INFLUENCE OF LEAF REMOVAL FROM THE FRUIT CLUSTER ZONE ON THE COMPONENTS OF EVAPORATIVE POTENTIAL WITHIN GRAPEVINE CANOPIES

Removal of leaves from around grape clusters reduces development of botrytis bunch rot. In past laboratory experiments, growth of Botrytis cinerea was negatively vffected by evaporative potential, the capacity of air to evaporated water. In the present study removal of leaves around clusters in grapevine canopies increased evaporative potentials significantly over those in canopies in which leaves were not removed. The relationships between evaporative potential and other microclimatic variables were evaluated. Vapor pressure deficits were very similar in grapevine canopies with or without leaves removed from around grape clusters, but wind speed was significantly greater around clusters where leaves were removed. The significant increases in evaporative potential associated with removal of leaves were correlated with increases in wind speeds within canopies. In contrast, the evaporative potential above the vineyard canopy was influenced most strongly by vapor pressure deficit and to a lesser extent by wind speed. Evaporative potentials within vine canopies were predicted accurately by wind speed and vapor pressure deficit using multiple-regression methods. Evaluations of these relationships and their impact on disease should provide insight into possible manipulations of other cropping systems to control disease. © 1990.