Big savings in cutting spray use

Australian entomologist, Dr Paul Horne, told a recent Potatoes New Zealand research update breakfast meeting that he could give examples from his home country of hundreds of growers who had adopted IPM practices.

Not only had they done that, but had taken it further, reducing sprays for potato moth from ten to seven.

"That's not far-fetched - it's basic biology," Horne explained. "If you're prepared to put in the effort, you can do the same, I'm absolutel certain."

He pointed out how one grower of 20 years' standing through adopting IPM was now using less chemical over his whole growing operation than he had previously used on just one crop.

"It works," he says.

Based in Victoria, most of the work of his company, IPM Technologies, is in reducing insecticide use by showing growers and their advisers the impact of chemical on beneficial species. He and colleague Jessica Page, who have worked on IPM strategies and training for over 25 years across a range of crops in Australia, are now developing an IPM strategy for tomato potato psyllid (TPP) both in Australia and NZ.

For many crops there were only three control agents: pesticides, management practices and biological control.

"There's nothing else," he says. "That's what you've got to look at."

Horne added that an IPM system was never static and will change over time. Growers could try to add on as many options as they could to build into their strategy.

"People ring us when there's a crisis, when pesticides don't work," he says.

Pests were similar in New Zealand with the main problems for potatoes being potato tuber moth (PTM), which could cause significant damage where there was no cool storage on or offshore. Beneficial insects could be used such as parasitic wasps and damsel bugs, which were more important across the Tasman.

There were predatory thrips as well as pest thrips and a parasitic wasp which stung PTM had been introduced over 50 years ago. There were now three of these wasps established in Australia, compared with just one in New Zealand. Horne said a big advantage was that PTM caterpillars could be pulled apart in the field to find the wasp maggots, instead of needing to be bred up in a laboratory "and then telling the grower they should have sprayed three weeks ago".

"Use chemicals only as a supporting tool," he told growers.

"Consider the impact that spraying could have on beneficials, choosing them based on the insects they wanted to look after.

"You might choose a soft chemical, rather than blasting everything away. And if you choose the wrong product, you can make things worse."

Article: Potatoes NZ