by Lee Townsend, Extension Entomologist
University of Kentucky College of Agriculture
Boxelder bugs are common insects that feed on sap from leaves, twigs, and seeds of boxelders, as well other members of the maple family. Large numbers of them can be seen on tree trunks, or branches, or sunning themselves on the south or west sides of buildings in the spring and fall. These harmless accidental invaders may be a temporary nuisance as they move into and out of sheltered overwintering sites in the fall and spring.
Adult boxelder bugs are elongate, 1/2 inch long insects with sucking mouthparts. They are mostly black with some red markings. There are three narrow red lines on the segment behind the head, one down the center and one on either side and a thin red inverted "V" about the middle of the back. The wingless immature or nymphal stage has a black head, antennae, and legs. The red abdomen has an orange-yellow stripe and spot down the center of the back.
Boxelder bugs feed on plants during the summer. They move to sheltered areas (including nearby houses and buildings) in the fall and remain there during the winter. Sweep or vacuum up and discard those found inside. They will not multiply nor will they infest any household articles. These insects are only a nuisance or accidental invader; however, they may leave an odor and stain when crushed.
Exclusion is important in reducing numbers that get indoors. Check door sweeps and places outside the house that may allow them to get inside. If large numbers are present every year, removal of female boxelder plants should be considered because this is the major host plant for them. Other alternatives include controlling insects while they are on the boxelder plant or direct sprays of congregations of the insects on outside walls. Insecticidal soap provides a safe control alternative but it must be sprayed directly on the insects to be effective.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!