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Abstract
The effects of delayed pruning timing and bud number per cane (magnitude) on crop yield and fruit composition were evaluated in Chardonnay, Merlot, and Lomanto winegrape cultivars. Canes were “pre-pruned” to 5 or 10 buds in ‘Chardonnay’ and ‘Merlot’ and 4 or 8 buds in ‘Lomanto’. Vines were then pruned to two-bud spurs based on the developmental stage of the apical bud (E-L 4 or E-L 11). Overall, timing affected yield, magnitude had no effect, and chemistry was unchanged. In years without late spring frosts, delayed pruning reduced yield by 26.12%, 26.38%, and 20.94% in ‘Chardonnay’, ‘Merlot’, and ‘Lomanto’, respectively. Yet, delayed pruning (E-L 11) yielded 40.74% (‘Chardonnay’) and 72.40% (‘Merlot’) more than control when late frost was recorded. Delayed pruning at E-L 11 could be advantageous to maintain yield in areas prone to late frosts. However, if spring frost events are uncommon, proactive mitigation strategies may be unnecessary.