Gardenbite: Weird looking coneflower flowers: Aster yellows and rosette mites | #GoodGrowing

Welcome to the Good Growing podcast. I am Ken Johnson, horticulture educator with the University of Illinois Extension, coming to you today from Jacksonville, Illinois with a gardenbite. And on this Gardenbite, we're gonna talk about strange looking coneflower flowers. So purple coneflower is among the most widely planted native plants in our yards and gardens, and they have these attractive, flowers that have these orange oranges brown spiny centers, these lavender petals, and they have a a rather long bloom season compared to a lot of our other native plant species. But occasionally, people notice that they have some distorted or deformed flowers on their plants, often prompting the question, what is wrong with my cone flowers?

So there are two common causes for this. It's going to be Aster yellows and rosette mites. So Aster yellows is caused by a phytoplasma, which is a type of bacteria, and this particular pathogen is capable of infecting over 300 kinds of plants in 48 plant families. So it's a very wide host range. And a lot of times it can be a problem in the vegetable garden.

Things like carrots, onion, lettuce, and potatoes can be infected with Aster as well as a wide variety of ornamental plants, particularly those in the Aster family, thus the name, including things like purple coneflower. So with Aster yellows, it doesn't typically kill its host plant, but it can deform plants and cause them to decline over time. In coneflowers, there's several different symptoms we can see, with plants infected with Aster yellows. So first we see curled, chlorotic or yellowing of the foliage. We will often see stunted stems or the plants themselves will be stunted as well.

And probably the most noticeable, or at least one that people usually notice first, is that we will have distorted flower parts, so we have deformed cones, the flower petals turn green and spoon like, and we have clusters of secondary flower heads that emerge from the primary flower, almost looks like a crown sometimes. These are really interesting looking flowers, but unfortunately it's not really something we want in our landscape because this can spread to other plants. With aster yellows and other phytoplasmas are going to infect the phloem tissues of plants. So this is where the sugars and other items are moved around, the plant. And they're going to be spread by leafhoppers.

In the case of Astralelles, this is going to be the Aster leafhopper. So when a leafhopper feeds on an affected plant, it's going to ingest some of that pathogen and that pathogen is going to multiply within the insect. And with leafhoppers and other insects, they have that piercing sucking mouth part, so the mouth is kind of like a straw, when they stick that into whatever they're feeding on, in this case a plant, they're going to inject saliva into that food source and that's going to make it easier for them to ingest that fluid. When they inject that saliva, they're going to spread that pathogen if they are carrying it. In the case of Aster yellows, and the Aster leafhopper, it takes about ten to twenty one days from the time that leafhopper first ingests that phytoplasma from an infected plant until it is capable of spreading it.

So it's not immediate, it's going to take a little bit of time for that pathogen to multiply and move throughout the the body of that insect. So when it comes to Aster leafhoppers, they will overwinter in Illinois, but a lot of the the Aster leafhoppers that we get in the state are blown north, from Southern states in the spring on storm fronts and stuff. So while we do have an overwintering population, majority of them are probably coming from Southern states, when this happens, they can come up infected with Aster yellows already. Aster yellows is often confused with another problem we can see, and this problem is caused by the feeding of Coneflower Rosette mites, which are a type of aerophyte mites. So for these mites, they live and feed inside the developing flower buds and they can cause green to reddish green elongated rosette like tufts of stunted and distorted flower parts.

These are kind of gonna look like they're sprouting up from the tops or the sides of the cones. So for these mites, you're not really gonna, you're not gonna be able to see them with the naked eye, probably gonna need a special hand lens to do this. Eryophyte mites are small, so small, we need like a 40 x magnification to really be able to see these well. So if you were able to see them, these are gonna be cigar or carrot shaped mites and they're only going to have two pairs of legs and those are kind of going to extend from the front of their body. So the main difference between rosette mites and Aster yellows is that rosette mite damage is restricted to the plant's flowers, whereas Aster yellows affects the entire plant.

So when it comes to managing these issues, for Aster yellows, unfortunately, once a plant is infected, there's nothing that you can do to save that plant. That plant is going to decline over time. And as that's happening, as leafhoppers feed on that, they can pick up that pathogen and then spread it throughout the landscape. Landscape. So we do want to take some steps to manage this.

So first off, you have plants infected with Asteriela, so again, you have plants that are yellowing, they are stunted, we have these deformed flower heads, We want to remove those plants, including the roots, and destroy them, again, to help prevent that spread of that pathogen around your landscape. There are also, many plants that people widely consider weeds, things like dandelions, plantain, purslane, thistles, queen anne's lace, they're capable of being affected by this pathogen as well. So if you have these in your landscape, you may want to manage them, or keep an eye on them and if they are showing symptoms of Asterias, remove those so they are not serving as a reservoir for this pathogen to spread into your more desirable plants in your landscape. Even though Asteriolis has a wide host range, there are some plants that are not susceptible to it. Some things like coxcomb, geraniums, impatiens, flowering tobacco, salvia verbena are all plants that you could plant if you have issues with Asterillos.

And a lot times when we're talking about Asterillos in vegetable gardens, you know, we're talking about managing leaf hoppers, but in ornamental plantings, particularly if these are pollinator plantings, spraying for leafhoppers isn't practical and it's really not, effective. So trying to keep this disease out and removing plants that are infected are going to be the best way to manage this. So good sanitation is going to be important. One good thing about having hot, extended periods of hot temperatures is that the pathogen that causes estradiol becomes inactive. So if we have temperatures above 88, 90 degrees, for more than two weeks, this pathogen is going to be less likely to be spread by leafhoppers and we may see reduced symptoms in infected plants.

Those plants will still be infected, we still want to remove them, but the severity will be reduced in lot of cases. So there's your silver lining for hot temperatures. So in the case of rosette mites, a lot of times this damage is considered more of an aesthetic issue, but it can reduce the amount of seeds that are produced by the plants. So if you're wanting these plants to reseed, or if you're growing them to have, to provide food for birds during the winter, this may be something you want to manage. And again, sanitation is going to be key for managing the mites.

So if you have flower heads infested with rosette mite, you want to cut and destroy those flower heads and this is going help reduce mite populations over time. So for both of these, sanitation is the key. Remove infected plants or infected plant parts, get them out of your landscape so they can't spread. Well, that's all I've got for this Garden Bite. Hopefully, if you have some odd looking cone flowers, you'll be able to potentially diagnose what issues you have and manage those in your landscape.

The GoodGrowing Podcast is a production of University of Illinois Extension. Listeners, thank you for doing what you do best and that is listening or if you're watching on YouTube, watching. And as always, keep on growing.

University of Illinois Extension.