Late winter is a critical time period for key pruning decisions in the vineyard. The timing of exactly when to prune can be a tricky bit of prognostication.
The immediate strategy is based on predicting spring bud break because the earlier you prune, the earlier bud break will occur. If bud break happens too early there is danger of damaging the fresh green growth with a late season frost. If bud break occurs too late, there is danger of being behind in the ripening process. The annual pruning date decision can be an educated guessing game. However, there is another determining factor that comes into play which relies on meteorological predictions (which are slightly more accurate than throwing darts at a calendar): the weather.
When it comes to weather forecasts, the important thing to remember is do not prune if there is precipitation on the horizon! Freshly pruned shoots are essentially like open wounds on the vine and any rainfall activates a specific kind of fungus known as Eutypa and causes it to proliferate and emit spores into the atmosphere. These spores can settle into the newly created and vulnerable pruning wounds on the vine and essentially permanently infect the vine. No getting rid of it. Over time, this will cause the vine to produce lower yields as well as decrease the quality of the grapes. Both of these symptoms of infection are obviously terrible for wine production so timing on the pruning once again proves to be of utmost importance.….whew…already the quality of next harvest is on the line!