Several diseases and pests affect coneflowers. While your coneflowers may never get any of them, it can be troubling if they do.
This disease typically occurs in overly moist conditions or from a lack of airflow. Plants that are already weakened by pests or disease may be especially susceptible. Avoid powdery mildew by spacing plants properly and planting in well-drained soil.
Floral damage caused by eriophyid mites mimics some of the symptoms of aster yellows (see below). In this case, the damage is only cosmetic and won’t affect the health of the plant, although it will reduce seed production. Mites feeding on the flowers cause tufted growth or rosettes to form on the cones. The deformed flowers are unsightly and similar in appearance to aster yellows. Removing the affected flowers will improve the ornamental display and reduce the mite population.
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