While arthropod generalist predators (AGPs) have a potential to provide biocontrol service in various agricultural systems, their diet composition in the field over time has rarely been quantified. To fill the knowledge gap, this study first surveyed arthropod communities over crop stages in organic and conventional rice farms (n = 7 for each farm type), and then applied stable isotope analysis (δ13C and δ15N) to quantify AGPs’ diet composition over time. The specific aims of this study were to 1) examine the trophic niches (resource partitioning) of AGPs, 2) quantify AGPs’ diet composition from potential prey sources (rice herbivores, tourist herbivores, and detritivores), and 3) investigate the effects of farm type (organic and conventional) and crop stage (tillering, flowering and ripening stage) on rice herbivore (pest) consumption by AGPs.
Results/Conclusions
The results showed that AGPs in both organic and conventional farms shifted trophic niches over crop stages. In addition, AGPs in both farms consumed a higher percentage of rice herbivores in their diet at late than at early crop stages (e.g., 90-93% at ripening vs. 34-55% at tillering stage), suggesting an increasing potential for top-down control of pests by AGPs over time regardless of farm type. Surprisingly, AGPs consumed a slightly higher percentage of rice herbivores in conventional than in organic farms at tillering and flowering stages, highlighting their underappreciated role as biocontrol agents in conventional farms. In conclusion, this study demonstrates that AGPs have a high biocontrol potential (per capita pest consumption) in both organic and conventional rice farms. Therefore, we encourage modern agriculture to develop techniques to facilitate AGPs and their associated ecosystem services.