Ground Cover Supplement : GC Supplement - Integrated Weed Management
15 INTEGRATED WEED MANAGEMENT GROUND COVER FIGHTING RYEGRASS WITH RYEGRASS Growing diploid ryegrass for sheep feed created the large seed bank of annual ryegrass that germinates in the crop phase as weeds. Therefore, it seems hard to believe that sowing more ryegrass is being used by growers as a method of tackling herbicide-resistant ryegrass. Bevan Addison, manager, technical and professional services at Elders Ltd, explains. "We noted Bill Roy's work showed that a break from cropping is required to reduce the seed bank, so we looked for a way of making that break as financially productive as possible," he says. "By growing tetraploid ryegrass, stocking rates have increased and can be sustained for longer, potential for conserved forage is increased and the chance of ryegrass toxicity is minimal, as seed is rarely set." Mr Addison points out that the tetraploid annual ryegrass being sown in this novel control program has some essential differences in comparison to the diploid annual ryegrass. First, the tetraploid varieties being sown have a very long growing season, so they compete with diploid ryegrass right through the growing season. They are usually burnt- off before any seed is set. Tetraploid ryegrass is more competitive than the older diploid ryegrass varieties; so the tetraploid is suppressing the growth and seed production of the diploid. To ensure good levels of competition, a seeding rate of 20 to 25 kilograms per hectare is recommended. "At these seeding rates tetraploid ryegrass is more competitive to diploid ryegrass than an oat crop," Mr Addison says. To ensure good productivity and ryegrass suppression, well-managed rotational grazing and adequate fertiliser inputs are required. Spray-topping to prevent diploid ryegrass from setting seed is also part of the package. Another benefit of the system is that should the tetraploid and diploid ryegrass cross-pollinate, a sterile triploid would be produced. This is not occurring, as the tetraploid and diploid species currently in the paddock flower at quite different times. However, this mechanism provides another backstop in the system, should outcrossing occur. "The huge boost to sheep and pasture productivity, at the same time as reducing the seed bank of ryegrass, including resistant plants, is a real win-win situation," Mr Addison says. "But it has to be managed properly." More information: Bevan Addison, 08 9422 2391, firstname.lastname@example.org EARLY WEED KILL New options for trifluralin HERBICIDES WITH NEW MODES OF ACTION ARE BEING DEVELOPED AND TESTED TO HELP CONTROL RYEGRASS WITH RESISTANCE TO TRIFLURALIN (GROUP D) BY PETER BOUTSALIS FIGURE 1: EFFECT OF ALTERNATIVE PRE-EMERGENCE HERBICIDES IN A PADDOCK AT ARTHURTON ON THE YORKE PENINSULA 0 20 40 60 80 100 Control (%) Boxer Gold NuFarm 2 + Dual Gold Untreated Triflur X KIH NuFarm 2 NuFarm 1 NuFarm 1 + Dual Gold KIH + Dual Gold Triflur X + Boxer Gold Triflur X + Avadex Xtra KIH + Avadex Xtra WIDESPREAD RESISTANCE TO Group A and B herbicides in annual ryegrass has resulted in many farmers increasing their reliance on trifluralin as the pre-emergent herbicide option to target these resistant weeds. Baseline monitoring of ryegrass has shown different levels of resistance across southern Australia. In the upper Yorke Peninsula and mid-north regions of South Australia, 49 per cent of populations tested in 2003 were resistant to trifluralin, compared with only 0.2 per cent tested in WA and 4.5 per cent of those tested in 2005 in the Victorian Mallee and Wimmera regions. The confirmation of high levels of trifluralin resistance across the upper Yorke Peninsula and mid- north South Australia is alarming and has prompted research to identify alternative herbicides with different modes of action to trifluralin. The availability of new herbicides would aid in managing trifluralin- resistant ryegrass and minimise the further selection of trifluralin resistance. Between 2005 and 2006 the efficacy of trifluralin was compared with a range of new mode of action pre-emergence herbicides from Kumiai Chemical Industry, Nufarm and Syngenta (Figure 1). The results in Figure 1 are for a paddock of Sloop barley (80 kilograms per hectare), sown with knife-points and 'The huge boost to sheep and pasture productivity, at the same time as reducing the seed bank of ryegrass, including resistant plants, is a real win-win situation' NOTE: KIH is being developed by Kumiai Chemical Industry. Boxer Gold is being developed by Syngenta. NuFarm 1 and NuFarm 2 are being developed by Nufarm. Important note: all products with the exception of Triflur X and Dual Gold are registered for ryegrass control in barley. Always consult chemical label before application.
GC Supplement - Nutrient management
GC Supplement - Adapting to climate change