Sooty blotch and fly speck model for apple

There are several versions:
The simplest version and original version is by Brown and Sutton, North Carolina State University:
The model begins 10 days after petal fall. If a wetting period, rain or heavy dew exceeds 3 hours, the number of hours is recorded. The first symptoms are expected when the accumulated hours of wetting reaches the range of 240 to 290.

There is a version of this model that estimates that rainfall amount and fungicide application information can be used to predict flyspeck appearance. This is a quote from an article by Dave Rosenberger of Cornell University in the Scaffolds Newsletter "Five days later, and after exactly 270 hr of accumulated wetting counting from the fungicide wash-off date of 22 Aug., incidence of flyspeck jumped to 27-64% in all except the Pristine plots. Data from this trial suggests that none of our fungicides (with the possible exception of Pristine) will provide fruit protection through more than 2 inches of rain, and the results verify the accuracy of the 270-hr incubation period for flyspeck."