Insect abundance in field beans altered by intercropping

Densities of four herbivorous insect species were compared on field beans (Phaseolus vulgaris) grown in monoculture and those grown in relay intercropping with winter wheat. In three years of study in New York State, population densities of Empoasca fabae (Harris) and Aphis fabae Scopoli were significantly less in plots intercropped with winter wheat than in those grown in monoculture. In contrast, intercropping was associated with greater densities of Lygus lineolaris (Palisot de Beauvois) and Systena frontalis (F.). An increased density of L. lineolaris may be an economic risk factor in beans intercropped with wheat because only this species of the four studied feeds exclusively on the flowers and developing seed pods.