Articles
The efficacy of 1-aminocyclopropane-1-carboxylic acid (ACC) in thinning apples: Chilean experience
Article number
1449_19
Pages
141 – 148
Language
English
Abstract
In Chile, apple trees commonly show a high fruit set: ~2.0-2.5 fruits cluster-1; therefore, strong chemical thinning is needed to avoid or reduce hand thinning. 1-aminocyclopropane-1-carboxylic acid (ACC; Accede®), an ethylene precursor has been registered as flower or fruitlet thinner.
Then, it must be validated according to weather conditions and cultivars.
This study aimed to assess the efficacy of ACC concentrations from bloom to later “rescue” treatments and its integration into commercial chemical thinning programs (CCTP). Six trials in ‘Brookfield Gala’ and 5 in ‘Fuji Raku Raku’ were done during four seasons.
ACC used alone or as part of CCTP reduced fruit set in a dose-moment-cultivar specific manner.
For ‘Gala’, ACC at full bloom (224 and 448 mg L‑1) was highly effective in thinning flowers.
From petal fall to 10-12 mm fruit diameter, 448 mg L‑1 reduced fruit set, and a higher concentration (672 mg L‑1) was required when fruits reached 18 to 25 mm.
However, 672 mg L‑1 or higher concentrations with a coadjuvant or oil showed slight to moderate leaf drop between 18 to 25 mm, depending on the season.
For ‘Fuji’, a higher ACC rate was needed; 672 mg L‑1 at full bloom reduced the fruit set from 2.5 to 1.5 fruits/cluster, which is considered good thinning for ‘Fuji’. From 4 to 10-12 mm fruit diameter and under good weather conditions for thinning (i.e., less carbohydrate availability), 448 to 672 mg L‑1 reduced fruit set, but not under cold nights and hot sunny days.
Similar results were observed for “rescue” treatments, with only 896 mg L‑1 reducing fruit set until optimal fruit set (0.8-1.0 fruits cluster-1) under favorable weather conditions, while medium rates (448 to 672 mg L‑1) plus coadjuvant produced moderate thinning.
In conclusion, ACC is a promising full bloom and late “rescue” thinner for apples, particularly at the 18 to 25 mm stage when other thinners are ineffective.
Then, it must be validated according to weather conditions and cultivars.
This study aimed to assess the efficacy of ACC concentrations from bloom to later “rescue” treatments and its integration into commercial chemical thinning programs (CCTP). Six trials in ‘Brookfield Gala’ and 5 in ‘Fuji Raku Raku’ were done during four seasons.
ACC used alone or as part of CCTP reduced fruit set in a dose-moment-cultivar specific manner.
For ‘Gala’, ACC at full bloom (224 and 448 mg L‑1) was highly effective in thinning flowers.
From petal fall to 10-12 mm fruit diameter, 448 mg L‑1 reduced fruit set, and a higher concentration (672 mg L‑1) was required when fruits reached 18 to 25 mm.
However, 672 mg L‑1 or higher concentrations with a coadjuvant or oil showed slight to moderate leaf drop between 18 to 25 mm, depending on the season.
For ‘Fuji’, a higher ACC rate was needed; 672 mg L‑1 at full bloom reduced the fruit set from 2.5 to 1.5 fruits/cluster, which is considered good thinning for ‘Fuji’. From 4 to 10-12 mm fruit diameter and under good weather conditions for thinning (i.e., less carbohydrate availability), 448 to 672 mg L‑1 reduced fruit set, but not under cold nights and hot sunny days.
Similar results were observed for “rescue” treatments, with only 896 mg L‑1 reducing fruit set until optimal fruit set (0.8-1.0 fruits cluster-1) under favorable weather conditions, while medium rates (448 to 672 mg L‑1) plus coadjuvant produced moderate thinning.
In conclusion, ACC is a promising full bloom and late “rescue” thinner for apples, particularly at the 18 to 25 mm stage when other thinners are ineffective.
Publication
Authors
V. Beyá-Marshall, A. Verdugo, G. Reginato
Keywords
Malus domestica, ethylene precursor, fruit set
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