Research into industry’s best grass herbicide strategies a boon for growers

Independent, ″showpiece″ trials investigating the best upfront herbicide strategies put forward by crop protection companies against annual ryegrass are proving highly valuable for growers’ weed management planning.

Growers need to keep track of changes in chemical availability and pricing to assist with optimal decision-making. However, being aware of industry research results remains a key consideration to ensure they maximise weed control in their cropping programs.

Showpiece trials comparing the best pre-emergent and early post-emergent herbicide strategies against annual ryegrass will continue this year by specialist private research and extension group, SLR. They have been conducted in Western Australia for the past three seasons.

 The herbicide treatments are evaluated in a similar way to GRDC National Variety Trials™ (NVT) research, with last year’s trials being conducted at Dalwallinu, Goomalling and Kellerberrin in the State’s wheatbelt region.

 The trials compared a wide range of popular standard herbicides, including trifluralin, pyroxasulfone, Terrain^® Flow, Callisto^®, Boxer Gold^®, Overwatch^®, Mateno^® Complete, Luximax^® and Voraxor^® applied in a variety of combinations pre-emergent and early post-emergent.

Farm consultancy group, Synergy Consulting, has kept a close eye on the research over the past three years and has hosted several groups of growers at the sites. The trials have also been visited by numerous other growers during field walk events.

 Principal consultant David Pfeiffer said the SLR showpiece trials program was a relatively new concept and the research into the best herbicide strategies against annual ryegrass was ″a powerful tool for growers″.

″It’s great that there will continue to be opportunities for growers, and grower groups, to look over these trials,″ David said.

Last year’s trials once again showed the clear benefits of achieving strong weed control from effective early post-emergent herbicide applications.

In early August at Dalwallinu, standard incorporated-by-sowing (IBS) treatments including pyroxasulfone resulted in 78-85% control of annual ryegrass, whereas following a pre-emergent application of trifluralin with pyroxasulfone in the form of Mateno Complete at the early post emergent stage increased the control to almost 92%.

Mateno Complete also contains aclonifen and diflufenican and has been targeted for early post-emergent application by more and more growers in recent times to help achieve longer control, particularly of annual ryegrass, across the entire soil surface compared with IBS herbicides.

Mateno Complete also proved more powerful when compared to an early-post emergent application of Boxer Gold following pyroxasulfone IBS at Dalwallinu, improving the control from 85% to 92%.

In November at Kellerberrin, the early post-emergent application of Mateno Complete following IBS application of trifluralin showed 99% control, an increase of nearly 13 percentage points compared with pre-emergent application of pyroxasulfone, trifluralin and Callisto. This resulted in a 600 kilograms per hectare yield advantage at harvest. Control from Mateno Complete following Terrain Flow was also about 10 percentage points higher than the pre-emergent application of Terrain Flow with pyroxasulfone.

Earlier in July, all of the early post-emergent Mateno Complete applications demonstrated 98-99% annual ryegrass control, compared with all pre-emergent pyroxasulfone applications showing 88-92% control.

It was a similar story at Goomalling, with annual ryegrass plant counts taken in June, July and September consistently showing the lowest counts per square metre in the Mateno Complete treatments.

At all sites, there was also an early post-emergent application of Mateno Complete following pre-emergent use of Boxer Gold, compared to pre-emergent application of pyroxasulfone followed by post-emergent use of Boxer Gold, and there was up to a 9-percentage point annual ryegrass control benefit where the Mateno Complete was applied.

David said last year’s showpiece trials were ″pretty conclusive″ in showing that an early post-emergence application of Mateno Complete was the best strategy to achieve optimum annual ryegrass control, and the evidence in the previous trials was similar.

He said the challenge for growers, particularly with large-scale operations, was effectively managing their spraying logistics to target weeds before they became too big, and prior to weather events, to ensure they maximised control from applications of the herbicide.

″The post-emergent strategy is a no-brainer – Mateno Complete is much more robust for theseapplications and it consistently wins every time. You get a weed kill over thewhole surface, you don’t have to load as much (pre-emergent herbicide) upfront,which is also better for crop safety because there will be less likelihood ofdamage if there’s a heavy downpour, and it pushes the weed control later intothe season.″

″If there arebroadleaf weeds present, it will also sufficiently control both those weeds andthe ryegrass.″

This was also demonstrated in last year’s trials, with the Mateno Complete applications largely being the only treatments to almost completely control volunteer canola.

 David said growers needed to have the spraying capacity to undertake post-emergent applications of Mateno Complete.

″Having sufficient capacity can be difficult, so it can be best to nominate a percentage of your program, covering the bad grass areas, for these applications.″

David said the research was showing growers largely had two options for their early annual ryegrass control – apply pyroxasulfone in a tank mix pre-emergent to achieve near 90% control, or apply Mateno Complete early post-emergent for 95% plus control after upfront application of herbicides like trifluralin or Boxer Gold.

He said prosulfocarb and diflufenican were other suitable herbicide options for early post-emergent applications; however, their weed control performance was not as consistently good as that seen with Mateno Complete.