- 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 (see Fact 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.
Pacific Pests, Pathogens, Weeds & Pesticides
Cabbage grey leaf spot (310)
Photo 2. Grey leaf spot, Alternaria brassicae, on cabbage. Note the concentric rings typical of Alternaria infections.
Cabbage grey leaf spot
Alternaria brassicae. Another Alternaria fungus, Alternaria brassicicola, cabbage black leaf spot, also occurs, and causes similar symptoms (see Fact Sheet no. 133). Microscopic examination of the spores is needed to distinguish between the two species (Photo 4).
AUTHOR Grahame Jackson and Eric McKenzie
Information from Diseases of vegetable crops in Australia (2010). Editors, Denis Persley, et al. CSIRO Publishing; and 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) Eric McKenzie (2013) Alternaria brassicae: PaDIL - (http://www.padil.gov.au). Photo 1 Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org. Photo 2 Yuan-Min Shen, Taichung District Agricultural Research and Extension Station, Bugwood.org. Photo 3 Howard F. Schwartz, Colorado State University, 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.