Three Cornered Alfalfa Hopper Abundant In Some Alfalfa Fields
DR. LEE TOWNSEND
LEXINGTON, KY.
Three cornered alfalfa hoppers (Figure 1) have been abundant in some south central Kentucky alfalfa fields. They prefer legumes but will feed on other plants, too. These small green triangular sap feeders puncture stems and petioles. Older nymphs can girdle plants a few inches above the soil surface as they feed (Figure 2). A thickened callus, which usually develops at the feeding site, is a good indicator that this insect has been active. The girdling reduces water and nutrient movement and can cause stems to become brittle and break.
Figure 1. Three cornered alfalfa hopper adult (left; Photo: UC Davis
Integrated Viticulture) and spiny nymph (right; Photo: C. Lewallen)
Figure 2. Girdling damage to soybean stem.
Photo: David Adams, Univ. Georgia
Treatment guideline for soybean: This insect rarely causes economic damage because soybean plants can compensate for damage. Control is recommended If 50 percent of the plants are girdled OR if fewer than 4-6 ungirdled plants remain per row- foot in conventional rows (30-40"rows) and three cornered alfalfa hopper nymphs are still present. It is rare that an insecticide application would be justified in alfalfa.∆
DR. LEE TOWNSEND: Extension Entomologist, University of Kentucky