CONTROL OF BOTRYTIS FRUIT ROT - INFLUENCE OF FLORAL STAGE AND NUMBER OF CHEMICAL SPRAYINGS

The main fruit rot disease in strawberries is grey mould (Botrytis cinerea). Three-year trials were carried out in 2006-2008 to examine the influence of the floral stage (0, 20, 40, 60, 80 and a 100% blossom opening) and the frequency of applications during the flowering period (1, 2, 3, 4 and 5 sprays). The weather conditions showed large variations among the three years. 2006 was characterized by heavy rainfall during flowering and a dry harvest season. In 2007 the rainfall started in the middle of the flowering period and stayed until the end of harvest, with severe problems with Botrytis fruit rot in the commercial strawberry fields. In 2008 we had only some rain during flowering, but replicated rainfall during the harvest.
Single applications had an effect against Botrytis at any time; however spraying at 60% flowering was most effective. In terms of application frequency, good results were achievable with as few as three sprays (25, 50 and 75% flowering). A sequence of four applications (20, 40, 60 and 80% flowering) gave only marginal further improvements to Botrytis control.