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Autumn 2002
WAHRI NEWSKnockdown Resistance - playing the odds! WAHRI has developed a model to track the evolution of glyphosate and paraquat resistance in ryegrass populations. Simulations have shown that annual use of glyphosate alone for knockdown weed control can be sustainable for up to 30 years, but only where this is combined with full cut cultivation at seeding. This may not be an attractive option for growers committed to no-till seeding systems who want to maintain the many advantages of this establishment system. Annual use of glyphosate followed by no-till seeding, however, is not sustainable. The model predicts that under this scenario, glyphosate resistance will result after between 12 and 15 years (applications) in many paddocks. These predications are consistent with oberservations in the field where glyphosate resistance has developed. In short, glyphosate plus no-till equals resistance. There are alternatives which do not require a full scale return to full cut cultivation. Modelling results indicate that incorporating a full cut every third year can increase the life of glyphosate considerably (up to and beyond 30 years). For those who remain fully committed to no-till it is crucial that greater use is made of the alternative knockdown Spray.Seed. This can be achieved by simple alternating Spray.Seed with glyphosate (model results show that this will double the life of glyphosate in no-till systems). Without doubt the best strategy in no-till systems is the 'double knockdown' - a FULL RATE of glyphosate followed by 7-10 days later with a FULL RATE of Spray.Seed (full rates of both herbicides is crucial). This strategy, even when only used in years where the seasonal break allows the necessary delay in seeding, can prevent resistance to both herbicides well beyond 30 years. One thing is clear, glyphosate resistance is here and the first reported case in WA will not be a freak occurrence. Few will disagree that the widespread loss of glyphosate would greatly compromise current systems. The measures that are put in place now will decide how much of a problem glyphosate resistance becomes. These may involve extra expense, but can we afford glyphosate resistance? This article was recently featured in the latest edition of e-weed from the WA Department of Agriculture. If you are interested in being added to the e-mail list to receive e-weed please provide your e-mail address direct to Vanessa Stewart via the contact details below:
During 2002, WAHRI (Paul Neve) and the WA Department of Agriculture (Abul Hashem) are once again offering a free testing service for cropping and other weeds suspected of resistance to the knockdown herbicides, glyphosate and paraquat. Where unusually high numbers of survivors are present following the application of these herbicides and this failure cannot be explained by other agronomic or climatic factors, please send samples to WAHRI or WADA. Surviving plants (30-50 plants) should be taken from the paddock and sent to Paul Neve or Abul Hashem in overnight express post envelopes. On arrival these will be trimmed, repotted and following 7-10 regrowth will be sprayed with field rates of the appropriate herbicide. 'Resistance kits; consisting of pre-addressed express post envelopes and a short questionnaire giving details of application rates, dates and history have been distributed to local onseller agronomists and district WADA Offices. If you are unable to obtain a 'kit' please contact Paul Neve or Mechelle Owen at WAHRI.
WAHRI has another fine crop of fourth year project students for this year as listed below: Perceptions and economics of herbicide resistance mobility: Debbie Allen Thermal requirements for after-ripening in ryegrass seed: Gavin Bignell Evaluating the chaff top system for ryegrass seed control: Darren Chitty Herbicide resistance in wild radish: Ben Parkin Determining fitness costs and a resistance profile for WA's first glyphosate resistant ryegrass biotype: Jemma Sadler Can herbicide pelleting on crop seed control germinating weeds: Clare Smith
Ten undergraduate agriculture students at the University of WA undertook their fourth-year projects with the WA Herbicide Resistance Initiative during 2001. All of these students were from country regions of WA. Seven projects focussed on annual ryegrass, two on wild radish and one involved multiple weed species. more
WAHRI researchers presented the following papers at the Agribusiness Crop Updates held in Perth in February 2002. The papers are available as a PDF file from the Department of Agriculture website: Seeding rate, row spacing and herbicides for weed control Role of tillage implements and trifluralin on the effectiveness of the autumn tickle for stimulating annual ryegrass emergence link to paper Timing of autumn tickle is important for non-wetting soils link to paper Wild radish and ryegrass seed collection at harvest: Chaff carts and other devices link to paper Michael Walsh and Wayne Parker Ryegrass RIM model stands the test of IWM field trial data link to paper Multi-species RIM: An update link to paper RIM survey feedbank link to paper Effects of historic input and product prices on choice of ryegrass management strategies link to paper Alister Draper and Martin Bent Living with ryegrass - trading off weed control and economic performance link to paper Martin Bent and Alister Draper Glyphosate resistance in WA and Australia: Where are we at? link to paper We need your weeds: A survey of knockdown resistance in the WA wheatbelt link to paper A test for resistance testing link to paper 'Haircutting':Does the number one cut work? link to paper Role for Roundup Ready® Canola in the farming system link to paper Congratulations to Vanessa Stewart (WA Department of Agriculture) on being awarded the GRDC Seed of Light award for her contribution to IWM extension. HR Workshops for Agronomists WAHRI recently conducted a full day herbicide resistance workshop for Elders agronomists, including a visiting group from Victoria. The day included a comprehensive presentation on herbicide resistance ("what it is, why it is, where it is") by Professor Steve Powles. Other members of WAHRI outlined the current status of glyphosate resistance, survey results indicating the extent of resistance in WA and the efficacy of non-herbicide weed management options. The agronomists were then given the opportunity to "test-drive" the new multi-species Resistance and Integrated Management (RIM) model. WAHRI is keen to offer similar workshops to other groups interested in herbicide resistance and weed management issues. For more information please contact Robert Barrett-Lennard.
Australia's first weed conference in the 21st Century will be held in Perth, Western Australia, from 9 to 13 September 2002. On the final day of the conference (Friday 13 September 2002) there will be a symposium organised by Professor Stephen Powles 'Herbicide Resistant Crops & Weeds'.
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