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Aster yellows

Quick facts

  • Aster yellows is a plant disease that can infect many common vegetables, annual flowering plants, perennial flowering plants and weeds.
  • Infected plants have yellow, stunted growth, and small malformed flowers.
  • Aster leafhoppers can carry the aster yellows pathogen. Plants become infected when fed upon by these leafhoppers.
  • Once infected with aster yellows, a plant will never recover.
  • Plants infected with aster yellows should be removed from the garden and composted.

Symptoms of aster yellows

A petunia plant with discolored leaves and stunted, discolored flowers
Infected petunia did not develop to normal size or color
  • Leaves are discolored pale green to yellow or white.
  • In some plants, red to purple discoloration of leaves occurs.
  • Leaves may be small and stunted.
  • Flowers are small, malformed and often remain green or fail to develop the proper color.
  • Plants infected early in the growing season may remain small and stunted.
  • Many thin, weak stems grow close together forming a witches' broom.
  • Tap roots of carrots are thin, small, covered in many root hairs, and often taste bitter.


How to manage aster yellows

  • Once a plant is infected with aster yellows, there is no way to cure it.
  • Completely remove infected plants from the garden.
  • Compost infected plant material. Aster yellows will not survive once the plant is dead.
  • Remove perennial weeds from the garden. If infected with aster yellows, the bacteria will survive in weeds from one season to the next.
  • Protect plants from aster leafhoppers with light colored or reflective mulches that disorient the insects and can reduce feeding on plants.
  • In the vegetable garden, floating row covers can be used to prevent leafhoppers from feeding on plants.
  • Pesticides are not effective in reducing aster yellows in the home garden.

Understanding aster yellows

Aster yellows is caused by a phytoplasma, a very small specialized type of bacteria that can live only within the veins of a plant or within a sap sucking insect called the aster leafhopper.


    Michelle Grabowski, Extension educator

    Reviewed in 2018

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