INCREASING THE YIELDS OF VICTORIA PLUM WITH HORMONE SPRAYS
Excessive fruitlet abscission in late May and June, frequently the cause of poor Victoria plum yields, was considerably reduced by sprays of GA3 + 2,4,5-TP at 4 and 6 weeks after 50% petal-fall. Yields were more consistent, and cumulative yields increased, following annual sprays of GA3 (75 ppm) + 2,4,5-TP (10 ppm). Good fruit size and quality were maintained throughout the 3-year experiment. Although floral bud numbers were reduced by the treatments in some years, regular spraying of trees resulted in no decline in cropping. Endogenous IAA in fruitlet seeds changed from the esterified to the free form during fruit development. ABA levels in fruitlets increased until late May then slowly declined; levels in seeds declined rapidly during June.
Webster, A.D. and Treharne, K.J. (1983). INCREASING THE YIELDS OF VICTORIA PLUM WITH HORMONE SPRAYS. Acta Hortic. 137, 297-306