• Worldwide distribution. Temperate as well as tropical countries. Members of cabbage family, including broccoli, cabbage, cauliflower, mustard, oilseed rape, and cruciferous weeds are hosts, including weeds. An important disease, although the spots are mainly on the outer leaves which are removed before sale.
• Spots with ring patterns, and dark spore masses on underside of leaves. Spots fall out when old. Rots occur on heads of broccoli and cauliflower. Worse in cool areas.
• Seed infection causes damping-off, and lower quality.
• Spread in water splash, wind-driven rain, and in seed.
• Cultural control: seed - hot water (50°C for 25-30 mins.); nursery hygiene: clean trays, pasteurise soil or use soilless mixes, and discard infected seedlings; weed; space plants to allow air movement; avoid overhead irrigation; collect and destroy debris after harvest; crop rotation.
• Chemical control: seed - captan or thiram; field - copper, mancozeb, chlorothalonil.

Cabbage black leaf spot

Alternaria brassicicola. Another Alternaria fungus, Alternaria brassicae, grey leaf spot, also occurs, and causes similar symptoms (see Fact Sheet no. 310). Microscopic examination of the spores is needed to distinguish between the two species (Photo 5).