01/04/2026

GROWERS are increasingly adopting latest herbicide strategies in canola for improved weed control, helping to alleviate some of the concern over herbicide resistance and the over-use of some popular options, as well as crop safety.

Weed resistance to clethodim and glyphosate herbicides is a rising issue in many regions, while applications of traditional options such as propyzamide, including in tank mixes, can retard crop establishment.

However, the enhanced use of Tenet^® herbicide and particularly its registration for post-emergent application has opened the door for more effective weed control strategies that also are taking the pressure off traditional herbicides and allowing crops to flourish.

Developed by ADAMA Australia, Tenet contains the active ingredient, metazachlor, and is the only Group 15 herbicide that can be applied post-emergent or incorporated by sowing (IBS) in conventional and herbicide-tolerant canola.

The company’s Market Development Manager in South Australia, André Sabeeney, confirmed that with clethodim activity starting to fail in areas, Tenet was proving to be an excellent residual option in mixes with post-emergent herbicides.

“We have seen a dramatic increase in ryegrass control in some trials, especially where clethodim is losing its edge. Growers and agronomists are often trying to balance spraying when weeds are small, but allowing enough time to ensure the population has emerged and then using Tenet as a mix partner at an early spray timing helps reduce these escapes due to its residual activity,” André said.

“It’s taken up mostly through the roots and you can mix it with pretty much anything post-emergent in canola. In fact, it is strongly recommended to be applied in mixes with glyphosate, Liberty^®, atrazine, clethodim and imidazolinone herbicides. And add oils too – it doesn’t increase crop damage from other herbicides in the mix.”

He said in southern areas, many growers wanted to use Tenet post-emergent because other options were limited and they wanted to avoid damaging crops, whilst they also were using different mode of action herbicides pre-emergent. 

“The effective use of robust pre-emergent herbicides in canola has become standard practice and most growers are doing this well, but many of these herbicides are incorporated by sowing (IBS), which removes the herbicide-treated soil out of the furrow to increase crop safety. This system often allows early ryegrass germination in ‘untreated’ furrows and that’s where Tenet has a perfect fit.”

André Sabeeney, Market Development Manager with ADAMA Australia in SA, says applying Tenet herbicide in canola at an early stage in mixes with clethodim – and with glyphosate in glyphosate-tolerant crops – allows improved weed control and some residual activity against later germinating weeds.

ADAMA has continued to develop Tenet over recent years. “We now have an expanded registration for EPE use in the works looking at a broader rate range and broader crop timing, in addition to reduced plant backs,” André said.

In the mixed farming region of North Central Victoria, Nutrien Agronomist Chris Dunn said most of the canola was devoted to triazine-tolerant varieties and clethodim had been an important herbicide in these programs, however, up until the ability to tank mix with Tenet for post-emergent application, there also had been concerns for its longevity.

He said the ability to use Tenet post-emergent now allowed growers to separate the use of clethodim from triazine applications and apply it with the residual herbicide, which also was helping to achieve better results.

“Growers might now go up front with trifluralin and bixlozone, trifluralin with propyzamide or trifluralin by itself, come back PSPE (post-sowing, pre-emergent) with atrazine and terbuthylazine, and then in the early post-emergent window, depending on the ryegrass pressure, apply clethodim with Tenet. Going post-emergent with Tenet has really helped,” Chris said.

“We also noticed no crop effects with Tenet and clethodim, whereas you do get effects with propyzamide. Tenet is definitely softer than propyzamide. Before we could apply Tenet post-emergent, we played around with applying propyzamide with clethodim, but it hurt the crop a bit.”

Agronomist with Nutrien at Elmore in Victoria, Chris Dunn, pictured in a local canola crop, says the ability to apply Tenet herbicide post-emergent in canola is helping to extend the life of clethodim herbicide and achieve improved weed control.

Bailey Parsons, Agronomist with Nutrien at Pingelly in WA, said Tenet had proven popular where there was resistance to clethodim (Group 1) and glyphosate (Group 9), which was becoming more of a problem within the area.

“In addition to the knockdown benefit from clethodim or glyphosate, you also still get the residual control later in the season from Tenet, which is especially good for our non-wetting soils, where we have multiple germinations of ryegrass,” Bailey said.

Market Development Manager with ADAMA Australia in WA, Bevan Addison, said with the ongoing concern over future paraquat herbicide applications, achieving good grass control and safeguarding glyphosate effectiveness was becoming even more important for growers.

Bevan said herbicide applications with Tenet in canola had continued to show encouraging results and demand for the product had escalated as growers increasingly recognised its value in their programs. “Tenet is really taking the pressure off herbicide tolerant canola systems herbicides. It’s also become an invaluable tool within whole farm weed management and crop rotation programs, significantly reducing annual ryegrass panicle numbers and seed set for subsequent cropping,” he says.

Bailey Parsons, Agronomist with Nutrien at Pingelly in Western Australia, says applied in mixes with clethodim or glyphosate in canola, Tenet herbicide provides the benefit of residual control later in seasons. This is especially good for the area’s non-wetting soils, which cause multiple ryegrass germinations.

Growers interested in further information about Tenet herbicide can contact their local Nutrien Branch or visit the ADAMA website.

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