Boxelder bug populations vary from year to year and place to place, depending on weather (especially temperature and rainfall during May through July). There is no easy way to determine when and where boxelder bugs will be a problem until the problem starts. By then it may be too late for effective treatment. Boxelder bugs can be controlled on the trees in mid-summer with yard and garden insecticides such as diazinon, Orthene and Sevin. The limited effectiveness of this treatment and the difficulty of spraying large trees makes tree spraying impractical.
The best deterrence against boxelder bugs and similar invaders (e.g., crickets, attic flies and elm leaf beetles) is to prevent entry by caulking and sealing possible entry sites (cracks and gaps). A lawn and garden insecticide (such as Sevin, diazinon or Dursban) or soapy water spray can be used on masses of boxelder bugs seen on and along the foundation in the fall. A soapy water spray made with 5 tablespoons of liquid detergent per gallon of water works effectively on boxelder bugs sprayed directly, but it has no residual activity. Soapy water sprays will have to be repeated frequently. Reducing the number outdoors should limit the number that will get into the house.
Unfortunately, there is no easy cure for eliminating boxelder bugs already inside the house. They are generally not killed by the aerosol household insecticide products, and the residual insecticides such as "ant and roach killer" are not of much benefit. A sure control for boxelder bugs already in the house is to remove them as they appear, by vacuuming, sweeping or picking them up and discarding.
This article originally appeared in the March 17, 1995 issue, p. 25.
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