Timing of Zinc Foliar Sprays. I. Effects of Application Intervals Preceding and during the Bloom and Fruit-Set Stages. II. Effects of Day VS. Night Application

Foliar zinc sprays were applied to three trial vineyards (cvs Thompson Seedless, Petite Sirah, and Muscat of Alexandria) at various intervals beginning with a fall spray in October 1977 and then at weekly intervals in the following spring. The spring treatments started four weeks prebloom and continued to the fruit-set stage. Vine response as measured by fruit-set and development at harvest was maximum from sprays applied two weeks prebloom through full bloom. Some earlier and later spring treatments also responded, although degree and consistency were less. The fall sprays gave little or no response. Day (1:00 PM) vs. night (11:00 PM) spray applications were compared in a Thompson Seedless vineyard. Both treatments gave similar responses as measured by shoot-tip zinc levels, berry analyses, and fruit yields.