Purple Coneflower Clinic: What's wrong with your Echinacea flowers?
Healthy Echinacea can be a beautiful mass planting in a native-inspired garden. Modern breeding has improved the colors and forms available to gardeners. Photo by Amanda Bratcher
Purple coneflowers (Echinacea species) are absolute powerhouses in the Southeastern landscape. Native across the Midwest and Eastern United States, these tough perennials have become garden royalty thanks to modern breeding that gives us a rainbow of colors and sizes. They tolerate our clay soils, handle full sun to part shade, and pull in a lot of traffic from pollinators. You’ll see bumblebees and butterflies working the blooms all summer long, followed by hungry goldfinches picking at the seed heads in the fall.
While coneflowers are remarkably tough, even these native rockstars encounter a few pests and diseases during hot North Carolina summers. If your coneflowers are looking a little funky this month, here is your quick diagnostic guide.
Echinacea Eriophyid Mites
You would never notice the mites themselves, unless you put your flowers under a microscope! But you would certainly notice how the “cone” part of your flowers would start to become misshapen and discolored. Usually the petals will also fall away, leaving you with a green, black or red glob. It will also not form seeds, making it useless to birds for food.
The mites are so small they can carry on the wind and can show up in even the healthiest patch. The key with eriophyid mites is to remove the flowers as soon as you start to see irregular spikes and masses forming on your flower heads. The mites can show up year to year, but early detection and sanitation (i.e. removing the flowers) can keep the infestation from spreading and ruining your overall floral show. Chemical applications are generally not recommended because infested flower removal can generally control the issue.
Quick Diagnostic Cheat Sheet: Mites or Yellows?
Just the flower looks weird, but leaves are normal? Then you have Mites and you need to cut off the flower.
The whole plant is stunted, leaves are yellow, and flowers are green? Then you have Aster Yellows and you need to dig up the whole plant.
TOP TIP: Make sure to clean your tools with isopropyl alcohol between cuts to minimize spreading the mites and phytoplasm to healthy stems!
Aster Yellows
Inevitably every year someone is excited on social media that they have found a cool, new green variety of Echinacea in their garden. The flowers start to change from purple, or whatever color, to a long, strappy green, and then start shooting up mini flowers from the cone part of the flower. It is pretty cool to see in its advanced stages, but you should never let it get to that point. You have aster yellows (why don’t they call it aster greens?!) and it is both terminal and can spread via piercing sucking insects, like aphids, leafhoppers and mealy bugs, in your garden!
Aster yellows is caused by a phytoplasma, a bacterium-like organism that can move through the vascular system of the plant and cause distortions in the tissues. This organism doesn’t kill the plants outright, but can serve as a source of the phytoplasma and can continue to infect other Echinacea and some other members of the sunflower family.
The best thing to do is to remove the entire infected plant and place the debris in your trash, rather than your compost pile. Keep an extra close eye on any additional plants near the infected one to make sure it hasn’t spread. There is no way to prevent the disease from coming into your garden, or curing your plants once it has the phytoplasma. Removal is the only option.
Sunflower Caterpillar
Echinacea is a member of the sunflower family, Asteraceae, and thus can be susceptible to some of the moth species that use it as a host plant. The sunflower moth, Homoeosoma ellectellum, is a DBM (aka darn brown moth) whose larval (aka caterpillar) stage will eat the flower head of members of the sunflower family. You’ll notice matted webbing, insect frass (poop), and chewed, brown patches across the central cone. The moths in their adult form are less than an inch long and are migratory. You probably wouldn’t even recognize it as a moth if you saw it, as it is tubular in form and light tan to grey, blending in well with the profile of the petals of the plants.
We generally do not have an issue with this caterpillar in North Carolina, but we can have them pop up especially when we have strong winds from the south, as these are present and active year-round in Mexico and Central America. It is generally recommended to scout for them and remove any flowers you see with the caterpillars present and throw them into your trash. This native caterpillar is commonly parasitized by flies and wasps, so the populations do not reach destructive levels.
Petal Predation = Something ate my “flower”
Echinaceas are members of the sunflower family, so they feature a composite structure made of two flower types: outer ray florets (the colorful "petals") and central disk florets (the fertile cone that produces nectar, pollen, and seeds).
The long, strap-like petals are easy food for many petal-eating insects, especially beetles, like Japanese beetles. We do not generally recommend treating Echinacea flowers to protect the petals. While it can be unsightly to come out to your garden and see holes in your ray florets, or petals, you can rest assured that the pollinators will still have nectar and pollen available to them, and the birds will be able to get seeds later in the season.
I had to do a double-take in the garden! This diseased leaf looked just like a goldfinch male in profile, such that I had to look twice to notice that it was a discolored leaf and not a bird. Wow! Photo by Amanda Bratcher
Mid-Summer Leaf Spots
If the bottom leaves of your coneflowers are developing dark purple or brown spots and yellowing in July, don't worry. Our humid air creates ideal conditions for fungal leaf spots (Septoria or Cercospora). Simply prune off the ratty lower leaves to improve airflow around the base of the plant.
The Verdict: Low-Stakes Pests
Despite this hit list, Echinacea remains one of the most reliable, low-maintenance perennials you can grow in the southern native garden. These minor summer bugs and diseases rarely kill an established stand, and the ecological benefits to our native bees and birds far outweigh a few chewed petals! Try adding one to your garden this fall!
Let’s Grow Together
Amanda Bratcher is the horticulture agent with N.C. Cooperative Extension- Lee County Center. You can reach out to the office at 919-775-5624 for more information or questions regarding this article, but also any other questions about your garden, farm, land or plants! We’re here to help! You can check out our website's events page for more information and to register for upcoming programs.
