Issue No. 12, Article 4/June 10, 2005
Identify Insects in Soybeans Accurately
As people scout for soybean aphids and twospotted spider mites in soybeans, they undoubtedly will encounter other insects. One of these insects--potato leafhopper--occasionally is mistakenly identified as an aphid or a mite. The activity of potato leafhoppers in alfalfa has increased significantly over the past weeks, and potato leafhoppers are being found along the edges of soybean fields, too.
Close-up of a potato leafhopper nymph (left) and adult (right) (photo courtesy of Marlin Rice, Iowa State University).
After hatching, potato leafhopper nymphs are very small and pale in color, and they can easily be misidentified without the use of a good hand lens. When magnified, potato leafhopper nymphs clearly are more elongate than soybean aphids and spider mites. In addition, soybean aphids are mostly sedentary, whereas potato leafhopper nymphs are rather active, characteristically moving sideways and backward rapidly when disturbed.
Soybean leaves with characteristic symptoms from potato leafhopper injury (University of Illinois).
Soybean plants with severe injury symptoms (stunting, yellowing) from potato leafhopper injury (University of Illinois).
Like soybean aphids and twospotted spider mites, potato leafhoppers have piercing-sucking mouthparts, and they remove liquids from the plant tissues. Symptoms of feeding by potato leafhoppers on soybeans include distorted leaf veins, curled leaves, and yellowing. The yellowing usually is bright yellow, and it appears along leaf margins first.
Potato leafhoppers have not been known to cause large yield losses in soybeans, but injury to soybeans early in the season could be an exception. Although our focus right now should be primarily on soybean aphids and twospotted spider mites, keep your eyes open for potato leafhoppers, too. And don't confuse one with the other; accurate identification and diagnosis of the problem are essential for effective management.--Kevin Steffey