By Jodi Zirbel
What does it look like?
Easily identified by its black and red coloring, the boxelder bug, from the genus Boisea, is a nuisance pest swarming backyards in the summer before infiltrating homes in the fall in hopes of overwintering. Approximately1/2-inch long, the adult bug is black, but features three distinct red lines on its thorax in addition to fine red lines on each wing and along each side.
Host material and range
Abundant throughout North America, the eastern boxelder bug, Boisea trivittata, is found east of the Rockies while the western boxelder bug, Boisea rubrolineatus, is located west of the mountain range. The two species are almost identical, with the exception that the red coloring is slightly more prominent on the wings of the western boxelder bug.
Boxelder bugs feed on female boxelder trees beginning in mid-summer. Because they feed on the boxelder seed pods, which are only found on female trees, they rarely infest male boxelder trees, although they have been known to feed and lay eggs on maple and ash trees as well.
To lay their eggs, these bugs look for cracks in the bark of boxelder trees. Once the eggs are laid, the nymphs hatch within a few days and, after a series of molts, mature to adulthood. Boxelder bugs may produce two generations per year, so it is possible to experience nymphs in the fall, but only adult bugs survive the winter. In order to survive the winter, boxelder bugs look for shelter in tree trunks or other sheltered areas, including inside nearby homes, window casings and building foundations.
The bugs rarely damage trees, so boxelder bugs are not viewed as an economically viable pest. In addition, they don’t injure people or pests, so the biggest threat is being an annoyance. The pests often travel in large groups, so they can be found congregating — enjoying the sun facing southern or western exposures — in swarms outside homes. Once inside homes, the bugs may also spot curtains, clothing or furniture with their excrement.
Since the biggest threat is being a nuisance inside the home, keeping boxelder bugs out of homes is the best preventative technique. Homeowners are encouraged to take adequate steps to prevent their intrusion by repairing points of entry on window and doors, foundations and siding, and all other areas.
Another, more drastic measure is eliminating the host tree. Removing the pod-bearing boxelder tree is the most foolproof way of controlling the pest; however, it should be noted that winged adults can travel as far as two miles, so removing the tree may not completely eliminate their presence, especially if other female boxelder trees are in the neighborhood.
Although insecticides are typically not recommended to control boxelder bugs, the pests are prone to drowning, so one effective technique is an insecticidal soap applied in a forceful spray of water. This may help to reduce boxelder bug populations living on tree trunks, twigs and branches. When using this control technique, look for pyrethroid insecticides. Other chemical controls that have been found effective on boxelder bugs include those containing carbaryl, diazinon, chlorpyrifos, as well as insecticidal soaps.
What can you do?
Encourage homeowners to take steps to avoid a home invasion. Also, instruct them that boxelder bugs are not a serious issue every year, but are most abundant when hot, dry summers are followed by unseasonably warm springs. If chemical controls are utilized, be aware that while most insecticides are effective at temperatures warmer than 70 degrees, boxelder bugs tend to be visible when temperatures are slightly cooler.
Jodi Zirbel wrote this article on behalf of Mauget, a leader in micro-injection and micro-infusion tree care. Contact Mauget or visit www.Mauget.com to learn more about boxelder bugs.