Worldwide distribution. On plants in the cabbage family, especially Chinese cabbage and mustards. Important fungal disease, similar to cabbage black leaf spot (see Fact Sheet no. 133).
Damage: (i) seed infections cause pre- and post-emergence damping-off (seeFact Sheet no. 47); (ii) seed infection; and (iii) spots on head and/or outer leaves unsightly reducing quality and shelf life.
Grey leaf and stem spots, circular or irregular, mostly between veins, up to 25 mm diameter, with concentric rings, producing spores below. Centre of spots fall out with age.
Dark, sunken rots occur on heads of broccoli and cauliflower.
Spread by water splash, in wind-driven rain, on seed.
Cultural control: seed - hot water (50°C for 25-30 minutes; 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 - chlorothalonil, copper or mancozeb.