Box Elder Bugs

Boxelder Bugs

Although boxelder bugs cause little or insignificant damage to boxelder trees or other host plants, they are irritant pests in and around structures. Similar to multicolored Asian lady beetles, cluster flies and other seasonal invaders, boxelder bugs seek overwintering sites in and around buildings. Consequently, many people elect to call their pest management professional (PMP) to remove these unwanted pests. Besides their nuisance presence, if crushed, they may stain walls and white surfaces. Dead boxelder bugs in wall voids attract insects that love to feed on them. Examples are: hide beetles, larder beetles, carpet beetles and carpenter ants. From a pest management standpoint, it is necessary to prevent the invasion of boxelder bugs before they enter homes. This can be achieved by either physical or chemical pest management ways as we are going to discuss.

Studies have shown that dry and hot summers indicate a potential increase in boxelder bug numbers. This fact helps us to predict the infestation levels of boxelder bugs each year.

The consumption of dead insects (conspecific necrophagy) has been documented among the boxelder bugs during hibernation. This phenomenon increases the survival rate of the overwintering adults, whereas, “cannibalism” is also known among nymphs in the field.

Boxelder bugs develop by a gradual metamorphosis from egg to nymph and then to adult.  In spring, females lay irregular masses of eggs on leaves, in cracks and crevices of the host tree bark, or on grasses and stones near the host plant. Egg masses may have from 10-25 eggs.  Eggs usually hatch in 11-19 days depending on the weather conditions, such as temperature and relative humidity.  Newly hatched nymphs pass through five nymphal developmental instars. This may take up to 60 days before they become adults by mid summer. New adults mate and females lay eggs to start the second generation.  In the fall, boxelder bugs congregate on the trunk of female boxelder trees or on the ground level by the host plants, then they migrate to the sunny sides of the building. That is when they become noticeably visible by people.  The onset of the harsh winter weather causes all immature stages of boxelder bugs to die, while adults seek overwinter shelter, which may be your house.

Boxelder bugs feed by sucking sap from the leaves, tender twigs and developing seeds. Although the primary host plant of the boxelder bugs is the female (seed-bearing) boxelder tree, these bugs have been occasionally observed on other plants such as male boxelder, apple, ash, maple, almond, strawberry, etc. However, boxelder bugs usually cannot fully complete their life cycle on these occasional hosts.  Adult boxelder bugs hibernate in cracks and crevices in and around a structure.  In sunny and warm winter days, a few overwintering adults may become active and can be seen around windows or warm places.  During overwintering time, boxelder bugs do not feed or reproduce.  In the early spring, typically in late April to early May, boxelder bugs become noticeable to the eye again as they congregate on the sunlit sides (south/west) of the building. Then they fly off to a convenient host to lay eggs and start their life cycle.  Between mid May to mid July, adults and nymphs congregate on the low vegetation or ground near the female boxelder trees feeding on the fallen seeds produced the previous year.  From mid July to mid September, boxelder bugs congregate on the trunk of female boxelder trees and ground.  The migration of the second generation to the sunny sides of the building usually begins from mid September to mid October before adults finally overwinter in cavities in and around buildings.  Boxelder bugs are attracted to light meaning that they will move toward it. Therefore, they may enter homes through open windows or doors, especially at night when the interior light is on. Once indoors, they could be seen hiding or clustering near light fixtures or around windows and vents.