Hi master gardeners,
I have 9 Green Twister echinacea plants which I planted last fall. They all came up just fine initially, with the flowers looking as a normal coneflower should. However, in the last couple of months or so, I’ve noticed that the flowers on most plants are coming up distorted, with some green and red/green growth sprouting from the cone centers. I have been cutting off those blooms as I’d find them, thinking it was an erythroid mite issue (I have cut off MANY emerging blooms so far, as nearly all of them would show those symptoms). However, for the past few weeks I’ve left the blooms to fully form, to see how they turn out. Some of them have emerged with petals, and some without, and some with abnormally small, rounded, and green-looking petals, as you can see in the picture I’ve submitted. The leaves on the plants seem normal green, with no yellowing. My question is: do my plants have either Aster yellows, or erythroid mites (or somethingelse entirely?!), and what should I do regarding treatment? I am reluctant to remove/destroy the plants, but will obviously do so if you think it’s necessary. Please help!
Thank you for contacting the Toronto Master Gardeners with your question concerning your coneflowers.
Coneflowers (Echinacea) are a popular garden flower. They not only provide beautiful colour to the garden form summer through fall , they are also an excellent seed source for migratory birds.
While there are other issues that could affect your coneflower such as Japanese beetles, aphids and earwigs there are two serious problems that affect coneflowers: Coneflower Rosette Mite and the phytoplasma disease known as Aster Yellows.
The coneflower rosette mites live inside the developing flower buds and suck nutrients from the base of the flower causing the stunted and distorted flower parts, such as what appears to be missing petals.
Aster Yellow disease is caused by a phytoplasma. This small specialized bacterium which is spread by from plant to plant by sucking insects, infects the plant phloem tissue. The phloem tissue is responsible for conducting food that is made through photosynthesis from the leaves to all other parts of the plant. As a result, symptoms of aster yellows include chlorotic, curled foliage; stunted stems; and bizarrely distorted flower parts.
Since the overall health of your plant doesn’t seem to be affected, I believe that your coneflower is affected by Coneflower Rosette mites. It is important to cut back the infected plants to the ground in the fall and remove all plant parts from the area to prevent re-infestation next year. It is also important to not compost these plant parts, but instead to place them in a black plastic bag and dispose of them in your garbage.
Ohio State University has an excellent fact sheet titled Coneflower Cleanup which illustrates the effect of the two diseases on the coneflower.
Good Luck with your coneflowers.