Aster yellows, caused by the aster yellows phytoplasma, was first seen on E. purpurea and E. angustifolia at Brooks in 1994 and 1995. All three species of Echinacea are susceptible to aster yellows. However, E. angustifolia has shown a lower incidence of this disease than E. purpurea in field plots. Note yellowing of leaves. Phytoplasma infection causes proliferation of axillary shoots.
Healthy plant is on the right.
Small, secondary, sterile florets issue from the original flower heads. Phytoplasma infection in E. purpurea . Note greening and distortion in disk and ray florets. Normal flower appears on the right. Diseased plants are subject to winter kill and infections caused by soil-borne pathogens.