Impact of alfalfa perimeter strips on Lygus lineolaris and beneficial arthropods in June-bearing strawberry fields

Lygus lineolaris Palisot de Beauvois (Hemiptera: Miridae) is the primary insect pest of strawberry in eastern and central North America. Strategies to minimize L. lineolaris colonization of strawberry at bloom and peak fruit susceptibility without impacting pollinator health must be developed. To this end, we examined the potential of alfalfa perimeter strips to reduce L. lineolaris populations in June-bearing strawberry fields. Over a three-year experiment, L. lineolaris densities and beneficial arthropod abundance were monitored in commercial strawberry fields with and without alfalfa perimeter strips. Alfalfa perimeter strips were found to concentrate L. lineolaris populations and led to a 36% reduction in L. lineolaris densities in adjacent strawberry plots compared to controls. When a protein immunomark-capture experiment was conducted to examine the extent of movement between the alfalfa strips and adjacent strawberry plots, it was determined that approximately three times as many L. lineolaris migrated from strawberry to alfalfa than vice versa. Moreover, adult females were overrepresented among immigrants to alfalfa, suggesting that alfalfa may be a preferred oviposition site for L. lineolaris. While the presence of alfalfa perimeter strips increased beneficial arthropod abundance and diversity in experimental plots overall, these increases were limited to the alfalfa itself, with little spillover into adjacent strawberry plots. These data suggest that preferential utilization of alfalfa by L. lineolaris underlies the observed population reductions and that alfalfa acts as a trap crop in June-bearing strawberries.