Responses of the Russian wheat aphid (

Aphids are economically important pests of cereal crops globally. They feed on the sap of plants, which can directly reduce yield and grain quality. Many species are also proficient at transmitting important plant viruses. Two of the world’s most damaging cereal aphids are the Russian wheat aphid (Diuraphis noxia) and bird cherry oat aphid (Rhopalosiphum padi). These species are present in all major grain-growing regions worldwide, with D. noxia recently invading Australia. In many countries, including Australia, chemicals are an important control option. Insecticide seed-dressings, in particular, are widely used to combat early-season infestations of aphids in establishing cereal crops. In this study we examined the length of protection provided by several insecticide seed-dressings against D. noxia in wheat, and compared this with R. padi. All seed-dressings examined were efficacious for up to 5 weeks after wheat emergence; however, notable differences were evident between aphid species. In most instances, R. padi was able to persist and reproduce on wheat at an earlier growth stage than D. noxia. These findings suggest that R. padi is more tolerant to certain insecticides and may therefore re-infest insecticide-treated wheat fields earlier than D. noxia.