Give those young trees a little attention now before you get busy. Growers may want to consider cluster thinning to control of crop size to balance the amount of fruit to vegetative growth. This is especially important if vines were stresses by drought last year. An optimum balance leads to maximum yields of high quality fruit and adequate vine growth for consistent productivity. Excess fruit production leads to poor fruit quality and reduced vegetative growth, resulting in lower potential production in the future.
Younger vines are particularly susceptible to weakening due to overcropping.
The first step in determining if crop reduction is necessary is to estimate the potential yield. To determine how much fruit a vine will yield, count the number of clusters and estimate the cluster weight based on cultivar and past performance of the vineyard. Multiply average cluster weight by number of clusters, then by number of vines to determine yields per acre. Cluster size is largely determined by genetics of the cultivar and is relatively consistent from year to year, however, factors that affect fruit set can have an effect on cluster weight. This is particularly true of pre-bloom cluster thinning.