DIV Model following Shane and Teng
Wolf P.F.J. et al (2001) were looking for the influence of moisture to the epidemiology of C.beticloa agin. Their findings are very much similar to the findings of other researchers before. Shane and Teng (1985) formulated their Cercopsora Model on base of the humidity needs of the disease. The DIV model is looking for the hours with relative humidity higher than 85% or with leaf wetness. On base of the number of hours and the average temperature during this period it points out a DIV (daily infection value) for this day. Depending on the susceptibility of the variety an accumulated div value over two consequitive days of 6 or more will indicate the need of the first spray. If we have more resistand varieties will can wait for higher accumlated DIV values on consequitive days. In our excample below we would spray susceptible varieties in the middle of June and more resistant vareities we could wait until the middle of July.