Understanding the Brown Marmorated Stinkbug
It does stink, and it's a nuisance. What's worse, the brown marmorated stinkbug (BMSB) is capable of inflicting devastating damage on numerous crops. In 2010, apple growers in the mid-Atlantic region lost $37 million due to this invasive pest. In addition, some sweet corn, peach, pepper and tomato growers reported total losses that year.
A native of Asia, BMSB (Halyomorpha halys) was documented in Allentown, Pa., in 2001, although many researchers believe it actually appeared in this country as early as 1996. There were outbreaks in Japan in the 1990s, and it's considered an agricultural pest in China, Korea and Taiwan, feeding on soybeans and a variety of fruit and ornamental trees.
Conditions were right in the mid-Atlantic in 2010 for BMSB to reproduce and feed voraciously. "I don't want to see another year like 2010," says Dr. Tracy Leskey, USDA research entomologist at the Appalachian Fruit Research Station in Kearneysville, W.Va.
In the fall of 2010, Penn State Extension entomologist Steve Jacobs noted that the warm spring and early summer allowed the stinkbug to reproduce at a faster pace. "Normally, you'd see one generation of stinkbugs per growing season, but this year we've had three generations, leading to higher and faster-spreading populations," Jacobs explained in a news release (http://bit.ly/M9ofZs).
Dr. Grzegorz Krawczyk, tree fruit entomologist at Penn State's Fruit Research and Extension Center in Biglerville, Pa., notes that BMSB is adaptable to the mid-Atlantic, and because it's not native to the U.S., it lacks natural enemies. Furthermore, the pest overwinters in houses and other structures until spring, and then moves into vegetative areas to reproduce.
"They are constantly in motion, and there is no exact time frame for reproduction; it begins sometime in May and continues through mid-October, depending on weather and food sources. The brown marmorated stinkbug is able to feed and develop on more than 300 different host plants, making this a problem for the entire agricultural community, as well as for homeowners," Krawczyk observed in a news release (http://bit.ly/1nKfMYK).
In June of 2011, tree fruit yield losses were so extensive in the mid-Atlantic region that the U.S. Environmental Protection Agency approved emergency use of the insecticide dinotefuran to manage BMSB populations, as well as azadirachtin and pyrethrins to help manage BMSB in organic production.
Unfortunately, since 2010 BMSB has been spreading to other states. The map compiled by the Northeastern IPM Center (http://www.stopbmsb.org/where-is-bmsb) shows that the pest has been detected in 40 states. Seven states report agricultural problems, including Washington, Oregon and the five states surrounding the six mid-Atlantic states, where there are severe problems. Leskey said, "In 2013, the stinkbug for the first time has caused agricultural problems in the West." Many entomologists fear it will reach their vulnerable crops soon.
"It's the worst pest I've seen in 40 years," said Dr. Galen Dively, professor emeritus of entomology and IPM consultant at the University of Maryland. "It's causing problems on the Eastern Shore's 7,000 acres of processing corn by injecting its enzymes right through the husks. That dissolves the kernels, and when blanched, any damaged kernels turn brown, making them off-grade."
Developing sustainable controls requires understanding BMSB behavior. A Specialty Crop Research Initiative (SCRI) program is establishing BMSB biology and phenology and developing monitoring and management tools. Leskey is the project director. A team of 50 researchers is committed to controlling this pest. A primary goal is to identify effective integrated pest management methods and help growers incorporate them into their control programs, thereby reducing pesticide usage.
Broad-spectrum pesticides will work on the stinkbug, but they also kill the beneficial insects that are part of IPM systems. Thus, the ecosystem becomes unbalanced. This can trigger an outbreak of secondary pests, driving more pesticide usage and threatening pesticide resistance.
Dively noted that BMSB has set IPM programs back almost to the point of starting from scratch. "Fruit growers for 30 to 40 years have been using softer chemistries," he said.
Dr. Peter Shearer, professor of entomology at Oregon State, agrees. "Complex systems over the years have been managing, but new invasive pests have come in, disrupting IPM programs," he explained.
Multiple strategies are being explored, including attract and kill, parasitic wasps that attack BMSB eggs, a fungus that targets BMSB, biological control methods, and techniques such as trap cropping.
Since some other stinkbugs look similar, identification of BMSB can be a challenge. Several states have projects that request growers and members of the public to report sightings in order to determine precise identification and better tracking. Detailed descriptions of adults and instars can be found on some university Web pages, and the Northeastern IPM Center's website has a video series (http://www.stopbmsb.org/video) with presentations that include identification, monitoring and controls.
The behavior of BMSB has made both monitoring and control especially difficult. Dr. Russell Mizell, professor of entomology at the University of Florida, and others have observed that BMSB moves over long distances.
Shearer said, "We've tracked some 'superfliers' that travel 40 miles."
Dr. Anne Nielsen, a fruit entomology specialist at Rutgers, notes that the nymphs are also mobile. Nymphs can develop on fruit and cause injury. Nielsen, who leads an effort to manage BMSB.