Arable News

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Make the most of autumn black-grass opportunity

Although the temptation will be to drill winter wheat straight after combining, growers are being advised to maximise the use of stale seedbeds

Although the temptation will be to drill winter wheat straight after combining, growers are being advised to maximise the use of stale seedbeds ahead of chemical control of black-grass, if difficulties with the weed are to be overcome on many UK farms. Dominic Kilburn writes.Growers have had a challenging time trying to control black-grass in recent seasons.Aim for 100 per cent control of black-grass this autumn, stated BASF’s Sarah Mountford-Smith who made the point that growers must do all they can by integrating cultural control options like stale seedbeds in order to optimise following chemical control this season.Speaking recently at a BASF-hosted discussion focusing on autumn weed control, Sarah, who is cereal herbicides and PGR product manager for the company, admitted that after the experience of last autumn and the difficulties growers had in getting crops established, the temptation to drill straight after the combine this time around was huge. However, she pointed out that this autumn, of all the recent autumns, could be the one where delaying drilling might make all the difference in terms of success at controlling black-grass.”There is a low dormancy forecast for black-grass seed and we’ve not had this since the 2006 season,” she commented. “If ever there was a year for creating stale seedbeds, then this could be the one,” she added.Sarah (pictured left) highlighted some of the difficulties that growers had faced in the challenge to control black-grass over the past two seasons relating to the poor weather conditions, and also emphasising the fact that resistant black-grass populations were an increasing problem around the country, as was the continued loss of herbicide actives for the future.”In 2011/12 growers had a very challenging year trying to control black-grass; there was high dormancy to start with and so limited opportunity to use stale seedbeds, and the driest autumn on record meant a lack of activation of pre-emergence products while post-em applications couldn’t compensate for them.”Then, in 2012, we had the wettest April on record which caused the black-grass to produce more fertile tillers than usual, leading to a lot of heads in June.”According to Sarah things then got even harder; high black-grass seed dormancy initially was followed by another record – this time the wettest autumn – with figures from a recent ‘Farm Panel’ survey highlighting the difficulties experienced by growers showing that herbicide-treated hectares in the autumn of 2012 decreased by 67 per cent. “There was quite a lot of spring germinating black-grass too,” she added. Sarah suggested that this has left growers facing some significant black-grass challenges ahead of this autumn’s establishment programme: “Everything that is done on farm must be integrated culturally and chemically,” she stressed. “Spraying off weed flushes will be hugely valuable and growers should define an appropriate herbicide programme tailored to each field. For pre-emergence sprays they should use the best herbicides at full rates and at the right time; as soon as possible after drilling, and within 10 days at the latest.”Applications shouldn’t be delayed even if it’s dry as little moisture is required to activate products,” she added.For the best start to the herbicide programme Sarah advocated Crystal (flufenacet + pendimethalin) at 4 l/ha + DFF at 100g ai/ha at pre-em, followed by a post-em at crop growth stage 11 of Atlantis (mesosulfuron + iodosulfuron) at 0.4kg/ha + Picona (pendimethalin + picolinafen) at 2.5 l/ha, or Auxiliary (clodinafop-propargyl + prosulfocarb) at 3 l/ha.She said that adding 20g/ha Lexus (flupyrsulfuron) to the pre-em application could be considered in severe infestations.As an alternative, she suggested that a pre-em of Avadex Excel (tri-allate) at 15kg/ha followed by Crystal and DFF at early post-em had been one of the best programmes the company had seen, pointing out that Avadex was a particularly good option in dry conditions.”Our advice is to get the herbicides on early rather than being caught out in a catchy autumn and, even if conditions remain dry, don’t wait to apply the pre-ems,” she added.Commenting on trials work carried out during the past three years, east Suffolk-based AICC agronomist Dan Robinson (left) of Agrivice agreed that a pre-em of Crystal + DFF is currently the best black-grass treatment. In 2010/11 trials, however, Defy (prosulfocarb) + Crystal + Liberator (flufenacet + DFF) worked better at peri-emergence where pre-em applications were not an option but the treatment was still a good option at pre-em as well, he said.”In 2010/11 we found that Defy worked better at peri-emergence, while there was also a good performance from Crystal + Lexus at 20g/ha, although this treatment needs some careful thought at pre-em where black-grass resistance to sulfonylureas is prevalent.”Crystal on its own is not quite so good but we have found flufenacet-based products better and more consistent than anything else,” pointed out Dan, who is part of a four-strong team of independent agronomists advising growers in the region.Regarding 2011/12 trials, he said that Avadex offered good control when applied on its own while sulfonylurea products were not quite so effective once applications were made at the peri stage of the crop.”That said, once black-grass has emerged then Avadex is not the answer,” he added, “but in difficult situations where bromes and wild oats are also becoming an issue as well as black-grass, then Avadex fills a gap.”It’s not a cure but it does improve overall control and consistency.”SeedbedsDan said that there was an onus on the farmer to get the seedbed right this season and many might have to turn to the plough for assistance. “Generally speaking, those that have the worst seedbeds usually have the worst black-grass,” he suggested. “A lot of fields are badly rutted and they will need attention and it could work out as expensive to do several passes with min-till gear as just one with the plough, although it’s difficult to advise people to plough when many of them have made an investment in one- and two-pass systems,” he conceded.“The plough is a useful part of the rotation and is a valuable tool. Some of cleanest farms I have got are those that have traditionally used the plough and I would certainly advise growers to plough for second cereals, or every three to four years,” he said. Dan added that, in winter barley, it will be the only sterile brome control option once chlorotoluron (CTU) is withdrawn from on farm use in June 2014.In terms of prioritising black-grass control this autumn, Dan said that there must be a focus on the worst affected fields first; where ploughing or cultivating early is essential to allow time to get things right. “My earliest drillers won’t begin until 15th September which should allow ample time for stale seedbeds,” he added.”Growers mustn’t focus on what happened last year – look at what is happening in the field this year, have a system and don’t forget the basics of cultivations,” he commented.”Ploughing, good cultivations and seedbed quality, stacked treatments and higher seed rates using competitive varieties are all key priorities this autumn where black-grass is a problem, and spraying must happen right after drilling.”The traditional practise of drilling the farm first and then spraying has gone – the sprayer must be going from field to field immediately behind the drill. If the pre-em is too late and the post-em fails, then growers can be in big trouble.”Dan said that if the weather is dry at drilling he would still advise people to spray in 90 per cent of cases. “My experience in 2011 was that if the wheat wasn’t germinating then neither was the black-grass. However, if we are talking weeks of dry weather then it might be best to hold off.”Stale seedbed advice

  • Low black-grass seed dormancy predictions mean there could be a good opportunity for stale seedbeds this autumn
  • To get the most from stale seedbeds shallow cultivate the top two inches as soon as possible after combining
  • Consolidate and apply glyphosate after a good round of black-grass germination
  • Aim for two rounds of stale seedbeds especially on fields with bad black-grass infestations
  • Stale seedbeds are vital; don’t compromise on black-grass control simply to get the crop in early
Grass weed active withdrawals
  • The last sales of chlorotoluron + diflufenican (DFF) products must be made by 31st December 2013 with use by farmers before 30th June 2014
  • Products containing pendimethalin + DFF are also being phased out and must be used up by 31st December 2014


  • Written by: Farmers Guide
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