The influence of bloom thinning and GA3sprays on flower bud numbers and distribution in peach trees

Bloom thinning mature peach trees increased shoot growth on sample limbs of 7.5-11 cm circumference by 53% when compared with trees hand thinned 44 days after full bloom (AFB). The number of flower buds per limb was increased by 103%. Bloom thinning increased the number of shoots which were 20 to 50 cm long by 86%. The number of buds on the basal five nodes of shoots 7-20 cm long was more than 2.2 times that of hand thinned trees. Shoots 7-64 cm long had more buds per cm shoot length. Application of 100 mg I"1 GA3, 0, 12, 36 and 47 days AFB inhibited flower buds and reduced the subsequent year’s cropping. Applications of GA3 36 and 47 days AFB inhibited flower bud development on short shoots more than when applied at 0 or 12 days AFB. None of the GA3 treatments affected flower bud development on the upper half of long shoots, but reduced numbers on short shoots. Fruit on long shoots were larger than those on short ones, and fruit on the upper half of all shoots were larger than those on the lower half. Later GA3 sprays resulted in more fruit on the upper half of all shoots. Flower buds were inhibited more strongly on short shoots.