How to Manage Pests
UC Pest Management Guidelines
Threecornered Alfalfa Hopper
Scientific Name: Spissistilus festinus
(Reviewed 11/06, updated 11/06)
In this Guideline:
DESCRIPTION OF THE PEST
The threecornered alfalfa hopper is a green, wedge-shaped insect with clear wings. The body, which is about 0.25 inch long, is higher and wider at the head end than and tapers towards the posterior. This insect gets its name from the hardened triangular (three cornered) area over the thoracic area as seen from above. It has piercing-sucking mouthparts. Nymphs are grayish white and soft bodied, with a line of saw-toothed spines on their backs.
Adults feed on numerous plants, including alfalfa. In alfalfa, nymphs are confined to the lower portions of the plant. Threecornered alfalfa hoppers can be found year-round. In the low desert, there are two population peaks for adults: one in late July/early August and a larger second peak in September/early October. In the San Joaquin Valley, threecornered alfalfa hoppers numbers usually peak in late September and October.
Adults and nymphs of the alfalfa hopper feed by inserting their mouthparts into stems and sucking out juices. Injury is also caused when adult female hoppers insert their eggs into stems. Feeding and egg laying can girdle stems, causing the portion of the plant above the girdle to turn red, purple or yellow.
Monitoring and treatment guidelines have not been developed, and there are no known parasites or predators effecting populations of this insect in California. Monitoring guidelines for sweep net sampling are difficult to develop because of the different alfalfa production systems and because the nymphs are concentrated on the plant at or near the soil line and not readily picked up by sweep nets.
This pest is not likely to cause severe damage in the San Joaquin Valley because it appears so late in the season, and treatment is rarely necessary.
In the Imperial Valley, damage is occasionally severe enough to justify control measures.
UC IPM Pest Management Guidelines:
Insects and Mites