Predator demographics and dispersal in alfalfa trap-cropped strawberry

Alfalfa, Medicago sativa L. (Fabaceae), is a highly preferred host plant of Lygus spp. (Hemiptera: Miridae). As such, intercropping alfalfa trap-crops in strawberry production can serve as a sink for both Lygus (primarily Lygus hesperus Knight) and its natural enemies. Here we investigated the population dynamics and dispersal characteristics of the generalist predator complex in strawberry fields with alfalfa trap-crops spaced 50 rows (62 m) apart. Predator abundance was determined by counting six focal taxa collected from strawberry and alfalfa. The data revealed that Orius spp. (Hemiptera: Anthocoridae) were the numerically dominant predator taxa, comprising 84% of the focal predator population. In general, the population densities obtained for the various taxa throughout this agroecosystem were unexpectedly uniform. Predator movement from a central alfalfa trap-crop row was determined using a protein mark–capture procedure. Most protein-marked predator specimens were collected less than 2 m from the centrally marked alfalfa row, indicating that the trap-crop often produces a predator sink. Results suggest that alfalfa is a useful cultural (trap-cropping) and a biological (refuge for natural enemies) control tactic for managing Lygus spp. in strawberries.