Wednesday, July 6, 2022

Glyphos hit by grass resistance

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The discovery of glyphosate resistant ryegrass in Marlborough has sparked calls for compulsory labels on agri-chemicals highlighting resistance risks.

Foundation for Arable Research (FAR) CEO Nick Pyke officially confirmed the discovery at a field day in Hamilton on Thursday.

The discovery came during work for a Sustainable Farming Fund (SFF) funded project on studying glyphosate resistance. It was identified in grasses from a vineyard after a call from a chemical company.

Pyke said it has been a case of “when not if” New Zealand officially had grass species with glyphosate resistance, and comes almost a decade after Australia got it.

In the United States farmers have also been grappling with glyphosate resistance for a similar period. It had been exacerbated by the use of genetically modified “Roundup Ready” crops. These enable them to spray crops with glyphosate based Roundup spray, without damage to the crop itself. Intense use had seen some weeds develop resistance.

Graeme Peters, head of agri-chemical group Agcarm, said resistance development is not new, in both crop and animal treatments.  However there were strategies to help reduce the incidence of resistance and the rate of spread.

But he believed due to widespread glyphosate use for weed control the time was right to bring in compulsory labelling to inform users about resistance risks and strategies.

“We are talking about information on product labels that state, if resistance is seen in treated plants, what to do about it.”

Agcarm produces a labelling guide with risk management labels, but at this stage it is only a voluntary requirement under labelling laws.

In Australia chemicals are coded for ease of understanding, and farmers advised to rotate their codes, similar to drench rotations.

Pyke said in general FAR would support initiatives that reduced the risk of herbicide resistance.

“The use of suitable labelling practices and resistance management strategies are examples of these.”

But Debbie Morris, director of Animal Compounds Veterinary Medicines (ACVM) division at MPI said the agency prefers to support projects promoting awareness among users of agricultural chemicals, development of relevant management solutions, and best practice.

“For example, the three-year ‘Avoiding Glyphosate Resistance’ project takes a cross-sector approach with the end goal of a total management strategy to guide users of glyphosate.”

There were three reasons why the troublesome resistance had taken so long to get to NZ.

The first was simply that Australians used glyphosate more frequently in their broad acre cropping systems than in NZ. Secondly the greater use of annual ryegrasses in Australia meant grasses were sprayed out more than in NZ’s perennial systems.

“And we usually have animals in our farm systems so if a resistant grass appears, it is often chewed out,” Pyke said.

Peters said while worrying, resistance development was neither unexpected nor unmanageable.

“With good resistance management plans you should be able to knock out any resistant ryegrasses and then go back to glyphosate.”

Massey University’s senior lecturer in weed science Dr Kerry Harrington said NZ’s experience threatened to mimic Australia’s. Intense use on roadsides and vineyards had contributed to resistance development there.

“For roadsides rotation of spray it is easy, you could move to something else, but glyphosate has been the cheapest and safest to use for years.”

For vineyards it can be more problematic. Sustainability standards have required the use of safe glyphosate sprays, and some alternatives including Paraquat and Amatrol can have residual toxicity or residue issues.

Harrington agreed glyphosate has been a victim of its own success, easily used, safe and affordable. Public pressure for safer sprays had often meant it was the only option suitable for some applications.

He encouraged users to consider rotation on a spray that “had been hard to get people to think about rotating”.

Glyphosate – as farming as….

Just as Redbands and the Hilux are must haves on a Kiwi farm, so too is Roundup, the most popular glyphosate spray in the world.

Developed by Monsanto and launched back in the mid 70s, two generations of farmers here have reached for it to control weeds in crop and pasture applications. 

Glyphosate was originally marketed as Roundup by Monsanto, but since the company’s patent expired in 2000 a plethora of other glyphosate products are now available.

Of New Zealand’s $300 million a year agrichemical market, herbicides account for half and the lion’s share of that goes to glyphosate based sprays.

Graeme Peters of Agcarm said it was easy to understand why glyphosate is regarded as the “wonder spray”.

It has been a cheap, effective and very safe means of controlling broad leaf weeds and grasses in multiple situations.

Pasture conversion, crop protection and weed control in recreational areas have meant it has never been far from use in any open space, both pastoral and public.

“Sticking to the label recommendations, rotating crops and chemicals and not exceeding recommended treatments each year will help keep resistance at bay,” Peters said.

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