How to Manage Pests

Pests in Gardens and Landscapes

Aster yellows

Aster yellows is a phytoplasma, a minute organism smaller than bacteria, that infects many weeds, vegetables, and flowers such as aster, Chrysanthemum, cosmos, gladiolus, Marguerite daisy, marigold, nasturtium, primrose, sunflower, and vinca. Aster yellows is vectored by several species of leafhoppers. Flower parts develop into leaflike structures and are yellow or green and dwarfed. Clusters or tufts of spindly, yellow upright shoots commonly develop around the base of infected plants, often on one side of the plant. Corms or tubers can mature early, be undersized, or have stunted roots if they are infected during the current season. When corms or tubers infected during the previous season are grown, they develop many thin, weak, yellowish leaves, distorted flower spikes, and green blossoms.


Plant pathogen-free plants and use good sanitation. Don’t plant near weeds that may host leafhoppers. Remove and destroy infected plants. Remove nearby weeds and control leafhoppers.

Flower parts develop into green, stunted growth

Flower parts develop into green, stunted growth.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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