Aster yellows on coneflower
IDENTIFICATION — One disease that can infect purple coneflower is aster yellows. It’s caused by a phytoplasma, a disease-causing organism smaller than bacteria but larger than a virus.
DAMAGE — Leafhoppers carry the disease by piercing leaves to feed on plant juices. Infected plants produce underdeveloped and deformed flowers, as shown in the photo.
CONTROL — There’s no cure, but you can stop the spread of the disease by pulling up all infected plants and destroying them. The phytoplasma needs a living host, so skip a season after the cleanup before planting more coneflowers.