Aster Yellows
Candidatus Phytoplasma asteris (aster yellows phytoplasma)
Overview
A phytoplasma disease transmitted by the aster leafhopper, affecting over 300 plant species including many vegetables, flowers, and weeds. Causes yellowing, stunting, and bizarre flower deformities.
Symptoms
Yellowing and stunting of plants. Flowers become green and leaf-like (phyllody). Witches' broom growth. Carrots develop hairy roots and bitter taste. Lettuce hearts fail to form. Reduced seed set.
Environmental Conditions
Variable
Prevention
Control aster leafhoppers with row covers or insecticides. Remove weed hosts. Remove infected plants promptly. Avoid planting near carrot or celery fields.
Management
No cure. Remove infected plants immediately. Control leafhoppers. Remove weed hosts (dandelions, plantain, wild lettuce). Row covers during leafhopper migration periods.