42 minute read
Concentrate on chemistry and cultural control
With late blight strain patterns continuing to evolve, and the loss of mancozeb on the horizon, how should potato growers structure their disease control programmes? Martin Rickatson gathered some thoughts from the industry.
Concentrate on chemistry and cultural control
As growers face up to a reduced pool of available actives in their armoury against blight, with multisite mancozeb the latest loss, industry advisers from across independent research groups and the agchem and agronomy sectors are underlining the importance of integrated disease management, using cultural tools as well as chemical and careful selection across fungicide groups, in order to protect the efficacy of remaining chemistry.
AHDB research charting how close to their resistance ratings varieties are when under extreme blight pressure suggests there is a good deal of scope to select variety by land location and hence ease of spraying – and that there is significant benefit in growing varieties in blocks according to ratings.
That’s the view of David Wilson, AHDB knowledge exchange manager for potatoes, who points to trials presented by AHDB at Eurofins in 2019, where spray programmes and resistance performance of some of the most popular varieties were assessed.
“This involved 12 varieties – including Russet Burbank, Maris Piper and Markies, with resistance scores from 2-9 against foliar blight – planted in two blocks in increasing order of resistance. The site was inoculated with 6_A1, 13_A2, 36_A2 and 37_A2 blight strains and while one block was treated with a strong fungicide programme, the other received a shorter, simpler spray regime.
Real differences
“Under the full fungicide programme, all performed well, but when this was reduced to three applications of Dithane [mancozeb] and three of Curzate [cymoxanil + mancozeb], real differences were detected. Orchestra, rated 2 for foliar late blight resistance, showed 75% foliar infection, and Maris Piper, rated 4, the figure was 60%, while for Markies, rated 5, just 15% of the foliage was infected.
He also suggested there was more potential to be had from growing varieties with similar blight ratings in blocks to aid spray programme planning and prioritisation in challenging circumstances.
“The demonstration trial highlighted the importance of foliar resistance ratings. Maris Piper is rated at 4 and Markies 5, yet when fungicide applications were reduced, on August 21 measurements showed Maris Piper with 60% defoliation, but Markies with just 15%.
Shifting UK blight populations have seen a decline in the prevalence of phenylamide-resistant 13_A2 and while mancozeb remains available then this means Fubol Gold (metalaxyl-M + mancozeb) retains a potential role in blight programmes as a highly-systemic programme option, particularly during rapid canopy growth, says Michael Tait, Syngenta technical manager.
Craig Chisholm, field technical manager for potatoes and vegetables at Corteva, points out that analysis of UK growers’ samples submitted to the James Hutton Institute suggest late blight is becoming increasingly aggressive.
“The data shows 6_A1 and 36_A2 are dominant, with both widespread across all potato- growing regions, underlining the importance of grower focus on interval and product choice.
Michael Tait With many current blight fungicides being single site-specific, there is a heightened risk of resistance development, warns Jeff Fieldsend.
SHINING BRIGHT
IN ALL SITUATIONS
While there may initially appear to be a wealth of active ingredients to deploy against late blight, the reality is not quite so straightforward, adds Mr Chisholm.
“Resistance to metalaxyl and reduced sensitivity to fluazinam diminish the options available. While the date of its withdrawal from the market is not yet confirmed, the situation will become further challenged by the coming loss of mancozeb, which of course is an important partner AI in a number of co-formulated fungicides.”
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growers to maintain an effective anti-resistance strategy by ensuring blight programmes use products from across the different chemical groups in accordance with FRAC guidelines, says Mr Chisholm.
Rapid growth phase
“During the rapid growth phase, spray programme inclusion of Zorvec Endavia [oxathiapiprolin + benthiavalicarb], which combines preventative and curative activity with systemic movement through the plant, will help establish a clean start and protect new growth even on a 10-day interval.
Two Zorvec applications at rapid growth will save one spray at a busy time across the rotation, and two further applications can still be used in stable canopy, particularly valuable in indeterminate varieties or crops destined for storage.
“Option [cymoxanil] has always been a valued curative tank-mix partner for preventative AIs when blight is locally active, or warnings are strong/ threats high. In the event of mancozeb being unavailable to UK growers, it will be invaluable as a partner for single AI products as part of an anti-resistance strategy, with up to eight applications allowed across the programme.”
FMC’s Jeff Fieldsend agrees the withdrawal of mancozeb will force a rethink of disease control strategies.
“With fluazinam having been shown to offer poor control of EU Dark Green A2_37 following many seasons of excellent activity on the other dominant strains – particularly EU Blue A2_13 and EU Pink A1_6 – many growers chose to not use the product for late blight control, restricting it largely for minor use only on seed crops for powdery scab and sclerotinia.
“However, the late blight pathogen continues to evolve and mutate, with new strains shown to be more common and aggressive, particularly EU Salmon A2_36, which has shown to be increasing particularly in eastern England.
Heightened risk
Regardless of the increased aggressiveness and change in the behaviour of the pathogen itself, with many current blight fungicides being single site-specific, there is a heightened risk of resistance development, adds Mr Fieldsend.
“With these factors in mind, plus concerns over aggressive new genotypes detected on the near continent, including
Lessons from 17 years of blight data
JSince AHDB’s ‘Fight against blight’ programme started in 2004, ‘blight scouts’ have sent in more than 10,000 samples of potentially blight-infested potato plants for genotyping. During winter 2020/21 Peter Skelsey, David Cooke and colleagues from the James Hutton Institute did some additional analysis on the data from all 17 years of samples. Here are some of their findings: rIn general the data was a good representation of the whole of the potato-growing area. There were some variations, with, for example, Herefordshire and the Scottish Borders showing a slightly lower frequency of blight sampling in comparison to other areas with similar levels of commercial potato growing activity rThe data also allowed the spread of blight genotypes across the country to be tracked. The take-home message here is that new genotypes can spread rapidly across the country. Using EU_37_A2 as an example, a strain that is insensitive to fluazinam, in 2017 outbreaks were moving at 3.2km a week, in 2018 that rate increased to 13.8km a week rAs expected, the closer you are to an area where lots of potatoes are grown, the higher the risk of a blight outbreak. Ultimately, the risk of blight is high in all potato growing areas and the threat of spread into growing regions depends partly on risk in the neighbouring postcode districts rThe researchers also looked at the risk of an ‘early’ blight outbreak. There was an added level of complexity in this work due to the variation of growing progress from year to year. Because of variable factors, such as time of emergence and weather conditions, it was difficult to find patterns in the data. In 2020 for example, the first samples of blight were found in Aberdeenshire
EU_41, 42 and 43, and the fact we are about to lose one of our mainstay fungicides, it’s crucial to protect the remaining products available.
“We’ve seen in trials both in the UK and Holland that, as part of a robust alternating strategy combining actives in a well-managed spray programme, Tizca [fluazinam] can still deliver effective control of late blight, even when new strains have been introduced. In addition, there is good activity on alternaria and control of sclerotinia.
“Don’t focus on whether product A is better than product B, but rather on how to combine actives to minimise the increasing risk of resistance and tackle the loss of mancozeb.
“As an industry this will help deliver sustainable performance not just on late blight, but also on the other key diseases.
“Fluazinam is still one of the most effective actives for sclerotinia protection when timed at early flowering and repeated 14 days later and although it’s not often widespread every season this is a disease that can cause rapid defoliation,” he says.
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Finding a variety which combines good yields with impressive disease resistance credentials has long been a difficult challenge for wheat growers. But independent trials are showing RGT Saki is offering growers just that.
RGT Saki will be a serious contender this coming autumn
Growers looking for a feed wheat for harvest 2022 should give serious consideration to RGT Saki, according to Chris Piggott, regional seed manager with Frontier.
He says: “Anyone considering a feed wheat should definitely look at RGT Saki and for those thinking about soft feed wheats it’s a no-brainer. Looking at feed wheats as a whole, RGT Saki stands out as being a nice well-rounded option.”
Dr Cathy Hooper, RAGT’s technical sales manager, says they have enough seed in the ground for RGT Saki to take 8-10% market share for harvest 2022 and current trials work will ensure growers have all the information they need to grow the variety.
RGT Saki made its debut at Cereals 2019 and has undergone extensive trials since then, providing an extensive data set.
Dr Hooper says: “RGT Saki has the unique combination of providing disease resistance and high yield. It used to be said that you could either fill the bucket with disease resistance or high yield, but you couldn’t have both. Well, RGT Saki provides both.
“Furthermore, it provides consistently high yields whether treated or untreated. There are other varieties out there which provide good yields and disease resistance when untreated but are not so good when treated.
“The breeders have done a fantastic job in bringing together these traits of disease resistance and high yields. They have also done a really good job on specific weights. These have tended to be an issue with soft wheats in the past but RGT Saki has an excellent specific weight of 76. It has a good Hagberg Falling Number, grain quality and excellent sprouting resistance which can also be an issue with some soft wheats.”
This year, independent trials have been conducted by Agrovista at Draughton, North Yorkshire; AICC in Sussex and Prime Agriculture, Norfolk; as well as RAGT’s own trials work. In all trials RGT Saki consistently delivered yields above the mean, whether treated or untreated. For instance, in Agrovista’s trial it yielded 12.3 tonnes per hectare untreated compared to a trial average of 10.55t/ha, and treated it gave 15.4t/ha compared to an average of 13.85t/ha.
In RAGT’s own trials in East Anglia it gave the highest yield of any of the first wheats tested and made a very respectable third place as a second wheat.
Parentage
Dr Hooper says: “Last year RGT Saki performed very well wherever we put it and it delivered the highest yields. It is very consistent, a trait which comes from its Santiago parentage, but with the addition of high disease resistance. Its disease resistance, including seedling yellow rust resistance, is second to none.
“We are now putting it back out to trial with Greencrop and Prime Agriculture and we are looking to obtain more detailed information including tillers per plant, tillers per sq.m, ears per sq.m, grains per ear and plant height.
“As more commercial growers adopt RGT Saki, these detailed trials will allow us to provide guidance for them to get the best out of the variety. We hope to be able to organise some open days towards the end of June or the beginning of July to disseminate this information.”
The issue of RGT Saki’s maturity score is something both Dr Hooper and Mr Piggott commented on.
Dr Hooper says: “Some growers are concerned about its maturity score, but it can be drilled early and performs very well in this ‘early drill’ slot. It
RGT Saki stood up well on Sam Morris’ Cambridgeshire farm.
credentials has long been a difficult offering growers just that.
RGT Saki in the field
Cambridgeshire grower Sam Morris was an early adopter of RGT Saki, growing 15 hectares for harvest 2020.
Mr Morris, who farms in his own right as well as contracting, says: “We drilled a small amount of Saki in autumn 2019. We have a particular issue with storage and we are looking to grow more soft wheats. Although it was a small amount and a difficult year, I was impressed with it.
“It did well all season with vigorous growth. It’s difficult to judge on a small trial but it needed less fungicide and gives flexibility on spray timings. The yield was really good. Difference
appears in the 2020 AHDB Recommended Lists Early Sown Trials and gave consistently good results.”
Mr Piggott says: “We definitely see a role for RGT Saki in that early drilled slot. This was something that stood out quite clearly to us because it has such a high early drilled yield. What is also interesting is that when it is sown later it develops more quickly through growth stages and therefore you won’t get a very late maturity. It is later maturing, but this is not as much of an issue as some may think.
“For early sowing it ticks all the boxes; it has really good disease resistance – particularly for septoria and rust – and it has stiff straw. These are the main traits you would look for.”
Overall, Mr Piggott says Frontier’s experience of RGT Saki has been very positive with excellent yields.
“Our trials show the fungicide contribution to yield is relatively low with RGT Saki across most sites and this has been a consistent pattern. We see this as a key factor at the present time as it lowers the risk when you are making decisions about which varieties to grow.
“The reliability of disease resistance and the decreased reliance on key timed inputs are critical elements.”
Frontier had commercial availability of the variety in 2020 and sold it to growers around the country, as well as putting it into its own trials programme.
“We grew it as far north as Coldstream in Scotland, as well as in Norfolk where we are trying to identify any issues with rust,” says Mr Piggott.
Positive
“The widespread use of RGT Saki across different regions is a reflection of its properties. Those in the North can drill early with confidence. Those who don’t want to drill early will see really good yields and excellent disease resistance.
“It was the highest treated yielding variety at our Lincolnshire site. RGT Saki gave consistently high yields across all sites from light sandy soils to quite heavy clay and this is also reflected in the AHDB data.
“When it came to looking at yellow rust, in our trials in Norfolk it performed as well as the most resistant varieties. Yellow rust is a big challenge for many growers and this is a particular strength of RGT Saki’s.
“We also saw a very good and consistent response to PGR across all our sites. Some varieties which appear taller don’t respond well to PGR, whereas RGT Saki responded very well. If you are looking for a variety that you want to shorten and keep stiff, RGT Saki is worthy of consideration.
“Last year was a very challenging season all round with a dry period in spring, but RGT Saki actually performed incredibly well. Our expectation for those who have it in the ground for this year is that they will also have good crops, which is why we would recommend it for harvest 2022.”
The chance to connect with industry experts through a series of live events, debate and discussion, Arable Weed Week is showcasing the latest thinking and best practice on weed management.
Showcasing the latest thinking in weed management
Taking place from June 14-18 in collaboration with The CropTec Show and Arable Farming, the event will bring together the best and brightest in the industry to tap into new thinking around weed control and ask: how exactly does it fit into new systems of farming? Is it time to rethink in terms of weed ‘management’? Could new technologies and tools provide solutions to some of the most pressing weed control challenges?
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series of activities in collaboration with industry partners, including BASF, Bayer, AminoA and Horsch UK, the week-long event will kick-off with a host of interactive content. Key information
rWhat: Arable Weed Week is a week-long interactive event focusing on the latest thinking and best practice on weed management in the context of the changing political and environmental agenda rWhen: June 14-18 rHow: Register your interest for all live content by visiting the Arable Weed Week online hub at croptecshow.com/aww rSocials: To keep up to date and get involved with the industry conversation and our weed-related poll questions, follow our social media platforms @CropTecShow @ArableFarming on Twitter and use #AWW21, as well as The CropTec Show Facebook page rOn-demand: All content, useful reader resources and a profile of our industry partners will be readily available to view on-demand at our dedicated online Arable Weed Week hub
Arable Weed Week action
JKicking off on June 14, the event will begin with a flurry of activity across social media, including Arable Weed Week content, interactive polls – which will continue to be held throughout the week – and culminating in a ‘Weed ID’ quiz, taking place on Twitter at 7pm.
Wrapping up the week on June 18, there will be various social media activities across all channels. Keep your eyes peeled for your chance to catch up on poll results and review the week’s exclusive series of interviews, debates and discussions with experts in the field and farmers on the ground.
BASF’s interactive weed workshops June 15
JBASF will be running a series of virtual events throughout the day, kicking off at 8am.
Highlights include a resistance management masterclass with a stellar line up of experts and farmers on the ground, to investigate the valuable role of integrated pest management (IPM) in a grower’s weed control toolkit. Plus, join BASF for an evening of first come, first serve beer tasting and an opportunity to connect with more than 40 farmers to discuss IPM weed control success stories and gain valuable advice from the experts. r8-9am: IPM is not just a nice to do, it is a need to do Panel discussion With Rob Gladwin, head of technical for BASF, Mike Green, sustainability manager for BASF and Phil Jarvis, chair of the Voluntary Initiative. r11am-midday: A sustainable future for arable weed control Panel discussion With Steve Dennis, head of business development for BASF, Stuart Kevis, business development manager for cereal herbicides for BASF and Yorkshire-based farmer Richard Hinchliffe r2-3pm: Resistance management masterclass Animated masterclass With BASF’s head of business development Steve Dennis r8pm: #IPMWeedControl with beer. This is a first come, first served beer tasting and success stories evening hosted by Ali Richards, campaign manager for BASF and joined by special guests
Bayer’s ‘new innovation’ exclusive weed webinar June 16
JBayer will be teaming up with NIAB to bring growers and agronomists the latest advice and insight into the UK status of ryegrass resistance, with a review of field trials and commercial experience with Proclus (aclonifen) at 800-hectare North Court Farm, near Faversham, Kent, where Sentry farm manager Ben Binder has been fighting a long-term battle with ryegrass.
Hear Ben’s experiences of combining cultural and chemical control approaches to tackle a long-standing ryegrass problem.
Hear also how grower Sam Markillie is making use of Bayer’s latest herbicide developments to tackle black-grass on his 1,000ha arable unit in Wisbech, Cambridgeshire.
Leading weed biologist and NIAB expert John Cussans will set the scene behind mode of action diversity and provide an insight into using different modes of action to build a diverse herbicide programme and prevent resistance. r12-1pm: New innovation: Maximise long-term control Webinar and live Q&A Experts will be on-hand throughout the webinar to answer questions and offer up technical know-how and practical solutions to weed-related challenges. r6:30pm: An evening with NIAB expert John Cussans Facebook Live John Cussans is set to join The CropTec Show’s Facebook Live event, where viewers will have the opportunity to put all weed management questions to the expert directly for an evening of in-depth discussion and debate.
AminoA’s tackling problematic weeds with the use of biostimulants
JAminoA will be sharing the exciting work it is doing to help tackle problematic grass-weeds with its new biostimulant range.
Managing director Richard Phillips explains how a combination of late drilling of wheat in November and the use of biostimulants has helped to minimise blackgrass and other weed challenges, while boosting yields and reducing herbicide costs.
JAlice Dyer, journalist by day, farmer by night, will be joined by a team of guest experts from BASF in this special weed control episode of Crop it Like it’s Hot to discuss a range of weed control topics and share some handy tips to implement on-farm. r12-1pm: Crop it Like it’s Hot EXTRA: BASF weed control special episode
The alarming results of a new Rothamsted Research study have highlighted the urgent need to reduce reliance on herbicides and rethink weed control. Alice Dyer reports.
Why weeds are gaining an advantage
The use of herbicides has allowed commercial farming to reach new heights in productivity in the last 60 years, but it has also seen weeds become more competitive.
This was the conclusion made based on data from the world’s longest running experiment – the Rothamsted Broadbalk wheat trial in Hertfordshire – which revealed that crops are now more vulnerable to weeds than ever before and although yields have been steadily increasing, on plots where herbicides have not been used, losses to weeds have also escalated since the 1960s.
Dr Jonathan Storkey, plant ecologist at Rothamsted Research and lead author of the study, says these results demonstrate that weeds now represent a greater inherent threat to crop production than before the advent of herbicides.
The study showed that, in the absence of herbicides, less than a third of the harvest was lost to weeds in the first 10 years (1969-1979) of the dataset, but between 2005-2014, this had risen to more than half.
Dr Storkey says the results from the study suggest the effectiveness of herbicides has lulled the industry into a false sense of security when it comes to managing the impact of weeds.
“Because herbicides have been so effective, we’ve been able to control weeds really well for the past 30-40 years. But under the radar, the weeds have been gaining an advantage and, if the efficacy of herbicides continues to decline because of resistance, we would be in a worse situation now than before we had herbicides.”
The study suggests weeds present an unprecedented threat to food security, but whether that threat is realised depends on how herbicide use is sustained and how resistance is suppressed going forward.
Dr Storkey says: “There’s an argument that herbicides are a once-in-a-generation opportunity. They’ve been a fantastic tool that has allowed us to realise these yield gains and we know from the experiment you can get up to 80% yield loss from weeds if you don’t control them with herbicides.
“However, we’re already seeing with black-grass that we’re losing the battle in terms of protecting herbicide active ingredients, with sulfonylureas the latest chemistry to start losing efficacy.
This means growers should be X
Dr Jonathan Storkey
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Weeds such as black-grass have benefited from the use of fertilisers as much as crops.
thinking more about diversified weed strategies including improving soil management and cultural weed controls, such as delayed drilling, more diverse rotations and short-term leys, to take the pressure off herbicides.
“We’ve got to work at making our systems more naturally resilient or competitive to weeds. It’s almost a hidden enemy that’s creeping up on us and as herbicides stop working, black-grass starts to win,” says Dr Storkey.
Best results
In the Broadbalk experiment, delaying winter wheat drilling until the second week of October has continued to deliver the best results in terms of cultural weed control. In years where the crop was drilled later, up until the second week of November, there was reduced weed competition and a clear benefit to delayed drilling. Beyond that date the benefits dropped off.
However, as well as causing weeds to become more resilient, the changing climate is threatening the ability to delay drilling, made evident this autumn when many growers chose to drill early, rather than risk not getting the crop in the ground at all.
Dr Storkey says: “Climate change is causing warmer winters and adverse weather events to occur more regularly and there is the risk of not being able to travel.
“The drilling windows are getting narrower and more unpredictable, so there’s an unwillingness to take the risk of delaying drilling because opportunities for getting on the land are getting tighter. You could argue if
Breeding for better control
JIn addition to the rise of herbicide resistance, the adoption of shorter crop varieties – favoured for putting more nutrients into the grain and not the stem – has also led to increased yield losses as the shorter crop is outcompeted by much taller weeds. This plant breeding was done under the assumption that pest, weed and disease control could be taken care of with chemistry, says Dr Storkey.
“Crops have been bred for high harvest index or thousand grain weight and what the study showed is that more modern cultivars are inherently less competitive against weeds, so if you take the herbicides away you don’t actually realise any of those yield advantages.
“You could argue, if we didn’t have herbicides, the direction of travel for crop breeding would have been different. We would have perhaps selected for traits that would have made our cultivars more naturally competitive against weeds. The Recommended List is based on yield and disease resistance.”
Going forward, this means crop breeding will, at the very least, need to focus more on traits that allow the crop to thrive without the support of chemical crop protection or inorganic inputs, he says. However, it has been found that varieties with the genetic make-up to compete against weeds tend to show a trade-off between those traits and traits that make a variety high yielding in weed-free situations.
Competitive
Dr Storkey adds: “For example, a slightly taller cultivar is more competitive, but it has a lower harvest index. A cultivar with floppier leaves tends to shade out the weeds but the canopy is less efficient in capturing light in weed-free situations so there’s a trade-off.
“We did find some traits give you a win-win, which tended to be associated with the early growth phases. If you had a particularly vigorous cultivar early on which covered the ground quickly, it tended to be more competitive against weeds that didn’t have a yield penalty in weed-free situations.”
you’ve got a reduced tillage system and a better soil structure then you have got more days you can travel in autumn and that might help you with weed control as well.
Fertilisers giving weeds a helping hand
JIt is not just herbicides which are responsible for the evolution of more resilient weeds; the increased use of nitrogen fertilisers was also cited in the study.
Data analysis showed that weeds reduced wheat yields proportionally more on plots with higher rates of nitrogen fertiliser. On comparable plots where weeds were controlled with chemicals, higher wheat yields were achieved when more nitrogen fertiliser was added – meaning herbicides are most beneficial on the highest yielding wheat fields.
Modern crop varieties with high fertiliser inputs are, therefore, more vulnerable to higher yield losses if herbicide resistance becomes a greater problem.
Dr Storkey says: “Blackgrass is one of the main weeds on the plots, but it’s more competitive and abundant in plots that have high nitrogen fertiliser.
Selection
“This was another thing that we discovered had made weeds more competitive that was masked under the use of herbicides. By adding fertilisers we’ve selected for more competitive weeds such as black-grass. These species also respond more to climate change.
“If you have mild autumns and winters, which is what we’ve been getting, the relative benefit between the weed and the crop shifts towards the weeds. The weeds benefit from climate change more than the crop.”
The increase in bur chervil (above) is a country-wide issue (left).
Grass-weed control has long been the focus, but a shift in management systems could pose a new challenge as different weeds come to the fore. Alice Dyer reports.
The battle against black-grass has been widely studied, documented and reported in the last decade, leading to many growers taking action and getting on top of the weed.
However, some of the changes made to cropping systems on the back of grassweed control are leading to
New generation of weeds emerging
new problems emerging in arable fields.
This is according to John Cussans, weed biology specialist at NIAB, who says: “When you think back to where we were with black-grass in around 2012 it shows what can be done. There are some spectacular success stories out there and a lot of people feel they have all the tools and knowledge to fight the weed now by using a range of approaches.
Umbelliferous
“However, we’re now starting to see some umbelliferous weeds that are particularly problematic. I get the impression on soils that are more forgiving with less rainfall, there’s more adoption of conversation ag, which is probably partly responsible for the increase in weeds like
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JOHN CUSSANS
Seasonal outlook
JDamp conditions last autumn meant herbicides generally went on in good conditions and grass-weeds have been well controlled. However, the cold, dry spring has made herbicide timings in spring crops a challenge, Mr Cussans says.
“Normally we struggle with weed control in autumn and spring is the clean-up, but this year it’s different.
“The level of surviving weeds from autumn in most fields is pretty low. The challenge is going to be in these conditions where it’s cold, weed growth is stopstart. We need the weed to be growing actively to get the herbicide to work.
Unsatisfactory control
“For people using springdrilled cereals for grass-weed control, it’s been cold but also very dry, so pre-ems are just not going to be as effective and for mayweed, groundsel and fat hen we’ll see a lot of unsatisfactory control.”
The crops themselves have also been adding to the hit and miss spring, with some patchiness and open ground as a result of the cold spells resulting in late germination of weeds in places and poor weed suppression.
hemlock, willow herb and bur chervil.”
Until a few years ago, bur chervil was an oddity, rarely seen in Britain’s arable fields, but growing concern over the weed caused Mr Cussans to explore it further. He says its increase represents the changes being made in arable systems, including fewer deep cultivations, growers dropping pre-ems in oilseed rape and the loss of cereal herbicides including IPU, trifluralin and flupyrsulfuron, which all once offered good control.
“All those small changes come together to give you this weed,” says Mr Cussans.
Sulphonylurea (SU) herbicides can deliver 100% control of bur chervil, but with only one mode of action available, there is a high risk of resistance developing, says Mr Cussans.
He has received more than 30 samples of bur chervil this spring, sent by growers from the Scottish Borders right down into the South West, and is aiming to explore differences between populations across the country, including sensitivity to SU herbicides.
Conundrum
“The conundrum is bur chervil is an autumn-germinating weed and it comes up shortly after the crop. You can spend quite a lot of money on grass-weed herbicides but not get any control of it.
“Because bur chervil establishes as a seedling in autumn, by springtime it has been growing for months and is already quite big and well established, so you get really
variable control. Getting perfect herbicide application conditions is also much harder in spring compared to autumn.
Fat hen is another spring weed which seemed particularly prevalent last year after many farms were forced into spring drilling.
“Fat hen is a classic spring-germinating weed. The more we use spring crops to combat grass-weeds, the more we’re going to see things like bindweed, persicaria and fat hen come in, which I suspect a lot of arable farmers have not seen before. There are new weeds too like rat’s tail fescue, which has recently become an established arable weed and is certainly on the rise now. Not everything is black-grass anymore.”
As well as the new weeds coming to the fore, Mr Cussans warns growers not to take their eye off ‘older weeds’ such as wild oats, bromes and perhaps of most concern, Italian ryegrass.
While all of this presents arable farmers with new challenges, there are also benefits to be had in terms of weed diversity promoted by regenerative systems.
“Regenerative agriculture presents really positive potential impacts on traditional problems that stem from loads of cultivations, autumn- dominated crops and bare ground.
“We’re not talking about black-grass’ existential threat to crop production now being replaced by bur chervil. It hopefully will no longer be the case that one weed is a threat to sustainability. There will be more diverse weed flora; we probably won’t see one weed [black-grass] dominating like we have before, which is a positive thing.”
Knowledge base
This situation will require a much bigger knowledge base to combat these new weed challenges and their life cycles, meaning farmers and agronomists may have to ‘relearn’ what they have been previously taught about spring-emerging weeds and their management, Mr Cussans says.
“Just as we’re going to have diverse weed problems, we want diverse solutions. We still want herbicide-based solutions, but we need more modes of action and less selection for resistance. We want people to understand how their cultural controls impact on different weeds and the importance of using a diverse set of cultural approaches.
“It’s a real boom time in terms
Declining sensitivity in ryegrass and black-grass to flufenacet is the first evidence of resistance in a pre-emergence herbicide.
of people rethinking weed management and new technology, such as spot spraying, precision inter-row mechanical weeding and seed capture helps to give us a diverse set of tools.
Serious concerns over growing flufenacet resistance
JResistance to post-em, contact acting herbicides is widely documented, but it is the discovery of reduced sensitivity in black-grass and ryegrass to flufenacet that is the latest cause for concern, because it is the first evidence of resistance in a pre-em.
Mr Cussans says: “This is not a case of ‘just another active with resistance’. The change from only impacting post-em contact herbicides to starting to see it in a pre-em herbicide is quite a fundamental change because up until now we’ve been getting around resistance in post-ems by boosting our upfront weed control. Using more pre-ems has, to some extent compensated for a lack of activity from ALS and ACCase herbicides.”
Currently, the issue with flufenacet is most acute in Italian ryegrass, where in some populations the active will now no longer control the weed at the field rate. In black-grass, resistance has not progressed as quickly, but reduced sensitivity has been seen.
Mr Cussans adds: “Resistance to pre-ems should be much harder to select for as we tend to use mixtures and follow up on any surviving weeds with a post-em.
“If you try hard enough you can get resistance to anything and with flufenacet, the price has dropped; it is being used straight or mixed with something ineffective and when it started being made available straight, it became like DFF where you just add it in. That’s not sustainable use of a herbicide.”
JOHN CUSSANS
Championing oilseed rape
Only winter oilseed rape hybrids are grown at McGregor Farms in the Scottish Borders, where they grow 700 hectares of the crop.
The vigour and traits which hybrids offer combine to produce a consistently high gross output which, according to Tom Hoggan, graduate trainee manager at the business, has secured their place in the rotation indefinitely.
He says: “We see hybrid seed as an investment. If you are putting good quality hybrid seed in the ground, you are giving yourself a really good chance of getting that crop up and away and looking well through winter – a much better chance than if it were conventional seed.”
Enhanced vigour is the primary reason for their choice of hybrids.
Mr Hoggan says: “Autumns are often quite wet here and a large percentage of our oilseed rape area is drilled from August 20 onwards, into September, after wheat because we don’t grow much winter barley. You can get away with drilling hybrids slightly later than you would conventional varieties because of their vigour. We want the crop to be up and away before our main pest, slugs, cause problems.”
Cabbage stem flea beetle (CSFB) has not been an issue on McGregor Farms as yet. Establishment is done by a one-pass system and surface trash provides the ideal environment for slugs.
Mr Hoggan says: “Growing hybrids definitely ensures the crop marches on and grows away from slugs.”
Making a hybrid
A HYBRID is obtained by crossing two pure parental lines which are considered genetically distant. The resulting seeds, F1 hybrid seeds, are generally more vigorous and productive than the initial parents. This hybrid vigour is called heterosis. A conventional seed variety, also called an ʻopen-pollinatedʼ variety, is developed by combining plant crossings with a succession of self-pollinations and selecting steps. The results are the so-called ʻpure lineʼ varieties of oilseed rape.
Traits
It is not only the hybrid vigour which is greatly valued by Mr Hoggan, the traits hybrids exhibit are also important.
“When choosing a variety, oil content is of primary consideration along with pod shatter resistance and disease resistance. We deploy clubroot-resistant hybrids where the effects of this soil-borne pathogen have been seen.”
One of the hybrids grown at McGregor Farms, BASF’s early maturing InVigor® 1035 (InV1035), has pod shatter resistance, excellent disease resistance and verticillium wilt
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Tom Hoggan is graduate trainee arable manager at McGregor Farms, Scottish Borders.
tolerance, as well as some of the best oil contents available.
Mr Hoggan says: “We grow oilseed rape for gross output rather than just seed yield, so it is important to try and get the premium for the oil content.”
Achieving a five-year average yield of 4.9 tonnes per hectare, Mr Hoggan adds: “We just try and do the basics right and if
Championing oilseed rape
you are putting good hybrid seed in the ground then you are giving yourself a better chance of consistently achieving high yields, a much greater chance than you would sowing conventional varieties.”
David Leaper, Agrii seed technical specialist, says: “InV1035 has been our biggest selling variety over the last few years because of its growth characteristics. It excels in challenging establishment conditions and has very vigorous growth over the three months up to Christmas.
Resilience
“By building the canopy and creating a big plant you are building resilience into your crop and potentially saving money. We know oilseed rape has an optimum green area index and if you can build the canopy before Christmas, you’re reducing the need to apply as much fertiliser in spring.”
Research over the last five years has shown that a big canopy, a big root collar size and a more robust plant in autumn provide more resilience against CSFB.
Mr Leaper adds: “We have seen massive strides forward in oilseed rape breeding and the quality of varieties now is a step apart from what we used to grow. It is noticeable that the number of breeders who breed conventional varieties has dwindled, with some companies, such as BASF, exclusively breeding hybrids.
“Plant breeding is giving us varieties with more resilience and the ability to cope with extremes which will certainly be experienced in the future.”
Mr Leaper acknowledges that in the short term, there are issues with regard to the area grown because of CSFB.
“However, the future is positive because oilseed rape produces a very healthy oil and has a good fit within UK arable rotations.”
Breeding technology is driving developments
DIRK Decherf, BASF European breeding manager for oilseed rape, says: “Breeding a hybrid starts with the creation and selection of parental lines. “The combining ability of these parental lines is evaluated in test hybrid combinations where we measure yield and vigour to obtain the highest yielding hybrids.
“As breeders, we want to deliver a yield increase and yield stability while balancing this with the transfer of genetic information which delivers the traits which are of interest to the grower.
“For certain traits, such as clubroot and phoma resistance and pod shatter reduction, it is sufficient to have the trait in only one parent to obtain the trait in the hybrid.”
For the UK, resistance to diseases such as light leaf spot, phoma and turnip yellows virus (TuYV) are critical. The recent introduction of the trait which confers TuYV resistance to hybrid varieties, a virus which is endemic across the whole of the UK, delivers 7-10% more yield alone.
Dirk Decherf
Mr Decherf says: “Looking ahead, our BASF InVigor® breeding programme continues to stack different traits into our elite parental lines.
“In the spring and winter oilseed rape pipeline ‒ especially for CIS and Eastern European countries there are hybrids which combine the Clearfield® trait with our patented pod shatter reduction trait and improved TuYV, clubroot and phoma resistance in the winter hybrids. Thinking specifically of the UK pipeline, we have a winter hybrid with the Clearfield® and clubroot traits, phoma resistance and pod shatter currently in registration trials. “Techniques, such as the use of genetic markers and predictive breeding, have transformed the breeding process over the last 20 years and there has been a phenomenal success rate in the introduction of genetic traits, allowing hybrids to reach growers faster than in the past. However, breeders need to be anticipating and working on what the growersʼ needs for the crop will be in 10 yearsʼ time.
Quality
“For example, breeding for potential climate change impacts,drought tolerance, future sustainability requirements, nitrogen efficiency, protein quality and insect resistance in the OSR crop are all in progress. “The outcome of the current UK consultation around the technologies which fall under the umbrella of genetic modification, such as gene editing, will dictate the future speed of progress.”
Find out more
FOR more on this project, visit the hub at fginsight. com/ChampionOSR
