Aster Yellows

Need to know

• Aster yellows is a disease that can cause bizarre symptoms on many plants.
• Typical symptoms of aster yellows include veins that turn pale, yellowing of new leaves, abnormally bushy growth, deformed flowers, and stunting.
• Symptoms are more pronounced in hot weather, a plant can be infected without showing any symptoms.
• No treatment is available to save a plant infected with aster yellows.

Overview of aster yellows 

Aster yellows is a disease that can cause bizarre symptoms on a wide variety of plants. The disease can be found on hundreds of plants, including many flowers and vegetables, such as coneflower, daisy, marigold, zinnia, snapdragon, chrysanthemum, tomato, carrot, and lettuce.

Symptoms of aster yellows

Typical symptoms of aster yellows include veins that turn pale, yellowing of new leaves, abnormally bushy growth, deformed flowers, and stunting. Infected plants often have a stiff, upright appearance, with branches joining the stem at narrow angles. The appearance of this disease varies with the host plant. On coneflowers, the most typical symptom is the replacement of flowers by tufts of small, green, deformed leaves. Infected carrots roots may be excessively hairy and bitter, and in lettuce, inner leaves may be curled and twisted, whereas outer leaves do not develop fully and have pink or tan spots. On onion, leaves are small, twisted and yellow.

Signs of aster yellows

No signs are visible, specialized nucleic acid testing is required to confirm this fastidious bacteria-like organism causing the symptoms.

Disease cycle of aster yellows

Symptoms are more pronounced in hot weather,  a plant can be infected without showing any symptoms.

Aster yellows is caused by a tiny organism called a phytoplasma, similar to a bacterium. The phytoplasma is carried from plant to plant by aster leafhoppers, which feed on the sap of the plants.

Type of Sample Needed for Diagnosis and Confirmation

The Iowa State University Plant & Insect Diagnostic Clinic can help you to investigate and confirm if your plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each state's diagnostic laboratory for U.S. residents.  If your sample is from outside of Iowa please do not submit it to the Plant & Insect Diagnostic Clinic without contacting us.

Want to submit a sample? select special testing on our submission form, and follow the foliar instructions at Submitting Trees and Shrubs page. 

Management of aster yellows

No treatment is available to save a plant infected with aster yellows. Aster yellows is best managed by removing infected plants from the garden to minimize spread. Management of the insect vector is not usually feasible in a home garden. Manage weeds in the garden area as many of them may serve as symptomless hosts.  Always inspect new plants for symptoms before you purchase them or plant them in the garden.