Tom Creswell, PPDL Director
Coneflower, reliable and iconic, holds a special place in the Mid-western gardener’s lexicon. It has relatively few problems but aster yellows, caused by a phytoplasma (a bacteria-like organism) shows up with some frequency. When leafhoppers feed on the coneflower they suck out plant sap, move to another plant and repeat the action, carrying the pathogen along for the ride.
This coneflower shows some of the symptoms associated with aster yellows: showy petals fail to develop, flower buds may stay green and tightly bunched; and leaves may be strap shaped.
As with virus diseases of plants: once infected = always infected; because the pathogen moves throughout the plant. Diseased plants should be removed to prevent spread to other susceptible hosts nearby.
The Missouri Botanical Garden offers some good advice on management of this problem and more details on which plants are most susceptible.