In what’s been a challenging season to say the least, CPM looks at how the ever-changing climate has impacted weed pressure this year as well as the proactive steps growers are taking to win the war against grassweeds.
“We as an industry should pat ourselves on the back with how far we’ve come with regard to IPM.”
By Charlotte Cunningham
Casting back to autumn 2023, good stale seedbeds and plenty of soil moisture had growers’ hopes pegged on a promising season ahead. However, after several years of kind autumns and springs, few anticipated such stark contrast this season with storms wreaking havoc for drilling and autumn herbicide plans, which had a knock-on effect – largely in terms of grassweed control.
A recent survey carried out by CPM and BASF delved further into the impact of the season, starting right at the beginning with stale seedbeds and winter wheat drilling dates.
According to the survey, 48% of those who created stale seedbeds said they were quite satisfied with the weed flush ahead of drilling and the majority of growers (51%) had wheat in the ground during the first two weeks of October.
A small proportion (8%) were as late as mid/end of November, highlighting the challenges of the season, says John Cussans, weed scientist at ADAS. “As ever, every farm is different. But what we do know is there was definitely a lot of people who struggled with both drilling and getting herbicides on. Though many farmers would have been in a reasonable position going into the autumn, worst-case scenario this season saw people either get nothing drilled or not apply any chemistry until the spring.”
BASF’s Stuart Kevis concurs: “Considering the autumn we’ve had, it’s always reassuring to see so many people did get crops in the ground – 90% in total by the end of October. Storm Babet hit around 18 October so anyone who was aiming for that later, delayed window may have been caught out.
“One positive with the stale seedbeds this year is that the soil moisture meant they were, in general, much better than the previous year. Last season was very dry meaning lots of growers didn’t get the blackgrass chit and the glyphosate didn’t really do as an effective job.”
Among those growers who did get crops in the ground is Freya Morgan. Farming 1600ha in Bedfordshire, Freya’s rotation typically consists of winter wheat, winter and spring barley, oilseed rape, winter beans and spring oats. This year she had all but 20ha of wheat in the ground, by the middle of October.
However, even for those who did get crops in the ground, the knock-on effect of poor conditions after drilling and delayed herbicide applications has been increased weed pressure and poor control, with all growers noting the presence of key weeds including blackgrass, ryegrass and brome in their winter wheat areas this year.
But how does pressure compare with a typical year? Perhaps rather interestingly, almost 40% of growers said their blackgrass pressure was much higher than last year. Brome pressure was deemed slightly higher by 23% of growers, while the majority (35%) said ryegrass levels remained largely unchanged. In terms of pre-em applications, the majority of growers (57%) said they planned and applied their autumn pre-ems on time, while the rest didn’t, once again highlighting a mixed picture.
Although conditions have exacerbated the prevalence of weeds, Stuart says it isn’t totally unexpected. “Thinking back to the previous year – autumn 2022 — stale seedbeds didn’t work as well which put a lot of pressure on herbicide chemistry and left many feeling they weren’t as robust performance-wise as they could have been,” he suggests. “The impact of this, coupled with a very wet start to the year, was quite a lot of blackgrass heads in May/June time and therefore a high seed return going into autumn 2023.
“We’ve been building towards a high-pressure year, which – on top of the weather — has led to such widespread challenges with weeds this year, particularly blackgrass.”
Looking at how the pressure has changed since January/February, blackgrass remains in the spotlight with 55% of growers saying the pressure is higher than they originally thought. Almost a third (32%) said brome pressure is also greater than they anticipated and 25% said the same for ryegrass. “It’s important to separate out the species here,” notes John. “Ryegrass and rye and meadow bromes germinate later so we’re likely to see that flush later on.”
With regard to the blackgrass, Stuart says this increased pressure is perhaps an indication of continued weed germination throughout the spring, and with few-to-no post-em options, this reinforces the importance of ‘throwing everything you can’ at the crop in the autumn.
John continues: “The ultimate challenge with grassweeds is that if you don’t apply pre-ems as planned, then it can be really devastating for control.”
Freya is among those who noted higher blackgrass pressure than initially expected this year. “We tend to delay drilling the worst blackgrass fields until last, but we probably shouldn’t have done that this year as we couldn’t control the blackgrass in these areas. This was made worse by the fact we didn’t get pre-ems onto these fields either.”
That said, it’s ryegrass which has proved particularly problematic this season, she continues. “We don’t usually suffer from that much, but I think because it was so wet, and then we had a very mild winter, it didn’t help.”
Stuart warns that if this ryegrass pressure becomes more of a general issue, there could be control concerns. “The worry is, it’s a harder weed to control than blackgrass due to its protracted, sustained germination period.”
Of course, taking action against weeds doesn’t just incorporate chemistry and the importance of a strategy which involves IPM techniques has been a focus for many during recent years.
Everything from rotational ploughing to stale seedbeds, spring cropping and delayed drilling, were all highlighted as regular tactics in the IPM approach, albeit a growing percentage said they’d be undertaking more of these measures this coming season.
“A multi-faceted approach is very much the strategy here – with blackgrass particularly, one measure just doesn’t work on its own,” says Freya. “Where we did get pre-ems on this year, we have managed good control of blackgrass, but that’s down to the combination of measures we use like spring cropping, for example.”
Looking at the opportunity to tackle weeds pre-harvest, slightly more growers said they’ll aim to carry out roguing, spraying off the worst patches – or whole fields – this year, while 36% said they’ll also consider mapping high pressure areas. This is in contrast to 29% who did this pre-harvest last year. “We’ve sometimes found you have to plough to reset, so we do use rotational ploughing on the worst areas where required,” says Freya. “But that’s not something we’d want to do every year.”
With a number of tactics being deployed already, Stuart says it’s good to see there’s a zero tolerance to grassweeds. “I think the increase in spraying off whole fields is likely to be a reaction to the autumn – there’s been a lot of talk of people having to ‘reset’ fields. It’s a drastic approach, and not nice, but long-term there’ll be a benefit on high pressure farms.”
For those growers who choose to venture down the path of mapping high pressure areas, Stuart says it might also be an apt time to test resistance levels. “It can be complex, and populations within fields do vary, but getting a very broad understanding of what chemistry and modes of actions will and won’t work is a very useful tool for growers.”
While the ‘best’ combination of IPM techniques will vary farm-to-farm, John says the overarching message is a positive one for agriculture as farmers are making such concerted efforts to tackle weeds. “The picture across the response to this survey is a gradual uptick towards more attention to detail.
“I think we as an industry we should pat ourselves on the back with how far we’ve come with regard to IPM – it’s not something that’s done just in a reaction to a bad year, it’s becoming really embedded in the ethos of farming.”
When a sound IPM strategy is in place, good chemistry is primed to be even more effective, continues John. And since its launch two years ago, BASF’s Luximo/Luxinum Plus (cinmethylin) has been hot in the headlines, offering growers grappling for grassweed control an additional tool in the armoury in the form of a new mode of action.
Half of growers surveyed revealed they indeed tried the new active on their winter wheat area this year, but 50% didn’t – so what are the benefits for those who are yet to try it?
Based on the active Luximo, Luxinum Plus is a residual herbicide for the control of blackgrass, ryegrass, annual meadow grass, bromes and poppy in winter wheat and spring barley, designed to be used as part of an IPM strategy. “I’m surprised more people in the survey haven’t at least tried it,” says John. “It’s good chemistry and I’d say if you have Italian ryegrass, specifically, causing an issue on farm, then you really should be using it in those fields.”
Looking at the plans for this coming autumn, while the jury is still out for 22% of growers, the majority (a combined 73%) said they’re likely to use Luximo. “The data sets we have are really consistent – Luximo has set a new benchmark for soil residual chemistry,” says Stuart.
“Trial work shows it outperforms flufenacet. A Luximo-based programme applied pre-em is the best start you can get to your winter wheat grassweed control programme. If you’re not using the best, you’re behind the game plan from the get-go.”
Freya says she’ll be using Luximo once again this autumn after seeing good results this year where it was applied, despite the difficult circumstances. “I was a little concerned through the winter that everything would be washed away, and we wouldn’t have any residual activity, but that proved not to be the case. It’s given us another tool in the armoury to help us keep some of these challenging weeds at bay. We’ll definitely be using it on the worst fields again this autumn.”
This article was taken from the latest issue of CPM. Read the article in full here.
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