RESISTANT RYEGRASS TRIAL CONFIRMS EARLY SEASON WEED CONTROL CHANGE

With last season’s arrival of a new cereal pre-emergent and early post-emergent (EPE) herbicide offering growers a potential step-change in their early season weed control, a high-profile Western Australian researcher last year conducted extensive trials featuring multiple herbicide-resistant weeds to confirm the value of the herbicide.

Mateno Complete contains aclonifen (Group 32), a new herbicide mode of action to the Australian industry, in a complementary co-formulation with pyroxasulfone (Group 15), which also is the active ingredient used in Sakura®, and diflufenican (Group 12) herbicides.

ryegrass population, Mateno Complete can control it, as long as the population is not K (Group 15) resistant.’’

The news was good, and hence growers can now be confident of having an effective new tool at their disposal.

Roberto Busi, Weed Scientist with the Australian Herbicide Resistance Initiative (AHRI) at the University of Western Australia, said there were few grass postemergent herbicide options available in wheat and most already had weed resistance levels of up to 50 per cent (pc).

This had resulted in a reliance on preemergent herbicides, which are particularly important with no-till seeding systems, for effective weed control, and where weed resistance has developed over time.

Roberto said resistance to trifluralin, one of the most popular pre-emergent herbicides, was now consistently found at 15 pc, which is one in every six paddocks treated with trifluralin.

Last year, Bayer released the pre-emergent and EPE herbicide, Mateno® Complete, for grass and broadleaf weed control in wheat and barley, which followed the earlier extension of Boxer Gold for EPE control of grass and broadleaf weeds. Roberto has assessed the value of the new herbicide in controlling multiple herbicide-resistant annual ryegrass populations.

Roberto said he wanted to study the longterm efficacy of the herbicide in worstcase scenarios. He valuated it against three annual ryegrass populations with some resistance to prosulfocarb and pyroxasulfone. These included one from Western Australia and two from Victoria, and three populations with some resistance to trifluralin, all of which were from South Australia, and included one that also featured resistance to prosulfocarb and pyroxasulfone.

The extensive plot trial included three replicates and compared a range of standard pre-emergent or incorporated by sowing (IBS) herbicides; Mateno Complete applied pre-emergent, post-emergent following the IBS treatments, postemergent stand-alone, and also in a tank mix with Buctril® broadleaf herbicideThe application of a mixture of Sakura Flow and Brodal® Options post-emergent was also investigated

The trial assessed weed control rate and biomass suppression through to the reduction of weed seedset, which Roberto said was important to evaluate longevity of control.

He said the trial showed the EPE application of Mateno Complete was very convincing, giving growers confidence it would control annual ryegrass post-emergent across the full soil profile, including in the furrow.

“It was impressive to observe the efficacy of Mateno Complete as a true postemergent herbicide capable of fully controlling ryegrass in pots,’’ Roberto said.

“Mateno Complete controls it no worries. If you have a herbicide-resistant annual

He said the trial outcome in the worst-case scenarios was clear that in those tough situations, it was best to use Mateno Complete following an IBS application of an effective pre-emergent grass herbicide with an alternate mode of action.

“Even with the better performing IBS treatments, the weed control runs out; with the EPE application of Mateno Complete giving an improved period of control.’’

The trial generally showed a 10 to 15 pc improvement in control and more than 20 pc in some cases following the IBS application of an effective pre-emergent herbicide.

Roberto said the post-emergent application of Sakura and Brodal Options, undertaken to understand the benefit of the aclonifen component that features in Mateno Complete, was the worst recorded in the trial.