pl.n.(used with a sing. verb) A widespread disease of plants caused by a phytoplasma, usually resulting in stunted growth and yellowing of infected individuals.
aster yellows
aster yellows
[′as·tər ′yel‚ōz] (plant pathology) A widespread virus disease of asters, other ornamental plants, and many vegetables, characterized by yellowing and dwarfing; leafhoppers are vectors.