No abstract

Abstract. In the last decade, impacts of climate change on cool climate viticulture were most obvious concerning cluster infections caused by Botrytis cinerea, the causal agent of grey mould. The control of primary and secondary fungal pathogens is economically most important since bunch rot may severely affect the annual harvest with regard to quality and quantity. Trials with UV C applications, a new approach to control bunch rot, were conducted in 2013 and 2014, representing years with intensive bunch rot epidemics. UV C irradiation was applied by a prototype at an experimental site of Hochschule Geisenheim University. At both canopy sides, leaves and cluster zones were irradiated repeatedly at a dose of ≤160 mWs/cm 2 alone or in combination with chemical control. The results of our experiments indicated that irradiation with UV C, in addition to fungicide treatments at reduced number of applications, was able to significantly decrease infection with grey mould to a degree of efficiency of 82% compared to standard chemical treatment that achieved 51% efficiency in 2014. Accordingly, the new technology is suitable for reducing cluster infection with mould fungi allowing a prolonged grape ripening time, which leads to a better harvest quality and a decreased yield loss.