Grassweeds are going to have to put up an even bigger fight to conquer chemistry thanks to the recent registration of a new active in cereals. CPM finds out more about Isoflex.
“It’s rare a new active comes to market and probably even more rare that two come at the same time.”
By Charlotte Cunningham
Two years on from CPM’s first look at Isoflex active (bixlozone) in FMC’s French trials, it’s good news for growers grappling for grassweed control solutions as the active has now received registration in Great Britain, with products expected to be filling tanks by next autumn.
The journey to market has been a lengthy one, concluding most recently with three years of extensive trials with growers, distributors and industry bodies to see if Isoflex really can ‘flex’ its potential when it comes to controlling some of the most yield-robbing grassweeds.
Delving into the details, Isoflex active is based on FMC’s novel new herbicide, bixlozone – from the isoxazolidine family – which has been classified by the Herbicide Resistance Action Committee as a Group 13 herbicide, explains Geoffrey Bastard, marketing and plant health lead (UK and Ireland) at FMC.
“Bixlozone was discovered a while ago and when we began looking at it, we quickly realised it had some really interesting levels of control against key grassweeds – specifically blackgrass and ryegrass, but also annual meadow grass which will also be on the label,” explains Geoff. “I think there are now only 11 primary autumn cereal herbicide active ingredients available at the moment, but there’s likely to be some significant changes to that space between now and 2030. So to be able to bring a new mode of action in cereals to market is something we see as being really important, especially given that the product will have both winter wheat and winter barley on label.”
So how exactly does bixlozone work? “It inhibits susceptible plants from producing carotenoids – pigments that are critical to protecting photosynthetic processes and ensure normal plant growth and development. Essentially, it’s a bleaching herbicide as it stops the photosynthesis in target weeds,” explains Geoff. “Trials have shown that where it’s used pre-emergence or early peri-emergence in wheat, we get either lack of weed emergence, emergence with bleaching or, particularly in blackgrass and ryegrass, this pinky/purpley colour before dying.”
Studies of tolerant crops show that these symptoms are transient with little to no effect on the vigour and yield, continues Geoff. “In addition to inhibiting the production of carotenoids, Isoflex active slows down the production of key amino acids in susceptible plants. It’s also able to control weeds through the combination of disruption of light reactions as well as protein turnover and degradation.”
ADAS’ John Cussans says having this family of actives available in a cereal herbicide for the first time is a real positive for growers. “What this means for grassweed control in cereals is that we’re bringing in a totally new mode of action – a very different piece of chemistry. In order for herbicides to be sustainable in crops we really have to maximise the diversity of what we’re applying, so this is a really welcome addition.
“Adding in diversity to your early residual soil acting herbicide stack should be a priority – particularly at the moment – so it’s quite neat that Isoflex active has come along at this time.”
The first Isoflex-containing herbicide coming to market – and expected to land next autumn – is a co-formulated product which actually brings two new herbicide active ingredients to UK markets, explains Geoff. “What we’re offering is a co-formulation which brings together bixlozone and beflubutamid – which is also new. It’s rare a new active comes to market and probably even more rare that two come at the same time.”
By pairing it with beflubutamid, growers will also benefit from enhanced broadleaf weed control too, points out John. “That’s something we’ve missed as we’ve lost products like trifluralin and isoproturon. As a result, we’ve landed with programmes that only deal with grassweeds and consequently, growers end up with broadleaf weeds emerging. I’m quite keen on co-forms because they bake in multiple modes of action and diversity of chemistry in one ready-to-go product.”
Looking at this weed control spectrum in more detail, Geoff says Isoflex active will have 21 broadleaf weeds on label including cleavers, groundsel, mayweeds, red-dead nettle and speedwells, and four grassweeds – blackgrass, Italian ryegrass, annual meadow grass and rough meadow grass – making it one of the broadest labels in the autumn cereal herbicide market.
While Isoflex will provide good activity across a broad range of weeds, John warns that it’s important to be realistic about the expectations of products alone and advocates using Isoflex as part of a programme and integrated weed management strategy. “It will add an option and diversify the herbicide base,” he says. “In some scenarios it might be an alternative to existing approaches, but in high grassweed pressure situations I don’t see it as necessarily replacing things already in the programme, in every single field. Instead, its inclusion as part of a programme will bolster control and bring in a great diversity of controllable weeds.”
Geoff agrees and concurs that Isoflex should be used as part of a programme, rather than alone. “I think Isoflex active will be a nice confidence tool for growers,” he says.
“Every farm, every field, every patch of ground has a different dominant set of weeds and this is a product that, in the pre-emergence slot, will give growers the confidence that they’re covering a broad base with one product, which they can then build on as a part of a sequence to make sure they get crops off to a good start and stay weed-free. The autumn slot is the first chance to control weeds so getting that off to a good start is vital.”
Considering how Isoflex active has performed in trials, FMC has looked at the levels of control possible when used alone and as part of a programme. “Firstly, looking at blackgrass control and, based on 64 UK trials at a rate of 1 l/ha pre-emergence, Isoflex active alone gave an average control of 53% on high-pressure sites – where blackgrass counts were on average 332/m2, which would be considered quite high-pressure sites,” explains Geoff. “This level of control increased to above 65%, compared with untreated, where blackgrass headcounts were <150/m2.”
On ryegrass, the performance has been particularly strong, giving control levels upwards of 64% – across 27 trials – when applied alone in similar high-pressure ryegrass fields, and reaching above 75% on more average pressure sites. “However as mentioned, solo use isn’t advised, especially when targeting key grassweeds such as blackgrass and ryegrass, and should always be used as part of a herbicide programme utilising other modes of action,” says Geoff. “Where we’ve trialled Isoflex active in typical mixes/programmes with other available actives, significant control – over 95% – can be achieved.
“Alternating modes of action is vital for both herbicide efficacy and resistance management. There’s no silver bullet.”
During the coming 12 months ahead of its official launch on the market, Geoff says FMC will be continuing to trial Isoflex active to fineness how and where it’s best used, with demo sites across the country to showcase the product to growers. “If we use this active correctly, I’m confident that we’ll be able to keep it on the market for a long time – which is absolutely vital for long-term, sustainable weed control.”
This article was taken from the latest issue of CPM. Read the article in full here.
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