FLOWERING AND FRUITING IN PATTERSON APRICOT (PRUNUS-ARMENIACA) IN RESPONSE TO POSTHARVEST APPLICATION OF GIBBERELLIC-ACID

In July or August of 1988 and 1989 which was approximately 2 or 6 week s, respectively, after fruit harvest, cultivar 'Patterson' apricot (Pr unus armeniaca) trees were sprayed with a single spray of either 10, 5 0 or 100 p.p.m. gibberellic acid (gibberellin A(3), GA). GA sprays of 100 p.p.m. applied in early July reduced flower number per centimeter of limb length in the year following treatment. Flower number per cent imeter of limb circumference was reduced by sprays of 50 and 100 p.p.m . GA applied in July. Fruit set was not affected by GA sprays. The yie ld and fruit number of hand thinned trees was equivalent to that found on trees treated with 50 and 100 p.p.m. GA sprays in July. Individual fruit weight (size) was increased by GA sprays of 50 and 100 p.p.m. i n July compared to hand thinned trees. Fruit maturity was advanced whe n yields were reduced by GA sprays. In July, GA sprays of 10 p.p.m. re sulted in increased individual fruit weight without reduced total yiel ds per tree compared to non-thinned control trees. Results showed that the use of GA sprays the year before flowering (July) decreased flowe r numbers, eliminating the need for chemical or hand fruit thinning of 'Patterson' apricot.