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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 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.
  • Taproots of carrots are thin, small, covered in many root hairs, and often taste bitter.


Plants with aster yellows symptoms

How to manage aster yellows

  • Completely remove infected plants from the garden. Once a plant is infected with aster yellows, there is no way to cure it.
  • 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.

Disposal options for infected plant material

  • Bury it in your home compost pile or in the ground, making sure it is completely covered so insects cannot feed on the infected plant materials. Aster yellows will not survive once the plant is dead.
  • Burn it. Check fire restrictions in your area prior to burning.
  • Note: It is against the law in Minnesota to put any plant materials in residential garbage.

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, former Extension educator

    Reviewed in 2021

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