Chemical control of tree growth of plum (prunus domesticaL.). I. Preliminary studies with the growth retardant paclobutrazol (PP333)

Abstract

SummaryFoliar sprays of paclobutrazol (PP333) reduced the total new shoot growth on three European plum cultivars. High-volume sprays (3 000 mg l-1 applied once, or 1 500 mg l-1 applied twice) in May or early June reduced the numbers of extension shoots on Grove’s Late Victoria and similar sprays to Laxton’s Cropper and Marjorie’s Seedling reduced the mean shoot length. Soil drenches of paclobutrazol (4 kg ha-1) applied in May also slightly reduced the current seasons’s shoot growth of Laxton’s Cropper and Marjorie’s Seedling; drenches applied to the former cultivar had an even stronger effect in the subsequent season. Two sprays of GA3 (75 mg l-1) + 2,4,5-TP (10 mg l-1) applied four and six weeks after 50% petal-fall, reversed the effects of paclobutrazol on shoot growth of Grove’s Late Victoria, but in the following season the growth of these trees was reduced. Foliar sprays of paclobutrazol severely reduced the yields of Grove’s Late Victoria and this effect was only partially alleviated by sprays of G...