Authors: Dr. Randy Hudson, Dr. David Adams, University of Georgia, Department of Entomology.
The threecornered alfalfa hopper is a triangular-shaped insect with piercing-sucking mouthparts. The green, wedge-shaped insects are approximately 5-6 mm in length. Nymphs are heavily spined and shaped somewhat similar to the adults. The mature nymph will be just slightly less in length than the adult and lack the protective shield-shaped wings.
Peanut, vegetables, soybean, alfalfa, and other legume pastures and forages.
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 will often 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 on peanuts will often cause limb die back thus reducing yields and increasing the potential for rots.
Threecornered alfalfa hoppers overwinter as adults around field margins or as eggs in protected plant tissue. Adults may remain active during the winter during warm periods. Adults will emerge in the spring and feed on winter grasses and other weeds. Adults and emerging nymphs from overwintered eggs will feed, develop, mate, and migrate into peanuts, soybeans or other preferred hosts in May and June. Females then lay eggs that hatch in 14-40 days. The immatures develop into adults in 3-10 weeks. It is believed there are 2-3 generations per year in Georgia.
Treatment for threecornered alfalfa hoppers in soybeans should be initiated when 10% of the young seedlings are injured and threecornered alfalfa hoppers are present in the field. In peanuts, treatment should be initiated when injury and symptoms are present and numerous hoppers are found in the field. Early season damage to peanuts and soybeans is responsible for greater yield reductions.