Stinkbugs on the move
Even small populations of the brown marmorated stink bug can cause serious economic injury, and the numbers grow rapidly.
Adult brown marmorated stinkbugs feed on ripe peaches, a preferred fruit.
It did major damage to orchards in the Mid-Atlantic region in 2010—especially in Pennsylvania, where it destroyed more than half of the peach crop. It’s now in 27 states, including the Pacific Northwest, where it’s sitting on the fringe of the fruit-producing area of Oregon and not far from Washington State.
In six states of the Mid-Atlantic area—Pennsylvania, Maryland, West Virginia, Virginia, New Jersey, and Delaware—the bug has reached epidemic levels. It has growers extremely worried. It was the subject of at least one session at every horticulture show in the East this winter.
George Behling, a fruit grower in Gerrardstown, West Virginia, said: “This bug has the potential to affect the food supply of the whole country.” While that sounds like exaggeration, the bug is attacking not just fruit crops like apples, grapes, peaches, and raspberries, it takes on vegetable crops and field crops, like corn and soybeans. It’s polyphagous, feeding on more than 300 plants, preferring fruit but eating foliage, too.
Dr. Greg Krawczyk, a Penn State University entomologist in Biglerville, Pennsylvania, said, “The brown marmorated stinkbug is bigger than any pest we’ve ever dealt with.”
Marmorated, by the way, refers to the color, the brown-flecked coffee-with-cream color of marble.
Michigan State University entomologist Dr. Larry Gut called it “quite a beast” as he described it to growers in northwest Michigan last month. What sent a chill down his spine was hearing one Mid-Atlantic grower say he’s sprayed 19 times for the stinkbug—and still had 40 percent damage on his apples.
“We have to kill the adults,” Gut said. “There are not many chemicals now that target adult insects.” While the bug was not yet reported in Michigan, Gut can’t believe it wasn’t there, since it’s in both Ohio and Indiana. Two weeks later, it was found in Michigan, having been collected earlier but not identified.
Dr. Dean Polk, the statewide IPM Extension agent for New Jersey, said: “In my thirty years doing this, I have never seen a bug like this.”
With other pests, entomologists have been able to find a critical time in the life cycle to target with controls. But this bug feeds on fruit throughout its nymphal and adult phases, Polk said, and every phase is present in orchards at the same time—eggs, five nymphal instars, and adults. It loves grapes, settling in the clusters at harvest time. Will that taint juice or wine? Initial reports are that ten bugs in a lug of grapes can be tasted in the juice. That’s being investigated by viticulturist Dr. Joe Fiola at the University of Maryland. Blueberries are another fruit easily tainted by bugs in the harvested fruit, Polk said.
The bug has spread rapidly. It flies well and hitchhikes easily. Entomologists across the entire eastern United States are on alert, working with it now or expecting its arrival soon. USDA says it’s been found in 27 states—including the Pacific Northwest, 3,000 miles from its thought-to-be 1996 introduction site in Allentown, Pennsylvania, where it probably arrived in a container from Asia.
In Asia, its numbers are kept somewhat under control naturally, but it’s an exotic, invasive species in the United States and running out of control.
Apples in storage
Mark Seetin, director of regulatory and industry affairs for the U.S. Apple Association, surveyed apple storages in the Mid-Atlantic area earlier this winter after receiving reports of problems in stored apples.
Growers didn’t see damage when the apples went into cold storage, but when they pulled them out, some were damaged so severely they wouldn’t make juice grade, Seetin said.
The bug feeds on apples all season long, beginning in early May as overwintered adults enter orchards to feed on developing fruit. Late in the season, during the preharvest interval when sprays aren’t used, it feeds, usually at the top of the apple near the stem. What start out as tiny pinpricks from a bug’s piercing-sucking mouthparts become sunken bitter-pit–like depressions, with white corky tissue that turns brown and internal brown streaks heading toward the core. The bug injects its saliva when it feeds, and the saliva magnifies the injury.
Seetin’s view: “Imagine a pack of hungry teenage boys descend on your house and open the refrigerator. They eat everything, sweet stuff first, and then move to the next house.
“I’ve never seen anything like it,” he said. “It will eat anything, and it’s mobile. Its appetite is unquenchable. It likes peaches, loves Asian pears, and eats apples, but it will bore into tender bark on nursery stock and eat that, too. If ordinary stinkbugs are guppies, these things are 20-foot white sharks.”
Dr. Tracy Leskey, an entomologist at the Appalachian Fruit Research Station in Kearneysville, West Virginia, is one of the leaders of the Brown Marmorated Stinkbug Working Group, many members of which are collaborating in applying for a massive grant and planning or carrying out a number of studies. Her own lab is evaluating pesticides for efficacy and submitting results to a FIFRA (Federal Insecticide, Fungicide and Rodenticide) Section 18 working group for evaluation. Her group will soon begin evaluating the bug’s responses to wavelengths and intensities of light.
Damage in commercial orchards affected by the bug has reached critical levels with some growers losing entire blocks of stone fruit, and with severe injury also being detected in apples and Asian pears, she reported.
Even small populations can cause serious economic injury if left unchecked. Aggressive spraying appears to reduce economic injury, but concerns regarding IPM programs and resistance management must be carefully considered.
Three stinkbugs marched together across Leskey’s keyboard the day of our interview, and she’s routinely hit in the head by flying stinkbugs—in her office in West Virginia. “Our offices are infested,” she said. They provide a constant reminder to stay on task, she added, jokingly.