The reasoning is simple, he says. The cover crop (which has to be established by Oct 1 under the Basic Payment Scheme rules) allows a healthy population of blackgrass to establish underneath the canopy, depleting the seedbank, ▲ he explains. The main objective is to kill <strong>this</strong> off and not stimulate further blackgrass germination when drilling the following spring crop. “The idea is to collapse the canopy to gain access to the blackgrass and other weeds lurking underneath. You generally need to burn off the cover about six weeks before the planned drilling date, so to establish a spring cereal crop you’ll be looking at a glyphosate (2 l/ha plus adjuvant, such as Companion Gold) Diversity key to preventing glyphosate-resistant blackgrass On the very day the news broke that bacterial resistance to last-resort antibiotic, colistin, has been detected in China, a cross-industry group gathered at Harper Adams University, under the auspices of the Soil and Water Management Centre, to discuss the unthinkable –– the possibility of glyphosate-resistant blackgrass. It hasn’t happened yet but if we don’t practice good stewardship then glyphosate resistance, in some form or other, will appear in the UK, believes Barrie Hunt of Monsanto. A sobering thought, with glyphosate currently forming the last chemical defence for UK growers against herbicide-resistant blackgrass, and there are more than 1.2 million ha with some degree of blackgrass resistance in the UK. Glyphosate resistance is already a major problem in the United States, where the whole-scale switch into transgenic crops massively increased the selection pressure on the once stalwart herbicide. Professor Thomas Mueller, from University of Tennessee, outlined their experience with glyphosate-resistant weeds to illustrate how growers in the UK can perhaps learn lessons and avoid fighting a desperate rear-guard action. “The uptake of Roundup Ready was huge in the US. Farmers liked it because it was easy, it worked and yields went up,” explained Thomas Mueller. “Farms got bigger because timeliness was no longer important and farmers no longer cared about, or even understood, basic weed control principles. Glyphosate alone captured 50% of the total herbicide market and we got resistance. “<strong>In</strong> the US, our driver weeds are Conyza canadensis (Canadian fleabane) and Palmer amaranth (pigweed) and resistance has spread rapidly across states. The cost of herbicide programmes has increased by 200-250% in the effort to control them. Here in the UK, your driver weed is blackgrass.” <strong>In</strong> Tennessee, soil erosion is a big problem and no-till is normal practice because of the benefits it brings in terms of soil stabilisation, structure and porosity. “Where we have glyphosate resistance, some growers have had to return to tillage, losing all the benefits of the no-till regime. There’s also a renewed awareness of the importance of the seed bank, with some growers resorting to costly hand weeding to reduce seed return.” The parallels to the UK are obvious –– herbicide resistance, a driver weed and reduced tillage systems. Harper Adams visiting professor, Dick Godwin, told the assembly that no-till is seeing a resurgence in popularity in the UK because of the significant operational and cost benefits it offers to growers, as well as improvements to soils and erosion. “No-till also throws up some big challenges to growers – one of which is the control of grassweeds and weeds not controlled by glyphosate,” he said, explaining that stale seedbeds and a reliance on glyphosate is one of the fundamentals in a no-till situation. Agrii has been looking at the impact of establishment systems on blackgrass control at their Stow Longa site. “Given current financial restraints, every farmer is looking to reduce establishment costs,” said Andrew Richards of Agrii. “Every agronomist is seeing a reduction in available chemistry and what we do have, in many cases, has a reduced level of efficacy. We need sustainable establishment systems that perform under a range of conditions and we need to think about the pressure we’re putting glyphosate under.” One of the results from the Agrii work that challenges the beliefs of the most evangelical of no-tillers, is that rotational ploughing can bring useful cultural control of blackgrass. “If ploughing is utilised in a year of high seed return there are huge benefits in fully inverting the soil in terms of blackgrass control. If shallow cultivations are then employed, the majority of blackgrass seed remains undisturbed at depth,” said Andrew Richards. But won’t ploughing lose all the benefits the no-tillers have strived to obtain? It’s something Dick Godwin believes we need to find out. “Although ploughing is contrary to the no-till religion, we need to find the answer to the question, what is the effect of occasional Experts lined up to sound warnings on glyphosate resistance – (from L to R) Barrie Hunt, Dick Godwin, no-till farmer Edward Bradley, Thomas Mueller, Tim Chamen of CTF Europe, Andrew Richards and Prof Shane Ward of SWMC. ploughing in a no-till system?” Barrie Hunt pointed to the new glyphosate stewardship guidelines which highlight that one of the high risk factors for developing glyphosate resistance is ‘no cultivation’, as is commonplace in the US. “Sustainable use of glyphosate is business critical for UK growers and, by using integrated programmes, we’ve a chance of keeping resistance at bay for a few years to come.” It’s a message that’s being shouted from the rooftops but some growers still want the answer to resistant blackgrass to come in a can, suggested some of the speakers. When asked why we’re not getting new chemistry coming through, Andrew Richards made a valid point. “If we had something new, how long would it last? We need to learn how to make chemistry last longer and prevent it breaking down to resistance by changing practices. The efficacy of Atlantis has lasted less than 10 years.” Diversity is the key to avoid falling into the resistance trap, said Thomas Mueller. “Diversity in the chemistry we use to control blackgrass, diversity in our cropping and diversity in our cultivation systems.” Cultivation system Blackgrass ears/m 2 Min till, Claydon OSR, Claydon Oct, Claydon Sept, Claydon Sept 501 Plough, Claydon OSR, Claydon Oct, Claydon Sept, Claydon Sept 266 Claydon Oct, Plough OSR, Claydon Sept, Plough Oct, Plough Oct 1.3 Source: Agrii Cultivations Systems study 2010-2015. Blackgrass population in 3rd wheat Edgar, 2015 20 crop production magazine december 2015
SPRING SEEDS Lamport blackgrass trial results Blackgrass heads/m 2 Year 1 Year 2 (2013/14) (2014/15) Winter wheat with full herbicide 55 274 Winter wheat – untreated ≥2000 ≥2000 Stale seed bed fb spring wheat 15 36 Cover crop fb spring wheat
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