ProCrop
Black Spot (Alternaria) of Canola
Black spot occurs in wet years. It produces gray to black spots on leaves, stems and
pods. Often the spots are surrounded by a light green or yellow halo. Severely infected
leaves may wither and spotted pods may contain shrunken seeds. Infected pods may split
open. Black spot was common in 1994 and contributed to shattering in the swath.
The black spot fungus survives the winter on infected plant debris and on seed. Several weeds in the mustard family are hosts of the fungus.
Control. Plant well-cleaned seed free of shrunken kernels and plant debris. Use crop rotation and control volunteer rapeseed plants.
