Experience on Vitimeteo-OiDiag in Southern Germany

Abstract: In 2010 and 2011, powdery mildew (P.M.) caused severe problems in a lot of vineyards in Southern Germany. About 200 vineyards planted with susceptible varieties were selected randomly and evaluated for P.M.-disease severity. All growers were carefully questioned on their spray schedules and the used spraying technique. Organic as well as non-organic cultural practices ranging from small to large estate vineries were included. Furthermore a broad range of spraying techniques was used. Using data of the nearest representative Vitimeteo-station, we counted the number of gap-days (gap-days = number of days, for which OiDiag-rules were passed) differentiated for the two OiDiag-Tools tool-1: gap days before first spray, tool-2: sum of gaps starting after the first spray. In 2010, no gaps could be detected for tool-1, yet a highly significant correlation between the numbers of gap-days for tool-2 and P.M. severity was found. In 2011, similar results were found for all varieties except Trollinger (= Vernatsch). We suppose that overseen P.M. in the previous year in the neighbourhood of the small scattered Trollinger vineyards caused these problems. Thus, we propose not to use tool-1 until the problems are cleared up otherwise the complete OiDiag system is endangered. Yet, tool-2 proved to be very helpful for the growers and should be consequently applied in future.