|Authors: ||J. Vercammen, A. Gomand|
|Keywords: ||Malus × domestica, Amid-thin, GA4/7, Prohexadione-Ca, anti-ethylene effect, June drop|
We investigated plant growth regulator treatments in several field experiments to improve fruit set of ‘Jonagold’, especially in a year with (severe) frost damage or in the “off” year in biennial orchards when there are only few flower buds.
A treatment with a low dose of Amid-thin (0.25 kg/ha) or GA4/7 (0.5 L/ha Novagib) 3 to 7 days after full bloom showed a trend toward improved fruit set.
Such a treatment with a low dose of Amid-thin or GA4/7 can be an insurance and the effect is comparable with a spraying with boron at low doses during flowering time.
The combination of Amid-thin and GA4/7 resulted in reduced fruit set.
The increased fruit set observed after a treatment with Amid-thin or GA4/7, is often transient and is often lost during June drop.
Regalis (Prohexadione-Ca) sprayed between 2 and 4 weeks after full bloom showed a trend of reducing June drop, but the moment of spraying may be important and the effect is short (4 to 5 days). In contrast to pears we do not recommend to combine Amid-thin or GA4/7 and Regalis with apple.
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