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72 p r a c t i c a l w i n e r y & v i n e ya r d J U ly 2 0 1 4 W I N E G r o W I N G bloom. The acceleration of ripening cannot be underscored enough; in 2012 the block was picked 130 days post-bloom. At the outset of the experiment, our hope was to separate healthy vines from those with virus. Unfortunately, multiple leafroll strains (or more insidious viruses) are spread throughout the block (Figure 7). Their involvement in the ripening kinetics (pH especially) cannot be ignored, but also cannot be quantified at this time. What might be misconstrued as a com- pensation effect by vines that were thinned earlier was actually an increase in ripening and growth rate. The interval between treatment and control berry weight peak and harvest date was nearly identical (a gap of 20 days). Peak berry weights differed by 0.05 grams, but when peaks are compared together they are not significantly different. In this experiment, it appears that the phenomena previously described as compensation is actually due to acceler- ated ripening. During this period, more fermentable sugars were produced, more anthocyanin was synthesized and degra- dation of tannin early in the growing sea- son was more rapid, while having slightly less overall vine water demand. Further tannin analysis showed that although control-vine tannins were less sticky, they contained more total tannin than treatment vines. Control vines also synthesized more tannin in the skin, which were also more polymerized than control vines. However, there were no differences in wine or seed tannin concentration, or polymerization. Previous studies have shown that more polymerized tannin have a greater tendency to bind to cell wall material (more sticky), and are then not able to be extracted into wine during maceration. 2 We hypothesize that the earlier thin- ning pass had two effects on the vines, physiologically: • The treatment accelerated the onset of véraison, and thus altered the timing of the end of tannin synthesis and the start of anthocyanin synthesis, leading to ber- ries that were "flavor ripe" sooner. • The treatment also increased the speed of sugar synthesis — with little effect on other ripening parameters — leading to berries that were "sugar ripe" sooner. Conclusion For Lytton Estate Block X in 2013, the lag- phase thinning appears to have been a major success for the wines produced from this block, as it has been selected for a flagship wine for the first time. In 2014, we are executing a similar study on a much healthier ranch with the potential to produce higher yields than Lytton Estate Block X. Perhaps on more vigorous vines we may observe a true compensation effect. However, in most underperforming, inconsistent or virused Zin fandel blocks, we plan to implement lag-phase thinning as a stan- dard policy, starting in 2014. PWV Berry Weight ★ Denotes significant differences 3.0 2.5 2.0 1.5 1.0 0.5 45 75 90 105 120 135 150 60 Days post bloom Control Treatment Average weight (g) ★ ★ ★ Figure 3. average single berry weight (n = 300) taken from the trial areas. Brix, pH 30 25 20 15 10 5 0 5.0 4.5 4.0 3.5 3.0 2.5 45 65 85 105 125 145 Days post bloom 2013 Treatment Brix 2013 Treatment pH 2013 Control pH 2013 Control Brix Brix pH Figure 4. Brix and pH data from early July through harvest. Figure 7. Sampling areas, sap flow sensors overlaid on red leaf symptoms.