Effect of Paclobutrazol On Vegetative and Generative Development of Apple-trees and the Shelf-life of Fruits

In 1985 Paclobutrazol was applied on apple trees cvs ''El star'' and ''Gloster 69'' on M9 as sequential (P+P+P: before full bloom, at petal fall and after "June drop"; P+P+:at petal fall and after "June drop") or single (after fruit "June drop") applications spraying a total concentration of 3.240 g/ha ai. In 1986 the same treatments were repeated on half of the trees; residual effects were observed on the remaining trees. In 1985 Paclobutrazol modified fruit drop pattern. Initial fruit set was increased by the earlier sequential application only in ''Elstar''. As a general effect the chemical reduced yield/tree, fruit size and color, delayed ripening and improved fruit keeping quality. Vegetative activity was greatly reduced by the earlier treatments. Paclobutrazol increased fruit bud differentiation in ''Elstar''. In 1986, repeated treatments as well as those performed only in 1985 modified fruit drop pattern and decreased fruit growth rate. Shoot elongation was reduced by the repeated treatments, while, as residual effect of Paclobutrazol applied in 1985, an increased vegetative activity was observed.