Threecornered alfalfa hoppers (Spissistilus festinus) have a wide host range that includes alfalfa, clovers, cowpeas, various grasses, small grains, soybeans, sunflowers, melons, tomatoes, and weeds.
The threecornered alfalfa hopper is a triangular-shaped insect with piercing, sucking mouthparts. The green, wedge-shaped bugs are approximately 5 to 6½ millimeters in length. It is a treehopper that takes its name from the hardened triangular (three cornered) area over the thorax. The male is slightly smaller than the female and has a red or orange stripe on its “shoulders.”
Nymphs are grayish white and soft bodied, heavily spined and shaped somewhat similar to the adults. The mature nymphs are slightly smaller than the adult and lack the protective shield-shaped wings.
Threecornered alfalfa hoppers range as far north as Canada, but they are an occasional problem only in the southern U.S. and in northern Mexico. In Florida, they are an occasional problem in vegetables primarily in the northern part of the state.
Both the adult and nymphs of threecornered alfalfa hopper damage plants by feeding on stems and leaves. The insect feeds by inserting its beak into plant tissue and sucking out plant juices. Damage to peanuts and soybeans is characterized by small, brown, chlorotic lesions on stems.
Lesions often will callus over to cause small bumps or raised areas on the stems. In soybeans, callused areas will often break and allow the soybean plant to lodge as soybeans begin to mature and gain weight in late season. Stem feeding in other crops may girdle the stem causing limbs to die-back, reducing yields and increasing the potential for rot.
Survival And Spread
Threecornered alfalfa hoppers overwinter as adults around field margins or as eggs in protected plant tissue. Adults may remain active in the winter during warm periods.
Adults and nymphs emerge in the spring as the weather warms and feed on winter grasses and other weeds. They feed, develop, mate, and migrate into hosts. Females deposit 30 to 40 eggs in host plant stems. Nymphs hatch in two to six weeks. On the average, 50 days elapse between egg deposition and adult emergence. The adults are strong flyers and readily migrate to new fields. There are several generations a year in Florida.
Damaging infestations by the threecornered alfalfa hopper often can be avoided by destroying weedy borders around fields.
In peanuts and other crops, treatment should be initiated when injury and symptoms are present and numerous hoppers are found in the field.