Thursday, July 7, 2022

Confidence is growing in crop pest nets

Growers shouldn’t bet the house or farm on it but pest nets look like a credible alternative to conventional chemicals, Lincoln University researcher Charles Merfield says.

A second, more rigorous season of monitoring covered, organic crops has bolstered Merfield’s belief that mesh could ward off plagues such as tomato potato psyllid (TPP) and potato blight.

A tightly sealed cover could create the sort of Star Wars security dome the late American President Ronald Reagan had in mind, Merfield said.

Compared with an unprotected plot, the organic crops under mesh at the Future Farming Centre showed almost no sign of TPP, yield was 24% higher, and the marketable tuber yield was 125% higher.

Canterbury had the lowest psyllid count in New Zealand but Lincoln trials had shown enough to conclude yield increases would be dramatically higher in the country’s TPP trouble spots.

Merfield had long been aware mesh had to do more than what you’d expect to see in a high school etymology class (Farmers Weekly, January 21).

Growers would need to be sure covers didn’t create counter-productive influences like blight, he said.

Compared with an unprotected plot, the organic crops under mesh at the Future Farming Centre showed almost no sign of TPP, yield was 24% higher, and the marketable tuber yield was 125% higher.

The first year of the trial had provided ideal cool and wet conditions for blight but the past summer had been less challenging.

The nets would need to be tested in conditions like Pukekohe but the contrasting seasons in Canterbury had already given Merfield reasonable confidence something real was going on.

His prognosis for TPP was also optimistic. Chemical control of the psyllid could interfere with integrated pest management plans for other pests but mesh removed that problem and could be used in a variety of ways on a single crop, perhaps dealing simultaneously to aphids, potato tuber moth and TPP, he said.

Or they might be useful for kiwifruit, mesculin salad mixes, carrots, and parsnips.

The United Kingdom-bred Merfield has seen enough of the mesh in Europe, and now at Lincoln, to call the mesh a one-stop response to destructive pest outbreaks.

It might give growers an off-the-shelf solution without having to wait years for a chemical or other solution, he said.

Merfield’s estimate of the cost of nets earlier this year was about $10,000/ha for product that lasted about 10 years.

Even if the cost of buying and applying mesh was similar to conventional chemical control, growers would have the advantage of marketing organic product at premium prices.

The material was also relatively easy to lay and maintain, provided staff were trained properly and it was stitched closely to a base.

A couple of European mesh suppliers involved with the Lincoln trial were interested in selling to NZ growers but that was a chicken and egg situation, Merfield said.

Distributors wanted to be sure of demand so they could price product competitively, while producers wanted a good deal before committing to it.

Growers generally seemed to be saying it was an interesting idea but it was going to take a bit of getting their heads around, he said.

Merfield hoped the next step in his research would be a three-way study comparing covered organic and chemically-treated, non-covered crop with a control plot. 

MORE: http://www.bhu.org.nz/future-farming-centre/information/crop-management/pest-management/tpp

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