Ecological balance at the heart of IPM

ECOLOGICAL BALANCE

AT THE HEART OF IPM

Words by Geoff Lewis

Mike Parker with folder showing 'beneficials'

Mike Parker has been in the growing business for more than 40 years and is currently a member of the Vegetables Research and Innovation (VR&I) board and a director of Vegetables New Zealand Inc.

Over 20 years ago he was also one of the leaders in the development of Integrated Pest Management (IPM). IPM is a strategy designed to manage the natural tendency of horticultural pests – insects, weeds and fungi – to develop resistance to commonly used agricultural pesticides. These days, Mike grows sweet corn, maize, rockmelon and watermelons on his property near Hamilton. It wasn’t long ago when he was growing significant quantities of brassicas – cabbages, cauliflower, broccoli, brussels sprouts and forage brassicas – supplying major supermarket outlets with fresh produce alongside LeaderBrand and fellow grower, Mike Arnold, until it became unprofitable to do so. Mike's interest in IPM began in the 1990s when he and Mike Arnold discovered a then new chemistry on the market, methamidiphos, an organophosphate that was useful in combatting the diamondback moth problem. These creatures would chew holes in his brassicas and render them unsaleable.

“We started to see the development of resistance,” Mike says. “Being an organophosphate, it also killed the beneficials – insects like hoverflies, spiders and ladybirds which would normally prey on the moths and white butterflies (lepidoptera). “We sat down with the Crop and Food people, now Plant & Food Research Ltd, and worked out how to retain the effectiveness of the products. “Together, we came up with a process of rotating different products and chemicals that didn't affect the beneficials and to apply chemicals only at various thresholds. “The Crop and Food guys would take us into the field and train us as ‘crop scouts’ determining the level of pest damage in brassicas and lettuce and working out the thresholds for applying insecticides. After doing this for about six months we started getting lacewings everywhere – a beneficial scientifically known as Chrysoperla rufilabris that is widely used to control many different pests. “We also learned about the use of BT – Bacillus Thuringiensis – a bacterial toxin effective in the control of white butterfly.”

IPM has come a long way since and is now tailored to the specific community of pests and beneficials which come with different crops. IPM also means dividing the year into heat units or periods of time in which the pests are likely to come in numbers, and rotating the chemistry through these windows so as not to promote resistance.

IPM is an integration of cultural factors including soft chemistry, timing and scouting. Using nature itself to provide more beneficials and fewer chemicals

“In the old days I'd spray once a week. Now, by using IPM, I only apply sprays once or twice in the life-cycle of the crop and not at all in winter.”

“IPM is an integration of cultural factors including soft chemistry, timing and scouting. Using nature itself to provide more beneficials and fewer chemicals. I don't think you'd get away with not using chemicals at all and we can't use BTs too much or we'll get resistance to them too,” Mike says. Mike is a member of the Reassessment sub-committee of Vegetables NZ and vice-chair until recently. “We did a reassessment of (the herbicide) Paraquat and had to justify why it was so important and why we had to continue using it. The sub-committee included clover seed producers, lucerne growers and some kumara growers. “We are doing the same thing with glyphosate (commonly marketed as Roundup) which is also an organophosphate. Some are quite useful against threats like the brown marmorated stink bug and fall army worm.” These damaging horticultural pests are currently chewing and burrowing their way through Australia. All horticulture representative groups are part of the A Lighter Touch programme which endeavours to reduce chemical treatments. However, those people who are trained and experienced in recognising pests and beneficial predators are ageing and becoming fewer, says Mike. “There will soon be the need to train a new cohort of crop scouts.”

According to the European Commission, glyphosate is currently approved for use in the European Union until December 2022. Austria became the first EU country to ban glyphosate in July 2019. Germany announced it will also phase out the controversial weedkiller by 2023.

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