- Worldwide distribution. On seeds, bulbs, tubers, fruits and flowers of coconuts, maize, onion, peanuts, rice, and sorghum, and many other hosts. A cosmetic problem.
- A fungus, usually on organic matter in soil, attacks stored fruits, seeds, roots/tubers, if they are wounded. On onions, it infects dying leaves in the field after harvest; from there the bulbs become infected, often along the veins. It also infects onions when “topped” before storage, especially in hot, wet weather.
- Spread occurs as spores in the wind. The fungus is seed borne.
- Cultural control: well-drained land; ensure seed is clean, or treat in hot water (60°C for 15 min.); dry bulbs after harvest, before storage; varietal resistance (those with red scale leaves); collect trash and burn after harvest.
- Chemical control: seed treatment: mancozeb or thiram.
Pacific Pests, Pathogens, Weeds & Pesticides
Onion black mould (187)
Photo 2. Black mould, Aspergillus niger, on onion. The bulb on the left is showing large spore masses, whereas the mild infection on the right is mostly along the veins.
Black mould, collar rot, neck rot
AUTHOR Grahame Jackson
Information (and Photo 2) Diseases of vegetable crops in Australia (2010). Editors, Denis Persley, et al. CSIRO Publishing; and from CABI (undated) Black mould of onion Aspergullus niger. Plantwise Knowledge Bank. (https://www.plantwise.org/knowledgebank/datasheet/7444#SymptomsSection). Photo 1 Kohler F, et al. (1997) Diseases of cultivated crops in Pacific Island countries. South Pacific Commission. Pirie Printers Pty Limited, Canberra, Australia. Photo 3 Black mould, Aspergillus niger 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.