With spring feeling tantilisingly close, what’s the state of play for autumn-drilled wheat crops and the impact this may have on management approaches for disease and weed control? CPM opens up the conversation.
“The survey suggests rust control is the main focus of T0 sprays.” TOM WHEELHOUSE
By Janine Adamson and Rob Jones
With brighter, much improved weather on the cards at the time of writing (late February), there’ll understandably be a readiness to hit the fields and start ticking off crop management tasks as soon as possible. It’s a stark contrast to the position many were in last spring which in ways could heighten the desire to truly maximise weather windows, however, a recent survey suggests tough decisions will have to be made as a result of increasingly squeezed schedules.
UPL’s Tom Wheelhouse says perhaps unsurprisingly, applying nitrogen was cited as the top priority for 52% of farmers surveyed, followed by drilling spring crops (32%). But when it comes to sprayer-related tasks, the results were more mixed, he adds.
“Applying micronutrients and herbicides tended to have a greater focus than applying fungicides and PGRs. It suggests a crowded to-do list, where realistically, everything has to be done.
“As such, it’s no surprise that every respondent is tank mixing at least two products – more than 20% said they typically mix four. Tank mix compatibility and worries about crop scorch are
cited as the main reason why they don’t consider bigger mixes,” explains Tom.
The survey was conducted by UPL as part of the company’s Good Growing Club. It also explored fungicide use. “Looking at T0s, three quarters of participants regularly apply at this timing with azoles and strobilurins cited as the main chemistry, followed by multi-sites folpet or Thiopron (sulphur), and plant health elicitors.
“This suggests rust control is the main focus of T0 sprays for farmers since strobilurins and older azoles like tebuconazole have little effect on septoria,” suggests Tom. “It’s a significant change since the days of chlorothalonil when most fungicide programmes began with a T0 multi-site application.”
The survey results also indicate that more than 75% of farmers identify the weather as the main challenge when applying a T0, with others highlighting workload constraints and ensuring correct timing as concerns.
Consequently, almost 80% said if their chosen fungicide had greater tank mix and application flexibility, it would help with early disease control. “There’s clearly a demand for greater flexibility in fungicide products used at T0, so farmers could consider other options such as plant health elicitors.
“Once applied, a product like laminarin (Iodus) moves through the plant, stimulating its defences. The mode of action means there’s more flexibility in when it can be applied, because it doesn’t necessarily have to go on leaf four like a conventional T0 fungicide,” comments Tom.
Despite the more optimistic conditions, Farmacy agronomist, Tom Smith, reminds that because many winter wheats are exhibiting a range of growth stages as they enter the spring, extra care will be required when it comes to crop management.
In fact for some, the variability will be reminiscent of last season, with many early-sown forward wheats showing good growth and excellent potential, while some later-drilled crops will have struggled to get going in cold, wet soils, he continues.
Tom Smith, who oversees crops throughout Essex and Suffolk, says some of the most forward wheats in his area were up to growth stage 25 in mid-February, with the majority around GS23/24, while those drilled in mid-November after potatoes were back closer to GS13.
“These are the extremes, but there’s a lot of variability out there which poses challenges for early fungicide planning, and reinforces the importance of applying treatments according to growth stage, not calendar date.
“Growers should also recognise that those later, backward crops, often go through growth stages quickly as temperatures and day length increase, potentially complicating spray timings.”
Hutchinsons’ head of integrated crop management, David Howard, says building potential, irrespective of current growth stage, all starts with a T0. “We’ve seen before that growers can sometimes be reluctant to invest in thinner crops, cutting back on early T0 and T1 sprays only to find they then had to chase disease hard at T2 to get it back under control.”
He highlights that yellow rust in particular can be more pronounced in late-sown or stressed wheats, and thinner crops are also more reliant on lower leaves to help them to catch up, therefore protecting photosynthetic capacity is key despite the possible lower yield potential.
Furthermore, with recent seasons indicating rust and septoria are becoming more aggressive and better adapted to changing weather patterns, effective early disease control is vital to stay on the front foot in any crop, says David.
He agrees with UPL’s survey results regarding rust being a focus disease. “Historically, septoria was the main target at T0 and while its control remains important in high-risk varieties and regions – particularly the West and South-West – for many, the focus has shifted towards managing rust.
“Last year saw a particularly early appearance of brown rust in some crops, and after a high pressure season, there could be more inoculum around this spring although much depends on the impact of winter frosts in reducing inoculum, or at least delaying onset. Equally, milder conditions like last season could result in earlier rust pressure,” he explains.
David believes rust management is a numbers game. “You must act early to slow it down before inoculum builds. An effective T0 is a ‘no-brainer’ for anyone growing wheat in higher rust-risk areas of Eastern Counties.” And if the weather closes in before successfully applying a T0 at the optimum time, he says there could still be a benefit to be had. “Typically, many wait for GS30 but crops are sometimes beyond that by the time of application. When catchy weather delays spraying, some may then wait until T1 and perhaps try combining the two. “Having a gap between T0 and T1 is beneficial though, so be flexible with the early timing. If disease is present and you’re 2-4 weeks out from T1, it’s worth treating, subject to product label restrictions,” he advises.
PLAXIUM TRIAL RESULTS
Moving to later in the season, independent AHDB trials indicate the performance of Bayer’s recently authorised Iblon-based fungicide, Plaxium (isoflucypram+ fluopyram+ prothioconazole).
The data shows compared with the other products in the trial, Plaxium was comparable in controlling Septoria tritici, was either equal to or better than other products against yellow rust, and the strongest against brown rust.
Plaxium received regulatory authorisation for use in winter and spring wheat, barley, rye, triticale, spelt and oats in late 2024. In data recently published to highlight its performance in trials 2019-2021, AHDB says: “Plaxium was shown to be highly effective against Septoria tritici in both protectant and eradicant situations.”
Against yellow rust, AHDB adds that Plaxium showed a level of activity above that seen from Ascra Xpro (bixafen+ fluopyram+ prothioconazole) and Revystar XE (fluxapyroxad+ mefentrifluconazole), comparable to Univoq (fenpicoxamid+ prothioconazole), and close to that of Elatus Era (benzovindiflupyr+ prothioconazole). These differences were carried through to harvest with Plaxium-treated plots yielding comparably to Univoq.”
On brown rust, AHDB explains Plaxium offered superior control compared with the other mixture products tested… and was comparable in efficacy to Imtrex (fluxapyroxad) and Elatus Plus (benzovindiflupyr).
Trial partner, Niab’s Stuart Knight, believes the results indicate a clearefficacyandyieldresponse advantageofPlaxiumcompared with Ascra Xpro. “This reflects the boost to foliar disease activity provided by isoflucypram, in place of bixafen in this three-way mixture.”
The work was repeated in barley trials where it gave the best all- round control of rhynchosporium, net blotch, ramularia and powdery mildew; Plaxium showed good control of all four diseases.
RHYNCHOSPORIUM
Against rhynchosporium, in both protectant and eradicant situations, AHDB says: “Plaxium gave excellent disease control, comparable with or better than Siltra Xpro (bixafen+ prothioconazole) and Ascra Xpro, and similar to the level of control provided by solo active, Miravis Plus (pydiflumetafen).”
Similarly, against net blotch, Plaxium showed a high level of efficacy even at 50% of label rate, performing comparably to Miravis Plus and Ascra Xpro, added AHDB. Against ramularia, Plaxium matched the control of Revystar XE and was slightly better than Ascra Xpro.
Another trial partner, SRUC’s Professor Fiona Burnett, highlights the performance of Plaxium and the combination of multiple modes of action along with the restrictions on use that would ensure good product stewardship.
“Plaxium adds another robust mixture option for control of barley diseases and is carefully stewarded to manage resistance risk,” she says.
Against powdery mildew, AHDB notes that although disease pressure was relatively low in these trials, Plaxium gave the highest level of protectant activity of any of the mixture products tested.
However, important to note is advice from Bayer, with the company stressing that Plaxium has strict use limitations – it can be applied only once per crop with no more than 75g/ha of isoflucypram applied to the same field every two years.
This article was taken from the latest issue of CPM.
For more articles like this, subscribe here.
Sign up for Crop Production Magazine’s FREE e-newsletter here.
