Autumn pruning topped the list of topics at a recent field day on John and Mary Bowen's avocado orchard at Katikati.
Prune now, and your avocado crop will perform later.
This was the message from New Zealand Avocado at a recent field day on John and Mary Bowen’s orchard at Katikati.
NZ Avocado research manager Phillip West said a variety of topics were covered at the event, including the importance of maintaining pruning and updates on research relating to pest and soil moisture management.
As the NZ Avocado Growers’ Association, the organisation supports growers through advocacy, research, market development and fruit quality standards.
West said a primary focus of the field day was orchard pruning.
During autumn, there is obviously less risk of sunburn on trees, and buds have “committed” to become leaves or flowers when they emerge in spring.
“By waiting until mid-April to start pruning, you can maximise the amount of flowers you have in spring,” West said.
“Pruning in late summer/early autumn can shift more buds to be vegetative, reducing flowering and yield.”
This was based on the tree’s energy allocation and environmental conditions.
West said the buds undergo a series of development stages, starting with vegetative buds that produce new shoots and leaves.
Through late summer and early autumn, the young buds on the tree commit to becoming flowers or new leaves, with energy being directed towards flower development.
Flower panicles then elongate in spring to become bunches of flowers that emerge from the branch tips.
Uniquely, the flower’s male and female phases occur at different times, promoting cross-pollination and fruit set.
West said this process was crucial for the avocado tree’s reproductive process and the production of fruit.
“Trees that have produced a good amount of fruit the season prior can have their resources depleted.
“So, ideally, growers want to promote as many flowers as you can get going into the season ahead.
“If you get too many, you can always prune some off in the spring to achieve a balanced crop-load.”
He said pruning could be ongoing, from April to November.
“You can chip away at it through winter, so it is all done by spring.”
West said October was the peak month for full flowering, followed by fruit set.
While some fruit would fall in December, and again in January to early March, the balance will stay over the summer.
Remaining fruit will “size up” and accumulate dry matter ready for harvest from around July onwards.
West says pruning also produces an “open canopy”, which reduces the amount of fruit rot fungi in an orchard.
Regular pruning, done by the orchard owner or a contractor, “smooths out” production from one year to the next.
He said material removed during pruning could be “recycled” as a nutritious mulch and spread under the trees.
Also discussed at the field day was a pest research programme.
West said the project aimed to investigate the potential impact of insects present at flowering on avocado fruit set and yield in New Zealand.
Some native insects were present in orchards at flowering, and there is growing evidence that they might be damaging flowers and impacting fruit set.
These insects were found in all the main avocado-growing regions, and spray trials suggest they could be impacting the yields of some orchards.
West said observations point to their feeding on the internal parts of the flower and preventing fruit set or preventing a healthy seed from developing.
“Without a seed, avocados remain very small and are not marketable.
“The small size of the fruit is less attractive to consumers and affects the marketability and value of the avocados.
“It can also cause premature fruit drop, which can be detrimental to the overall health and productivity of the orchard.”
West said research was now focused on developing a better fundamental understanding of the insect lifecycle and potential control options.
Once there’s a better understanding of this potential pest, an assessment can be made as to whether it should be incorporated into an integrated pest management (IPM) system for growers.
The field day also reflected on summer storms, which devastated several avocado orchards in the Bay of Plenty.
“Wind damage is one of the biggest downgrades of fruit,” West said.
He said orchard owners should be mindful of tree height relative to their shelter, making them susceptible to wind damage.
“Shelter will generally only protect trees out to eight times the distance between the top of the shelter and the top of the trees.
“If you have a 10m-high shelter and 7m-high trees, then there is only a 15m protection area at the tops of the avocado trees.
“Avocado trees can have a lot of fruit at the top, and often this can really get knocked around by wind.”
West said avocado trees will shelter themselves to some extent, but pruning trees to a lower height may significantly improve an orchard’s resilience to strong wind events.