Virulent blackleg of canola/rapeseed is a fungal canker or dry rot disease of the actively growing crop that causes stem girdling and lodging (Figure 1). In heavily infested crops, up to 100 per cent of the stems may be infected, resulting in major yield loss.
Two types of blackleg fungus infect canola weakly virulent and virulent. The weakly virulent, or mild type, has always been common in canola fields. The disease appears on leaves and stems in August but does not usually cause significant damage