Aster yellows

When spring southern winds bring aster leafhoppers infected with the aster yellows phytoplasma (Candidatus Phytoplasma asteris) up from the southern United States, and conditions in a field are favourable for leafhoppers, watch for aster yellows disease. It is often first spotted in plants that are noticeably taller than the rest of the crop (through flowering to podding stages). Infected plants turn a blue-green colour and leaves will show a red or purple tinge late in the season. Sterile, green, leaf-like structures will replace the flower and round or oval, blue-green, hollow, flattened bladder-like structures replace seed-bearing pods in infected plants. Although there have been instances when economic thresholds have been reached, such as in outbreak years, generally few fields reach an economic level of loss. 1

For information on Aster yellows, please visit Aster Leafhopper.


  1. Agriculture and Agri-Food Canada. 2018. Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management Field Guide. Retrieved from:

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