Biological control of insect pests is dependent on biotic and abiotic conditions influencing species interactions. We can potentially alter interactions between species by managing in-field habitat using winter cover crops to enhance biocontrol services. This relies on strengthening predator communities and encouraging a key function of predation in agroecosystems, top-down control of pests. Importantly, the functioning of predator communities is likely dependent on composition of species present, and frequency of interactions between predators and prey. However, empirical studies are just beginning to tease apart the roles of managing habitat on altering the structure and feeding behavior of predator communities in agricultural systems. In this study, we investigate the effect of two different cover crops on predator community structure and prey consumption throughout the cotton growing season. We established 0.4 ha replicated cover crop treatments (crimson clover, rye, and no cover crop) in fall of 2017 and 2018, terminated covers in spring, and sampled predators at six major cotton stages each year. We conducted molecular gut-content analysis on whole body DNA extractions of predators using multiplex PCR for eight different prey groups including cotton pests and alternative prey. PERMANOVA was used for comparison of predator communities and trophic interactions among treatments.
Results/Conclusions
Over 3100 predators were collected and screened for prey DNA over two years. Our results suggest interactions between predators and prey are strongly influenced by both cover crop species and seasonality. The availability of early season cover crop habitat significantly improved predator abundance and diversity as well as altered predator community structure among cover crop treatments. Early season predators had increased predation incidence on non-pest collembolan and dipteran prey, with a rye cover crop continuing to support high predator abundance and increased consumption of alternative collembolan prey into the mid-season. We found no difference in predator community structure or prey consumption among treatments in the late cropping season. We attribute a portion of the observed late season similarities in predator communities and predator-prey interactions to plant structural changes driven by the breakdown cover crop residue and growth of uniform crop habitat. Unfortunately, independent of cover cropping treatment, predation of key economic pests was low across all treatments in both years. Combined our results demonstrate that cover crops can build predator communities early in the cropping season by providing food resources to primary and secondary consumers, though consumption of key cotton pests was unaffected.