The three-cornered alfalfa hopper is a green, wedge-shaped, sap-feeding insect (Figure 1) that causes distinct physical injury. Adults and nymphs girdle stems, lateral branches, or petioles as they feed on legumes and a variety of other plants. Symptoms include yellowing and wilting above the callus tissue that develops at the injury site. Damaged plants may also break or lodge.
Low numbers of three-cornered alfalfa hoppers are probably present in many Kentucky fields in late summer, but they can reach damaging levels during late summer in alfalfa and double-cropped or late-planted soybeans.
Generally, an insecticide application is not needed at this point in the season.
By Lee Townsend, Extension Entomologist