Canopy Management Strategy 1 - Dillon Strategy
The Katikati System has been the first canopy management strategy that the PGP BOP Working Group has attempted to describe.
The strategy has been developed by Contractor Michael Dillon. Michael is a full time pruning contractor in the BOP. He has been pruning as a contractor for more than 10 years and participated in the Pruning Trial that NZ Avocado implemented in 2011.
The main principles of this strategy are common to many other strategies and are described here.
Michael describes the method as a set of tools used to achieve certain goals. These tools are independent of tree height or spacing; they apply to any size or shape of tree targeted by the grower.
The tools are divided between structural and maintenance cuts. Some of these tools are likely to be common to other strategies and we will better define them as we work through the project.
Structural cuts will determine the size (including the height) and shape of the tree targeted by the grower. Usually (after a number of pruning events), the structure will be 2-5 well spaced main limbs and associated branches.
In trees where the structure has not been defined previously, large cuts will need to be done. The philosophy is that if it needs to go it will go.
An exception is done with branches that are loaded with fruit in autumn. They are marked in autumn and strip picked before being pruned in spring.
Shape and height
The final shape and height of the tree will be determined by the shape and height of the scaffold. The scaffold needs to leave a margin of 1-2m for fruiting wood. This means that the scaffold needs to be at approximately 1-2m within the final shape of the tree.
In trees that need to have their volume (including the height) reduced, reaching the final shape and height could be a multi-year process.
Main branches can be pruned to reduce the volume of overgrown trees; particularly at the beginning of the process, bigger branches (even main branches) will most likely be eliminated or cut back. With time, maintaining the shape and height of the tree will require smaller cuts.
In trees that have been pruned since an early age, the cuts will most likely be small.
Vertical and horizontal overlapping and competing branches need to be eliminated to create enough room for fruiting wood to develop between main branches.
Sweepers are horizontal main branches that run lower than
0.5 m from the ground.
Sweepers need to be eliminated to ease management unless they are providing support and stability for the remainder of the tree.
Branches that go from one side of the canopy to the other side of the canopy need to be removed.
Secondary cuts are made to favour the development of fruiting wood; either by eliminating competing wood, or by eliminating wood that is impeding the development of new fruiting wood in the desired places.
Watershoots: unwanted growth, excess regrowth (new shoots up to 2 years old)
Watershoots need to be removed since they compete for light and resources with less vigorous fruiting wood beneath them.
Removing branches that are too close to fruiting wood beneath them, shading it or shading the area in the scaffold where the substituting fruiting wood needs to grow. This usually refers to horizontal, weeping (hanging) branches.
Thinning out clustering branches
Some fruiting wood needs to be thinned, eliminating some branches to favour the development of better branches.
Spent wood needs to be cut. This mainly refers to fruiting wood that has already produced a certain amount of fruit and most likely won't produce any fruit in the next couple of years. These branches are generally in the outside of the canopy. They usually present dead or very weak spindly branches.
Shaded branches inside the canopy need to be eliminated.
Thinning young excess fruiting branches for light access to remaining fruiting wood.
Flower Pruning and Fruit Pruning
Pruning of exposed or excess fruit in summer, or excess flower in spring.
This method is described in detail in the document Pruning to Balance Avocado Trees