MSU Extension Integrated Pest Management

Phytoplasmas

Pathogen

Aster yellows phytoplasm.

Hosts include

Anemone, Bellis, Campanula, Chrysanthemum, Coreopsis, Delphinium, Gaillardia, Rudbeckia, Salvia and Scabiosa.

Symptoms

Symptoms vary, depending on the host. Possibilities include stunting, yellowing, twisting, distortion of flowers or flower petals, and bushy, broom-like growth.

Witches’ brooming symptom on Limonium caused by aster yellows

Infected plants have stunted and, possibly, malformed roots. Infected Echinacea and Rudbeckia may have deformed, yellowish flower heads.

Spread

The pathogen is vectored by aster leafhoppers (Macrosteles fascifron), as well as a few other leafhopper species. Aster leafhoppers can migrate into production areas on air currents, bringing the pathogen with them.

Management

Infected plants cannot be treated and should be removed and destroyed. Susceptible field-grown perennials should be scouted regularly for leafhoppers. Good control of leafhoppers in the growing area is important to limit spread of the disease. Weeds can be infected; many are symptomless hosts. Maintain good weed control, especially of overwintering weeds, to reduce sources of inoculum.

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