Articles
IMPROVEMENT OF THE FRUIT SET OF ‘JONAGOLD’
Article number
884_42
Pages
357 – 362
Language
English
Abstract
Each year, around flowering time most (apple) growers get nervous.
After all, this is a crucial period, because a good yield is based on a good fruit set.
Even abundant flower buds are no guarantee of a good yield.
The quality of the flower buds and the weather during and after flowering are very important factors.
Consequently, growers want to exploit all the possibilities that can contribute to a good fruit set, especially in a year with (severe) frost damage or when there are relatively few flower buds.
A treatment with a low dose of Amid-thin (0.25 kg/ha) or GA4/7 (0.5 L/ha Novagib) can improve fruit set.
But there must be still flowers without pollination (=flowers that are closed) and there has to be pollen available from the pollenizers.
Also the weather must be good.
Both products can improve pollination, but the pollination period is shorter.
High doses (compared with low doses) dont give a better final fruit set, no improvement of the fruit quality, but more deformed fruits and more biennial bearing.
Do not combine both products during or after flowering and dont add any acids or surfactants.
After bloom an increase in fruit set can indeed be observed after a treatment with Amid-thin or GA4/7, but often this benefit is lost, for the most part during June drop.
Therefore, we also conducted trials with Regalis (Prohexadion-Ca). It acts also as an anti-ethylene agent when it is sprayed between 2 and 4 weeks after full bloom.
Regalis can reduce June drop, but the timing of spraying is important and the effect is only short (4 to 5 days). So it is better to spray 2 times 0.5 kg/ha 2 and 3 weeks after full bloom.
Higher doses offer no improvement.
The sprayings have to be done before the occurrence of stress.
Stress can be caused by dryness, not enough light (= 2 to 3 dark days), poor weather conditions and other factors.
After all, this is a crucial period, because a good yield is based on a good fruit set.
Even abundant flower buds are no guarantee of a good yield.
The quality of the flower buds and the weather during and after flowering are very important factors.
Consequently, growers want to exploit all the possibilities that can contribute to a good fruit set, especially in a year with (severe) frost damage or when there are relatively few flower buds.
A treatment with a low dose of Amid-thin (0.25 kg/ha) or GA4/7 (0.5 L/ha Novagib) can improve fruit set.
But there must be still flowers without pollination (=flowers that are closed) and there has to be pollen available from the pollenizers.
Also the weather must be good.
Both products can improve pollination, but the pollination period is shorter.
High doses (compared with low doses) dont give a better final fruit set, no improvement of the fruit quality, but more deformed fruits and more biennial bearing.
Do not combine both products during or after flowering and dont add any acids or surfactants.
After bloom an increase in fruit set can indeed be observed after a treatment with Amid-thin or GA4/7, but often this benefit is lost, for the most part during June drop.
Therefore, we also conducted trials with Regalis (Prohexadion-Ca). It acts also as an anti-ethylene agent when it is sprayed between 2 and 4 weeks after full bloom.
Regalis can reduce June drop, but the timing of spraying is important and the effect is only short (4 to 5 days). So it is better to spray 2 times 0.5 kg/ha 2 and 3 weeks after full bloom.
Higher doses offer no improvement.
The sprayings have to be done before the occurrence of stress.
Stress can be caused by dryness, not enough light (= 2 to 3 dark days), poor weather conditions and other factors.
Authors
J. Vercammen, A. Gomand, L. Denruyter
Keywords
amid-thin, GA4/7, prohexadion-Ca, anti-ethylene effect, June drop
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