Coneflower Phytoplasma (Aster Yellows): Identify and Control Deformed Blooms

In 2004, gardeners reported a surge in bizarre coneflowers: misshapen cones, tiny secondary flowers emerging from the center, and green petals instead of purple or white. The culprit: aster yellows phytoplasma—a bacterium-like organism spread by planthoppers and leafhoppers.

Symptoms

• Distorted, tufted central cones
• Green, leaf-like petals (phyllody)
• Stunted, witches’-broom growth

Vectors

Planthoppers leave white, waxy residue on vertical stems of hosta, aster, azalea, and black-eyed Susan. Leafhoppers also transmit the pathogen.

Management

1. Remove and destroy infected plants immediately—they serve as inoculum sources.
2. Control vectors with labeled garden insecticide when seen.
3. Monitor nearby susceptible plants (asters, rudbeckias, echinaceas).

Phytoplasma cannot be cured; prevention and sanitation are the only controls.

Green petals on coneflower (phyllody)

Tiny flowers emerging from coneflower cone

Distorted coneflower blooms

Planthoppers on plant stem