Controlling growth of ‘Delicious’ apple trees with low- dosage applications of Uniconazole or BAS111

Abstract

Foliar applications of 30, 60 or 120 mg I-1 uniconazole were made to ‘Delicious’ apple trees at full bloom or one, two or three weeks after full bloom. Application at full bloom reduced fruit weight and length/diameter ratio more than when applied two or more weeks after full bloom. In another experiment, a single application of uniconazole was applied to ‘Delicious’ trees three weeks after full bloom at 15, 30, 60, 120, 240 or 480 mg I-1. Posages of 240 or 480 mg I-1 controlled vegetative growth to about 50% of the control values at ten weeks after treatment. Thereafter, the rate of shoot elongation was similar to that of the controls. The lowest dosage to reduce vegetative growth was 15 mgl-1. In a third experiment, uniconazole was compared with BAS111 for controlling vegetative growth of ‘Delicious’ trees. Uniconazole or BAS111 applied six times at 350 mgl'1 reduced growth to 46% and 81% of that of the controls, respectively. Increasing the rate of surfactant from 0.1% to 1.0% reduced growth by an addi...