Integrated Allium white rot control using composts and Trichoderma viride

Project Headlines • Allium white rot (AWR) disease results in 15% onion yield loss in the UK. This can be reduced by Windrow Onion Waste Compost (OWC) treatments or T. viride S17A- colonised green waste compost.

• Windrow treatments applied 18 months prior to planting reduce AWR disease and give an onion yield of at least three times higher than Folicur-treated sets.  Folicur is under threat from the new EU legislation  (Directive 91/414)

• T. viride S17A-colonised green waste compost  applied 2-4 weeks before set planting controls AWR disease for up to 2 onion growing seasons, and gives comparable or higher yields to Folicur-treated plots

Action points for growers

• Semi-commercial scale production and application of T. viride S17A-colonised compost is currently being conducted.  If successful, the treatment should be available to growers from 2010.
• Windrow composting is an effective method of onion waste disposal and the resulting compost can be used to suppress AWR on infested land.

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  Growers should reduce organic fertiliser applications to land where composts are applied.

Allium white rot (AWR) caused by the sclerotium-forming fungus Sclerotium cepivorum is a major soil-borne disease affecting Allium crops.  A loss of 15% of the UK onion crop due to this disease equates to approximately £7M per annum. 

In addition, in some heavily infested areas in the UK, land has been taken out of production.  The efficacy of AWR control with fungicides can be variable and tebuconazole (Folicur) is under threat from new EU legislation (Directive 91/414).  Alternative control measures for AWR are therefore required. 

Objective 1: Determine the ability of various green waste composts to support the growth and proliferation of T. viride S17A and assess the enhanced composts for their ability to destroy S. cepivorum sclerotia and control AWR.

Objective 2: Develop a method to apply T. viride S17A to onion sets and assess the ability of this treatment to control AWR.

Objective 3: Determine the ability of sulphur-containing composts produced from different waste streams to destroy S. cepivorum sclerotia and reduce AWR and identify any physical and chemical properties including sulphur content and volatile sulphur-containing compounds as factors influencing the efficacy of the composts.