Articles
The efficacy of 1-aminocyclopropane-1-carboxylic acid (ACC) as a chemical thinner on apples
Article number
1341_3
Pages
15 – 24
Language
English
Abstract
The purpose of this study was to evaluate a new chemical thinning molecule, 1-aminocyclopropane-1-carboxylic acid (ACC), on Fuji and Cripps Red apples.
ACC was evaluated over two seasons at a range of concentrations from 140 to 560 mg L‑1, applied at different phenological stages from petal fall to 15-20 mm fruitlet diameter.
The fruit industry needs a chemical thinning agent that can successfully be applied during the later thinning window (15-20 mm fruitlet diameter) on apples.
ACC was compared to industry standard applications, 6-benzyladenine (6-BA) and 1-napthaleneacetic acid (NAA), applied as a tank-mix or individually.
In all the trials, ACC proved to be a stronger thinner than the industry standard applications.
During both seasons, trials on Fuji were disappointing as neither ACC nor the industry standard applications caused satisfactory thinning.
ACC application in the 2017/2018 season to young Cripps Red trees was not successful.
However, ACC proved to be very promising when applied to a mature Cripps Red orchard during the 2018/2019 season.
ACC applied at the 15-20 mm fruitlet diameter, thinned successfully, and increased fruit size without decreasing yield.
We concluded that the rate of ACC should be between 280 and 560 mg L‑1. No negative effects on stem-end russet, fruit maturity and leaf drop were observed.
Further research, however, is needed before final recommendations can be made.
ACC was evaluated over two seasons at a range of concentrations from 140 to 560 mg L‑1, applied at different phenological stages from petal fall to 15-20 mm fruitlet diameter.
The fruit industry needs a chemical thinning agent that can successfully be applied during the later thinning window (15-20 mm fruitlet diameter) on apples.
ACC was compared to industry standard applications, 6-benzyladenine (6-BA) and 1-napthaleneacetic acid (NAA), applied as a tank-mix or individually.
In all the trials, ACC proved to be a stronger thinner than the industry standard applications.
During both seasons, trials on Fuji were disappointing as neither ACC nor the industry standard applications caused satisfactory thinning.
ACC application in the 2017/2018 season to young Cripps Red trees was not successful.
However, ACC proved to be very promising when applied to a mature Cripps Red orchard during the 2018/2019 season.
ACC applied at the 15-20 mm fruitlet diameter, thinned successfully, and increased fruit size without decreasing yield.
We concluded that the rate of ACC should be between 280 and 560 mg L‑1. No negative effects on stem-end russet, fruit maturity and leaf drop were observed.
Further research, however, is needed before final recommendations can be made.
Publication
Authors
K.I. Theron, G.F.A. Lötze, D.A. Scholtz, J.S. Reynolds
Keywords
1-aminocyclopropane-1-carboxylic acid (ACC), 6-benzyladenine (6-BA) and 1-napthaleneacetic acid (NAA), thinning, yield, leaf drop, fruit size
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