The effect of an aphid-resistant soybean genotype on intraguild predation of a soybean aphid parasitoid

Soybeans containing the rag1 gene, which may reduce soybean aphid size, productivity and/or density, will soon be commercialized. This may affect Binodoxys communis, a parasitoid currently being released against the soybean aphid as part of a classical biological control program. First, the rag1 containing soybeans may affect B. communis establishment directly via reduced aphid availability. Establishment may also be affected indirectly by altering the strength of intraguild predation of B. communis, which is known to vary with aphid density. We determined how soybeans containing the rag1 gene affected intraguild predation and establishment of B. communis by planting plots of soybean that contained either the rag1 gene or were a rag1-free near isoline. We released B. communis into each plot and followed its establishment and predation throughout the summer. To be able to compare intraguild predation with establishment, we also independently measured intraguild predation of B. communis by outplanting known densities of B. communis mummies. We discuss the results of these studies as well as the implications for soybean aphid biological control.