Behavioral and Reproductive Response of Caged Empoasca fabae (Homoptera: Cicadellidae) to Vegetation Density of a Host Legume and a Non-Host Grass

Behavior and reproduction of potato leafhopper, Empoasca fabae (Harris) (Homoptera: Cicadellidae), were examined in the laboratory in response to varying densities of leafhoppers, a host legume (alfalfa, Medicago sativa L.), and a non-host grass (large crabgrass, Digitaria sanguinalis L.). A series of caged treatments with increasing crabgrass density per cage resulted in a corresponding series of decreasing oviposition and decreasing number of primary oocytes per female. Oviposition and number of primary oocytes were reduced by approximately 30% at the highest grass density. However, adult activity as measured by percentage of leafhoppers observed on alfalfa, in flights per minute, and on sides of cage, remained unchanged with increasing crabgrass density. When responses given at crabgrass densities were compared with pure alfalfa of equivalent vegetation density (plant surface area), activity in the presence of crabgrass was two to four times larger than alfalfa alone of equivalent vegetation density, with the highest increases occurring after 1700 h and with greatest crabgrass density. Results suggest that greater relative activity induced by crabgrass volatiles may have been responsible for reduced oviposition and reduced tenure time on alfalfa nearest to crabgrass in two-choice tests.