Harmless insects become household nuisances in fall

10/16/2002

Ah, autumn. A time for cool nights good for sleeping, cricket serenades, changing colors, harvest festivals, and box elder bugs.

Huh? Box elder bugs?

If you don't know what these half-inch black insects with red trim are all about, you may want to count your blessings. Firsthand knowledge of box elder bugs usually means that a homeowner has had to deal with them. Not just one or two of these slow-moving, lethargic characters, either, but hordes, legions of them.

This time of year, box elder bugs are leaving their outdoor homes, where they laze through the summer feeding on leaves, flowers, and seed pods of the - what else? - box elder tree. Cooler weather prompts them to seek winter homes, and that could mean your home.

Don't panic, though. Box elder bugs are harmless. They will not bite. They will not eat the furniture, the drapes, your wardrobe, the carpet, or the woodwork. They will not bother house plants, will not reproduce in the house, are not poisonous. They are not dirty and are not known to carry disease.

But they can be a huge nuisance, especially if they swarm inside by the hundreds or thousands.

“The only enemy of the box elder bug is a fungus disease, so they do well during long, dry summers,” said Phil Pellitteri, an entomologist at the University of Wisconsin. “They are quite a nuisance.”

Standard chapter and verse once held that to get rid of box elder bugs, you simply cut down the box elder tree in your yard - if you have one. But that won't work, says Dr. Dave Shetlar, the “Bug Doc” at Ohio State University.

First, box elder bugs usually only inhabit the female, or pod-bearing, tree. So a male box elder tree poses little threat as a bug condo. But more important, the bugs also live on ash and maple trees - relatives of box elder trees.

Box elder bugs are good fliers, too. They have been known to beat their way up to the upper reaches of 18-story office buildings. They can migrate a quarter mile or more - which means their summer homes may be in the neighbor's trees, the park across the street, or that scenic river-bottom nearby, said Dr. Shetlar. He is an associate professor of urban landscape entomology for OSU's Cooperative Extension Service, and he trades bug-war stories with colleagues on the Internet.

He recalled a case in Columbus in which a home under renovation was found to be infested by thousands of box elder bugs, most of them immature nymphs, but with some adults. The older nymphs were feeding on some of the younger ones, so the bugs even practice cannibalism.

Other than their mere presence - which itself can be intolerable to many householders - box elder bugs produce a certain problem: bug poop. The bugs' feces can leave a dark-brown resinous stain on the siding of homes. Ditto inside.

Overwintering adults usually den up under tree bark, in dead trees, and around the home - in attics, under siding, or, as Dr. Shetlar puts it, “other protected voids.”

He said that the bugs will begin moving to shelter anywhere from the end of September through mid-October, and even into November and December. They will be up and wandering on sunny days after finding their wintering sites, however. Even during the winter they like to emerge and sun themselves, which means the south and west sides of a home are leading targets for infestation.

To eliminate box elder bugs indoors, use a shop vacuum or a carpet vacuum with a hose. Simply suck them up and trash them. Do not use a sweeper with a beater-brush, however, because crushed bugs emit a foul odor and staining fluids that will permeate the bag or canister and leave an olfactory reminder of their passage.

Soapy water is as effective as commercial insecticides for use on swarms on house siding. Load up a garden sprayer with dish-soap water and hose them down. The soap penetrates the bugs' micropores or enters their respiratory systems and kills them. But be careful to thoroughly rinse off any soapy residue, lest it stain or streak the paint or siding.

On the other hand, the OSU bug-man said, “There are many over-the-counter insecticide products that kill creeping and crawling insects. They will do a pretty good job of knocking them down.” Still, he added, homeowners need to understand that more bugs may return after the insecticide residue is gone.

Some sources also advise against using the sprays indoors because they may leave a nasty, oily film.

It still is difficult to forecast the degree of box elder bug infestation this fall. Dr. Shetlar said that normally the bugs do well during mild winters and dry summers.

But this year it may be too dry because of widespread drought, partly because box elder trees themselves are in such poor, drought-stressed condition.

The entomologist theorized that if major box elder bug problems were afoot, he would have been summoned by now. The next month will tell the tale.

For other details on the box elder bug, or other insect pests, visit the OSU Extension Web site at bugs.osu.edu.