Investigating multi‐trophic effects of St. Augustinegrass cultivar blends in the Southeastern United States

Abstract Warm‐season turfgrasses, including St. Augustinegrass [ Stenotaphrum secundatum (Walt.) Kuntze], are produced and installed as monocultures of single cultivars. Recent research indicates that blending St. Augustinegrass cultivars can increase turfgrass stand resilience to insect pests, establishment of undesired plant species, and abiotic stressors without reducing plant performance. However, effects on specific key turfgrass insect pests are less documented and the mechanisms driving changes in turfgrass stand resilience are unclear. Moreover, it remains unknown if the effects of cultivar blends on biotic resistance vary across St. Augustinegrass’ range. Here, we pair a regional common garden observational field study with a controlled greenhouse experiment to isolate the effects of cultivar blends on the recruitment of predatory arthropods (top‐down pest regulation) and on southern chinch bug [ Blissus insularis Barber] performance (bottom‐up pest regulation). We find that cultivar diversity has no effect on natural enemy recruitment but natural enemies do vary predictably with changes in geographic location. In contrast to our hypothesis, southern chinch bug reached higher densities in cultivar blends compared to cultivar monocultures, although this effect was driven by specific cultivar blends. Despite higher pest densities in turfgrass blends on average, blends of four St. Augustinegrass cultivars maintained a higher percent green cover than cultivar monocultures, suggesting that cultivar blends can persist longer under elevated pest densities compared to cultivar monocultures. Our findings can guide future research focused on blending warm‐season turfgrass cultivars as an integrated pest management strategy for more resilient and sustainable turfgrass lawns.