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A Technical Note on Application of CultarŪ ( Paclobutrazol) for Mango Flowering Enhancement in Sri Lanka

Mango has an annual growth cycle. The main growth and development stages of this cycle are production of major leaf flush after harvesting of fruit, maturing of leaves, flowering, fruit set, fruit development, fruit maturity and harvesting. However, due to irregular climatic and environmental influences this growth cycle is interrupted. Consequently, flowering and fruit production of such trees become irregular.

Cultar (Paclobutrazol) is a plant growth regulator that can be used to regulate growth and development cycle in order to enhance flowering in mango trees. It prevents excessive vegetative growth of mango trees by inhibiting synthesis of Gibberellins. Thus mango shoots mature without any interruption and brings about early and uniform flowering.

Cultar must be applied to mango trees at right time with right amounts to effectively enhance flowering in trees.

The best time to apply this growth regulator is about 2 weeks after leaf flush emergence when leaf flush is fully expanded (after 3rd stage in the figure below). The chemical is absorbed into the tree with water and transported to the terminal bud of shoots through the xylem. There it prevents the growth of terminal bud for about 3-4 months and thus the shoot become mature enough to differentiate the terminal bud into a floral bud. Thereafter, when the growth of the terminal bud is stimulated flowering occur.

The amount of Cultar to be applied to a tree depends on the size of the tree. The rate is determined by the diameter of the tree canopy. For variety Willard a rate of 0.50 g/meter of canopy diameter is recommended. For other mango varieties, a rate of 1.0 g/meter of canopy is recommended. The amount of commercial formulation of Cultar to be applied must be determined after taking into account the concentration of the formulation used because Cultar is marketed as 10% and 15% WP and 25% EC formulations. The required amount is dissolved in 1-2 l of water and applied as a collar drench uniformly around the base of the tree trunk as shown in the followinf figures.

It is important that the right amounts are used since excessive rated cause compact panicles that again affect fruit set and proper fruit development. In addition fertilizer application, irrigation and timely pest and disease control measures must be adopted to get the full benefits of Cultar application.