The brown marmorated stink bug or BMSB (Halyomorpha halys) is a relatively new pest for the Chicago area. It has been a serious crop pest in many Eastern states for a number of years. In the Chicago area, it is mostly a nuisance pest, showing up in homes in fall. There are many species of stink bug, but they are not all pests. Some are predators feeding on other insects and some are plants pests but do only minor damage. In many Eastern states, the brown marmorated stink bug has become a pest of many fruits, vegetables, and other crops, as well as a number of trees and shrubs. BMSB is non-native; it was introduced from Asia.
The adult is about 1/2 inch long. Like many stink bugs, BMSB is a flat insect with a shield-shaped body. There are some markings that will separate this stink bug from others (see photo below). The antennae are marked by light and dark alternating bands. The legs are also banded, but the bands are not as distinct as those on the antennae. The edges of the abdomen have very distinct dark and light bands, but this feature can be seen on other species of stink bugs as well. The insect’s “shoulders” are somewhat rounded, while other stink bugs have sharply pointed “shoulders”. The overall appearance of the body is a marbled color, with a row of creamy dots behind the head and on the edge of the scutellum (the triangle on the back of the insect).
BMSB spends the winter as adults in homes and other protected sites. They may be easily spotted in the home in late autumn as they enter the home through cracks and crevices. Once in the home, they hide in attics and other out-of-the-way places. While in the house, this insect does not feed or reproduce. BMSB does not bite and doe not carry diseases.
As outside temperatures begin to warm in spring, the overwintering adults emerge from hiding and try to find their way outside. Once outside, the adults will mate and egg-laying will begin. Eggs can be laid from May through August. Eggs are light green in color and laid in a cluster on the undersides of leaves. The young nymphs that hatch out are reddish-orange and black. They will molt five times as they mature into adults. Nymphs will vary in appearance from molt to molt. Both nymphs and adults can feed on plants, so they can be a season-long pest.
At this time (2020’s), for homeowners in Northern Illinois, BMSB is mostly a nuisance pest, coming into homes in the fall and spending the winter. They do not reproduce or feed indoors. Anyone who has them in their home may find them in fruit and vegetable gardens outside this summer, as well as on some ornamental trees and shrubs. These insects feed by sucking out sap from fruits and seed pods, damaging them and making them unusable. This damage may also occur on stems and leaves as well. For commercial growers, BMSB can be a serious pest, reducing the quality of crops so that they cannot be sold.
To prevent BMSB from entering the home, caulk cracks and crevices around doors, windows, air conditioners, and any other access points into the home. The University of Illinois recommends an insecticide containing deltamethrin for treatment of outside walls, soffits, and gables where the insect may be found in groups. Individual insects that enter the home can be removed by hand and discarded outside or into a bucket of soapy water. Handle the insect carefully, as it will smell when crushed. Groups of BMSB can be swept up with a hand-held vacuum and dumped into a bucket of soapy water.
If the insect becomes a problem in gardens, there are stink bug traps available for sale that can be used to reduce populations outside.
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