Standardization of schedule for Plant Growth Regulators in Grapes

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Plant growth regulators play an important role in grapes. The better quality grapes can be produced through the management of nutrients, water, canopy and more precisely by use of plant growth regulators. To achieve the better results the stage and optimum concentration of bioregulators are very important because the less or overdose causes no effect or adverse effects, respectively on the vine health and berry quality. Therefore, it is always advisable to use the bioregulators judiciously in viticulture. The bioregulators are being used for fruit bud differentiation after back pruning to control vigour of shoots, for elongation of rachis, berry growth and development etc.

Following are the recommendations of the Institute based on research data generated on use of bioregulators:

After April pruning:

Number of days after foundation pruning Practice to be followed Purpose
30-40 Nitrogen application to be stopped in case of vigorous vines* To reduce the shoot growth
40-60 Reduce irrigation level to one-third to that of the vegetative phase** To reduce the shoot growth

* Petiole-Nutrient guide has to be followed.

** This period generally coincides with the onset of rainy season. Irrigation may or may not be required.

After October pruning:

  1. Swabbing of the buds only once with 1.5 to 4.0 % (a.i) of Hydrogen Cyanamide with in 24-48 hours after forward pruning for early and uniform bud break based on cane thickness and prevailing temperature. Farm workers should use hand gloves while using this chemical.
  2. Application of 6BA @ 10 ppm along with CCC @ 250 ppm to increase panicle size and to reduce the filage.
  3. Application of Gibberellins and Cytokinins for bunch and berry development as shown below

Pre-bloom application of GA3 for better panicle growth

Stage of plant Concentration of chemical pH adjustment while using chemical Compatibility with other chemical Purpose
Parrot green stage of panicles GA3 @ 10 ppm 5.0 - 6.0 Urea phosphate +any fungicide for control of downy mildew Elongation
3-4 days after 1st spray 15 ppm GA3 5.0 - 6.0 Citric acid or phosphoric acid and depends on situation any fungicide Rachis elongation
3-4 days after 2nd spray 20 ppm GA3 5.0 - 6.0 As above Rachis elongation
50% flowering 40 ppm GA3 5.0 - 6.0 Nil This should be selective that means if rachis are not elongated enough then only it should be given.

GA3 application for berry growth

For meeting Agmark quality grades
3-4 mm berry size 30 ppm GA3 + 2 ppm CPPU
Or 1 ppm Homobrassinolide
Or 6BA @ 10 ppm**		 Acidic Berry elongation and for round berries
6-7 mm berry size 40 ppm GA3 + 1 ppm CPPU
Or 1 ppm Homobrassinolide
Or 6BA @ 10 ppm		 Acidic Berry elongation
For local market
3-4 mm berry size 40-50 ppm GA3 + 10 ppm 6BA Acidic Berry length
6-7 mm berry size 40 ppm GA3 Acidic Berry length

Application of CPPU, Homobrassinolide and 6BA has to be decided based on the canopy

While dealing with bioregulators, time of application and dose are important and are to be complied for their better bioefficacy and ultimate benefit.

Shelf life

1. Application of calcium @ 0.5 to 1.0% to increase shelf life in export quality grapes.

2. Application of NAA (Naphthaline acetic acid) @ 20 ppm 8-10 days prior to harvest for reducing berry drop in raisin grapes.

* This was based on deliberations of the meeting organized by Maharashtra State Grape Growers’ Association (MRDBS) and NRC for Grapes on 30th April 2010 at NRC Grapes Campus for the management of plant growth without the use of CCC.

By: Dr. S.D. Ramteke