Canker

At least two fungi cause canker on parsnip: Itersonilia and Phoma.These diseases are very common in wet seasons, causing a leaf spot on the foliage and a rusty brown to black decay of the roots. Root infection usually begins at the crown or at points where carrot rust fly larvae have wounded the root.

Control

1. Gladiator is the most resistant variety recommended in BC. In Ontario, Andover is said to be resistant to both Itersonilia and Phoma canker.
2. Rotate crops. Do not replant parsnips for at least one year after a canker-infected crop has been grown.
3. The leaf spot phase may be quite destructive to the foliage under wet conditions. A fungicide spray program such as that used for foliar blights of carrots will reduce damage. See Table 3, Parsnips Disease Control.
4. The leaf spot phase may be an important source of inoculum for the exposed shoulders of the roots under conditions of frequent rainfall or irrigation. Hilling the shoulders with soil will reduce the number of infections.
5. Carrot rust fly wounds may be followed by canker infection. These infections can be prevented by closer attention to rust fly control.