Uso de 2,4-D e GA3 no controle da queda natural da Laiwja "Hamlin"

Abstract

Objetivando retardar a queda natural ou pré-colheita cie laranjas `Hffinlin', aplicaram-se ácida 2,4-dic1orofenoxiactico (2,4-D) e Acid° gibeiélico (GA3) em frutos nos estádios de maturação verde e, ou, em mudança de coloração. Foram pulverizados 2,4-D e GA3, respectivamente, nas concentrações de 20 mg/i, e 10 mgf,. No experimento, utilizou- se o delineamento em blocos casualizados, com cinco blocos e com os seguintes tratamentos: 1) testemunha; 2) 2,4-0, aplicado com os frutos verdes (FV); 3) 2,4-D, aplicado com os frutos em mudança de colora0o (FMC); 4) 2,4-D, aplicados com FV e com FMC; 5) GA3, aplicados com FV; 6) GA3, aplicado com FMC; 7) GAS, aplicado com FV e com FMC; 8) 2,4-D + GA3, aplicado com FV; 9) 2,4-D + GA3, aplicado com FMC; e 14} 2,4-D + GA3, aplicado com FV e com FMC. Avaliou-se a queda natural dos furtos peia contagem semanal de frutos caídos por planta.. O efeito dos reguladores sobre as caracteristicas físicas e químicas dos frutos foi avaliado quinzenalmente, determinando-se diâmetros longitudinal e equatorial, acidez titulável do suco, teor die sólidos solúveis do suco, porcentagem de suco, peso dos frutos, espessura da casca, resistência da casca à penetração da ponteira do penetrômetro e teor de clorofila total na casca.

Aiming to . . delay «pre-harvest fruit drop of “Hamlinª orange trees, 2,4- dichlorophenoxyacetic acid (2,4-D) and gibberellic acid (GA3) were applied on fruits in the following degrees of ripening: green fruits and/or fruits at color break. GA3 and 2,4-D were sprayed, respectively, at 20 mg/L and 10 (mg/L. A complete randomized block design was used with tive replications “and the folloWing treatments: ]) control; 2) 2,4-D, applied on green fruits; 3) 2,4-D, applied on fruits at color break; 4) 2,4-D, applied on green fruits and fruits at color break; 5) GA3, applied on green .zfruits; 6) GA3, applied on fruits at color break; 7) GA3, applied on green fruits and fruits at color break; 8) 2,4-D + GA3, applied on green fruits, 9) 2,4-D + GA3, applied on fruits at color break; 10) 2,4-D + GA3, applied on green fmits and fruits at color break. Natural fruit drºp was evaluated by dropped fruit counting per plant weekly. Growth regulators effects on physical and chemical fruit properties were fortnightly measured. In “Hamlinª trees, natural fruit drep, which usúally occurs during the pre-harvest period, was significantly delayed due to 2,4-D and GA3 applications. The attack of fruit Íly was also evaluated by counting the fruits attacked per plant weekly. The degree of ripening factor did not interfere with the 2,4-D application results. Two applications of GA3 (green fruits and fruits at color break) provided the best pre-harvest . &uit drop control. Longitudinal and equatorial fruit diameter, acidity, soluble solid content, juice percentage, pee] thickness and fruit weight were not affected by 2,4-D and GA3. Peel fruit strength, measured by a penetrometer, increased with GA3 applications, whereas a smaller peel chlorophyll degradation occurred when applying GA3 and 2,4-D GA3. Applications of GA3 decreased the susceptibility of fruit fly onset.