Martin Moran

Pruning after budburst to delay and spread grape maturity

Background and Aims The shift in phenological development is the most conspicuous biological effect of climate change in vineyards worldwide. Associated with the advancement in maturity there has been a compression of the harvest period that places significant pressure on vineyard and winery infrastructure. Our aims were to test the feasibility of using delayed pruning as a tool to delay ripening and decompress maturity, to establish how much pruning can be delayed before compromising yield, and to compare the response of Cabernet Sauvignon and Shiraz. Methods and Results Five pruning dates (from winter up to 3 weeks after budburst) were applied in a commercial vineyard, and we monitored phenology, fruit maturation, and measured yield and its components. The maturation, as determined by sugar concentration, was delayed by up to 3 weeks in Shiraz and by 2 weeks in Cabernet Sauvignon. The yield response varied between pruning dates. The Shiraz vines pruned at the latest phenological stage (E-L 15) recorded a reduction in yield of over 50%; the yield of the other treatments ranged from a 24% reduction to a 55% increase relative to that of the Control. Conclusion Maturity was delayed with mostly neutral or positive effects on fruit composition. Significance of the Study Delayed pruning offers a real and cost-effective tool to allow the Australian wine industry to adapt to climate change by delaying ripening and decompressing harvest.

Late pruning and carry-over effects on phenology, yield components and berry traits in Shiraz

Background and Aims Global warming is shifting vine phenology, compressing harvests and altering the balance of fruit traits relevant to wine. Our aim was to test late pruning as a tool to delay maturity and to assess carry-over effects from repeated late pruning on phenology, yield components, dynamics of leaf area and berry traits of Shiraz grown in the Barossa Valley of Australia. Methods and Results A trial was established in a commercial vineyard comparing three pruning times during four consecutive seasons: (i) winter (Control), (ii) budburst and (iii) 2–3 leaves emerged. Compared with the Control, TSS in berries of vines pruned at 2–3 leaves reached 12°Be 7 days later in the first three seasons, and 14 days later in the last season; the budburst treatment was intermediate between that of winter and of 2–3 leaves. Yield was unchanged by late pruning in three seasons and increased in one. Leaf area index at harvest in 2–3 leaves was greater or similar than in the Control. Late pruning shifted the onset of anthocyanin accumulation against TSS, increasing the anthocyanin concentration and the anthocyanin-to-sugar ratio in two seasons. Conclusion Late pruning delayed maturity with neutral or positive effects for yield and berry traits. Carry-over effects on phenology, yield, leaf area and berry traits were negligible. Significance of the Study In a context of global warming, delaying pruning to 2–3 leaves can effectively spread the harvest and partially restore the anthocyanin : sugar ratio with no penalty for yield in Barossa Valley Shiraz.