Dispersal responses of cereal aphids to wheat cultivar and planting configuration

Abstract

Cultivar mixtures are advocated as an agroecological strategy for suppressing cereal aphid vectors and reducing barley yellow dwarf virus (BYDV) transmission, yet their effects on within‐crop dispersal remain largely untested, particularly across vector species and virus infection states. We quantified the walking dispersal of Sitobion avenae and both BYDV‐PAV‐viruliferous and non‐viruliferous Rhopalosiphum padi through wheat stands comprising a 1970s cultivar (Maris Huntsman) and a Bdv2 ‐carrying BYDV‐resistant cultivar (RGT Wolverine), arranged as monocultures, alternating‐row intercropping and randomised mixtures. Dispersal responses were species‐specific, cultivar‐dependent and fundamentally altered by virus infection status. S. avenae colonised non‐source plants at comparable rates across all treatments. Non‐viruliferous R. padi showed strong cultivar‐mediated responses as colonisation on Maris Huntsman monocultures was 67%–69% lower than on Wolverine, with a steep distance‐decay gradient (64% decline per unit distance) indicating rapid arrestment on the preferred host. Within randomised mixtures, R. padi preferentially colonised Maris Huntsman, but the presence of Wolverine plants disrupted arrestment and produced spatially uniform dispersal resembling that on Wolverine monocultures. Source plant cultivar, rather than surrounding planting configuration, was the primary driver of R. padi dispersal in mixtures. Critically, BYDV‐PAV infection eliminated all cultivar‐specific responses in R. padi as viruliferous aphids dispersed uniformly regardless of cultivar arrangement, consistent with virus‐induced behavioural manipulation overriding host‐acceptance cues. These findings demonstrate that this cultivar combination does not provide consistent associational resistance and can create associational susceptibility for non‐viruliferous R. padi , indicating that species‐specific vector ecology and virus‐mediated behavioural modification must be integrated into the design of cultivar diversification strategies for BYDV management in cereals.