Paclobutrazol - Soil Drench Application For Enhanced Flower Promotion | Anti-gibberellin Properties, Optimal For Tree Growth Regulation

SOME IMPORTANT CONSIDERATIONS IN THE USE OF PACLOBUTRAZOL

How does paclobutrazol act?

Available evidence strongly suggests that flower initiation depends on the presence of an unknown flower-promoting factor or factors synthesised in the leaves. At the same time, there are other factors in the shoots which work against the flowering factor or factors. It is believed that a group of plant hormones called gibberellins act as inhibitors to flowering. When paclobutrazol is applied to the soil, it moves up through the roots into the shoots and, due to its anti-gibberellin properties, blocks the synthesis of flowering inhibitors, thereby allowing the flower-promoting factor(s) to work.

How and when to apply paclobutrazol?

The application of paclobutrazol to soil as a drench around the tree trunk (collar drench) is the most effective method, as it ensures proper uptake by the tree. The required quantity is mixed in approximately one litre of water and poured onto the soil around the trunk in a circular band. In the Top End, the ideal time to apply paclobutrazol is from soon after harvest to early January. In dry conditions, a light irrigation is recommended after application. Foliar sprays have been ineffective.

At what age should trees be treated and when should treatment be repeated?
The size of trees at first application is important. This depends on the age of the trees and the spacing between them. Apart from promoting flowering, paclobutrazol also restricts tree vigour.