Monday, July 13, 2009
Aster Yellows is turning out to be a major problem for Echinacea across the world. Aster Yellows doesn't effect just coneflower but also infects asters, leucanthemum, coreopsis, dianthus, glads, petunias, and marigolds.
The first sign that your coneflower may have aster yellows is the loss of color or chlorophyll in the leaves. Other signs are the yellowing of new growth and stems, leaves, and flowers don't develop properly. The flowers often have cones with sporadic petals or misshaped flower heads. The plants can often be stunted as well. You may think you have a new cool flower but be careful.
The disease is caused by a tiny organism called phytoplasma (sounds like something from Ghostbusters) and is spread through leafhoppers. You may think you just have a bad case of leafhoppers but they are actually just the carrier.
Now the bad news, once you have aster yellows there is no cure. You are going to have to dig up the plant and dispose of it properly. Neem oil and other insecticidal soaps are effective on leafhoppers if caught early but proper weeding is the most effective. Leafhoppers love dandelions and if removed greatly improves conditions. Oat straw is said to be a repellent as well but we haven't tried it to say yea or nay.