With funding from the North Central Soybean Research Program, we are determining if aphid-resistant soybeans can be use with a “refuge-in-a-bag” or RIB. Refuges of pest-susceptible varieties are often included when a pest-resistant variety of a crop is used. By including a refuge, we can produce a population of avirulent aphids so that they can inter-breed and swamp out the genes of virulent aphids that are capable of surviving on the aphid-resistant soybeans. We have completed two field seasons of experiments in which large plots of soybeans comprised of either 100% aphid-susceptible or 100% aphid-resistant isolines are compared to mixtures of susceptible and resistant plants. These mixtures included 25% or 10% susceptible seeds. Overall, we observed no effect on yield when the aphid susceptible seeds were included. We observed more aphids with an increasing % of susceptible seed. In 2018, survival and reproduction of field-collected aphids generally increased as the proportion of susceptible seed mix decreased. This suggests that plots with susceptible seeds may produce a higher proportion of avirulent individuals than all-resistant fields. Thus, for locations experiencing virulent soybean aphid populations, inclusion of an interspersed refuge may be a viable resistance management strategy.
Beginning in 2019, with support from the North Central Soybean Research Program, we will collaborate with colleagues from CortevaTM Agriscience (Jessie Alt and David Onstad) to evaluate elite soybean germplasm with aphid-resistant genes. Our goal is to determine if these lines provide optimal yield without insecticide use. These results will allow us to prepare a response for farmers dealing with insecticide-resistant soybean aphids.
What does it mean for farmers: With the growing threat of insecticide-resistant soybean aphids, farmers are in need of novel approaches for managing this pest. We will advance the development of commercially-available, herbicide-tolerant, aphid-resistant soybean. By developing a resistance management plan for aphid-resistant soybeans, we can ensure sustainable use of these traits for farmers.