Kiwi Apple Success Story

May 2020

Farewell Silent Spring, the science of pesticide reduction in the NZ apple industry

The domestic apple industry has come a very long way since the bad old days of nicotine and arsenic in the 30s and 40s and organophosphates from the 50s. By the 60s it was clear to orchardists, exporters and chemical companies that both insect pests and overseas buyers were developing resistance to their “spray by the calendar” regimes. Talented scientists from the UK were invited to New Zealand to join DSIR and set up a programme of research into integrated pest control. 

That long-term programme has resulted in numerous innovations in terms of pest trapping, monitoring, mating disruption, and targeted treatments aimed at meeting European demands for residue-free fruit and Asian pest-free requirements. 

The evolution of successful apple growing over that period has been detailed in a book by Howard Wearing, entomologist and former DSIR scientist, called Farewell Silent Spring – the New Zealand Apple Story. Dr Wearing came to NZ in the late 60s to join the DSIR research programme and work on the nemesis of apple growers – the codling moth. He continued leading research into apple pest management until his retirement in 2001. In 2014 he started work on documenting the successful collaboration between researchers, growers, industry bodies and chemical companies and the changes in attitudes, technologies and management strategies that ensued. The book is a 280-page compendium of well written, illustrated and referenced resource material for anyone with an interest in the industry. 

Howard came to New Zealand in 1967 because he wanted to be involved with integrated pest management, which he encountered as a student. “I was employed initially to work on codling moths within the integrated pest management programme. There were very few insecticide choices back then and so we tried a product called Ryania that wasn't toxic to some of the natural enemies of the moth. It was being used in Nova Scotia but it wasn’t as successful here because our environment was more favourable to moths. They were able to produce many more eggs and we didn’t have the predatory bugs that Nova Scotia had,” he says. “The granulosus virus from Mexico was promising but we needed a broader approach to biological control that would include leaf rollers. The attempt to introduce predators of codling moths was not successful but leaf roller parasitoids were successfully established and have gradually spread. It has taken perhaps 50 years for the numbers to build up but we now can see they have significantly reduced the leaf roller populations around orchards, as well as within them.” 

Mites were also a pressing problem and they were developing resistance to miticides and organophosphates but in Nelson researchers found that mite predators had also developed resistance over a period of about nine years. Resistant predators were bred and spread to other parts of the country and so it proved possible to implement a national programme of biological control of mites. “Not having to use miticides was a major cost advantage. Everybody got behind us and we tested 40 or so orchard chemicals on these predators to identify the products they were resistant to,” says Howard. “At the same time, we worked on the long-term objective of producing pest-free fruit without having to use organophosphates. Pheromone work got going particularly in the 1980s with the discovery of the pheromone for codling moths in the USA. First, it was put in sticky traps and the catches were used to monitor the appearance of codling moth in orchards. It also triggered research on pheromones of leaf rollers and other pest species.” 

The leaf roller situation in New Zealand was complicated with the discovery that there were four native species as well as one (the light brown apple moth) from Australia. This led to work on mating disruption using female pheromones to flood the orchard and disrupt the ability of males to find females. It was not easy because the compounds are volatile and are carried by the wind but eventually a plastic capillary dispenser containing pheromones of the important leaf roller species and codling moth was developed. It comprises a narrow tube containing the pheromones and a specially constructed wall that releases pheromones slowly over time. 

“The big development in the 1990s was the implementation of integrated fruit production IFP, which involved minimising toxic chemicals and maximising biological controls to look after both human health and the environment. This idea was extended to the whole production system, not just pest management, including tree culture, soils etc. The concept of IFP was very strong in Europe and was implemented fully in New Zealand by 2001,” says Howard. 

“Since then the focus has been on improving it, getting chemical residues down to the minimum, in a program called Apple Futures, which is very important to New Zealand’s exports to more than 70 countries. Each country has its own regulations and requirements with regard to residues, pests and biosecurity so it has been a real challenge to develop a comprehensive system that apple growers can use without having to think exactly which market fruit is going to end up in. The exceptions are some markets like Taiwan and Japan that are codling moth sensitive and for which a special system has been developed in New Zealand.” 

Dr Wearing says the industry’s progress over the past 50 years is the result of the collaboration of all stakeholders, including research and development staff, extension workers, chemical companies and marketers, producing a sustainable pest control system that encompasses the safety of human health and the environment. 

“I think the horticultural and agricultural sectors get criticised for paying lip service to sustainability, but this story shows very clearly their commitment from the 60s right through to the present day. The orchard ecosystem is very complex, and you need teams of people who are collaborating and cooperating rather than competing for funds to achieve a successful outcome. Control systems that suit New Zealand can't be bought overseas. Every apple growing area of the world has its own unique features and problems – you can’t just shift things around and expect them to work.” 

Allan Pollard, CEO of Apples & Pears NZ, says the research programme has allowed the NZ industry to claim the high ground in reduction of chemical residues and insect control, and has expanded to meet the diverse requirements of more than 70 markets. He adds there is tremendous value from the long-term research programme to the industry and the regions in which apples are grown. It has allowed the New Zealand industry to meet the phytosanitary and food safety requirements of global markets and grow exports to take advantage of markets in Europe and Asia. 

The Apple Futures program has maintained the high status of the New Zealand industry. Every year there is an international assessment done on all countries producing apples looking at sustainability and other issues and New Zealand has emerged as No.1 for last four years. 


Showdown Productions Ltd – Rural Delivery Series 15 2020 3