It's Weevil Time Again

Two of our most consistent perennial pests are the strawberry root weevil and the imported longhorned weevil (two insects with names much longer in proportion than their actual size). At this time, the imported longhorned weevil (ILHW) is active and common; the strawberry root weevil (SRW) will come slightly later in July. Both weevils are active from mid-July to mid-August, and both are harmless but annoying pests.

ILHW and SRW are similar in appearance, biology, habits and control. Distinguishing between the two is not critical although it is easy. The adult weevils are approximately 1/4 inch long and are shaped like a pear or a light bulb. SRW is shiny black while ILHW is mottled tannish-gray (these are the colors of the living insects; preserved specimens both appear black). The weevils have six legs and a pair of antennae that can give rise to a vague similarity to a tick. Legs and antennae seem rather long for the size of the insects, and the antennae have an 'elbow' or bend in the middle.

A color picture of the imported longhorned weevil was included in a recent ISU Integrated Crop Management newsletter. See page 124, July 1, 1994.

These weevils cause little if any damage to landscape plants. Their pest status is as "accidental invaders" that crawl into houses from outdoors by mistake. The weevils are harmless; they do not damage the house or furnishings, and can not bite or sting people or pets. They are merely a nuisance by their presence.

SRW and ILHW larvae live in the soil and feed on the small roots of many different plants, including aster, clover and turfgrass. They do not cause apparent damage to the plants and control of the larvae in the soil is not practical nor necessary.

Invasion by these and other accidental invaders can be prevented (or at least reduced) by exclusion techniques that close their routes of entry; that is, look for and seal cracks through which the adults can crawl into the house. These include small cracks and gaps in the foundation or siding, and around windows and doors. Spraying malathion, Dursban or diazinon insecticide on and along the foundation outside according to label directions may reduce the number outside and thereby, hopefully, reduce the numbers that wander in. Weevils already inside the house need only be vacuumed or swept up and discarded. Household aerosol insecticides are not very effective for controlling these weevils and their use for this pest is discouraged.

This article originally appeared in the July 15, 1994 issue, p. 109.


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