Above photo: Boxelder bugs (adults and nymphs) on a boxelder tree. Photo by John E. Woodmansee
I don’t know about your household, but at mine, the boxelder bugs are knocking (so to speak) on our door wanting in. If you have a boxelder tree or trees on or near your property, you may also be experiencing these hopeful visitors.
Adult boxelder bugs are about one-half inch long and black with reddish-orange line markings on their bodies. Nymphs, or immature boxelder bugs, are primarily red. Boxelder bugs cluster on the sides of boxelder trees, occasionally moving to cluster on the sides of houses, and eventually finding their way indoors. Their sheer numbers can alarm anyone.
Boxelder bugs can fly easily, so even if you don’t have boxelder trees in your yard if they are in the neighborhood, you may see these bugs around your house.
Boxelder bugs prefer female boxelder trees, the ones which produce seeds. Seeds resemble the helicopter-like seeds maples produce. In fact, boxelder trees are actually in the maple family of trees. Their scientific name is Acer negundo. The genus name, Acer, refers to maples, and negundo is the species boxelder. Since it has a compound leaf with 3-5 leaflets (rarely 7), boxelder is also sometimes called ‘Ash-leaf maple’ or ‘Ash-leaved maple’.
The good news with boxelder bugs is that they cannot bite or sting. They are like lady beetles in that they are only nuisances when they invade homes and cannot find their way back out. They cause no appreciable damage to landscape trees.
In the fall of the year, adults search for protected cracks and crevices to pass the winter. Near homes, they may squeeze into cracks in the foundation, windows, doors, or under siding and shingles. And, some manage to find their way into our homes.
When the weather warms up, they begin to move about again looking to mate and lay eggs in a suitable place. Eggs are usually laid on the bark of female boxelder trees, but can also be found on other trees.
Dr. Tim Gibb, author of Purdue Extension publication E-24-W, entitled, “Boxelder Bugs,” discussed potential control measures.
Dr. Gibb said a non-chemical control option for boxelder bugs is to pour hot (165º-180ºF) water on clusters of insects. This will readily kill both adults and nymphs.
“One of the best controls for boxelder bugs is to spray infested trees during late summer while the second brood of bugs is still immature and concentrated on the trees,” said Gibb. “Carbaryl (Sevin) and permethrin (Spectracide Bug Stop, Eight) are labeled for this purpose.” Other insecticides may also be available (no endorsement of these products is implied). Note also that at least one of these brand names may now include multiple or different ingredients under the same brand name. Choose products that are labeled for the control of boxelder bugs.
Gibb said that perimeter foundation treatments with chemicals also may provide good control if the spray is applied to all surfaces over which bugs crawl. Gibb said that homeowners may choose any of several insecticides labeled for “homeowner use” as a foundation or outside perimeter treatment against invading insects.
Homeowners can caulk around windows, doors, and utility entrances to help prevent entry by these and other insects. Broken doors, windows, and screens should be repaired. Inspect potential entryways via crawl spaces and attics.
Once inside the home, Gibb suggests that household sprays containing pyrethrins or resmethrin may give temporary control. However, a fly swatter or vacuum cleaner is often the best way to rid the home of these pests.