Canopy manipulation of Okanagan Riesling vines for improvement of winegrape quality

Vigorous, Geneva Double Curtain-trained Okanagan Riesling vines were subjected over a 2-yr period (1987–1988) to four canopy manipulation practices: shoot positioning; shoot positioning plus postbloom hedging to 12 leaves per shoot; basal leaf removal; and an untreated control, in combination with the presence or absence of iprodione (Rovral 50WP) fungicide sprays. Shoot positioning and shoot positioning plus hedging reduced weight of cane prunings relative to control vines in 1988, but increased yield, cluster weight, and berries per cluster. Shoot positioning, shoot positioning plus hedging, and basal leaf removal reduced °Brix in 1988, but tended to reduce titratable acidity in both seasons. Shoot positioning plus hedging reduced pH in 1987, while shoot positioning and shoot positioning plus hedging reduced pH and potassium (K + ) in 1988. Neither Rovral nor canopy manipulation appeared to have any significant impact on the percentage of bunch rot-affected clusters. Shoot positioning of Geneva Double Curtain-trained Okanagan Riesling is recommended as a method to reduce titratable acidity, pH and K + , hence improving potential winegrape quality.Key words: Vitis, grape, hedging, shoot positioning, leaf removal, canopy management