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Stink bugs are coming: Damaging insects making way to Midwest, scientists say

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FRANK J. SCHULTZ
July 9, 2011
— First they invade your house. Then they stink up the place.

It’s only later that they start making noticeable dents in farmers’ profits.


That’s the likely scenario for the newest invasive insect, which is spreading from the East Coast to the Midwest, said insect expert Phil Pellitteri of the UW Extension.


The United States is home to dozens of kinds of native stink bugs. They are not the problem. A new species arrived from Asia sometime in the late 1990s, experts believe. It’s called the brown marmorated stink bug, or BMSB.


BMSBs have been sighted in Wisconsin, Illinois and Minnesota. They probably hitchhiked with humans who visited states in the East, experts say.


A breeding population has not been confirmed here, but it’s only a matter of time, experts say. Scientists are still working on how to stop the bugs, who appear to have few natural enemies here.


Pellitteri said if these bugs do what they did in Pennsylvania and other mid-Atlantic states, homeowners will be the first to raise the alarm.


These stink bugs are similar to the Asian ladybugs: They are very good at crawling through tiny openings, and they seek warmth in the fall. Homeowners may notice them congregating on the sunny sides of houses, or maybe their first clue will be large numbers of them inside the house.


Break out the vacuum cleaner? Yes, but be prepared. Disturbing the any kind of stink bug causes it to exude a pungent, long-lasting stink from its scent glands.


“The odor lingers for two or three days,” Pellitteri said. “It’s pretty powerful. That will make it unpopular with people, I know.”


Some have compared the odor to rotting almonds, rotting coconuts or rancid cinnamon.


It’s a very stale, musty smell,” said Tom Klubertanz, a crop-pest expert at UW-Rock County.


It may take several years for the population to build up before farmers notice the BMSB is sucking up profits.


But when it happens, look out. These are not like the emerald ash borer, another Asian invader that kills only ash trees. These guys like just about any fleshy fruit or seed pod, UW entomologist Eileen Cullen said. They like juicy, sweet things, such as apples and peaches but also soybeans and sweet corn.


“It’s just amazing at how omnivorous they are—almost every agricultural plant,” Klubertanz said.


They don’t take bites out of the fruits.


“If you see chewing on leaves, it’s something else,” Cullen said.


Instead they use their “piercing, sucking mouth parts” to insert a needle-like probe into the fruit of seed pods and suck the juices out.


That’s right. Stink bugs suck.


While they’re sucking, they taint the fruit with an enzyme that helps them digest it. The enzyme leaves an odd taste as well as discolorations that make the fruits or crops unmarketable.


The bugs leave brown splotches inside apples and dry, white areas on tomatoes.


Pellitteri said the bugs reached critical mass last year in Pennsylvania and New Jersey, costing farmers income through apples, peaches, soybeans, sweet corn, raspberries, tomatoes and peppers.


“This is packing a wallop,” he said, but it will take time before BMSBs become numerous enough to do the damage they’re doing out east.


Humans have a hand in spreading the bugs, Pellitteri said, but there’s little people can do because BMSBs are experts at crawling into crevices on campers and cars.


“I think it’s just a matter of time,” he said.


How bad could it get for commercial growers?


“Like any insect, it’s going to depend on how many you have in a field or that farmscape,” Cullen said. “It has the potential to become what we call a key pest.”


A key pest means it is a regular problem that cuts into growers’ bottom lines.


BMSB is certainly a threat, and nobody know how much of a threat.


Klubertanz offered one scenario: About 12 years ago, the soybean aphid was terrorizing farmers.


“It was just frightening. There were fears about how bad this pest could get,” he said. “And it did get very bad. It has since quieted down.”


But it hasn’t gone away.


Scientist: Bugs are already here

UW Extension entomologist Phil Pellitteri believes the brown marmorated stink bugs are already here. He points to a cluster of bugs a Wil-Kil exterminator found on the sunny side of a Madison motel in March.


That cluster probably was emerging from winter hibernation, Pellitteri said.


It’s the Department of Agriculture, Trade and Consumer Protection, however, that decides when to declare that a new pest has made its home here.


Ag department spokesman Mick Skwarok said there’s still not enough evidence.


“Stink bugs in homes, etc., is a nuisance problem and is better addressed through Extension and/or Phil,” Skwarok said in an email. “We only deal with them in an ag setting.”


Skwarok confirmed the report at the Hampton Inn on Madison’s west side, but “an over-wintered population does not necessarily equate to a reproducing population,” he wrote.


“The Hampton stink bugs, if not controlled by Wil-Kil, will almost certainly become a reproducing population,” Skwarok wrote. “We don’t know where they came from or when they arrived in Wisconsin, and they were all adults.”


Pellitteri thinks there’s enough proof: “My own personal opinion is that yes, I think they’re established.”


The ag department is not sitting on its hands, however. It has set traps for the invading bugs in 14 apple orchards across the state. The closest to Janesville are in Dane and Racine counties.


State officials have also alerted farmers, orchard owners and pest controllers.


Stink bug facts

Ooh, that smell: Stink bugs get their name from their ability to exude a smelly substance when they are disturbed.


Do they bite? No. They are not known to transmit disease or cause physical harm. They do not feed on human blood or tissue.


What do they look like? Common stink bugs locally are the green and brown stink bugs. They have shield-shaped backs, just like the invasive brown marmorated stink bug. Experts say it’s hard to tell the difference. That’s why people who find bugs are asked to bring them to their UW Extension office for identification.


The invasive brown marmorated stink bug’s distinguishing characteristics include white banded antennae and an alternating light and dark pattern along the lower back. BMSB adults are about 5/8 of an inch long, or 17mm. They often feed in clusters.


Brown what? “Marmorated” means to be veined like marble.


Where are they from? North America is home to dozens of stink bug varieties. The BMSB is at home in China, Korea, Japan and Taiwan.


Where are they in the United States? California, Connecticut, Delaware, Idaho, Indiana, Illinois, Iowa, Maine, Maryland, Minnesota, Mississippi, Missouri, New Jersey, New York, Nevada, North Carolina, Ohio, Oregon, South Dakota, Tennessee, Utah, Virginia, Washington, West Virginia, Wisconsin and Wyoming.


What is their life cycle? They winter as adults in cracks and crevices. They mate in the spring and lay clusters of eggs on plants through the summer. The hatchlings go through five nymph stages, and they’re already able to feed in the second stage.


How do you fight them? Homeowners can better their chances by caulking up crevices around their houses. If the bugs are found congregating on the house, pyrethroid insecticide sprayed around the perimeter of the house is best, said UW entomologist Eileen Cullen. Gardeners and farmers have fewer options. A pheromone-baited trap will capture them, but chemicals that target these particular bugs have not been developed.



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