Immediate post-bloom through about 3 weeks post bloom is the most effective time for leaf removal on tight clustered varieties such as Vignoles, Seyval, and Pinot gris. That time will be coming up soon in southern Indiana. Removal of 3 to 5 leaves in the cluster zone can greatly reduce risk of Botrytis bunch rot. Exposure to sun makes the berries less susceptible to Botrytis and allows more rapid drying after rain or dew. Spray penetrate in the cluster zone is also improved. Leaf removal also improves fruit quality in aromatic varieties such as Traminette, and most red varieties, where sunlight exposure improved anthocyanin development. Delaying leaf removal increases the risk of sunburn, as does removal of too many leaves, especially on the west side of the canopy. Most growers remove leaves only on the east side (on north-south rows).
Post bloom leaf removal in the cluster zone on VSP trained vines.