Table 2 Tercile disease ranges and cluster counts used for percent photosynthetic photon flux (% PPF) categorical comparisons at each location. The 1st tercile range is lowest one-third of all mean disease severity ratings for individual vines or panels (10 clusters/unit); the 3rd tercile range is highest one-third of all mean disease severity ratings. The data show the range of disease severity for the tercile in each experiment. Cluster count for each vineyard is the number of clusters for which a %PPF was calculated by CEFA in the EPQA model.