Use of growth regulators in Grapes

Use of growth regulators

        Growth regulators—CCC, GA and hydrogen cyanamide—are being used commercially in grapes. The CCC is used to suppress the vigour of vines and increase the fruitfulness of buds. It is sprayed at 500 ppm concentration at 5-leaf stage after back pruning. If weather is cloudy, cool and rainy, it is sprayed on the foliage once again at 10-leaf stage. Gibberallic acid (GA) is used invariably in all seedless varieties. It is sprayed at 10 ppm to elongate the clusters, 22–25 days after forward pruning (4–5-leaf stage). It is also sprayed on clusters @ 40ppm at 50% bloom stage for thinning the berries. For increasing the berry size, the clusters are dipped in 60ppm GA alone or in a mixture of GA (30ppm) with 10ppm BA or 2ppm CPPU at pearlmillet or bajra grain-sized berries and again at redgram sized berries. Care must be taken not to treat the clusters with GA before bajra grain-sized berries. Otherwise, berries of uneven size form a cluster. For increasing berry size, vines are girdled. Girdling is a process of removing 2–3mm wide strip of bark around the stem without injuring the wood. This is also to be done at the bajra grain-sized berries.

            Hydrogen cyanamide is used to hasten and increase the bud-break at winter pruning. Buds are swabbed with cotton soaked in 1.5% solution of hydrogen cyanamide 48 hr after pruning. Hastening the bud-break with hydrogen cyamide also hastens the ripening of grapes in the north. Thiourea (4.0%) mixed with 1% Bordeaux mixture is also used to increase bud-break in south.