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:
- 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.
- Application of 6BA @ 10 ppm along with CCC @ 250 ppm to increase panicle size and to reduce the filage.
- 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