Three-Cornered Alfalfa Hopper In Alfalfa

DR. RIC BESSIN

 LEXIGTON, KENTUCKY

Last week, UK Extension Entomologists had reports of high numbers of three-cornered alfalfa hopper (TCAH) on alfalfa in Meade County. This insect can be an occasional pest of both alfalfa and soybeans, but rarely gets to economically damaging levels. While TCAH feeds like potato leafhopper, it does not inject any toxins while feeding. High numbers in the field can result in reddening or yellowing of plants.

Description

TCAH is a triangular, wedge-shaped ¼ inch long bug that feeds with piercing-sucking mouthparts. Both male and female adults are green in color, but the male has a thin reddish orange stripe along its ‘shoulders.’ The nymphs are straw colored, also wedge shaped, but with many branched spines. Nymphs can be found feeding near the base of plants and are less likely to be collected by sweep net.

Damage

TCAH damages stems during feeding and egg laying. Both the nymphs and adults weaken the stem by repeatedly inserting their needle-like mouthparts to remove sap. This can result in girdling, yellowing of leaves and, in some instances, stem breakage.

Management

Economic yield loss is uncommon but is more likely to occur when alfalfa is less than 10 inches tall. Economic thresholds have not been established and recommendations for treatments vary from an average of 1 to 2 adults per sweep to more than 4 per sweep in order to justify spraying. Another strategy to limit losses is through early harvest.

DR. Ric Bessin: Entomology Extension Specialist, University of Kentucky