Many of us gardeners are preparing to spend the next five months indoors, out of the elements where it is warm and dry. Unfortunately, there are several outdoor pests preparing to do the same. Many are looking for protected locations to spend the winter months. Leading the way is the notorious boxelder bug. When you answer the door later this week, be prepared to have more than just trick-or-treaters on your doorstep trying to get in.

Adult boxelder bugs are about half an inch long and dark brown to black in color with a red line across their back. The young nymphs are generally similar in shape to the adults but have no wings. The smaller nymphs are solid bright red, but the older nymphs are mostly red with a few black markings.

Boxelder bugs do not bite or damage buildings, furnishings, clothing or food. The worst they can do is spot curtains and walls with fecal material and leave a stain if crushed. Because of this, they are mainly a nuisance pest that crawls and flies about rooms and accumulates in light fixtures.

Boxelder bugs have to overwinter as adults. To do so, the bugs move to warm sheltered areas in late summer and early fall. They become household pests as they crowd into cracks and crevices on the south and west sides of buildings, patios and concrete walls, eventually making their way into wall voids, where they can end up in the home.

Control is not simple. Start by insect-proofing your home. Caulk cracks and crevices around vents and other gaps on the exterior of the home. You will exclude the bugs and save on energy costs. Second, check all screens and storm doors. Make sure they fit snug and secure. Finally, clear the yard of clutter. Lumber, stored firewood and similar materials can serve as a source of overwinter shelter.

Boiling water can be poured on small masses of bugs. Take extreme caution not to scald yourself during the process. Those that you can reach with hot water will be killed instantly. Likewise, a mild liquid soap solution sprayed on bugs kills them. Take care not to spray valuable landscape plants as the soap may damage the foliage.

Insecticides, such as Diazinon, Sevin, Cyfluthrin and other synthetic pyrethroids work marginally at best. Choose an outdoor spray concentrate or a ready-to-use product that lists boxelder bugs or similar nuisance pests on the label. Choose products that are safe to spray on both ornamental plants and outdoor building surfaces. Spray existing bug masses as well as ground cover plantings, foundation walls, tree trunks and other outdoor sites where bugs are found.

Indoor alternatives are more limited, and safety is an issue where pesticides are concerned. A vacuum cleaner can be used to capture the bugs, but be sure to destroy the bag after use. If you must use an insecticide indoors, use a household aerosol or ready-to-use spray labeled for control of flying insects. Pyrethrins and resmethrin are examples of safer indoor products.

Bruce Chladny is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him at 843-7058 from 8 a.m. to 5 p.m. weekdays.