BY Sarah Busdon
Boxelder bugs are a common nuisance pest in Idaho homes and yards. Although not particularly harmful, these insects can be aggravating when they are searching for places to spend the winter.
Boxelder bugs develop through three life stages: eggs, nymphs, and adults. Adults are the most commonly encountered life stage. Adult boxelder bugs are flattened, elongate insects approximately 1/2-inch long. Overall upper body color is slate gray to black. Reddish-orange lines appear behind the head and along the sides of the body. The rest of the body under the wings is red with two rows of black spots. Legs and antennae are black.
Boxelder trees are the primary host plant for insect egg-laying, feeding and development. Boxelder bugs suck sap from leaves and stems but prefer to feed on seeds. These insects have been observed feeding on a diverse group of 20 other types of plants, ranging from weedy grasses to ornamental flowers to small fruits.
The onset of winter is the time when boxelder bugs wander into residences. Boxelder bugs overwinter in bark crevices and hollow tree trunks or under rocks and surface debris. They can also be found in protected places around home landscapes and inside unheated parts of buildings.
In May, overwintered adult boxelder bugs fly to host trees, where they lay several hundred eggs in small batches. Eggs hatch in 10 to 14 days. Nymphs initially live on the ground or in low-growing vegetation. In southern Idaho, nymphs develop into adults by midsummer. Only wadults survive the winter and any remaining nymphs die when freezing temperatures arrive.
Boxelder bugs become a nuisance pest by their sheer presence in and around residences. Two periods of nuisance activity occur from late summer through mid-fall when bugs leave their host trees for overwintering sites, and in mid-spring when overwintered adults again become active and search out places to lay eggs.
Other than being a nuisance, boxelder bugs do not cause any significant harm. They are inconsequential landscape pests but can cause deformities by feeding on fruits. Plant feeding by boxelder bugs seldom cause damage to boxelder or maple trees in home landscapes.
There are a few management options when boxelder bugs become a nuisance. To learn more about boxelder bug management, please contact the University of Idaho Extension office, (208) 788-5585.
Sarah Busdon is an administrative assistant with the University of Idaho’s Blaine County Extension office. For more information, visit extension.uidaho.edu/blaine or call (208) 788-5585.
