University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Boxelder Bugs Problems in Fall

October 11, 2001

Even though the multicolored Asian lady beetle now seems to be the dominant insect problem of fall, boxelder bugs are also nuisances around many homes this time of year. Both insects are similar in why they become nuisance pests when autumn arrives.

Boxelder bugs are about 1/2 inch long and are dark brown or black with conspicuous red markings on their backs. Nymphs of the boxelder bug are small and bright red. Seeds, flowers, and leaves of the boxelder tree are their primary food source, so they spend most of the season in and around boxelder trees. They may also feed on the closely related maple, along with ash, cherry, and apple.

As fall arrives boxelder bugs, like multicolored Asian lady beetles, move to structures. They spend the winter between the walls of homes and garages and emerge again in spring to return to trees to feed and lay eggs. On warmer, sunny days, boxelder bugs may congregate in large numbers on south and west facing walls. They do not lay eggs indoors, however. Eggs are laid on trees early in the season.

Even though these insects do not feed or reproduce indoors, homeowners facing this large population of insects want to do something to reduce the numbers. Direct control measures toward keeping insects out of the home. Caulk cracks and crevices along foundations, windows, and doorframes, and keep screens in good repair.

Groups of boxelder bugs on outside walls, tree trunks, under eaves, or other areas they have gathered can be controlled using insecticidal soap. The insects should be sprayed directly for this treatment to work effectively. Spraying is not suggested indoors. Another option for next summer is to apply carbaryl (Sevin) to tree foliage where boxelder bugs are feeding to reduce numbers.

As we get further into fall and some hard freezes occur, boxelder bugs should begin to die if they cannot find shelter.

 

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