Matt Montgomery, Extension educator in crop systems in Springfield, has found a pest of soybeans that we don't encounter very often in Illinois. He found imported longhorned weevils in a field of soybeans in Sangamon County. This insect rarely causes economic damage to soybeans, but it can cause considerable injury in early vegetative stage soybeans when a large population is present.|
The imported longhorned weevil adult is small (about 4 millimeters long) with a broad snout, wide pronotum ("neck"), and swollen elytra (wing covers) covered with rows of short, stiff hairs. It is mottled gray with 20 shallow grooves extending the length of the elytra. The antennae are elbowed near the middle.
Adult imported longhorned weevil. (Photo courtesy of Matt Montgomery, Extension Educator in Crop Systems, Springfield.)
These weevils eat leaf tissue and smaller veins, which results in a ragged leaf bordered with a scalloped edge. Injury usually is most prevalent along field margins. As you scout for grasshoppers and twospotted spider mites, look for the imported longhorned weevil, too. An insecticide would be warranted only if damage along the field margin is severe.--Kevin Steffey