Farm Horizons, August 2012

All about box-elder bugs

By Christine Schlueter, McLeod County Master Gardener

Soon, you will see the gathering of box-elder bugs. They are a pest, but this year they may be in big numbers.

The adult box-elder bug, leptocorouos trivittatis, is one-half inch in length. Its black and red cross pattern on its back makes this insect easy to distinguish. The box-elder bug sucks the sap from leaves and flowers of its host plants, but doesn’t cause much damage.

Most years, the number of box-elder bugs found in and around the yard is insignificant. If winters have been mild, large populations may build up and may become a nuisance. The bugs can be found in large groups on the sunny side of tree trunks, fences, garages, and houses. They are most numerous in areas where box-elder trees grow.

They normally survive the winter by crawling into cracks and holes in bark, but also swarm into houses or crawl under siding or cracks in concrete, windows, and doorsills.

They produce no odor, nor do they bite. They are harmless, and cause no damage, other than occasional spotting of windows and draperies.

Box-elder bugs have few natural enemies. There are no major insects or diseases that affect their populations, and spiders are considered a minor predator. Birds fail to feed upon them in any significant numbers, probably due to the ability of the bugs to emit an offensive odor (which undoubtedly makes them taste bad, as well).

The bugs, themselves, are gentle and will not harm humans, even when handled.

Box-elder bugs are in the order Hemiptera. Most bugs in this order are considered good bugs, meaning that they feed on other insects that are nuisances. The box-elder bug is not a predator like other Hemipteras, but feeds on plants, mainly box-elder tree seed pods.

The three life cycle stages of box-elder bugs are egg, nymph, and adult. After hatching, the nymph slowly metamorphoses into an adult. It lays its eggs in bark of the box-elder tree or other protected places.

How to control box-elder bugs

Hot water (165-180 degrees F) applied directly to the insects will kill them.

Removing female box-elder trees is the most permanent solution to the problem, although this may not be practical or desirable.

A treatment of carbaryl around the perimeter of the tree or house will also provide good control. Remember, always read and follow all label directions before using pesticides.

Eliminate hiding places, such as piles of rocks, boards, and debris near buildings. In the home, hand-collecting, repeated vacuuming, or a household spray containing pyrethrin is recommended.

Laundry detergents offer a safe, effective control when applied directly to the insects, but these may damage vegetation. Spraying nymphs and adults with a soap mixture can be used as an alternative to synthetic insecticides Mix about one-half cup of a laundry detergent into one gallon of water and pour in a squirt bottle. Spray mixture directly on box-elder bugs as often as necessary. Remember, the mixture only kills the bugs that are being sprayed and has no residual effects once dry.

For long term control, you must deny the bugs access to your home. Carefully inspect your home to determine points of entry and repair these areas.

Caulk or seal openings or foundation cracks, windows, and around plumbing, gas, or electrical conduits. Weather strip around doors and windows.

Avoid squishing adults, because they can leave a stain on fabrics and can release a foul odor.

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