Strip intercropping peanut with maize for peanut aphid biological control and yield enhancement

Abstract

Increasing crop biodiversity, such as by strip intercropping, is recognized as an effective biological control measure. However, few studies have focused on the process of strip intercropping to increase natural enemy abundance, reduce pests and subsequently reduce crop damage. In the context of organic peanut (Arachis hypogaea L.) production, maize (Zea mays L.) intercropping with peanut was proposed to provide habitat for predators that suppress peanut aphid to enhance pest control in peanut. To test this hypothesis, we compared predator communities across monoculture and intercropping systems, investigated shifts of predators in response to strip intercropping systems, and evaluated their prey consumption via PCR-based gut content analysis under realistic field conditions. Last, we assessed the biological control of peanut/maize strip intercropping in peanut production. Our results demonstrated that intercropping significantly increased ladybeetle density and significantly reduced the number of peanut aphids. In the peanut/maize strip intercropping plots, peanut aphid density was significantly related to ladybeetle density. Moreover, in the intercropping plots, more than 90% of the predators prefer to inhabit on maize, and less than 10% of the predators inhabit on peanut. Further molecular gut-content analysis revealed that the ladybeetles inhabited on maize exhibited significantly higher predation on peanut aphids in the intercropping system. Visualization of the food chains indicated that peanut aphid population in intercropping system was effectively suppressed by predator abundances in the early season. In the yield experiments, compared with the monoculture systems, the strip intercropping system presented significantly higher peanut production. Linear regression analysis revealed that peanut aphid significantly reduced the pod maturity index and peanut yield. Our results indicated that peanut/maize strip intercropping could enhance the predator number, suppress pest and reduce peanut loss. This research incorporating field studies and molecular tools demonstrates the successful conservation and biological control of peanut aphids.