Pruning for the best out of avocados
A number of growers are facing the daunting task of pruning as their avocado trees grow to unmanageable heights causing lack of light in the orchard, declining production and increasing costs.
Pruning to manage these issues is an essential practice that should take place for the entire life of the trees. If done correctly, and in a simple uniform way, it can improve orchard productivity, tree performance, and orchard management.
In the early years of the tree’s life, pruning is aimed at manipulating growth for an improved fruit bearing structure that will achieve optimum yield. In later years, and with unpruned trees showing decline, the emphasis shifts to promoting rejuvenation and ensuring maximum sunlight to penetrate the tree canopy.
ISSUES WITH UNPRUNED TREES
As trees grow taller and denser, the lower and interior limbs lose their ability to produce fruit because of increased shading. Over time, most fruit will be produced on the outer periphery of the tree primarily at the top, as this is exposed to the most sunlight. Unfortunately, the top of the tree is also where the most wind damage, sunburn, and poorer quality fruit occurs as spray penetration to these heights can be less effective.
The cost of managing and harvesting unpruned trees proportionally increases with the tree height, resulting in smaller returns.
TYPES OF PRUNING
There are predominately two types of pruning – heading cuts / tipping and thinning.
Heading cuts or tipping removes the growing point thereby breaking apical dominance and stimulating lateral bud break and branching.
Thinning is used to increase light penetration by removing competing or crowding shoots or limbs.
Advantages of regular pruning: • Improved light distribution into the canopy which is
essential for flower bud development, fruit set and growth. • Improved bearing structure which increases production
potential and encourages regular crops. • Growth of new shoots with high quality flower buds. • Better spray penetration and therefore improved pest
control. • Better air movement throughout the canopy, improving drying conditions and reducing the severity of fungal diseases. • Successful regrowth of diseased or damaged wood.
CONSISTENCY IS KEY
There are many approaches to and opinions on pruning being discussed in the industry. Whichever approach you decide to apply, ensure that you remain consistent and apply it to each tree so that the resultant light penetration within the tree and orchard is uniform.
In order to determine what approach to take when pruning, first ask yourself what you are trying to achieve and what you need to do to get the tree to respond accordingly. Depending on the tree age, size and planting density your approach will vary. You also need to understand the plant physiology and development
and how it responds to different types of pruning
It must also be remembered that when pruning off a branch, the production of that branch is lost, either by pruning off the existing fruit, the flowers or the potential flowers. The economic loss in the long run, will be the same regardless of whether you can see the fruit or not. The presence of fruit therefore, should not influence where the pruning cut should be.
POST PRUNING MANAGEMENT
Managing the prunings, newly exposed branches within the tree, and the regrowth is essential to ensuring that pruning efforts will be effective and
Sunburn on exposed branches and new pruning cuts as well as secondary rots and cankers can cause irreparable damage affecting tree health, performance and yield.
To protect the exposed limbs and pruning cuts against sunburn, a mixture of white acrylic paint, water and copper oxychloride can either be painted or sprayed on.
Prunings left under the tree can significantly increase the inoculum levels of fungal diseases, thereby increasing the incidence of anthracnose and post-harvest rots. However, once chipped, the mulch spread evenly under the tree from the dripline to the trunk becomes a valuable resource improving root health, soil microbiology, water holding capacity, and weed suppression.
“Thin regrowth to minimise competition for light and resources and enable stronger and more productive regrowth.”
Finally, management of pruning regrowth is essential at an early stage. Thin regrowth to minimise competition for light and resources and enable stronger and more productive regrowth. Tip regrowth to break apical dominance and encourage lateral branching for optimal production.
Rejuvenating large trees with pruning will improve light distribution into the canopy which is essential for flower bud development, fruit set and growth.
As trees grow taller and denser, the lower and interior limbs lose their ability to produce fruit because of increased shading.
Thinning opens the interior to light and air, and defines the structure of the plant. When thinning, a combination of cuts can be used. Thinning or
Heading reduce overall size and encourages new plant growth.
Thinning regrowth is essential to minimise competition for light and resources.
Protect exposed limbs and pruning cuts against sunburn by applying a mixture of white acrylic paint, water and copper oxychloride.
Tip regrowth to break apical dominance and encourage lateral branching for optimal production. Newly exposed branches are vulnerable to sunburn which can cause irreparable damage affecting tree health, performance and yield.