University of Illinois Extension

University of Illinois Extension

Hort Answers

Phytoplasma Disease

Aster Yellows
unnamed phytoplasma

Aster yellows on chrysanthemum.
Aster yellows on chrysanthemum.
2 (1 = rare 5 = annual)
5 (1 = very little damage 5 = plants killed)
Calendula sp., Echinacea sp. (Coneflower), Tagetes (Marigold), Callistephus chinensis (China Aster), Chrysanthemum sp. (Mums), and other plants.

Plants Affected
On cone flowers (Echinacea sp.) the disease causes a witches broom in the flower head, greening of petals sometimes, stunting and possible death of the plant. On other herbaceous plants, the disease causes stunting, yellowish-green foliage and flowers followed by browning and death of plant. Symptoms can vary from plant to plant, area to area depending on the different strains of these aster yellows phytoplasmas.

Life Cycle
Phytoplasmas are bacterial-like, but lack rigid cell walls. The aster yellows pathogen overwinters in insects especially leaf hoppers. Infested hoppers infect the plants when feeding.

Infected plants should be destroyed as soon as possible to help reduce the number of hoppers that will become infested when feeding on an infected plant. Try to minimize leaf hopper overwintering sites by mowing tall grass and reducing tall, brushy areas.

Related Resources
Home, Yard & Garden Pest Guide
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic