Above-ground impact of biofumigation: Soil biofumigation alters aphid host preference and reproduction through host-mediated mechanisms

Cultural control, a component of integrated pest management, can provide crops with a competitive edge against pests and reduce the frequent need for insecticide applications. Soil biofumigation using Brassicaceae cover crops and seed meal is gaining attention as a sustainable alternative to synthetic fumigants. While its effects on soil pests are well-documented, less is known about how biofumigation influences above-ground herbivores via host-mediated mechanisms. Moreover, despite their benefits, some studies have shown that soil biofumigation can negatively affect nontarget organisms, including those that contribute to soil health and decomposition. Some of these underground effects may influence plant physiology, subsequently affecting above-ground interactions between plants and insects. Using springtails, aphids, and wheat as our model organisms, we examined the impact of soil biofumigation, with brown mustard and canola plant tissue and brown mustard seed meal (BMSM) in the presence of springtails (Folsomia candida, Collembola: Isotomidae) on bird cherry-oat aphid (Rhopalosiphum padi L., Hemiptera, Aphididae) preference and reproduction. In our preference bioassays, aphids initially avoided the plants grown in biofumigated soil and visited control plants more frequently; this preference disappeared after 24 hours. Additionally, aphid reproductive performance was reduced on the wheat plant grown in the biofumigated soil as compared to the untreated control. Ongoing analysis includes root morphology (via WinRHIZO), shoot-to-root biomass allocation, and phytohormone profiling to identify physiological mechanisms underlying reduced aphid preference and performance. The findings from this project will help to inform the development of management practices that improve soil health while mitigating pest pressure in cropping systems.