Alternate bearing is an important problem of 'Montenegrina' mandarins (Citrus deliciosa Ten.). The aim of this work was to supress flower bud formation in 'off' or light crop years and thereby reduce biennal bearing. The experiment was carried out from april 2004 to august 2005, in Eldorado do Sul - RS, on a twenty-year-old orchard with trees budded onto Poncirus trifoliata Raf. Ninety six trees were rated as having very light fruit load. A randomized blocks experimental design with 3 x 4 factorial scheme with two plants per plot and four replications was used. The trees were sprayed with 0, 20, 40 e 60 mg.L-1 GA3. The foliar applications were made on April 30, May 20 and June 10, at the two years. GA3 did not suppress flowering and the number of fruits per tree and yield were not affected by the treatments. Histological studies on bud longitudinal sections, realized every fifteen days in 2005, between April 30 and August 30, showed that the period of flower bud differentiation, with emission of the first sepals, only occurs on the first half of August. This indicates that the induction of floral diferenciation may occur in july, after the timings of GA3 spraying in this research.
Citrus deliciosa; biennal bearing; flower bud differentiation; gibberellic acid
