Named for its smelly-foot-like odor when crushed, the brown marmorated stink bug (Halyomorpha halys) is relatively new to the U.S. Long a crop pest of China, Japan, Korea, and Taiwan, the bug is believed to have been brought into the eastern U.S. in the later 1990s.
Although stink bugs are becoming more than just a nuisance pest in agricultural areas of the eastern U.S., like squash and boxelder bugs, they are not known to breed indoors, cause interior damage, or harm humans. However, they can become quite alarming when they infest homes or other buildings, entering through cracks in search of shelter.
- Color. Although the brown marmorated is the most common stink bug in the U.S., a green variety of stink bug can also be found in the southeastern and south central states.
- Shape. All adult species are shaped like shields and are 1/2 to 3/4 inch long. The young are similarly shaped, but more rounded and may be black or light green.
- Behavior. Similar to boxelder bugs, stink bugs will congregate on exterior building walls in the fall, seeking hidden areas in which to overwinter (the entomological version of hibernate). They can also be a nuisance in the spring as they emerge from overwintering, and during summer as they feed on the bounty of crops and other vegetation.
The stink bugs are little more than a nuisance pest to humans as they do not sting or bite and cause no structural damage to homes or buildings.
However, they can cause significant damage to trees, shrubs, and vines, as well as numerous agricultural products such as tree fruits, blackberries, corn, beans, tomatoes, peppers, and soybeans. Although they have a preference for wild plants, they are known to feed on more than 52 different vegetation varieties.
The stink bug's needle-like mouthpart will pierce seeds to feed on the nutrients within. The extent of damage to the plant is then dependent on the developmental stage at which the bug fed. The stink bug can also transmit yeast-spot disease to plants while it feeds.
The stink bug's odor repels many potential predators, but a number of common bird species do prey on the insect for food. However, with so few natural predators, the stink bug can become quite obnoxious to humans.
Unfortunately, according to Rutgers University Extension Service, "there are no viable strategies for control of the Brown Marmorated Stink Bug. The use of insecticides has very short-lived effect and there is evidence of resistance development. Even where insecticide is effective, repopulation occurs through migration from non-treated areas."
For this reason, as the adage goes, the best defense against the stink bug is a good offense.
- Home or Building Exterior. Insecticidal spraying by a licensed professional can provide limited control of bugs congregating on building walls. However, because sun and weather can break down the insecticidal properties, effectiveness will last little more than a few days to a week.
Thus, the best defense is inspection of the home or building exterior to find and seal all cracks and openings to prevent the bugs from entering. Caulk around incoming pipes, utility wires, and cables; repair window and door screens; ensure door and window seals are intact.
- Interior. If the bugs do get inside, entomologists highly recommend against use of insecticides. It is best to follow insecticide-free practices and vacuum up and dispose of the individual bugs. Because the dead bugs can attract other predacious insects, such as carpet beetles, any insects killed with insecticide would still need to be vacuumed or swept.
In addition, the bugs do not breed indoors, and, contrary to urban myth, dead stink bugs do not attract other stink bugs. However, live stink bugs will emit odors to attract other stink bugs.
- Exterior vegetation. According to the North Carolina Extension Service, "To determine when chemical control is necessary, shake the [soybean] plants on about 1 meter (3 feet) of row over a muslin cloth and count the number of stink bugs. The economic threshold varies from 1 stink bug per 0.3 meter (1 ft) of row to 1 bug per 0.9 meter (3 ft) of row, depending upon state extension service recommendations."
Although the guidance applies specifically to soybeans, it can be used as a general guideline in determining the extent of a crop infestation.