Phytoplasma Diseases (Yellows)
Phytoplasma spp. (Candidatus Phytoplasma asteris and others)
Overview
A group of diseases caused by phytoplasmas (cell-wall-less bacteria) transmitted by leafhoppers, causing yellowing, stunting, witches' brooms, and green flowers (phyllody). Includes aster yellows and many others.
Symptoms
Yellowing and stunting. Witches' broom (proliferation of thin, upright shoots). Phyllody (flowers turn green and leaf-like). Virescence (greening of normally colored parts). Bolting. Reduced fruit set.
Environmental Conditions
Variable
Prevention
Control leafhopper vectors. Remove weed hosts. Use insect netting. Remove infected plants promptly. Avoid planting near carrot or celery fields (common reservoirs).
Management
No cure. Remove infected plants immediately. Control leafhoppers with insecticidal soap or pyrethrin. Remove weed hosts. Tetracycline trunk injections for palms (limited effectiveness).