21 May 2023, New Delhi: Natural drying of leaves and berries is the best solution if rains are occurring/expected in short bursts only. No spraying should be done during the rains.
Below are a few measures that must be taken on time to prevent grape crop damage from unseasonal rains
- Irrigation should be stopped so as to prevent the building up of turgor pressure which might lead to berry cracks.
- If leaf wetness period exceeds more than 12 h, application of Chitosan @ 2mL/L may be done to avoid berry cracking.
- To strengthen the cell wall of berries, application of calcium chloride/calcium nitrate @ 2 g/L may be carried out.
- Manual shaking of the wires may be done to remove the accumulated water in grape bunches.
- Use of horticultural grade mineral oil @ 2 mL/l may be done to remove accumulated water within the bunches. This strategy may be adopted in case of bunches which are tight and has a higher load than recommended.
- Use of any “plant tonics” should be avoided. Such formulations may have deliberate mixing of pesticides, and their use might result in residue problem.
- The rains will cause a sudden drop in temperature and this might trigger the incidence of black fungus on berries and a wash with a silicon based adjuvant @ 1-2 mL/L will solve the problem.
If there is a mite attack, dusting with sulphur can be done @ 5-6 kg/acre which will also take care of the powdery mildew infections. However, care should be taken that there should not be any spots on the berries.
The above advisory has been issued by NRCG.
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