Boxelder Bug

Adult boxelder bugs are black, flat-backed, elongate, and narrow; about ½-inch long; and have three orange or red lengthwise stripes in the area right behind the head.

 Boxelder bugs feed primarily on the seed-bearing boxelder trees by sucking sap from the leaves, tender twigs, and developing seeds. They have occasionally been observed feeding on ash, maple, plum, cherry, apple, peach, grape, and strawberries. However, boxelder bugs seldom develop in large enough numbers to become a nuisance. Apparently,they do little actual feeding damage to boxelder trees. Outdoors, they can be found in large numbers on the sides of trees, buildings, and other structures.

Boxelder bugs are primarily a nuisance because they enter homes and other buildings, often in large numbers, especially during the warm days of autumn, to seek sheltered sites for overwintering. Fortunately, they do not bite people and are essentially harmless to property. When abundant, they can stain walls, curtains, and other surfaces with their excrement. Occasionally some may seek moisture and may be found around houseplants, although they rarely attack them. In the few cases when they do feed, boxelderbugs are very unlikely to injure indoor plants.

Large populations are often correlated with long, hot, dry summers. During warm winter and spring days, they may become active, moving from their hiding places into living spaces. They are attracted to lights and can fly in open doors or windows. Screen all windows, doors, crawl spaces, exhaust and roof vents and louvers. Clusters of bugs may be killed by pouring boiling water on them. Be careful to avoid killing grass and other desirable plants with boiling water.

The best management for boxelder bugs is prevention – take steps to keep them from moving indoors. This can be partly done through exclusion. Make any repairs by the end of August. Eliminate potential hiding places such as piles of boards, rocks, leaves, grass, and other debris close to the house. Rake leaves and grass away from the foundation in a 6- to 10-foot-wide strip, especially on the south and west sides of the structure. Be sure to caulk and close openings.

Should boxelder tree removal be impractical, treat the young, exposed boxelder  bug nymphs on the trees during spring and early summer to prevent potential large populations and indoor migrations in the autumn. Insecticidal soap can be used to kill congregrated boxelder bugs. Treating boxelder tree trunks with residual insecticides can kill migrating insects.

Adapted from: Ohio State University Extension, 1999; University of Minnnesota Extension, 2007