Articles
Chemical thinning of Nicoter
Article number
1346_57
Pages
447 – 454
Language
English
Abstract
Poor prices in recent years have compromised the income of Belgian apple growers.
To achieve a decent income, a maximum of fruits should be classified in the best paid sorting classes, as these apples are usually the only ones with a return above cost price.
For the newer diploid apple cultivars, fruit size is essential in determining the sorting class.
To obtain a higher average fruit weight in diploid cultivars, the number of fruits per tree has to be optimised, for which the new options will be discussed.
In Belgium, the following chemical thinning agents are authorised: 1-napthaleneacetamide (NAD Amid-thin W), naphthalene acetic acid (NAA Fixor), 6-benzyladenine (6-BA Globaryll 100, Exilis and MaxCel) and metamitron (Brevis). Besides, the foliar fertiliser ammonium thiosulfate (ATS) is used to thin apples by flower thinning.
The result of the chemical thinning depends on temperature, tree vigour, pollination (the number of seeds), the heterogeneity of fruit size and the light levels 14 to 30 days after full bloom.
Mostly the thinning effect of ATS and 6-BA on Nicoter is too weak, and over thinning rarely occurs.
Adding NAA to 6-BA can improve the thinning efficiency.
On the contrary, metamitron can excessively thin, especially with high night temperatures and low light levels.
Therefore, our advice is to use NAD or 6-BA (+/- NAA) when only a mild thinning is intended.
One treatment with 1.1 to 1.5 kg ha-1, Brevis (metamitron), is recommended on trees with abundant flower buds and ideal weather during bloom.
The optimal time for applying metamitron is at an average fruitlet diameter of 8 to 12 mm on the 2-year-old-wood.
A later application is possible, but the gain on average fruit weight is compromised, and results are more inconsistent.
An earlier application than the recommended timing is less effective.
To achieve a decent income, a maximum of fruits should be classified in the best paid sorting classes, as these apples are usually the only ones with a return above cost price.
For the newer diploid apple cultivars, fruit size is essential in determining the sorting class.
To obtain a higher average fruit weight in diploid cultivars, the number of fruits per tree has to be optimised, for which the new options will be discussed.
In Belgium, the following chemical thinning agents are authorised: 1-napthaleneacetamide (NAD Amid-thin W), naphthalene acetic acid (NAA Fixor), 6-benzyladenine (6-BA Globaryll 100, Exilis and MaxCel) and metamitron (Brevis). Besides, the foliar fertiliser ammonium thiosulfate (ATS) is used to thin apples by flower thinning.
The result of the chemical thinning depends on temperature, tree vigour, pollination (the number of seeds), the heterogeneity of fruit size and the light levels 14 to 30 days after full bloom.
Mostly the thinning effect of ATS and 6-BA on Nicoter is too weak, and over thinning rarely occurs.
Adding NAA to 6-BA can improve the thinning efficiency.
On the contrary, metamitron can excessively thin, especially with high night temperatures and low light levels.
Therefore, our advice is to use NAD or 6-BA (+/- NAA) when only a mild thinning is intended.
One treatment with 1.1 to 1.5 kg ha-1, Brevis (metamitron), is recommended on trees with abundant flower buds and ideal weather during bloom.
The optimal time for applying metamitron is at an average fruitlet diameter of 8 to 12 mm on the 2-year-old-wood.
A later application is possible, but the gain on average fruit weight is compromised, and results are more inconsistent.
An earlier application than the recommended timing is less effective.
Publication
Authors
J. Vercammen, A. Gomand, D. Bylemans
Keywords
NAD, NAA, 6-BA, metamitron, fruit weight
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