Since the first outbreak, Krawczyk has spent countless hours at Cherry Hill testing traps and pheromones for monitoring purposes, as well as overseeing spraying programs and making observations.

"His winter work in 2010 was to conduct bioassays for labeled spray materials to evaluate what products were most effective in controlling BMSB," Haas said. "Having this information for the 2011 and 2012 seasons has had a meaningful impact on fruit quality at Cherry Hill and for other fruit growers as well."

Krawczyk summed up the current state of BMSB research, noting that they are working on controlling the BMSB population instead of using preventative measures. Researchers noticed that what works for traditional native pests doesn't work on BMSB. Further, they're beginning to understand the biology, behavior and ecology of the BMSB. The research on developing effective management practices continues.

"After all, insects are live organisms, changing continuously, and BMSB is not a static exemption either. Until a comprehensive tactic, including elements of biological, cultural, behavioral and pesticidal management are established, we will continue to remain in the response, not preventative, mode. Controlling BMSB, [such as] killing with insecticides, is not that difficult; managing and preventing the pest occurrence is a completely different, much more complicated task," Krawczyk said.

Komancheck writes about Pennsylvania farming from her home in Lancaster County, Pa.