Predator demographics and dispersal in alfalfa trap-cropped strawberry

Authors: Hagler, James; NIETO, DIEGO - Driscolls; Machtley, Scott; SWEZEY, SEAN - University Of California

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2019
Publication Date: 2/12/2020
Citation: Hagler, J.R., Nieto, D.J., Machtley, S.A., Swezey, S.L. 2020. Predator demographics and dispersal in alfalfa trap-cropped strawberry. Entomologia Experimentalis et Applicata. 168(1):53-58. https://doi.org/10.1111/eea.12864.
DOI: https://doi.org/10.1111/eea.12864

Interpretive Summary: The lygus bug is a major strawberry pest. However, alfalfa is a more preferred by lygus than strawberries. As such, intercropping alfalfa trap crops in strawberry production fields can serve as a sink for both lygus and its predaceous natural enemies. ARS scientists at Maricopa, AZ teamed up with University of California scientists to study the population dynamics and dispersal characteristics of the lygus predator complex in strawberry fields embedded with alfalfa trap crops spaced 50 rows (62 m) apart. Predator abundance was determined by simply counting six focal taxa collected from strawberry and alfalfa. The data revealed that the minute pirate bug was the numerically dominant predator taxon, comprising 84% of the focal predator population. In general, the population densities obtained for the various taxa throughout this agroecosystem were uniform. Predator movement from a centralized alfalfa trap crop row was determined using a protein mark-capture procedure developed by the ARS scientists. Most protein-marked predator specimens were collected 0 to 2-m from the centrally-marked alfalfa row, indicating that the prey reservoir found in trap crops produces a predator sink. This study suggests that alfalfa is a useful cultural (trap cropping) and biological (refuge for natural enemies) control tactic for managing lygus in strawberries. The results from this study could lead to less pesticide usage and greater production of organically-grown strawberries.

Technical Abstract: Alfalfa (Medicago sativa L.) is a highly preferred Lygus spp. host plant. As such, intercropping alfalfa trap crops in strawberry production can serve as a sink for both Lygus (primarily L. hesperus Knight) and Lygus 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. 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 centralized 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 biological (refuge for natural enemies) control tactic for managing Lygus spp. in strawberries.