Wasps that parasitize brown marmorated stinkbug eggs are being screened in quarantine.
Bugwood
Apple growers in the Mid-Atlantic region figure they suffered $37 million in crop damage last year caused by the brown marmorated stinkbug, and that’s not counting damage to other fruits such as peaches, grapes, and cherries in the eastern United States. But scientists familiar with the pest say damage could mount into the billions of dollars if the bug becomes prevalent in the major fruit-producing areas of Washington and Oregon, which it looks set to do.
“It’s a national disaster,” says Dr. Peter Shearer, head of Oregon State University’s Mid-Columbia Agricultural Research and Extension Center at Hood River, who is one of more than 50 scientists from across the country who are cooperating in a proposed $9.7 million research project to tackle the pest. The project, which involves 11 research institutions, has been submitted to the U.S. Department of Agriculture for funding through the Specialty Crop Research Initiative. If granted, it would be the largest SCRI project ever funded.
The overall project leader is Tracy Leskey, entomologist with the USDA’s Appalachian Fruit Research Station in Kearneysville, West Virginia. The 50 researchers will work in teams, both by geographic area and by crop.
Much of the research that needs to be done is basic but critical, she said.
“We need to know more about its basic biology, preferred hosts, behavior, aggregation pheromone, and insecticides that are efficacious,” she explained. “All those things we have for other pests in tree fruit, but we don’t have for the brown marmorated stinkbug.
China
The pest, Halyomorpha halys, is a native of China. It is believed to have arrived in Allentown, Pennsylvania, in the mid-1990s and has since been found in 33 states and the District of Columbia. In 2010, populations increased dramatically in the Mid-Atlantic region.
Shearer was one of the first entomologists to work with the pest after it arrived in the East when he was at Rutgers University, New Jersey. “When I first saw it, my jaw dropped,” he recalled.
Leskey, who has been a research entomologist for 16 years, said it’s the most serious insect that she has ever observed. “There’s nothing that comes close. It just affects so many different crops.”
It’s not just an agricultural pest, but causes consternation when it moves into buildings to overwinter.
“It’s essentially a pest 12 months of the year,” Leskey said. “During the growing season, it’s an agricultural threat, and over the winter months, it’s annoying every business and home owner through the state. I don’t think there’s ever been an insect of that type in the past.”
The proposed SCRI project includes short-, medium-, and long-term strategies. Short-term issues include developing effective management programs. Many of the insecticides that work well against other stinkbugs are not effective against the brown marmorated stinkbug.
In the medium term, researchers will explore cultural controls, trap crops, biological control, and attract-and-kill methods.
Long-term approaches include understanding more about the landscape context and the host plants, including wild hosts, that are supporting stinkbug populations, and looking for natural enemies or pathogens that might reduce populations.
Broad impact
Leskey said the scientists must look beyond just tree fruits, and include vegetables, ornamentals, small fruits, and grapes, all of which are hosts of the pest. “It’s affecting everybody, and the impact is so broad, we have to think about it completely differently from other pests.”
The bug, which is far larger and more damaging than native stinkbugs, was first noticed in Portland, Oregon, in 2004, reports Dr. Helmuth Rogg, supervisor of the Oregon Department of Agriculture’s insect pest prevention and management program. For a few years, it seemed restricted to urban areas in northwest Oregon. Last year, following reports of ballooning populations in the eastern United States, the department did a quick survey of the pest and found that it was spreading out towards Oregon’s fruit production areas, possibly hitchhiking on vehicles.
Rogg said the range of plants that the bug attacks is astonishing, ranging from soybeans to hazelnuts. The department is trying to find out more about the phenology of the insect—when it appears and how many generations it goes through in a year—and where it overwinters. However, the new threat comes at a time when state budgets are being cut, he said. They don’t have the resources available that they would like, considering the risks that it poses.
Shearer said it has been found south of Portland, in the wine country around McMinnville, in the Salem area, and south as far as Corvallis. In northern Oregon, it’s been reported in Sandy, to the west of the cherry and pear growing regions of The Dalles and Hood River, and in Arlington to the east.
“It’s on either side of us and also coming up the Columbia Gorge on the Washington side,” Shearer said. “It’s a catastrophe. It’s worse than anything I have ever worked with.”
Sad day
What makes it particularly troublesome is that the only products that can deter this giant stinkbug are the harsh pesticides that growers have been urged to avoid using in order to preserve natural enemies of secondary pests.
“They are not friendly to our IPM (integrated pest management) programs, and it’s going to mean a lot more expense to the grower because we’re going to be spraying for both primary and secondary pests,” Shearer said. “It’s a sad day if we say goodbye to IPM.”
There is some hope on the distant horizon, though. USDA explorers have been to China and brought back natural enemies of the stinkbug, Trissolcus halyomorphae and three other species of Trissolcus parasitic wasps, which are in quarantine. It is reported that Trissolcus halyomorphae is an effective parasite of brown marmorated stinkbug eggs in other parts of the world and is able to reduce populations. The brown marmorated stinkbug is considered a nuisance in China but not a destructive agricultural pest, possibly because it is held in check by natural enemies, Shearer said.
Rogg said the bug was not a quarantine pest in the United States, probably because it was not listed as an agricultural pest in the country of origin. It probably arrived in the United States via a shipping container.
The parasitic wasps are going through rigorous screening to make sure that they don’t attack native stinkbug species, including some that are useful generalist predators, Shearer said. “Right now, it appears very promising, but until the studies are complete, it can’t be released. That could be a couple of years.”
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