|Written by Linda Langelo|
Ever heard of a phytoplasma? These are single celled microorganisms that live in the phloem of plants.
This phytoplasma is similar to a bacterium. This phytoplasma has no cell wall. It can infect over 300 plants in 48 different families. Some of those plants are listed below. The picture above is typical of aster yellow in Echinacea.
One of the more well-known phytoplasma is called aster yellows. This is vectored by the aster leafhopper and other leafhoopers. This leafhopper migrates from the southern United States to the northern United States. It is seen annually in many northern gardens.
Weeds such as horseweed, dandelion and Queen Anne’s Lace can harbor the aster yellows phytoplasma. There is an incubation period of aster yellows within the leafhopper before it can tranmit the disease. This also occurs within the plant before the disease appears.
The leafhopper feeds on plants that already have the aster yellows or the casual phytoplasma. The disease circulates in the leafhopper’s body. When it reaches the leafhopper’s salivary glands, it will be able to transmit the disease. The time frame for this to occur can be from 10 days to three weeks.
Aster yellows has many hosts besides the weeds previously mentioned. There are many ornamental plants and vegetables. Among the ornamental plants are asters, anemone, centaurea, chrysanthemum, coreopsis, delphinium, echinacea, gaillardia, limonium, phlox, scabiosa and veronica.
Among the vegetables damaged by this disease are head lettuce, carrots, New Zealand spinach, cauliflower, cabbage, dill, endive, escarole, onion, parsley, parsnip, potato, squash, tomato, pumpkin and celery. With all of the different crops listed above, the lettuce and carrots are effected over other crops.
Removing the infected plants is the most effective to help control the disease along with growing less susceptible plants. These plants include nicotiana, geraniums, salvia, cockscomb, portulaca, verbena and impatiens. Remove weeds within the garden area. Some weeds are symptom-less and can harbor the disease. The leafhoppers will carry the disease for their lifetime. The leafhoppers are difficult to manage in the home garden.
Holyoke Enterprise July 26, 2012