Disease attacks cotyledons, leaves, stems and pods. Seed may be an important means of pathogen dispersal. When seedling leaves are infected the fungus will spread systemically from leaf lesions down the stem.
During and shortly after cotyledon production, check for lesions on all plant parts. In later season, scout for girdling of stems and severed plants.
Avoid canola after canola and fields adjacent to residue from infected crops grown in previous three years. Control volunteer canola and wild mustard. Resistant cultivars have been developed, except in Brassica rapa cultivars.