Thursday, August 29, 2013

Aster Yellows

Echinacea is a favourite perennial of mine, and I have several colour variations of it.  Sometimes one puts on a funky show of flowers and although fascinating, it’s really a problem.  A week or so ago I posted photos of my funky flowers and with questions about the cause, I felt I should explain.
Echinacea 'Pixie Meadowbrite' before aster yellows infected it.

Aster yellows can affect asters, marigolds, coreopsis, chrysanthemums, purple coneflower and other flowers.  It also can be found on crops of canola, flax, sunflowers and alfalfa.  A disease caused by a bacteria-like pathogen, it requires living plant and insect hosts to survive, spread and reproduce.  The pathogen can only live in host plants and insects, and is not soil, air or wind borne. There are approximately thirty insect species that can transmit the disease, particularly leaf hoppers.
Leaf hoppers are tiny 0.6 mm - 3 mm insects that are poor fliers and rely on wind currents to glide between plants.  They can be distinguished by scuttling sideways when disturbed.  Leaf hoppers feed on the sap of an infected plant whereupon the bacteria then reproduces within the insect.   When the insect feeds on a healthy plant, the bacteria is transmitted.  The pathogen can overwinter in plant roots and be a source of the bacteria in spring, so it is essential to destroy affected plants by putting them in the trash, and not a compost bin.
During hot and dry conditions, asters yellow is not conducive to spreading but during a season of abundant rainfall, makes the plants more succulent to attract leaf hoppers.
With echinacea, secondary flower heads emerge from the primary flowers or sometimes few petals will develop on the head.  Other times the stems are twisted and the plant stunted.
When plants begin to mutate and produce odd looking flowers, there’s usually an underlying reason that needs to be investigated.
This year, practically every flower looked like this or had no petals at all.
I'm linking with:
Tracie at her Cottage Garden Party


  1. hello
    je suis envahie par les chenilles
    des vertes et des noires
    se sont de grandes gourmandes de feuillages
    à bientôt
    edith (iris) France

  2. Hi Judith, This was very interesting as we have been discussing adding several echinacea to out hillside this fall. I have had so much trouble with my usually fool-proof hydrangea this summer and I think it is from a combination of the hurricane/blizzard last fall followed by a very rainy summer and one incredibly intense heat wave. I thought the echinacea might do better! Thank you for the information. Linda

  3. I never knew what caused the deformities, so I appreciate the information. We had coneflowers at our former cottage and they started to look like this right before we moved. I guess the new homeowner will have to deal with it, LOL.

  4. Hi Judith. This was really interesting, considering I'm no a flowerologist at all! I like visiting your blog and learning something new.

  5. Hi Judith, I think this is a very common disease. I have seen it many times in my own garden, also in others' gardens, and even at the garden center at Lowe's. I have lost so many coneflowers because of this - my orange and my gold coneflower, the only "special" ones I had, as well as the purple coneflowers. I am fortunate, though, that I have so many and they re-seed themselves, that I continue to be able to grow them. I'm sorry you've lost yours because of it. It's always hard to lose a plant you enjoy.
    Hugs, Beth

  6. I have run across this before, not in my garden, but now I know what it is!

  7. So you must uproot all those echinaceas and start over. Point well taken about putting the plants in the garbage and not the compost heap. I have seen the little "fliers" that don't seem too stable, but had no idea. I've just sprayed them with death spray and have not noticed ant strange blossoms as you've shown.

  8. Oh dear. I've never heard of this before. What a loss to your garden. Thanks for sharing this information with us Judith. I'll be on the lookout for it.

  9. Artistic flowers just the same! I have never seen this but you are a way more experienced gardener than me. Very interesting but disappointing for you too.

  10. Echinacea, I have always thought about putting some in the garden but never have.. My whole garden was pretty much destroyed by some kind of a blackish color.. they started with my tomatillos, then my three beautiful squash plants to the tomatoes and now that they killed all that they are killing my green beans.. I never had this problem ever.. strange things going on.. Happy Thursday with love Janice

  11. Oh dear! I am learning a lot about gardening this year it seems! I'm sorry you are having to deal with this problem... all your beautiful Echinacea! I hope you can get it all under control again soon!
    Thanks for the info...

  12. I was too crazy-busy all summer and the garden shows it! I am happy to see other's beautiful flowers though. These were so pretty before the little devils got to them!

  13. Wow I've never seen or heard of this before. I do have some black spotting on my Black Eye Susans and wondered what it is.

  14. Thanks for yet another enlightening garden-related post! I wouldn't have ever guessed the culprit here!

  15. Sorry to hear this has infected your plants. I am trying to stay ahead of it here.


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