A new weapon is available for farmers plagued by apple scab.
Vinasse, a waste product of the sugar-processing industry, can reduce the unsightly markings on fruit by at least 95 per cent.
Researchers at the University of Wageningen in the Netherlands claim the finding represents a breakthrough for organic growers.
The researchers found that autumn application of vinasse accelerates leaf degradation in the winter, thus reducing the amount of scab fungus in orchards.
Apple scab, caused by the fungus Venturia inaequalis, results in a significant loss of sales each year because the resulting dark brown marks make the fruit unappealing to consumers.
To find the optimum application levels of vinasse, researchers experimented with concentrations equivalent to 50, 100, 200, 400 and 600 litres per hectare. Leaves with scab symptoms were treated with vinasse in autumn and left on the soil to degrade naturally.
In early spring, the leaves were examined for signs of apple scab. The highest reduction in ascospores — more than 95 per cent — was found in leaves treated at a dose level of between 200 and 400 litres per hectare.
Traditionally, organic growers have used copper, sulphur and lime sulphur to combat the disease. But with copper use banned in some countries and the EU set to do likewise, the vinasse research is timely.
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