This disease is caused by an organism called a phytoplasma which is a "virus like" pathogen. The disease is spread by sucking insects who move it in their saliva from on plant to another. The aster leafhopper is the most common vector of aster yellows.

Aster yellows can be difficult to distinguish from other problems such as nutrient deficiencies, incorrect soil pH and shade tree decline. The physical symptoms for all of these problems often look a lot like aster yellows. Therefore, it is imperative that you get a confirmed diagnosis from a university or other plant diagnostic laboratory.

The symptoms of this disease may vary rather widely from species to species of plant being infected. However, as the name implies, one of the key symptoms is that the foliage will turn yellow with green veins. There is a general loss of vigor with slow growth and leaves that are smaller than normal. Sometimes flowers are distorted and may be replaced by a tuft of deformed leaves.

IF aster yellows is diagnosed landscape, you can replace infected plants with others that are not susceptible to the disease. For annuals, verbena (Verbena), salvia (Salvia), flowering tobacco (Nicotiana), geraniums (Pelargonium), cockscomb (Celosia) and impatiens (Impatiens) are about the least susceptible bedding plants. See the list below for plants to avoid if aster yellows has been a problem.


 
  • Remove Diseased Plants - Aster yellows are at present, incurable, so any plants diagnosed with this problem need to be removed and destroyed. The disease is not fatal in itself but infected plants will lose their vigor and become aesthetically unpleasant.
     

  • Control Insects - Since the disease is spread primarily by sucking insects such as leafhoppers, controlling these pests will help prevent the spread of aster yellows. Unfortunately, in the home landscape, this can be very difficult.
     

  • Control Weeds - Common weeds such as plantain and dandelion are known to harbor aster yellows. Removing weeds from the lawn, beds and borders and surrounding areas may also help limit the spread of this disease.
     

  • Chemical Controls - Currently, there are no chemical controls for aster yellows.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.


Some flowering plants susceptible to aster yellows:
Anemone
Antirrhinum - Snapdragon
Aster
Calendula - Pot marigold
Caillstephus - China aster
Celosia - Cockscomb
Centaurea - Bachelor button
Chrysanthemum - Mum
Coreopsis
Cosmos
Delphinium
Dianthus - Pink, Sweet William
Dimorphotheca - Cape Marigold
Gaillardia - Blanket flower
Gladiolus
Helichrysum - Strawflower
Lobelia
Petunia
Phlox
Scabiosa - Pincushion flower
Tagetes - Marigold

 

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