Issue link: http://winesandvines.uberflip.com/i/573907
66 P R A C T I C A L W I N E R Y & V I N E YA R D October 2015 S M A R T V I T I C U L T U R E France, cut off higher, at 18 inches, and the dead trunk was useful support for replacement suckers and plastic vine guards during retraining. Whichever height is chosen, this should be approxi- mately 8 inches below any staining on the most affected vines. Aims and application of TTR Given that "trunk/cordon renewal" is an accepted strategy for trunk disease (in the sense that the infection may be removed), the pertinent question is when should it be applied? Should the process be initiated with observation of the first dead cordon or vine? Or, should one wait until the disease is seen to be more widespread throughout the vineyard (10% or 20% symptomatic vines). Should only the very devigorated vines be treated with trunk renewal, or perhaps should adjacent vines showing the very first symptoms— or even no symptoms—be included? There is the question of what should be done, and to how many vines? Removing all trunks in one year will cause obvious crop loss, yet some growers are inclined to treat all vines in a block the same way, even though they may suspect that infec- tion varies. Other growers compromise by doing portions of a block in consecu- tive years (including replacement of training wires), to spread out yield loss. In any event, the most expensive way of treating trunk disease is total trunk renewal in a block, as it involves unnec- essary crop loss for the sake of "man- agement uniformity." Sucker training to new trunks and arms can precede trunk removal, and no crop need be lost. Replacing the removed vine framework is achieved more quickly with two new trunks, although I understand that some Figure 3. A 30-year-old Sauvignon Blanc vine in Martinborough, New Zealand. Were the trunk not renewed 10 years ago, it would have died from trunk disease. Now it is healthy. RICHARD SMART Low infection Medium Infection High Infection Table 1 (0% – 2%) (2% – 10%) (more than 10%) Low risk 1 2 3 Medium risk 2 3 3 High risk 3 3 4