POTATO LEAFHOPPER (HOMOPTERA - CICADELLIDAE) POPULATIONS ON SOYBEAN RELAY INTERCROPPED INTO WINTER-WHEAT

Relay intercropping soybean, Glycine max (L.) Merr., into winter wheat, Triticum aestivum L., is an alternative to double cropping soybean following winter wheat in the more northern latitudes of the United States. Because increased crop diversity affects arthropod populations, a study was conducted to determine if a wheat-soybean cropping system might have an effect on the potato leafhopper, Empoasca fabae (Harris), a pest of soybean. Two soybean isolines differing in their pubescence (pubescent and glabrous) were grown in monoculture and a relay intercropped system during 1987 and 1989. Potato leafhoppers were sampled with a D-Vac sampling apparatus throughout the summer. In these years, leafhopper populations were extremely high, and potato leafhopper damage was severe on glabrous soybean grown in monoculture; whereas numbers of leafhoppers were moderate and damage was absent on pubescent soybean in monoculture. Potato leafhoppers were virtually nonexistent before wheat harvest on the pubescent and glabrous soybean that were relay intercropped; no damage to either isoline was evident. Following wheat harvest and removal of wheat straw, potato leafhoppers entered those plots, causing damage to the glabrous soybean. During the time period when wheat was present, both soybean isolines were protected from feeding by potato leafhopper. The ramifications for potato leafhopper control on soybean and other crops is discussed when a companion grass crop is grown. © 1990 Entomological Society of America.