USE OF FRUIT ZONE LEAF REMOVAL WITH VITIS-VINIFERA L CV RIESLING GRAPEVINES .1. EFFECTS ON CANOPY STRUCTURE, MICROCLIMATE, BUD SURVIVAL, SHOOT DENSITY, AND VINE VIGOR

Fruit zone leaf removal treatments were applied to Vitis vinifera L. cv. Riesling grapevines at two locations in the temperate Canadian Niagara Region during 1990 and 1991. Leaf removal treatments consisted of a control (no leaf removal), mechanical leaf removal (MLR) treatments applied either on one or both sides (2S) of the canopy, and hand leaf removal (HLR) treatments applied to both sides of the canopy. Treatments were applied early when the berries had reached pea size, late just prior to rapid berry sugar accumulation (veraison) or at both early and late treatment dates. The HLR treatments and to a lesser magnitude the MLR 2S treatments reduced the fruiting zone canopy parameters leaf layer number, percent interior leaves and percent interior clusters at the Grape Research Station vineyard. The effects of the leaf removal treatments at KEW vineyards, however, were limited mostly to the HLR and in a few instances the MLR 2S treatments. Slight differences in fruiting zone temperature occurred only at diurnal temperature peaks. Differences in cluster wetness occurred late in the season when the hand leaf removal treatment had lower values than the other treatments examined. The MLR 2S and HLR leaf removal treatments also improved light penetration into the fruiting zone at both vineyards. With the exception of a slight increase in bud survival at the Grape Research Station vineyard in 1990, there was no influence of the leaf removal treatments on bud fertility, shoot density or vine vigor at either vineyard.