grapevine yellows, generic term for a group of related phytoplasma diseases of grapevines which pose a serious threat to vineyards in many wine regions of the world because there is no known control. The best-known of these diseases, flavescence dorée, can kill young vines and makes old vines uneconomical. It is spread by infected plants from the nursery and further spread by insects called leafhoppers, to which many common vineyard weeds are alternative host plants. The disease occurs sporadically in epidemics, and varieties vary in their sensitivity to it.
