With high levels of weed seed shed looming, what can growers do to get back on track with grassweed control? CPM asks two farmers to discuss their strategies, as part of this month’s Real Results Roundtable.
“It’s been a really difficult year and on some farms, blackgrass control has probably gone backwards five years.”
By Janine Adamson
Throughout the past year, continued rainfall has impacted the ability of many farmers to apply the required chemistry to their cereal crops, while conditions have favoured the proliferation of both weeds and diseases.
As thoughts shift to harvest and next year’s crop, what can growers do to get on-top of grassweed control and mitigate further population increases?
For this Roundtable, CPM brings together BASF’s agronomy manager, Hugo Pryce; Suffolk-based farm manager, Graham Thomson; and Yorkshire farmer, Richard Hinchliffe.
Graham is the farm manager at PC Kindred & Son in Woodbridge, a system which operates across heavy clay soils to produce combinable crops, beans, sugar beet and grass seed, with the addition of an indoor pig unit. The farm has a ‘very strict’ policy when it comes to grassweeds, using the best chemistry alongside appropriate IPM techniques.
Richard oversees his 560ha family farm in Yorkshire and is a strong advocate for delayed drilling – even in clean fields work doesn’t start until mid-September.
The discussion for this Real Results Roundtable is getting on top of grassweed control in winter wheat and reflecting on this challenging year.
Current scenario
Hugo opened the discussion by sharing that where he is in Norfolk, there’s a lot of heavy land which tends to suffer from blackgrass, therefore, many growers aim to delay drilling. “However, Storm Babet arrived mid-October meaning in some instances, nothing had been planted before that.
“Seed was then perhaps often spun on resulting in fairly indifferent crops. Importantly, there hasn’t been the blackgrass control because it’s not been possible to apply post-ems, which many expected to be able to do.
“It’s been a really difficult year and on some of these farms, blackgrass control has probably gone backwards five years – there’ll be a massive seed return this autumn and fields which should have been whole cropped or completely sprayed off, weren’t,” he explained.
Richard agreed and said of his 560ha of cropped land, 150ha wasn’t drilled. Some has gone into winter bird food and the rest reserved for summer cover crops, ready for autumn 2024. “We’re the same as everyone else and have the good, the bad and the ugly. Crops which were drilled really early look decent, but what we’ve lacked is sunlight which is massively down this year and will have a significant impact on grain size and set.
“Blackgrass-wise, we have a zero tolerance regime so the only weeds left will be anything we’ve missed while roguing. But because we only applied pre-ems and missed our top-ups, we’ve spent longer roguing than usual.”
In contrast, Graham said he has the lowest blackgrass pressure he’s seen for some years. “We drilled relatively early (from the end of September) and have managed to apply all the required chemistry. It’s not to say the crops look brilliant, but grassweed-wise, roguing has been negligible.
“The only concern has been a late drilled wheat after sugar beet where we couldn’t apply herbicide – blackgrass has come up at what I’d class as a high level, for our standards,” he added.
Integrated approach
Richard listed a host of tactics which he strives to deploy at his farm for grassweed management such as optimising the rotation, adapting seed rates and choosing robust varieties. He also highlighted the importance of machinery hygiene. “I like to ensure machines such as combines are cleaned off in gateways due to them spreading seed around.
“In fact, we inherited a soft and meadow brome problem after having a demonstration combine on the farm, so that’s something we wouldn’t do again because it took a few years to get on top of. With us having a depleted grassweed seedbank, we can use no-till techniques but that means we’re seeing a slow shift in weed spectrum, particularly broadleaf species.”
Furthermore, he made the point that it’s important to look beyond just blackgrass due to increasing populations of brome, rat’s tail fescue and Italian ryegrass. “But diversity is key – nature loves everything being done the same because it has a chance to adapt to the conditions. Mixing things up always helps with control,” he said.
Hugo added that he hopes growers see an early weed seed chit in the coming months. “They want to be able to stimulate germination of the seed that’s been dropped and achieve one, ideally two, stale seedbeds before even thinking about drilling.
“Afterall, that was the problem in 2022/23 – it was so dry there wasn’t a chit and by October, growers couldn’t wait any longer.”
While discussing how long to wait for a stale seedbed to deliver, Richard reminded the Roundtable of blackgrass’ seed return and that it’s critical to achieve 98% control to ‘stay still’. “If you have 2% of blackgrass still coming through, you still have a huge amount of seed return. The bar is so high that to get below this threshold, you have to effectively achieve zero plants left over in fields.”
He also said he recognised there may be the temptation to drill early this coming autumn. “There’s a lot of heavy land around this country and motivation this year will be to go and get that drilled up. Once you have a crop growing and established, it’s a lot better than a bare field.
“But if people do this, they’re just committing to spending big on inputs in bad blackgrass situations,” commented Richard.
Programme choices
Historically, Graham said he’d use Anthem (pendimethalin) plus Liberator (flufenacet+ diflufenican) as the base of his grassweed control strategy. In some instances, he’d swap pendimethalin for prosulfocarb to provide additional ryegrass control.
But with blackgrass pressure increasing in autumn 2022 he turned to Luxinum Plus (Luximo/cinmethylin), although due to dry conditions success was limited. Having returned to use the active again in autumn 2023 following a recommendation from his agronomist, he said with good soil moisture, he’s achieved excellent results – the equivalent of a reset.
“This coming autumn, we’ll go again with Luximo and for the fields which require additional help, which I don’t think there’ll be many, we’ll top-up with Avadex Factor (tri-allate),” he explained.
As for Richard, he said for the majority of the farm he uses flufenacet plus diflufenican (DFF) at pre-em followed by flufenacet plus prosulfocarb at peri-em. On the most challenging land or areas he’d consider Proclus (aclonifen) at pre-em, and also has the capacity to spot-treat with Avadex.
Having lost his Luximo trial area to flooding last autumn, Richard said he’s keen to keep the product in his ‘back pocket’ ready to add to his herbicide programme as required, or as a means of alternating modes of action.
“But because flufenacet plus DFF is a very cost-effective option, it means we do have funds available should we have to invest in more chemistry.”
In response, Hugo acknowledged the role flufenacet has played in forming the base of grassweed control programmes for the past 20 years. However, he believes Luximo offers a viable alternative for those struggling to achieve adequate control.
“Where you do have high blackgrass or ryegrass pressure, I think Luximo would prove a good, starting building block,” he suggested.
Richard pointed out that the reason he’s able to achieve results using a reduced pre-em input spend is because of years of proactive management. “We’re in a fortunate position, but if I was in a bad blackgrass situation I wouldn’t dream of using flufenacet plus DFF.”
Luxinum plus
From a trial perspective, Hugo added that Luximo’s performance far exceeds that of flufenacet. “If you have high blackgrass or ryegrass situations, in places where you can’t hand rogue, it’s a really strong active. Both in combination and in sequence with other products it should be the starting point for a lot of people this coming autumn.”
An additional benefit of Luximo is its direct activity on weed seed, which given the amount shed this year, is particularly relevant, he raised. “If you have weed seed on the surface and you’re in a direct drilling situation, which is becoming more popular, then you’ll achieve good efficacy from Luximo acting directly on the seed.
“The caveat to that is you have to ensure drilling depth is correct so the crop seed is covered. But certainly, BASF has conducted quite a lot of trial work which shows at direct contact with blackgrass or ryegrass seed, Luximo is giving significant levels of control.”
Recognising these benefits, Graham said it’s likely around half of his hectarage will be treated with Luxinum Plus this coming autumn, adding that the reason why he’s not going ‘full out’ is due to resistance management.
Hugo agreed with this point and added that new chemistry doesn’t come along very often so it has to be protected – used at the correct rates and in combination with other active ingredients. “Although Luxinum Plus’ label is more flexible than other products, the sweet spot is pre-em application – that’s the key timing to achieve real bang for your buck.
“In trials, we’ve consistently seen Luximo offer considerably greater control at pre-em as opposed to post-em. It’s taken up by germinating seeds and roots, not through leaves, which is why timing makes such a difference.
“It’s about managing risk – if you leave Luximo to post-em you run the risk of the weather closing in and not being able to apply the most effective chemistry. Get it on first, and you maximise your chances of getting the control you require.”
Having used the product for a couple of years, Graham confirmed that Luxinum Plus is easy to use from an operator’s perspective and has caused no compatibility issues. “We’ve had no problems using it at all,” he concluded.
This article was taken from the latest issue of CPM. Read the article in full here.
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