By Mary-Jane Pilgrim, Master Gardener
Coneflowers (Echinacea), with their vibrant blooms and potential health benefits, are a favorite among garden enthusiasts. However, these beauties can sometimes face challenges, notably from insects and disease. While both can cause issues, they’re quite different in their effects and how they impact your beautiful echinacea.
Coneflower rosette mites, or eriophyid mites, are microscopic pests that can infest your echinacea plants. They’re like those unwanted houseguests that sneak in unnoticed and cause havoc before you even realize it. These mites suck the sap from the flower cones, leading to stunted growth and a generally unhealthy appearance. To treat for eriophyid mites, remove the flowers and do not compost. The flower heads below both show damage from mites.
On the other hand, aster yellows is a plant disease caused by a bacterium called a phytoplasma. It spreads through leafhoppers, which are tiny insects that feed on plant sap. Unlike erythroid mites, aster yellows is more like a viral cold that your echinacea catches. Plants infected with aster yellows show symptoms like distorted flowers, leaf-like structures in place of flowers, and overall stunted, often yellowed, growth. The plant may have growths out of its cone or tufts of green where the petals should be. Unfortunately, there’s no cure for this disease, so the best approach is to promptly remove and destroy infected plants (including the roots) to prevent the bacteria from spreading to others. The disease primarily affects black-eyed susan (Rudbeckia hirta) and coneflowers (Echinacea spp.)
Lastly, the main difference between mite and disease symptoms are the colors of the rosettes. Aster Yellows produces yellowish-green rosettes while the mites produce rosettes that usually retain some of the original color of the cones. Of course, the mites do not affect the rest of the plant; their damage is confined to the flower cones.
For an excellent side-by-side comparison with photos of aster yellows and eriophyid mites on coneflowers, check out this page from Ohio State University.
Resources
Ohio State University: Coneflower Calamities: Round 3
Minnesota State Horticultural Society: Aster Yellows vs. Eriophyid Mites on Coneflower
The Peterborough & Area Master Gardeners 