Sterile moths dropped to kill apple pest

Plant and Food entomologist Dr Jim Walker at NZ Apples and Pears' AGM in Napier. Photograph / Warren Buckland

Hundreds of thousands of sterile male Canadian moths are being dropped by drone on a Central Hawke's Bay orchard in a bid to rid Hawke's Bay of codling moths and to keep fruit chemical-free.

Speaking at NZ Apples and Pears' annual conference in Napier earlier this month, Plant and Food entomologist Dr Jim Walker said they were fed a diet turning them a distinctive red and imported during summer.

In a trial that was likely to be rolled out to the rest of Hawke's Bay, they overflowed the existing population.

"With 10 to 12 releases a season we can collapse the population," he said.

In the 2016/2017 season, just four wild moths were caught in the 100ha orchard, a 96 per cent decrease on the previous season.

"This year those four moths are going to be invaded by another quarter of a million sterile moths."

It would eliminate the need to spray for the insect, another example of Integrated Pest Management - preventing pest damage through a combination of non-chemical spray techniques.

IPM resulted in low chemical residues which opened overseas markets and "turned a threat into an opportunity".

He said insect pests, like people, were becoming global and advocated releasing natural enemies of some of the worst pests to pre-empt an incursion. NZ Apples and Pears New Zealand CEO Alan Pollard said the conference came at a time when the industry was on a roll.

"We have had five years of good growth, good returns and stable markets," he said.

There was a high level of investment, increasing production through new plantings and growing systems, new varieties for new markets and new jobs for Hawke's Bay.

"We expect to see over one million apple trees planted in New Zealand this year and nurseries have three-year back orders as growers work to meet a growing international demand for New Zealand apples."

Opening speaker at the Napier Conference Centre was Plant and Food chief operating officer Dr Bruce Campbell. He said the 2013 goal of the industry doubling exports by 2020 to $1 billion seemed ambitious at the time, but hindsight was showing it to be conservative, with exports sitting on $700 million in 2016.

Dr Campbell said there was a wave of change in the world and New Zealand needed to continue to "disrupt or be disrupted", with the meat industry facing huge disruption due to a rise in appetite for quality plant-based foods.

New Zealand was recently named the world's most competitive apple performer in the World Apple Report for the third consecutive year.