When early-season southern winds bring up leafhoppers that are infected with the aster yellows phytoplasma up from the United States and conditions in a field are favourable for leafhoppers, watch for aster yellows disease. It may be 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 some instances when economic thresholds have been reached, most fields in most years do not reach an economic level of loss.
Let us know if you liked the post. That’s the only way we can improve.