Household Accidental Invaders

It is once again the time when insects inadvertently enter homes and buildings from the surrounding landscape. Common accidental invaders include boxelder bugs, multicolored Asian lady beetles, pine seed bugs, spiders, hackberry psyllids and elm leaf beetles.

Accidental invaders are generally harmless to people and property. They do not feed on people, pets, houseplants, stored products, or furnishings. They cannot sting and they do not carry disease. Accidental invaders cannot reproduce indoors. They are nuisances just by their presence, especially when they occur in large numbers.

The preferred management for accidental invaders is prevention; stop them before they enter the house. Typical exclusion or pest-proofing activities include use of tight-fitting doors and windows; sealing openings and cracks around pipes and wires, windows, doors, chimneys, and foundations; repairing or replacing window, door and vent screens; and keeping siding, eaves, and soffits in good repair.

Residual insecticide barriers can supplement pest-proofing and may be applied by a professional pest control firm or by the homeowner. Insecticide protection is short lived and may have to be repeated. Homeowners may spray permethrin, chlorpyrifos (Dursban), or diazinon around the home's exterior. Additional insecticides are available to commercial pest control operators.

Treat the southern and western sides of residences where insects are most common. Apply the insecticide according to label directions to siding, foundation, windowsills, and door thresholds, and to the lawn or landscape for a distance of several feet from the building. Insecticides must be applied before insects begin to enter buildings to be effective (August to September for pine seed bugs, hackberry psyllids, and elm leaf beetles; early to mid-October for boxelder bugs and multicolored Asian beetles).

Direct application of insecticide to clusters of insects outside on the siding and foundation may reduce the outdoor population and limit the number that will get into the house. Begin spraying as the insects congregate in late summer and repeat as necessary. The insecticides mentioned or a soapy water spray (5 tablespoons of liquid detergent per gallon of water) can be used outside. The soap solution kills only the bugs sprayed. It has no residual effect and does not prevent others from coming to the site.

Remove insects that have already entered the home with a dustpan or vacuum. A household aerosol spray containing pyrethrins, resmethrin, or other materials labeled for indoor use provides some relief but is not a long-term solution to the problem. Aerosol sprays do not control concealed pests. Use insecticides indoors sparingly.

Insects that emerge from overwintering sites inside a home during winter and spring all entered the building the previous fall. They did not reproduce indoors. Unfortunately, there is no practical method to control insects before they emerge.

This article originally appeared in the August 27, 1999 issue, p. 117.


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