Calculate cDIV threshold for sugar beet cultivars

This function was written using summary data from Wolf and Verreet (2005), Table 1 and Table 2 to determine the equivalent cumulative daily infection value where epidemic onset begins. The average difference between 'high' and 'low' susceptible cultivars was 1.2 on the variety scale. The average difference between low and highly susceptible cultivars minimum cDIV on each starting time in Table 2 was 4.637.

Usage

calc_susceptibility(var_scale = 4)

Arguments

var_scale

numeric, bsa scale (1-9) of the sugar beet cultivars. 1 is the lowest susceptibility and 9 is the highest susceptibility. See https://www.bundessortenamt.de and Wolf and Verreet (2005) Table 1.

Value

numeric, cDIV threshold for the start of the epidemic