Biological control of cereal aphids in wheat: Implications of alternative foods and intraguild predation

Abstract

The overall objective of this proposal is to understand how realistic strategies for incorporating alternative foods into wheat fields affect the intraguild (IG) interactions of omnivorous and carnivorous predators and their efficacy as biological control agents. Cereal aphids are a primary pest of wheat throughout much of the world. Naturally occurring predator communities consume large quantities of cereal aphids in wheat, and are partitioned into aphid specialists and omnivores. Within wheat fields, the relative abilities of omnivorous and carnivorous predators to reduce cereal aphids depend heavily on the availability, distribution and type of alternative foods (alternative prey, sugar, and pollen), and on the intensity and direction of IG predation events within this community. A series of eight synergistic experiments, carefully crafted to accomplish objectives while accounting for regional production practices, will be conducted to explore how cover crops (US, where large fields preclude effective use of field margins) and field margins (IS, where cover crops are not feasible) as sources of alternative foods affect the IG interactions of predators and their efficacy as biological control agents. These objectives are: 1. Determine the mechanisms whereby the availability of alternative prey and plant-provided resources affect pest suppression by omnivorous and carnivorous generalist predators; 2. Characterize the intensity of IGP within generalist predator communities of wheat systems and assess the impact of these interactions on cereal aphid predation; and 3. Evaluate how spatial patterns in the availability of non-prey resources and IGP affect predation on cereal aphids by generalist predator communities. To accomplish these goals, novel tools, including molecular and biochemical gut content analysis and geospatial analysis, will be coupled with traditional techniques used to monitor and manipulate insect populations and predator efficacy. Our approach will manipulate key alternative foods and IG prey to determine how these individual interactions contribute to the ability of predators to suppress cereal aphids within systems where cover crop and field margin management strategies are evaluated in production scale plots. Using these strategies, the proposed project will not only provide cost-effective and realistic solutions for pest management issues faced by IS and US producers, but also will provide a better understanding of how spatial dispersion, IG predation, and the availability of alternative foods contribute to biological control by omnivores and carnivores within agroecosystems. By reducing the reliance of wheat producers on insecticides, this proposal will address the BARD priorities of increasing the efficiency of agricultural production and protecting plants against biotic sources of stress in an environmentally friendly and sustainable manner.