Vol. 72 No: 4

Title:
Use of Gibberellins on ‘Patterson’ Apricot (Prunus Armeniaca) to Reduce Hand Thinning and Improve Fruit Size and Firmness: Effects over Three Seasons

Authors:
S.M. SOUTHWICK, J.T. YEAGER and K.G. WEIS

pp: 645-652

Abstract:
‘Patterson’ apricot (Prunus armeniaca) trees were sprayed with an air blast sprayer over three seasons (1992, 1993, and 1994) in three application timings prior to and after harvest, with single sprays of 50, 75, and 100 mg l^-1 gibberellic acid (predominantly gibberellin A₃ (GA₃); Release LC, Abbott Laboratories, North Chicago, IL). A single pre-harvest timing (first week of June) and two concentrations (50 and 100 mg l^-1) were consistent across all three years and the effects of these treatments on flowering and fruit development were compared. In all years following treatment with 100 mg l^-1 GA, flower numbers per cm of limb length and circumference were significantly reduced. Fruit set was not affected by GA sprays. June 1993 GA sprays of 50 and 100 mg l^-1 resulted in total yields per tree in 1994 that were equivalent to hand-thinned control trees with 36% and 46% reduction in hand thinning, respectively. Individual fruit weights of fruits treated with 100 mg l^-1 GA sprays were equal to those of hand thinned (untreated) trees in two years out of three, and fruit weight was increased by 100 mg l^-1 GA in a single year. Fruit maturity (colour) was unaffected by GA treatment. Fruit firmness was increased by 100 mg l^-1 GA applied prior to harvest in one year. Use of GA sprays in the first week of June over three seasons decreased flower populations in the following season, reducing the need for hand fruit thinning of ‘Patterson’ apricot, and improved quality, without phytotoxic effects.

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