Effect of Split Applications of GA3 on Flowerbud Density of Mature Peach Trees

Abstract

The effect of divided GA3 applications on flowerbud density was investigated using mature `Redhaven' and `Sweet Sue' peach trees treated at 6, 12, and 24 g/acre in 1994 and `Redhaven' and `Loring', treated at 12, 24, and 48 g/acre in 1995. Flowerbud densities were found to be reduced, except in the cultivar Sweet Sue, which had poor vegetative vigor. The reduction averaged 10% for the 48 g/acre, single, and 32% for the split application of the same rate. For both `Loring' and `Redhaven', it was the basal most 10 cm that showed the largest effect of the split applications, flowerbud density was 86% (single) vs. 28% of control (split) for `Loring' and 94% vs. 42% for `Redhaven'. For the rest of the shoot the differences were not as marked, but were larger for the younger, more vigorous `Loring'. Vegetative bud densities were found to be increased in all cultivars, with the split applications showing a larger effect. The increases were most marked in the distal most 10 cm of the shoots, at the 48 g/acre rate densities were 127% vs. 195% of control for `Loring' and 159% vs. 233% for `Redhaven'. Other growth characteristics (node and blind node density, shoot length) were also evaluated, but significant changes were rarely found. Comparing the number of flower- and vegetative buds per node revealed that the GA3 applications were effective on nodes that had formed 10 to 15 nodes prior to the number of nodes present at spray application. The effect of split GA3 applications was visible on a larger number of nodes, showing that split applications were able to affect a larger portion of the continuously elongating shoot.