by Connie Oswald Stofko
Here’s a question from a reader:
Last summer we were warned about aster yellows destroying coneflowers. My coneflowers were all infected but I didn’t remove the plants from my garden. Now I’m watching them sprout and I’m wondering if I should be worried. Should I take them out now?
Yes, if you saw symptoms of aster yellows disease last year on your coneflowers and you didn’t pull out and carefully destroy the diseased plants, you should take the coneflowers out of your garden now, said John Farfaglia, extension educator with Cornell Cooperative Extension in Niagara County.
Throw the plants in the garbage; don’t put them on your compost pile.
If you didn’t have this disease on your coneflowers last year, you don’t have to pull up healthy plants, he said.
The symptoms will appear later in the season. Bizarre green tufts grow out of the flower, according to information on aster yellows disease from Cornell University. Another symptom is foliage that turns yellow while the veins stay green.
The reason it’s so important to pull out diseased plants as soon as you spot the symptoms– or to do it now if you didn’t do it when you noticed the disease last year– it that aster yellows is caused by a virus, Farfaglia said, and there is nothing to cure the disease.
If you keep diseased plants in your garden, they can serve as a source for the disease and help the disease to spread.
Aster yellows is a disease is caused by a microsopic organism called a phytoplasma. It is spread by small insects called leafhoppers. As a leafhopper sucks the sap of the plant, it spreads the disease to that plant. If the leafhopper skips a plant, that plant will be fine.
So the good news is that if you are visited by leafhoppers, you might not lose all your coneflowers to aster yellows disease. But it is important to pull out and dispose of any plants that do have the disease so it doesn’t affect your healthy plants.