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GRAPE GRO WING Leaf pulling View video in the Wines & Vines Digital Edition. Clay Shannon discusses using a flock of sheep to perform leaf pulling. is done early. Reduction of "green" flavors caused by methoxypyrazines occurs with early thinning, resulting in riper fruit fla- vors that wine drinkers like. By veraison you will have to drop almost half the crop to accelerate ripening. The same message applies—dropping fruit by about 25% three weeks after fruit set will give you the maximum benefits of concentrating flavors, accelerating ripening and creat- ing favorable vine balance. The longer you wait, the more fruit you will have to drop to get positive ripening results and an ear- lier harvest compared to vines that are not thinned at all. Shoot thinning Removing sterile shoots is often a practice used to improve airflow around clusters as part of an IPM program to reduce powdery mildew. If done early for varieties that tend to have numerous buds emerge along the cordon (Cabernet Sauvignon and Sauvi- gnon Blanc are particularly prone to this), it probably saves money at pruning time and makes handpicking easier, as it reduces stem congestion. The practice may also let more light into the canopy. It probably makes no difference in advancing or delaying ripen- ing, nor improving flavors or color. It may change fruit-to-shoot ratios. If you are go- ing to remove shoots, you should do it early in the season, when shoots are small and it is a relatively simple job. Green drop Winegrowers often remove green fruit at veraison hoping to make fruit more uni- formly ripe at harvest. Overall, dropping green fruit at veraison evidently has a similar effect as fruit thinning and doesn't necessarily improve ripe fruit uniformity. Studies of Pinot Noir, Cabernet Sauvignon and Syrah compared three treatments: dropping green fruit at veraison, dropping randomly selected clusters (both green and red) and a control. The two treatments that involved removing clusters accelerated rip- ening and color compared to the control. Randomly sampled clusters from the two fruit removal treatments were evaluated at harvest and did not show a significant dif- ference in uniform fruit maturity. WINES & VINES SEPTEMBER 2012 73 Leaf pulling has definite benefits for im- proving airflow around clusters to prevent powdery mildew and botrytis. In coastal climates with less sunlight, leaf pulling may help improve fruit color. It also helps to improve spray penetration: If you can't see the fruit, it is unlikely that any spray will reach it as effectively as if there had been leaf removal. It is a pretty routine practice with vigorous three-wire "Califor- nia sprawl" systems, for which high fruit quality is expected. Vineyards trained for vertical shoot po- sitioned (VSP) trellis systems typically have good light penetration, and leaf removal may not be needed in sunny and warm cli- mates. In fact, extreme leaf removal is more likely to result in sunburned fruit, which can reduce color and produce over-ripe fruit fla- vors described as "raisin/prune/fruitcake" by some winemakers. Sunburned fruit also may ripen through dehydration, creating unbalanced fruit chemistry with high sug- ars and high acids that result in unbalanced wines. Sunburned bunches should be sorted