These two insects are similar in appearance and habit and appear at about the same time in Iowa. Both are common "accidental invaders" that crawl into houses and buildings from outdoors by mistake. They are active from mid-July to early August.
The Imported Longhorned Weevil and the Strawberry Root Weevil are small, hard-shelled beetles with a narrow head and thorax and large, round abdomen. An easy way to describe them is "light bulb shaped." Both have rather long, elbowed antennae. Both are approximately 1/4 inch long, though to be precise, Imported Longhorned Weevil is 4 mm long and Strawberry Root Weevil is 5 mm long, making Imported Longhorned Weevil the lesser of the two weevils.
Imported Longhorned Weevil appears slightly earlier in the year though they overlap and both may be present at the same time in the same area. Imported Longhorned Weevil is mottled tannish gray and dull. Strawberry Root Weevil is shiny black with fine, indented lines visible along the top of the wing covers.
The weevils are harmless; they do not damage the house or furnishings; they can not bite or sting people or pets. They are an annoyance because of their presence indoors. Weevil activity is a temporary event that usually lasts only 2 to 3 weeks.
The adult weevils develop from larvae that live in the soil and feed on the small roots of many different plants. Imported Longhorned Weevil larvae feed mostly on aster, clover and turfgrass while Strawberry Root Weevil larvae feed on the roots of strawberry plants, evergreen trees and shrubs. The weevil larvae do not cause apparent damage to the plants and control of the larvae in the soil is not practical or necessary.
Some of the accidental invasion can be prevented by exclusion techniques that close their routes of entry. Look for and seal cracks and gaps through which the adults can crawl into the building. Spraying malathion, Dursban or diazinon or permethrin insecticide on and along the foundation and in outdoor areas of weevil abundance may be of some benefit. Unfortunately, spraying just on and along the foundation is usually not sufficient. It may be necessary to spray a considerable portion of the lawn -- out from the foundation 6 to 10 feet, or the entire lawn.
Adults already inside need only be vacuumed or swept up and discarded. Household aerosol insecticides are not very effective for controlling these weevils.
This article originally appeared in the July 30, 1999 issue, p. 107.