S16 - Session P2 - The efficiency of ACC in the fruit thinning of Maxigala apple applied in four stages and five concentrations

Authors: José Luiz Petri *, André Amarildo Sezerino, Marcelo Couto

The aim of this study was to evaluate the agronomic efficiency and practicality of different doses of ACC (1-aminocyclopropane-1-carboxylic acid) in chemical thinning of apples ( Malus domestica ), and its effect on the phytotoxicity of treatments, when applied in the stage of "end of flowering", fruits with 8-10 mm, 18-20 mm and more than 25 mm. The experiment was located in an orchard in the city of Caçador, SC, Brazil. A randomized complete block design was used, with seven treatments and six replications, using cv. MaxiGala. The treatments were: 1. Control (manual thinning); 2. ACC 0.25 ml/ha; 3.ACC 0.5 ml/ha; 4. ACC 0.75 ml/ha; 5. ACC 1.0 l/ha; 6. 1.25 l/ha and Ethephon 0.5 l/ha. For each application time (end of flowering, 8-10 mm, 18-20 mm, and more than 25 mm fruit) an experiment was considered the doses of ACC 1.00 and 1.25 kg/ha applied to the end of flowering provided excessive thinning in the apple tree. The doses of 0.25, 0.5, and 0.75 kg/h presented results similar to manual thinning (Control). For applications of ACC in fruits with 8-10 mm, the dose of 1.25 kg/ha was excessive, being efficient doses of 0.5 to 1.0 kg/ha, superior to the Ethefon treatment. For 18-20 mm fruits, dosages of 1.0 and 1.25 l/ha showed greater efficiency than smaller dosages. In fruits with more than 25 mm in diameter, although it reduced the percentage of fruit drop compared to previous stages. As a result, we can conclude that doses of 0.25, 0.5 and 0.75, 1.0, and 1.25 kg/ha of ACC have agronomic efficacy and can be recommended for thinning apple ( Malus domestica ) cv. MaxiGala. The dosages depend on the application stage, and doses of 1.0 and 1.25 kg/ha should only be applied in the stages of fruits above 18mm in diameter.