The common name reflects the fact that this species is a major pest of boxelder trees, Acer negundo. Boxelder bugs are primarily nuisance pests because they enter structures to overwinter. This species is found from eastern Canada, throughout the eastern United States, and west to eastern Nevada wherever boxelder trees are found.
Boxelder bug adults are about 1/2 inch long and elongate-oval in shape. They are black with reddish edge lines on the body and wings. The mouthparts are piercing-sucking and form a beak that is held beneath body when not in use. Nymphs are similar to adults but lack wings; although wing pads may be present, and are bright red in color.
Small eastern milkweed bugs (Lygaeus kalmii) have small white spots/markings on the outer portions of the front wings (visible on the rear upper surface when the wings are folded). Also, the thorax lacks a median red stripe and the head has a red mark between the eyes. These insects are associated with milkweed seed pods.
The overwintering boxelder bug adults emerge from hibernation and the females lay clusters of straw-yellow eggs on stones, leaves, grass, shrubs, and trees, especially in the bark crevices of boxelder and maple trees. These eggs turn red as the embryos develop and hatch in about 2 weeks. These nymphs feed on fallen boxelder and maple seeds and later on newly developing leaves, going through 5 instars (growth stages). In the warmer regions of the United States, there are 2 generations per year.
The overwintering adults emerge from hibernation when the boxelder and maple buds open and fly back to their host trees, typically in late April to early May. The primary host plant is the seed-bearing (female) boxelder tree, but they also occur on seed-bearing silver maple trees, Acer saccharinum. Occasionally, they will feed on the fruits of plum and apple trees.
In the autumn, boxelder bugs become gregarious and congregate on the south side of rocks, trees, and buildings having direct sun exposure. After large masses congregate, they may fly to nearby buildings to hibernate for the winter. Inside, box elder bugs are primarily a nuisance pest. However, their fecal material may cause a red stain, resulting in discoloration on curtains, drapes, clothing, and other resting places. When crushed or handled roughly, they produce a strong, disagreeable odor. They occasionally “bite” people, causing a skin irritation and producing a red spot similar to a mosquito bite.
Cultural Control & Preventative Measures
Control begins outside. Reducing the outside population can be achieved by calling upon an arborist or landscaping professional in the spring to spray all boxelder trees and maple trees on the property with an appropriately labeled residual insecticide. However, if the host trees are on an adjacent property, a cooperative arrangement must be sought with that property owner.
The use of preventative physical barriers involves exclusion. Although total exclusion is probably not possible, all vents (roof, gable, soffit / eave) should be screened with at least #16-mesh screening. Weep holes should be stuffed with copper gauze or steel wool. Silicone sealer should be applied around cable and utility penetrations, windows, doors, and overhangs. These steps should be taken before late August.
Temporary but immediate indoor relief from boxelder bugs can achieved by removal with a vacuum cleaner fitted with a hose attachment. To prevent entry of more bugs, it is important to seal the possible routes of entry using silicone caulk and similar materials. Entry points include around window pulleys window frames, doorframes, and baseboards. For electrical outlets and switch boxes and heating duct and air return vents, it is recommended to remove the cover plates, seal, and replace. For light fixtures and ceiling fans, one should remove the fixture to its base plate, seal, and replace.
If boxelder bugs are in a false ceiling area, the population can be reduced by installing an insect light trap; if used, it is important to periodically empty the catch tray or replace the sticky panels. An alternative is to install a continuously burning 60-watt fluorescent bulb, which attracts flying and crawling insects and causes them to exhaust their food (fat), and die near the light. The dead insects ought to be removed with a vacuum cleaner. To speed the process, adhesive fly strips or sticky traps can be suspended near the light in the ceiling void.
Sticky-capture devices should be replaced when filled or covered with insects. To reduce the number of boxelder bugs coming into a room from a false ceiling, all cracks through which light enters should be sealed using duct tape or caulk. In elevator shafts, a continuously burning 60-watt bulb can be installed just above the pit floor. Again dead insects should be removed periodically using a vacuum cleaner.
F&W Pest Control technicians prefer to apply treatments for boxelder bugs on strategic exterior surfaces of buildings in August and September. Preventative chemical barriers involve applying a long-lasting residual liquid insecticide (1) beneath the lowest course of siding at the foundation, (2) into structural junctures (e.g. molding, trim, seams and weep holes), and (3) on strategic, sun-lit vertical walls and the adjacent overhang. This application is made just before the late season search for overwintering sites begins. One application is required. If boxelder bugs have already begun to congregate and attempt entry into buildings, it may be too late for preventative action. Once buildings are entered, the best solution is physical removal with a good shop-type vacuum cleaner.
F&W Pest Control technicians prefer not to inject insecticides into the overwintering sites of boxelder bugs in buildings because the bodies of dead insects in wall voids attract dermestid beetles (e.g., larder beetles, carpet beetles and cabinet beetles). Dermestid larvae wander and will readily enter the living space, causing numerous complaints. However, temporary relief is possible by using a vacuum cleaner and sealing interior entrances.