Roundup Ready® technology shines - Elders Rural Services
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Roundup Ready® technology shines

Good annual ryegrass control in the canola phase is critical to setting up a cropping program for subsequent cereal rotations.

It’s a scenario that has played out in Western Australia’s Great Southern region, where high levels of weed escapes in triazine-tolerant canola have been negatively impacting whole cropping programs.

Getting annual ryegrass control right in canola can have a massive impact for growers, which is why Bayer teamed up with a local agronomy consultant to test annual ryegrass resistance across 39 glyphosate resistant ryegrass populations in the Great Southern region.

“What we don’t want is for a grower to go into a Roundup Ready® canola or a TruFlex® canola phase to find weed resistance, and then experience sub-optimal weed control results,” explained Hugh Trenorden, Bayer business development manager for Western Australia  and South Australia.

“So, as part of the trial, we added Roundup Ultra® MAX, a liquid 570 g ai glyphosate, a generic glyphosate 450, and Roundup Ready Herbicide with PLANTSHIELD®, a granule 690 g ai glyphosate tank mixed with clethodim, so we could do some shared learning.”

It was a targeted ryegrass sampling methodology, where growers and the crop consultant were looking for problematic annual ryegrass areas in paddocks.

“They tested those patches for resistance levels, so we would then know what the likely outcome would be when using different types of chemistry,” Hugh explained.

“The observations were as expected, and followed previously published small plot studies, but one of the significant outcomes of this approach was that this time we saw it play out in actual paddocks.”

The results uncovered a slight efficacy advantage when using Roundup Ultra MAX over a generic glyphosate 450, but even when using Roundup Ultra MAX there was still an expected level of annual ryegrass resistance.  

“We also looked at the clethodim by itself and found there was a level of resistance there too,” Hugh said. .

“However, when we did a tank mix of Roundup Ready Herbicide with PLANTSHIELD and clethodim, the data showed that it provided complete control of all but two of the 39 glyphosate resistant populations.

It’s not impossible for a population to be both glyphosate and clethodim resistant, so this mix is not a silver bullet, but it’s a really good way of getting a robust level of weed control in the canola phase.

Hugh believes the level of control achieved in the canola phase from a fully loaded, high quality glyphosate such as Roundup Ready Herbicide with PLANTSHIELD, mixed with clethodim, as well as a robust pre-emergent herbicide option, has shown where the future of crop management is going.

“That mix  is known to be quite robust – it’s been used in fallows and in vineyard operations for a while – but the advantage of doing it in your canola phase is that you can get really good crop competition from a hybrid canola on top of that,” he said.

“That mix can break down if you’re in a vineyard scenario where you’re doing it time after time trying to use that to just control your ryegrass.

“However, when you put it with a really good pre-emergent and then use it in canola, you can really knock your weeds down quite effectively and get those benefits that carry on for a number of years.”

Growers now have the tools to create some high-level flexibility with TruFlex canola, to effectively target populations of ryegrass using the appropriate rate of Roundup Ready Herbicides at the appropriate timing.

“Additionally, this data suggests that by introducing clethodim into that TruFlex canola system, it can really reduce the likelihood of having glyphosate resistant survivors coming through,” Hugh  said. .

“In agriculture you never get 100 per cent, but the likelihood of getting close to 100 per cent weed control is quite high given the data that we’ve seen both in plot trials and then this commercial scale trial that we’ve done this year.”

“By collating that data, the consultant’s customers at the local level can now all analyse the results and have some  confidence that when they put an integrated weed management plan together, that they’re going to get a good level of weed control.”

Roundup Ready canola allows for the application of Roundup Ready Herbicides from cotyledon to six-leaf, consisting of no more than two applications of a Roundup Ready Herbicide in crop.

TruFlex canola allows for an extension of this window beyond the six-leaf growth stage up to the first flower.  With TruFlex canola varieties, growers have the choice of either a two-spray program or a three-spray program, depending on application rates or the weed pressure in the paddock.

Article written by Bayer Australia for Seasons magazine. 

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Roundup Ready®, Roundup Ultra®, PLANTSHIELD® and TruFlex® are Registered Trademarks of the Bayer Group.

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