Benefits of copper spraying

Ross Mutton, a member of AVOCO’s Grower Relations Committee.

Examining the orchard practices of Australia’s biggest avocado growers has highlighted the benefits of spraying copper to optimise fruit quality.

In New Zealand, Avoco grower leaders are encouraging their peers to adopt similar practices to ensure more of their fruit reaches the consumer in premium condition.

Ross Mutton, a member of Avoco’s grower relations committee, was among a group of growers who travelled to Western Australia and Queensland last year to visit large-scale commercial orchards to learn more about the Australian industry and Avoco’s place in it.

The industry’s three largest growers are family owned and operated, all supplying in excess of one million trays of fruit most years. Most of it they supply to the domestic market, with their involvement extending to shipping and marketing the fruit as well.

Quality issues

Having such a direct relationship with the end consumer, Ross says quality issues quickly bounce back to the Australian growers who understand the importance of copper spraying their crops and preventing problems before they occur.

“Being at the sharp end of a call from a retailer means they’ll do whatever they need to,” says Ross, “so they don’t have any issues.

“They will put their copper sprays on, not like a lot of Kiwi growers do because it feels like here, we are so removed from the consumer.”

Copper spraying is considered the most effective way to prevent fungal rot - a problem which starts in the orchard through infection of fruit, but usually doesn’t emerge until post-harvest.

Fungal rot has been an industry-wide fruit quality problem over the past two seasons in New Zealand.

Avoco technical manager Colin Partridge and consultant Jerome Hardy support researchers who advise the problem can be mitigated by growers applying copper spray and removing dead wood and plant material from around their trees.

Wet climate

Financial costs and complacency are cited as reasons why some growers avoid spraying. But Ross says New Zealand’s wet climate and the distance of their fruit to market means Kiwi avocado growers must spray to preserve fruit quality.

“Growers here might think their fruit won’t be affected or that they’re safe in the mix of a grower pool, so they don’t do it,” says Ross.

“Smaller growers in New Zealand might have a copper bill of up to $4000, but Australian growers spend a whole lot more because they are much closer to the problems when they arise. “In reality, we have even more reasons to spray than the Australians because our fruit has further to travel, putting it at greater risk of post-harvest ripening disorders.”

Dead wooding

The “best practice” approach adopted by Australian growers extends to include dedicated dead wooding orchard programmes. Colin Partridge agrees that rot control is an integrated process and orchard sanitation is very important.

“We advise growers to get rid of dead wood and mummified fruit through mulching and pruning to let light in,” explains Colin.

“This, together with wind protection, trying to increase fruit calcium levels and soft fruit handling, are collectively as important as copper sprays.”

Avoco is New Zealand’s largest avocado export supply group, with support from more than 800 growers. In 2017-18, Avoco is expected to export about 1.3 million trays of fruit, with 81 per cent destined for Australia. Under the Avanza brand, Avoco also exports to developing markets in Asia.


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