Boxelder bugs (Boisea trivittata) are named for their primary host, the boxelder tree. One of the less destructive agricultural pests, boxelder bugs do infrequent damage to apples, peaches, grapes, strawberries, plums and non-fruiting trees including maple and ash. A bigger nuisance to homeowners, they seek and enter houses in colonies of hundreds, even thousands of insects as cold weather approaches, congregating in walls and warm basements, making themselves at home all through winter and occasionally emerging into kitchens, living rooms, bed rooms and other human-inhabited spaces. There’s nothing like watching your toddler bring a stray, otherwise harmless boxelder bug that’s making its way across the carpet up to her mouth. It’s an experiment children won’t likely repeat. Boxelder bugs, though mostly scentless, give off a pungent odor when disturbed or crushed. Also offensive: the accumulation of excrement and dead bugs that fall from the colonies inside walls and other hard-to-access places.
Adults, the stage most often seen in homes, are dark with three distinct orange or red stripes, the first centered behind its head, the other two running along the sides of its body. The adult’s abdomen is also orange. About 1/2 inch long, its dark wings cross along its back. Eggs, found on leaves, the seed pods of boxelder trees, and in ground vegetation, are yellow and clustered in groups that begin to redden as the nymph develops. Nymphs go through five stages, continuing to turn red as they mature. Adults are sometimes mistakenly identified as stink bugs, which they generally resemble.
Adults survive the winter sheltered beneath loose tree bark, in plant debris, or in homes, garages and out-buildings. They emerge as the weather warms in spring. Staying close to the ground, they feed for two weeks on boxelder seeds and other vegetation before starting the mating cycle. Female bugs fly up female boxelder trees and lay eggs on seed pods and the undersides of leaves. They will also leave eggs on stems and branches. Eggs take 10-14 days to hatch. During the summer, all stages of the boxelder can be found in and around host trees. While nymphs continue to develop into the fall, only adults survive cold weather.
Box elder bugs are sap suckers, penetrating plant tissue with their considerable proboscis and using secretions to make it consumable. They almost exclusively feed on the acer family of maple trees and vines that includes the boxelder and its spinning “helicopter” seed pods, but have also been known to feed on fruit during dry summers. Infestations on box elder trees may cause its leaves to yellow and curl or leave spots on stems and new growth. Most trees survive. Damage to grapes, peaches, and other soft fruits is mostly cosmetic, appearing as depressions, sometimes as bruises. While a nuisance, boxelder bugs do relatively little damage to fruit crops, preferring to feed and procreate in its namesake tree.
Indoors, the bugs can be a major problem. While they don’t normally cause structural damage to homes or contaminate food sources (individuals will occasionally show up in dried beans and flour if not stored in tightly sealed containers), they can be a source of filth, odor and displeasure due to their sheer numbers. Warm weather or an increase in home heating may convince individual boxelder bugs that spring has arrived and they will enter a family’s living space in search of a way outside. In late summer and autumn, then they gather in groups much like swarms of bees on the sun-facing, preferably white side of homes and garages where their sheer numbers will discolor the building’s side if allowed to stay.
Indoor and outdoor boxelder control are interrelated. Destroying boxelder colonies outdoors means few bugs looking for a way into our home come fall. Denying places in your home for boxelders to overwinter means fewer numbers laying eggs in your trees next spring and summer.
Most outdoor boxelder damage is minor and, most years, won’t require treatment most years. Some years will produce more boxelder bugs than others. Dry years may encourage the bugs to seek out fruit. Wind plays a great role in the dispersal of flying boxelder bugs.
Chemical pesticides are a poor option for boxelder infestations. Their use indoors can pose a hazard. Dusting of colonies may kill thousands of bugs but will only encourage other insects and rodents who feed on the dead bodies. The common and troublesome carpet beetle is attracted to dead boxelder remains. There it feeds and lays egg, guaranteeing another generation of increased numbers to damage in your home.
Boxelder Bug Prevention
In order to prevent boxelder bugs from invading homes, repair holes in window and door screens, seal cracks and crevices with a good quality silicone or silicone-latex caulk and install door sweeps to all exterior entrances.
When attempting to get rid of boxelder bugs that have already entered a home or building, no attempt should be made to kill them in wall voids because dead insect bodies can attract dermestid beetles. Rather, using a vacuum cleaner to remove them may provide temporary relief. The bag should be removed to prevent the bugs from escaping.
If a boxelder infestation is suspected, a licensed pest control operator should be called to evaluate and assess the problem.
Here are 10 cool facts I learned about boxelder bugs:
1. They are also known as the “Democrat bug,” the “zug” and the “maple bug.”
2. They feed mostly on maple or boxelder trees. (We saw a boxelder tree on the hike!)
3. They can invade houses or other man-made buildings.
4. They hibernate inside of walls in the winter.
5. They are sometimes called “Democrats bugs,” because they swarm during October, which is right before people vote.
6. Adults are 1/2 inch long.
7. Adults also are black with orange or red markings.
8. They cannot or do not bite people.
9. Their feces can stain walls and furniture.
10. They do not reproduce inside homes, only outside.