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Stink Bug Primer

Stink bug (photo by Steve Jacobs)In warm weather, homes and orchards across Pennsylvania are battling the brown marmorated stink bug, the latest invasive insect to find its way into the United States from Asia. Experts haven’t yet identified any good solutions for managing or eradicating the pest.

Stink bug adults are about three-quarters of an inch long and are shades of brown on both the upper and lower body surfaces. They are almost as wide as they are long, and their “shield” shape is typical of other stink bugs. The name “stink bug” refers to the scent glands that emit a distinctive odor when the insect is disturbed or crushed. They are not known to bite people or spread diseases.

This variety of stink bug first was found in the United States in Lehigh County in 1998, and it since has become a perennial nuisance to homeowners as the bugs seek winter shelter—sometimes by the thousands—in and around houses and other structures. This past year the problem was worse as stink bugs reproduced at a faster pace thanks to a warm spring and early summer. Normally, there would be one generation of stink bugs per growing season, but this past year there were at least two generations, leading to higher and faster-spreading populations.

Homeowners fighting an invasion of stink bugs have few options. Mechanical exclusion is the best method to keep stink bugs from entering homes and buildings. Caulk cracks around windows, doors, siding, utility pipes, behind chimneys, and underneath the wood fascia and other openings. Damaged screens on doors and windows should be repaired or replaced.

If bugs are found inside the house, try to identify their entry path and seal it off. A vacuum cleaner can be used to remove live or dead stink bugs, but be aware that the vacuum may take on the smell of the insects for a period of time.

Most pesticides will not stop a home infestation, and it is not recommended that homeowners apply insecticides to kill stink bugs indoors. Seek professional extermination help if mechanical exclusion fails.

In 2010 stink bugs became a serious agricultural pest, causing extensive damage in some Pennsylvania apple and peach orchards and feeding on blackberry, sweet corn, field corn, and soybeans. In neighboring states, they have also damaged tomato, lima bean, and green pepper crops. In all, they can attack an estimated 300 host-plant species.

There are few if any natural enemies in the United States to help control stink bug populations. Pesticides are not a particularly good option for growers, some of whom have lost 40 to 50 percent of their crops to stink bugs.

The broad-spectrum pesticides that work best on stink bugs will also kill the beneficial insects growers rely on as part of integrated pest management, or IPM, programs. It would also upset the balance in the orchard ecosystem—allowing other pests to become more of a problem—and could reverse much of the progress made in IPM, which has helped Pennsylvania growers reduce pesticide use by as much as 75 percent in recent decades.

Stink bugs do their damage by inserting mouthparts under the skin of the fruit, injecting saliva, and sucking out the juices. While not harmful to people, this feeding leaves exterior dimpling and dried, corklike areas in the fruit, making it unmarketable at the retail level.

Economic impact is high and puts growing operations at risk. Damaged fruit sold for processing or juice may bring $7 to $10 per bushel, compared to anywhere from $20 to $60 per bushel on the fresh-fruit market. Researchers in the college, other universities, and the U.S. Department of Agriculture are studying the brown marmorated stink bug with an eye toward developing monitoring systems and management tactics. Because this is a new pest in the United States, it will take additional resources and time before the problem can be addressed effectively.

A Penn State fact sheet about the brown marmorated stink bug is available online at ento.psu.edu/extension/factsheets/brownmarmorated-stink-bug.

Photo: Steve Jacobs