Allium white rot (AWR) caused by the fungus Sclerotium cepivorum is a major soilborne disease of onions and other Allium crops. The disease is very difficult to control as the pathogen forms long-lived survival structures known as sclerotia which remain in the soil for decades. These sclerotia germinate and infect roots through hyphae in response to specific chemical compounds released from onion roots. This results in wilting and subsequent plant death during the growing season with more sclerotia being produced and returned to the soil.

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White rot research

Research has focussed on understanding the biology and epidemiology of S. cepivorum, particularly the condtions required for the germination of sclerotia. Novel control approaches are also being investigated including microbial biological control agents and the use of garlic products to artificially stimulate the sclerotia to germinate in the absence of a crop host, thereby depleting their reserves and reducing their survival in soil.

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Research Projects

• AHDB FV449b Onions: Investigation into the control of White Rot in bulb and salad onion crops (2018-2022)
• Defra HH3230SFV: Factors affecting the inoculum potential of soilborne plant pathogens (2005-2009)Link opens in a new window
• HortLINK HL0176 LFV: Integrated Allium white rot control using composts and Trichoderma viride (2006-2009)Link opens in a new window
• Defra HH3204SFV: Integrated use of biological control agents for sustainable control of Allium white rot (2002-2005)Link opens in a new window

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Publications

• Clarkson JP, Scruby A, Mead A, Wright C, Smith B, Whipps JM (2006) Integrated control of Allium white rot with Trichoderma viride, tebuconazole and composted onion waste. Plant Pathology 55, 375-86.
• Coventry E, Noble R, Mead A, Marin FRM, Perez JA, Whipps JM (2006). Allium white rot (Sclerotium cepivorum) suppression with composts and Trichoderma viride in relation to sclerotia viability. Phytopathology 96, 1009-1020.
• Clarkson JP, Mead A, Payne T, Whipps JM (2004) Effect of environmental factors and Sclerotium cepivorum isolate on sclerotial degradation and biological control of white rot by Trichoderma. Plant Pathology 53, 353-62.
• Clarkson JP, Payne T, Mead A, Whipps JM (2002) Selection of fungal biological control agents of Sclerotium cepivorum for control of white rot by sclerotial degradation in a UK soil. Plant Pathology 51, 735-45.
• Clarkson JP, Whipps JM, (2002). Control of sclerotial pathogens in horticulture. Pesticide Outlook 13, 97-101.

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Further information

Please contact john.clarkson@warwick.ac.uk