Science of wine – Trevor Lupton
While many tear their hair out over vexatious problems like botrytis, powdery mildew and achieving nil-residue in wine, Gisborne's Trevor Lupton regards such things as challenges.
This means it is vital to maintain a tight fungicide cover from veraison to pre-harvest.
Leaf plucking will enhance air movement and light penetration within the canopy, and helps decrease bunch drying time and reduces the potential for disease development.
Continue monitoring for downy mildew into February. If infections are found, apply an appropriate fungicide in anticipation of conditions conducive for infection.
Magnesium is an important constituent of chlorophyll, a compound used by the vine in photosynthesis and activates many enzymes used for both carbohydrate and protein synthesis. Regular magnesium sprays (e.g. Hydromag) leading into harvest will aid the maintenance of good leaf condition.
Calcium is another nutrient of value to grapevines in the veraison to preharvest window. Calcium sprays (e.g. Stopit) during this time may help improve the cell wall integrity of berries, reducing the likelihood of berry splitting.
As sugar levels rise in berries, bunches become increasingly susceptible to Botrytis. Maintain a tight fungicide cover through until harvest, applying appropriate products, such as Serenade® Max, in anticipation of wet weather events. If bird damage is a perennial problem on your block, exclusion netting is the staple defence method. Care must be taken to seal the nets at the bottom and ends as starlings, in particular, readily exploit any gaps. ν
