1-aminocyclopropane 1-carboxylic acid (ACC) application to reduce the manual thinning of ‘Chimarrita’ peach trees

Under normal conditions, peach trees bloom and produce fruits abundantly, requiring a large amount of labor for the manual thinning of fruits. Chemical thinning is an alternative that can reduce the need for manual thinning. The objective of this work was to evaluate the 1-aminocyclopropane 1-carboxylic acid (ACC) application to reduce the manual thinning of ‘Chimarrita’ peach trees in the region of Serra Gaúcha, Brazil. The experiment was conducted in the 2022/2023 and 2023/2024 crop years. The experimental design was in randomized blocks, with four replicates and seven treatments, applied at full bloom: unthinned control (only in the first cycle); control (manual thinning); ACCconcentrations of 150, 300, 450, and 600 mg L-1, in addition to 750 mg L-1only in the second cycle; and ethephon concentration of 300 mg L-1. ACC application reducedthe need for manual thinning more effectively compared to ethephon in the first cycle. With increasing ACC concentration, fruit set and the need for manual thinning decreased significantly. However, the increase in ACC concentration, along with manual thinning, resulted in reduced fruit yield in the first cycle. Overall, ACC concentration from 300 mg L-1 reduces the need for manual thinning and shows potential as a chemical thinning agent for ‘Chimarrita’ peach trees.