South African apple breeder and specialist Nigel Cook said Goulburn Valley growers would benefit from understanding management strategies in South Africa, particularly in the face of climate change.
A leading South African orchardist has outlined strategies for adapting apple orchard management in the face of climate change, writes ANDY WILSON.
Physiologist and plant breeder Nigel Cook told more than 60 Victorian orchardists that a warming planet would require growers to adapt their management plans.
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Goulburn Valley orchardists joined with other growers from the rest of Victoria at this year’s Fruit Growers Victoria winter orchard walk at Merrigum in July.
The event was jointly hosted by Apple and Pear Australia Limited.
Dr Cook said Goulburn Valley growers would benefit from understanding management strategies in South Africa, due to that country’s entire land area sitting north of Shepparton’s latitude.
Dr Cook gave evidence for the impact of global warming on the apple industry.
“Everything that we do in apples in South Africa is north of Shepparton,” Dr Cook said.
“And we regularly hear climate change denialism, but here we are experiencing it first-hand.”
Dr Cook presented data comparing ‘chilling units’ measured in the past decade with the long term average.
“You can see that only one of the 10 years is colder,” he said.
A chilling unit is a calculated period of time at a temperature low enough to stimulate spring bud burst in fruit trees.
Apple trees typically require about 750 chilling units across the three months of winter.
Dr Cook said this sometimes lowered to 400-500 chilling units, which caused delayed foliation, lowering productivity.
“The tree bursts unevenly and it is not uncommon to have fruit and flower and buds and even dormant buds on the tree at any one time,” he said.
“We are seeing warming in terms of chill units up quite close.
“In cold areas, buds go (dormant) faster and into a deeper dormancy, but they also come out much quicker, whereas in a warmer area, that whole process is stretched out.”
Dormancy has typically been managed with a range of ‘rest breaking’ spraying agents.
Dr Cook said the effect in apples was noticed in the second year after rest breaking.
“Yes, you are manipulating this year’s flowering pattern, but more importantly, you are growing spurs for the yield a year later,” he said.
RedLand Apples bought Jeftomson Orchards in September 2023 and has begun major replanting projects.
Dr Cook also said refrigerating nursery trees before planting “worked like a charm” to help the tree’s bud burst and branching structure.
“Let’s stick nursery trees in the coldroom where every hour is a chill unit, and all the buds burst on the newly planted tree three months later and the leader grows,” he said.
A common theme returned to by APAL at its events is the need for orchardists to remove under-producing blocks of trees.
APAL industry services manager for grower development and trials Nic Finger said APAL wanted growers to critically review their production and make decisions.
“Can it be improved or should it be removed?” Mr Finger said.
“It can be an underperforming asset. It needs to perform or it needs to go.”
APAL strongly advocates for farmers to remove underperforming blocks of trees and replace them with newer varieties.
RedLand Apples orchard manager Brent Reeve took the attendees on an orchard walk to show where the company has replaced trees older than 25 years with two new varieties.
RedLand Apples bought Jeftomson Orchards in September 2023 and employs 500 staff during its peak season.
Mr Reeve said the company had planted 30 hectares of Sassy apples this winter with pollinator variety Pink Eve to replace underperforming trees and had plans to plant a further 100 hectares of Sassy and Dazzle.
RedLand Apples owns the rights for both varieties, which Mr Reeve said had been chosen for the Asian market.
RedLand Apples has planted 30 hectares of the variety Sassy for the Asian market
