Articles
THINNING OF ‘JONAGOLD’ AND ‘ELSTAR’ APPLES WITH THE COMBINATION OF ETHEPHON AND CPPU
Article number
653_12
Pages
93 – 97
Language
English
Abstract
The combined spraying of ethephon with synthetic cytokinin forchlorfenuron (CPPU) was investigated on seven-year-old Jonagold and Elstar apple trees / M.9. The application of ethephon a few times after petal fall (PF) at low concentration was aimed to enhance return bloom without affecting fruitlet abscission.
The problems of small fruit in high cropping trees should be overcome by spraying of CPPU since its application in general increased fruit size.
Successive applications of ethephon at 30 and 50 ppm, alone or in combination with CPPU 5 ppm, were done after PF at weekly intervals.
The single application of CPPU at 5 ppm at PF resulted in strong thinning response of Jonagold and non significant thinning of Elstar apple trees.
The yield of fruit from bigger size class was enhanced on both cultivars after CPPU 5 ppm single application.
Postbloom ethephon at 200 ppm alone spraying (PF) and/or five weekly applications of ethephon at 30 ppm or 50 ppm (starting at PF) thinned Jonagold trees but no significant additional fruit growth was observed.
Three weekly applications of ethephon at 30 ppm or 50 ppm (starting at PF) did not affect fruit set or fruit growth of Jonagold trees.
Moderate thinning of fruitlets was seen on Elstar with all ethephon alone treatments (200 ppm, 3×30 ppm, 5×30 ppm, 3×50 ppm, 5x50ppm, weekly intervals starting at PF) but the average fruit weight was not enhanced by treatment.
When 50 ppm ethephon was sprayed at five weekly intervals starting at 18 mm fruitlet diameter of Jonagold and Elstar trees, a weak thinning and no better fruit growth occurred.
The combination spraying of ethephon 3×30 ppm + CPPU 5 ppm or ethephon 5×50 ppm + CPPU 2×5 ppm (at weekly intervals starting at PF) resulted in strong thinning response and in enhanced fruit growth for both cultivars.
Return bloom was increased significantly and satisfactorily on well thinned Jonagold trees, while on Elstar no treatment affected better return bloom even in the case of pronounced thinning.
The problems of small fruit in high cropping trees should be overcome by spraying of CPPU since its application in general increased fruit size.
Successive applications of ethephon at 30 and 50 ppm, alone or in combination with CPPU 5 ppm, were done after PF at weekly intervals.
The single application of CPPU at 5 ppm at PF resulted in strong thinning response of Jonagold and non significant thinning of Elstar apple trees.
The yield of fruit from bigger size class was enhanced on both cultivars after CPPU 5 ppm single application.
Postbloom ethephon at 200 ppm alone spraying (PF) and/or five weekly applications of ethephon at 30 ppm or 50 ppm (starting at PF) thinned Jonagold trees but no significant additional fruit growth was observed.
Three weekly applications of ethephon at 30 ppm or 50 ppm (starting at PF) did not affect fruit set or fruit growth of Jonagold trees.
Moderate thinning of fruitlets was seen on Elstar with all ethephon alone treatments (200 ppm, 3×30 ppm, 5×30 ppm, 3×50 ppm, 5x50ppm, weekly intervals starting at PF) but the average fruit weight was not enhanced by treatment.
When 50 ppm ethephon was sprayed at five weekly intervals starting at 18 mm fruitlet diameter of Jonagold and Elstar trees, a weak thinning and no better fruit growth occurred.
The combination spraying of ethephon 3×30 ppm + CPPU 5 ppm or ethephon 5×50 ppm + CPPU 2×5 ppm (at weekly intervals starting at PF) resulted in strong thinning response and in enhanced fruit growth for both cultivars.
Return bloom was increased significantly and satisfactorily on well thinned Jonagold trees, while on Elstar no treatment affected better return bloom even in the case of pronounced thinning.
Authors
M. Stopar, P. Zadravec
Keywords
apple thinning, ethephon (2-chloroethyl phosphonic acid), forchlorfenuron (CPPU = N-[2-chloro-4-pyridinyl]-N’-phenylurea)
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