Doses de ácido giberélico na produção e qualidade de laranja Natal no estado de São Paulo, Brasil

Abstract

The growth and importance of the Brazilian citrus industry in the world involves the introduction of technologies such as the use of plant regulators such as gibberellic acid (GA₃). The effects of doses of 0, 5, 10 and 15 mg L^-1 of GA₃ (Pro-Gibb^®) associated with the surfactant Silwett L-77^® at 0.5 mL L^-1 were evaluated in an experiment by spraying the plants of a Natal orange orchard in the northern region of the state of São Paulo, Brazil. The treatments were applied annually, for two years, when the fruits were still fully green, but before the flowering of the next crop. The results showed, at the picking period, that the treatment of Natal sweet orange trees with gibberellic acid associated with silicone surfactant, reduced fruit abscission due to the lesser force needed to detach the fruits from the plants and significantly increased the peel resistance to puncture; The maintenance of the greener color of the orange peel, evaluated using a colorimeter, make them less attractive to fruit flies and make it possible the delay on insecticides treatments for flies control. Additionally, it allows the delay on harvesting by storing the fruits on the plants, with staggered harvest beyond the normal period for the variety. It is suggested doses of 5 to 10 mg L-1 GA₃ + surfactant (0.05% L77) to obtain the best responses in oranges of Natal cultivar, in the lowest possible dose. Treatments with GA₃ did not affect the productivity of the Natal sweet orange orchard, as well as the maturation and technological quality of the fruits.