Dr John Clarkson of Warwick HRI, speaking at last month's Onion & Carrot Conference in Peterborough, told growers that research work by himself at Wellesbourne in conjunction with ADAS had shown that temperature and soil moisture were largely responsible for the germination of S sclerotiorum sclerotia.
Sclerotia produce apothecia - the mushroom-like airborne ascospores that infect a range of crops including lettuce, carrot, Brassicas, peas and beans.
The research work has shown that they require warm and humid conditions to germinate. The forecasting model will therefore predict when these ascospores are present so that growers are able to time their fungicide applications accordingly.
Clarkson remarked: "Timing applications is difficult because sprays must be applied before infection occurs as the available fungicides have little or no curative effect." He added: "We believe that this model has some potential."
He said tests on commercial lettuce crops showed that a single fungicide spray timed according to their forecasting model was found to be more effective than a oneor two-spray programme applied early or mid-crop.
However, Clarkson warned growers that using this information as a fail-safe way to predict Sclerotinia disease risk may be difficult because these conditions regularly occur in "microsites" on the plants.