Master Gardener: Plants with Aster Yellows doomed
BY BRIAN JERVIS Ask a Master Gardener
Saturday, July 14, 2012
7/14/12 at 4:34 AM
Q. Some of my purple coneflowers have lost color and have bizarre shapes, they look like Frankenflowers. What is this? M. S., Tulsa
A. Your coneflowers are infected with an organism called Aster Yellows Phytoplasma. This virus-like organism is spread by an insect called the Aster Leafhopper. These insects overwinter in the southern part of the country and migrate through our area in the spring - mainly blown by the wind. When the insect carriers feed on plants, they infect them. There is no cure once a plant is infected.
Aster Yellows organism infects more than 200 plants - ornamentals, weeds and vegetable crops. Its favorite ornamental is echinacea, or coneflowers, but it also attacks asters, marigolds, black-eyed Susans, gladiolas and many others. Many vegetables, especially carrots, are susceptible.
The infection initially causes the plant's leaves to yellow, then induces stunting. The flowers produced are severely deformed and irregularly shaped. They often have extra shoots and even new flower buds growing from the middle of a blossom. This cluster of new growth causes a deformity often called "witches broom." It is easy to see how the name "Frankenflower" came to mind.
The whole plant is infected and should be removed, roots and all, to the trash, not the compost pile. Even though it is spread by insects, spraying insecticides is not recommended due to the unpredictable migration of the tiny insects from south of us.
There is another new infection occurring in gardens around the country. It is called Hosta Virus X and is said to be spreading rapidly around the world. It is not spread by an insect, but from plant to plant when divided. It develops slowly and often is not manifest in the nurseries.
The virus induces a wide variety of changes, including stunting, localized puckering and all sorts of twists and distortion. Pigment changes are common, lighter or darker; some pigments may appear to be smeared into an "inkbleed" pattern. Before the virus was discovered, these plants with unusual pigmentation were propagated and sold as new discoveries.
Many hostas are susceptible, but Gold Standard, Sum and Substance, and Striptease varieties seem to be very susceptible.
If you suspect a hosta of having this disease, there is a rapid test that may be done by the OSU pathology lab ( tulsaworld.com/pdidl) that is very accurate. If a plant is diagnosed as infected, it should be destroyed.
If you have a garden-related question you would like the Master Gardeners to answer in a future column, call 918-746-3701.
Original Print Headline: Plants with organism doomed
For all your plants, ornamental or vegetable, mulching and correct watering are keys to surviving the heat of the summer. Mulch conserves water and reduces ground temperature. Always water in the mornings. Watering less frequently and more deeply is better than daily shallow watering.
Obtain OSU's fact sheet "Fall Vegetable Gardening" ( tulsaworld.com/osufallgardening) to prepare for the fall vegetable season.
Brown Patch disease of fescue lawns is appearing now. Fungicides available to the homeowner have been shown by OSU to not be effective for this, but commercial fungicides for licensed applicators are effective in preventing new disease. Fescue needs 2 inches of water per week applied in the mornings to survive summer.
Coneflowers look more like Frankenflowers when affected by Aster Yellows Phytoplasma, a virus-like organism spread by one kind of insect. More than 200 kinds of plants are susceptible to the organism. BILL SEVIER/Courtesy