The bird cherry-oat aphid, Rhopalosiphum padi L. (Hemiptera: Aphididae), host preference and performance in well-watered and water-stressed plant species: Implications in barley yellow dwarf virus epidemiology

The cereal aphid-borne barley yellow dwarf virus (BYDV) is the most important viral disease in small grains, infecting a broad range of cultivated and non-cultivated grasses. Grassy weeds can serve as a reservoir for the aphid vector and BYDV until winter wheat becomes available. Although the cereal aphid preference for wheat is likely the reason they leave their natural reservoirs, there are not many studies quantifying aphid preference between wheat and grassy weed species in the presence of environmental stress and with respect to their BYDV status. Dual choice bioassays were set up to evaluate the host preference of BYDV-positive and negative bird cherry-oat aphids (BCOA) for wheat and the three grassy weed species green foxtail, foxtail barley, and downy brome. BCOA fecundity was also quantified and compared among the 4 host plants under well-watered and water-stressed conditions. BCOA preferred wheat over any of the three grassy weed species, a preference that was not influenced by drought. Aphid reproduction in response to drought stress was influenced by the host species, but overall a greater increase was observed in the reproduction of BYDV-negative than BYDV-positive aphids. Sugar concentrations in different host species did not correlate with the number of nymphs, indicating that the host species may influence the relationship between aphid reproduction and sugar content. Drought stress contributed to an increase in the reproduction of BYDV-negative aphids which could contribute to pathogen spread if the virus is present in the environment. Managing cereal aphid/BYDV reservoirs is critical in BYDV management.