August 4, 2016

Aster yellows: What does it look like?

Aster yellows. Source: Keith Gabert
Aster yellows. Source: Keith Gabert

Aster yellows is a phytoplasma infection that causes misshapen pods and flower buds. Most fields in most years have less than 1% infection, which is not an economic level of loss.

However, some infection will go unnoticed because not all infected plants show the obvious signs of infection. The plant looks normal but some pods are empty or contain misshapen seeds. Photos below show various aster yellows symptoms.

Aster yellows phytoplasma (Candidatus Phytoplasma asteris) is carried by aster leafhoppers, which come up each year on south winds from the U.S. Canola varieties are not known to have any difference in infection rates. If aster yellows is found in one variety, it will be found in all varieties.

Further reading:

Aster Yellows (Canola Encyclopedia entry)

Aster Yellows Q&A

Aster yellows. Credit: Jon Whetter
Aster yellows. Credit: Jon Whetter
Aster yellows can cause misshapen and malformed seeds, which often shrivel up and blow out of the combine. These can occur in pods that otherwise look normal.
Aster yellows can cause misshapen and malformed seeds, which often shrivel up and blow out of the combine. These can occur in pods that otherwise look normal.
These are less typical signs of aster yellows. Usually you'll see the deformed bladder-like pods. Source: MAFRI
These are less typical signs of aster yellows. Usually you’ll see the deformed bladder-like pods. Source: MAFRI
Stress from aster yellows can lead to purpling, as shown in this plant. Late or mild aster yellows infections may produce purpling even without the typical misshapen pods.
Stress from aster yellows can lead to purpling, as shown in this plant. Late or mild aster yellows infections may produce purpling even without the typical misshapen pods.

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