USE OF HYDROGEN CYANAMIDE FOR APPLE AND PLUM THINNING

Effects of various concentrations of Dormex (a.i. 49% hydrogen cyanamide) on fruit thinning of 'Rome Beauty' apple (Malus domestica Borkh.), 'Friar' and 'Simka' plums (Prunus salicina Lindley) were studied. A full bloom application of Dormex at all tested concentrations decreased 'Rome Beauty' apple fruit set and yield, and increased fruit weight. Dormex at 0.25% (v/v) resulted in adequate apple thinning, indicated by production of an optimum fruit weight (320 g). Prebloom and full bloom applications of Dormex at greater than 0.75% reduced plum fruit set and yield in 'Friar'. Full bloom application of Dormex at 0.50% showed a satisfactory fruit set, yield, and fruit weight in 'Friar' plum. Prebloom Dormex application had no significant effect on 'Simka' plum fruit set or yield, but full bloom application decreased fruit set and yield.