Sakura^® remains king of pre-emergent herbicides

Image: Demonstrating weed control for Sakura herbicide (on left) compared with trifluralin herbicide (on right) in a trial at Nyabing in WA.

Bayer Customer Advisory Representative Matt Willis said conditions ranged from ideal in Western Australia to extremely challenging and dry in New South Wales, and also included sites where there were high weed burdens, some weed populations with resistance to trifluralin, and later germinating weeds to test the residual activity of the herbicides.

Nine trials across WA, NSW and South Australia compared Sakura^® and a Sakura plus trifluralin tank mix against current standards including prosulfocarb, Boxer Gold^®, both also in mixes with trifluralin, and a single application of trifluralin.

Matt said all sites received knockdown herbicides and the treatments also included the early post-emergent application of Boxer Gold following incorporation of trifluralin at sowing, an increasingly popular use pattern adopted by growers today as a salvage spray to control weeds that have survived pre-emergent herbicides.

He said various growers consider the opportunity of the post-emergent application under suitable conditions, however spray timing according to weed size plus follow-up rainfall were critical and could otherwise reduce efficacy.

Image: Demonstrating weed control 82 days after seeding for prosulfocarb plus trifluralin applied pre-emergent in a trial at Calingiri in WA.

“Some growers have been coming back with this use pattern in conjunction with Velocity® or Jaguar® for broadleaf weed control,’’ Matt said.

However, the trials showed this application was less reliable.

Ryegrass panicle counts were conducted at all trial sites. Sakura applied alone, and also in mixture with trifluralin, outperformed the other applications.

Across seven trials, Sakura mixed with trifluralin and incorporated by sowing (IBS) achieved an average of 76% control of ryegrass panicles despite the challenging conditions and Sakura alone reduced panicle numbers by 75%, while the next best treatment was the IBS of trifluralin followed by the post-emergent application of Boxer Gold at 64% and the IBS of trifluralin with Boxer Gold at 63%. The single IBS of Boxer Gold recorded 59% control. Prosulfocarb alone achieved 49% control and, when mixed with trifluralin, this increased slightly to 52%, while IBS of trifluralin alone recorded only 38% control on average.

At Koorda in WA, where there was some suspected resistance to trifluralin, Sakura plus trifluralin achieved 89% control, while Sakura applied alone recorded 88% control of annual ryegrass.

Image: Demonstrating weed control 82 days after seeding for Sakura plus trifluralin applied pre-emergent in a trial at Calingiri in WA.

“There were a couple of sites where trifluralin performed poorly because of suspected resistance, while other sites with later germinating annual ryegrass put the residual control of the herbicides to the test, with prosulfocarb running out of puff,’’ Matt said.

“The residual strength with Sakura was a highlight at Calingiri because there was a late germination of ryegrass in a crop that was deficient in potassium and was therefore not overly competitive. We took a lot of people through the site and at four to six weeks after the IBS applications the control provided by prosulfocarb was looking good, but it fell away by the end of the season.

“At Temora in New South Wales, where the site was sown dry and then it didn’t rain for two months, it also showed the residual strength of Sakura compared with prosulfocarb and trifluralin.’’

He said the highest ryegrass panicle count of 1109/m2 was recorded in the untreated in the Nyabing trial in WA, and while Sakura plus trifluralin reduced this to 200 ryegrass panicles/m2, there was still 511 ryegrass panicles/m2 for prosulfocarb plus trifluralin.

Matt said the improved weed control translated to higher yields and return on investment, with the Sakura plus trifluralin and Sakura alone applications recording yields (average across all trials) up to 51.5% higher than untreated plots. This also amounted to about 13% higher average yield than the trifluralin followed by post-ermergent Boxer Gold treatment.

The Sakura treatment across the trials was 15-20% higher yielding than most of the other remaining treatments and this increased to a whopping 45% compared to trifluralin-treated plots.

At the high annual ryegrass population site near Nyabing, Sakura plus trifluralin achieved a yield two-and-a-half times that of the untreated.

Return on investment was calculated for four WA trials (two conducted in 2017 and two conducted in 2018) and showed the application of Sakura alone was the clear leader at these sites with an average return of $116.42/ha, compared to Sakura plus trifluralin, which costs around $9/ha extra and gave an average return on investment of $82/ha.

However, Matt said Sakura plus trifluralin applications were considered an “insurance’’ option in case there was not enough upfront moisture to allow uptake of Sakura herbicide.

Image: Return on Investment (ROI) data

Prosulfocarb application in the four trials gave an average return on investment of $70.60/ha, with trifluralin followed by post-emergent application of Boxer Gold at $48.53/ha, prosulfocarb plus trifluralin at $32.07/ha and Boxer Gold applied alone at $13.21/ha. Due to the suspected resistance to trifluralin at two sites, resulting in grain quality downgrades, this treatment recorded an average negative return on investment of -$49.80/ha.

Image: Bayer Commercial Sales Representative Mitchell Tuffley (second from left) takes Farmanco consultants Brent Pritchard, Mark Lawrence and David Turner through the pre-emergent herbicide trial at Nyabing in WA.

Matt said growers want to see consistency with return on investment and the Sakura treatments showed they were reliable across the sites.

Sakura contains the active ingredient, pyroxasulfone, to control annual ryegrass, barley grass, silver grass, annual phalaris and toad rush, and also suppress wild oats (black oats) and brome grass (great brome) in wheat (not durum wheat), triticale, chickpeas, field peas, lentils and lupins.