[Copesan University] Stink Bug Invasion

During the last few years, a new nuisance pest has made an appearance in the eastern United States. This outdoor insect has the habit of entering structures in the autumn to overwinter, sometimes in enormous numbers. Once inside, it can cause serious product contamination by both its physical presence and by imparting a pungent odor. This pest is commonly called the brown marmorated stink bug because of its brown, marbled color.

Whatfs its distribution? This pest is a recent introduction from eastern Asia. It was first collected in the United States in Allentown, Pa., in the fall of 1996, but not officially recognized or identified until September 2001. It quickly spread east to New Jersey and then to Virginia by 2004. According to Rutgers University, it is now being found throughout New England, the mid-Atlantic, the South and the Midwest. Its native range consists of China, Japan, Korea and Taiwan, where itfs an agricultural pest. So far in the U.S., itfs an overwintering nuisance pest in structures.

How can they be recognized? Adults are about Ý-inch to 5⁄8-inch (12-17 millimeters) in length and fairly easy to identify. Their shield-shaped body is distinctive. Their color is mottled or marbled brown, and the outer two antennal segments have broad whitish bands. Their wings do not completely cover the side margins of the abdomen, leaving alternating dark and pale bands of abdomen visible, and there is a darker area where wings overlap toward the rear. The first body segment behind the head (called the pronotum) has smooth lateral (side) margins, without spines or teeth. Their scent glands produce a pungent odor.

Whatfs their life cycle? Adults overwinter and become active in early to mid-April. They mate and lay clusters of 20 to 30 eggs on the undersides of leaves from May through August. The eggs hatch in about four to five days after being deposited, and the immatures or nymphs go through five stages/instars. Adults begin to appear on foliage in mid-August. There is probably only one generation per year.

Can they damage plants? In the United States, the brown marmorated stink bug has been observed feeding on many different ornamental plants and trees, including the crab apple, the American holly, the Norway maple, the pyracantha and the butterfly bush. It has also been observed feeding on raspberries, Asian pears, peaches, asparagus, and string beans. In general, adults feed on fruits, and immatures/nymphs feed on leaves, stems, and fruit. It is not clear if the marmorated stink bug will become a general and widespread pest in the eastern United States.

When does the invasion start? In Pennsylvania, flights to find overwintering sites begin in mid-September and peak the third week of October. In Virginia, the flights begin in early October. Like other overwintering insects, they often will mass on the sides of buildings, which causes concern for the occupants.

Preventive steps. Control should consist of a good IPM program. Before the bugs enter, use exclusion techniques, such as sealing holes in exterior walls larger than the diameter of a pencil, checking door and window frames for holes, and ensuring door sweeps, doors and windows are tight-fitting. This is best done during May through July, with a follow-up in late September. Since these bugs are attracted to lights, change exterior lighting to less-attractive yellow bulbs or sodium vapor lamps.

PMPs may recommend the application of a repellent pyrethroid insecticide to help discourage stink bug entry for structures with exteriors that are difficult or impossible to seal. The application should be made in early September.

Inside a facility. After the stink bugs have entered the structure, itfs best to isolate the affected room(s) by sealing the bugs out. Such rooms are usually located on the warm side of the structure. Typical entry points are those around door and window frames, electrical outlets, light switches, exhaust fans, skylights and ceiling light fixtures.

Because of the eventual problem of carpet beetles coming to feed on the dead bugs, itfs not advisable to kill these bugs inside walls with dusts. They can be harvested with insect light traps, but the glueboard type should be used since electrocution often causes them to release their pungent stink. Unfortunately, this means checking and changing the glueboards often.

If bugs come into a room, it also may not be advisable to remove them with a vacuum. After a few stink bugs travel down the vacuum hose, their smell can be quite noticeable and the hose will probably have to be replaced periodically. If the size of the invasion warrants, when the individual room is vacant, the pest management professional can make an ultra low volume (ULV) treatment. Then, a couple of hours later, the bugs can be swept up with a broom and dustpan.

 The author is director of technical services, Dodson Bros., Lynchburg, Va.