Pruning was a major feature of the Citrus Roadshow field sessions held at Riverina and Sunraysia in October 2017. Wind blemish is one of the main reasons of fruit being downgraded from class one, however it can be reduced by pruning. Annually pruning Washington navel trees after harvest enables growers to achieve up to 70% first grade pack outs. Wind speeds during spring and site topography (i.e. high or low wind site; exposed hillside or protected flat ground) also affect wind blemish, although pruning can significantly reduce the impact of these unfavourable situations. Pruning methods vary between farms depending upon tree size, varieties, tree age and the historical pruning of the block.
Mario’s Packhouse hosted the Riverina pruning Citrus Roadshow field session that was delivered by David Stevens (Nutrano crop consultant) and Steven Falivene (NSW DPI). The Sunraysia field session was hosted by Sunmar Orchards (Sunraysia) and delivered by Daniel Lazar (Sunmar) and Steven Falivene (NSW DPI). At both sites Vignesh Prathik from Ryset Australia demonstrated an array of Ryset pruning equipment including battery electric secateurs and chain saws.
Growers that prune annually aim to spend approximately two minutes per tree, costing about $1.80 per tree. Costs will depend upon individual orchard circumstance and the intensity of pruning. Most growers aim to prune 20-30 trees per hour. Generally battery powered electric secateurs are used for 6-10 year old trees, while small petrol or battery chainsaws are more efficient for pruning mature citrus trees.
Key messages on the day were:
- Annual pruning is critical to continually turn over the canopy. NSW DPI research showed that the effect of rejuvenating a branch lasts about five years. It also established that pruning approximately 20% of the canopy achieves a five year turn around and does not unbalance the tree.
- Late maturing navel varieties need a less aggressive pruning approach, preferring a few smaller window cuts than a couple of big “chunk” cuts. Large cuts made in late spring, around flowering and fruit set, can expose the limbs to a higher risk of sunburn and unbalancing the physiology of the tree than smaller window cuts.
- Battery powered chainsaws and secateurs are often more expensive than petrol models, but are usually easier to use and have less of work health and safety risks for example the chain spin stops as soon as the operator depresses the trigger). This makes battery pruners preferable for growers with considerable areas to prune.
- There are two options for battery powered saws; those with the battery carried on a belt or harness, or those with the battery on the saw. Both options are very good, hence personal choice will determine which one best fits the pruning style of the operator. A battery on the belt has the advantage of less weight in the hand but it will require a cable connected to the saw. This could make it a bit inconvenient if you have to put the saw down to remove a large branch.
- When pruning a mature unpruned tree, target the centre upright limb first to allow light in and to encourage new growth inside the tree. Then begin the process of reducing tree height. In subsequent years as more of the upper canopy is removed, shoots would already be established in the lower canopy ready to grow into productive branches. There are couple of considerations when removing upright limbs:
- If the centre limb holds a large volume of upper canopy, cut it at a height so that a moderate hole (e.g. 1 m diameter) will be in the top of the canopy. A hole any larger than this can expose limbs to sunburn and could produce excessive regrowth. More upper limbs can be removed in stages in subsequent years.
- If a complete upright limb is targeted for removal, cut it as low as possible; at approximately waist to shoulder height. The regrowth can be used to form new productive branches or limbs and these will need to be thinned out and possibly topped as the shoots reach 30 – 50 cm in height in early summer. Cutting a limb high up in the tree will produce regrowth and fruit high up in the tree. This then leaves the fruit prone to wind damage and is difficult manage and harvest.
- If trees are very large, top the trees lower than usual, or to the desired height, with mechanical hedging saws. This allows regrowth to commence inside the tree. Then hand prune selected centre limbs in following years.
An array of pruning resources are on the NSW DPI website including: