- 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.
Pacific Pests, Pathogens, Weeds & Pesticides
Cabbage black leaf spot (133)
Photo 1. Roughly circular leaf spots, with concentric rings, mostly between the veins on cabbage caused by black leaf spot, Alternaria brassicicola.
Photo 2. Cabbage leaf spot, possibly Alternaria brassicicola, showing dark brown areas where spores are forming, and a large spot (lower left) with a crack in the centre; later, the crack will widen and the centre of the spot will fall out becoming similar to Photo 5.
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).
AUTHOR Grahame Jackson
Information (and Photo 1) from Gerlach WWP (1988) Plant diseases of Western Samoa. Samoan German Crop Protection Project, Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) Gmbh, Germany; and (including Photo 4) Diseases of vegetable crops in Australia (2010). Editors, Denis Persley, et al. CSIRO Publishing; and Seemadua S, et al. (2011) Alternaria spot (Alternaria brassicicola): PaDIL - http://www.padil.gov.au; and from (including Photos 5) McKenzie E (2013) Alternaria brassicicola: PaDIL - (http://www.padil.gov.au). Photo 4 Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.