Yellow rust wheat threat mounts ahead of T1 fungicide sprays

Winter wheat growers face a heightened challenge of controlling septoria and yellow rust in their crops this season, with both diseases clearly visible in early spring.

Farmers Weekly visited North Yorkshire and Norfolk to check on the worrying upsurge in yellow rust and the ever-present septoria. Next, was a trip across to wetter Herefordshire where septoria is traditionally the main concern, but yellow rust is now a threat.

See also: Tips to improve spring weed control if conditions turn dry

North

Yellow rust is becoming the most serious disease to control in winter wheat, overtaking septoria, as early infections on susceptible varieties can cause yield losses of over 50%.

The overcoming of a vital yellow rust resistance gene last year saw the resistance scores of many leading wheat varieties tumbled, and early infections seen this spring are a big threat to yield potential.

Jonathan Blake, technical director for crop protection at consultant Adas, says yellow rust is coming into winter wheat crops earlier in the spring and now staying around longer in the season until June.

“Yellow rust, left untreated, can be more devastating than any other pathogen, as early defoliation does not allow the crop canopy to grow away,” he says.

The foliar disease was seen across most wheat variety plots at Bayer’s Crop Doctor site in North Yorkshire, especially those varieties with the YR15 resistance gene.

Last year, the failure of this YR15 gene was first detected on the Durham coast near Sunderland in late March and a new yellow rust race spread slowly across the country, but this season it is assumed to be nationwide.

Cool and damp weather this spring and the lack of any hard winter frosts has favoured its spread, and the disease was seen in Yorkshire as early as January this year.

Jonathan says the threat from the disease is greater this season than last year, as in 2025 weather conditions were not favourable for yellow rust as cold, hard frosts in the winter quickly turned to dry then hot weather through the spring and summer.

Early control is now considered essential this season at the T0 stage, usually in late March/early April in Yorkshire, or when the first signs of yellow rust are seen.

“Where yellow rust is a problem, it is an easy decision to use a T0, with timing more important than product, as azoles such as tebuconazole and prothioconazole both give good control at half-doses,” he says.

Yellow rust, left untreated, can be more devastating than any other pathogen, as early defoliation does not allow the crop canopy to grow away

Controlling yellow rust early, before the T1 stage in late April, can give a yield response of 1t/ha or more, as the disease affects early crop growth, and also creates inoculum of the disease which will be difficult to control later.

Indeed, failure over the season to control yellow rust in a potentially yielding 10t/ha wheat crop can cut yields by 5-6t/ha, more than the potential losses from septoria of  3-4t/ha, as yellow rust attacks the crop much earlier in the season, says Jonathan.

Yellow rust tends to favour cool and damp weather, while septoria likes wet and warm conditions, and the often later developing brown rust thrives in hot and moist weather.

A fungicide strategy should be about calming yellow rust down rather than looking for total control – which is difficult as it is almost impossible to get 100% spray coverage of a wheat crop.

“Chemistry is good at yellow rust control, but the lack of complete coverage, quickly emerging leaves, and the speed at which the pathogen cycles make complete control difficult,” he says.

Yellow rust can cycle in around 12 days, much quicker than septoria at 20 days, so unless the rust is controlled at T0 it will be difficult to contain at T1.

The decision over T1 treatments widens to include septoria considerations, so a broad spectrum product like those based around Iblon or Revysol is often used.

The plots at the Stockbridge Technology Centre at Cawood, a few miles south of York and close to the River Ouse, were drilled in early October into medium clay loam soils, and Tom Sowerby, Bayer’s commercial technical manager for Yorkshire, says yellow rust came into the site very early.

“We saw yellow rust in January as we had not seen any heavy frosts to dampen down any infection,” he says.

The trial plots had a tebuconazole spray in the first few days of April as a T0, and then most of the site is set to get a T1 of Bayer’s SDHI-azole mix Plaxium.

Nigel Scott, regional technical manager covering North Yorkshire and Durham for agronomy group ProCam, says yellow rust is easy to find in his area and he sees T0s as the bedrock of any fungicide programme and if missed growers will be on the backfoot.

“I saw the highest ever disease pressure last year driven by yellow rust rather than septoria,” he says.

His approach in such a rust-driven season is to use tebuconazole and the strobilurin azoxystrobin at T0, and then a rust-focused product at  T1 like Vimoy (Iblon) + Cello, and adding in a multisite, such as folpet or sulphur, both at the T1 and T2 timings. Cello  contains prothioconazole and also tebuconazole to boost rust control and spiroxamine for enhanced mildew and rust control.

East

Yellow rust is sitting on the lower leaves of many winter wheat crops in north Norfolk and an explosion of the foliar disease is likely with a move to warmer and damper weather, which points towards the need for a strong rust-active T1 later this month.

With many popular wheat varieties becoming more susceptible and the lack of sharp  cold frosty winter weather, this yield-damaging foliar disease has been seen as early as last November in Norfolk.

Bayer’s Crop Doctor site in north-west Norfolk, only a few miles from The Wash, was showing clear signs of yellow rust sitting on the tissue of wheat leaves – not active but waiting for more favourable conditions to start cycling and sporulating.

Aoife O’Driscoll, senior specialist in plant pathology at crop consultant Niab, says in this high-risk disease situation there is a clear risk of an explosion of yellow rust, and also septoria, especially in more forward wheat crops.

“We are seeing a higher level of disease this season with lots of yellow rust sitting on top of septoria in the more forward crops. The yellow rust is waiting for more warm and damp weather to start cycling and spread,” she says.

With the heightened risk of rusts this spring, she has advised wheat growers to use a tebuconazole/strobilurin mix at the T0 stage in late March, with the azole for a quick knock down of the rust and the strobilurin for more persistence.

It is likely to be the worst year for rusts, with yellow rust the key concern, and with an eye out for brown rust later

She has seen enough yellow rust around to recommend this twin approach at T0 with the strobilurin azoxystrobin used if yellow rust is the higher risk, or pyraclostrobin if brown rust is more likely.

In such a high-risk situation, she is advising a robust SDHI/azole at T1 aimed at protecting crops, with a multisite of folpet or sulphur added in high risk situations.

The Crop Doctor site is on father and son Clive and Andrew Melton’s Pear Tree Farm, Walpole Highway, just west of King’s Lynn, and a traditional “hot spot” for yellow rust with many moisture-laden sea mists, but with climate change the disease is now more widespread.

Andrew drilled the field with the breadmaking wheat variety Vibe on September 26, which established well in “perfect” drilling conditions following beans, with the trial plots drilled later on 10 October.

“Yellow rust is our main concern this year and it is going to come, while we will see how septoria develops,” he says.

Andrew has used tebuconazole as a T0 on his more yellow rust resistant wheat varieties, such as Vibe, and a tebuconazole-azoxystrobin mix for more yellow rust susceptible varieties like Dawsum and Beowulf.

He is planning to use an Iblon-based fungicide mix at T1, with the multisite folpet added if crops are at a high risk of septoria.

Darren Adkins, business manager at Bayer and in charge of the trial site, has given the trial site a T0 of tebuconazole in late March, and is now looking at a broad spectrum approach at T1 to cover the three main disease threats of septoria, yellow rust and eyespot. This is likely to mean Plaxium at T1, he says.

Mark Hemmant, technical manager at agronomy group Agrovista warns that this season is likely to be rust-dominated and hence his T1 advice is to be strong on rusts.

“It is likely to be the worst year for rusts in my experience, with yellow rust the key concern and with an eye out for brown rust later,” he says.

His approach has been to use tebuconazole at T0, keeping strobilurins for later as they can only be used twice in a season, and will likely figure at T2 and T3.

His T1 advice is likely to be to use Vimoy + Cello, to give a very strong protectant treatment for rusts.

West

Septoria is bubbling away in Herefordshire’s winter wheat crops and even if the weather turns very dry during April, these crops are likely to need a robust T1 fungicide as disease pressure is deemed very high.

Early drilling and extremely wet weather so far in 2026 has encouraged septoria, while yellow rust is also a big concern after the fall in disease ratings for many popular wheat varieties.

Chloe Francis, plant pathologist at consultant group Adas, says she is picking up the wet weather-loving septoria in all the wheat varieties across the Bayer Crop Doctor site at Callow, a few miles south of Hereford.

The trial site was drilled on October 6 into medium clay loam soil and followed oats, and although the winter rainfall was similar to the previous season, the rain came later and after the crops had established well.

As well as septoria, she is seeing yellow rust in varieties which have the YR15 gene such as Dawsum, Beowulf and Champion, and one pustule of brown rust in Champion.

All the plots and the surrounding area of the variety Champion received a T0 spray of   tebuconazole in the last days of March to keep a lid on yellow rust, and now attention is turning to T1 sprays applied in late April.

“Wheat growers will need a T1 with an active strong on septoria, something for yellow rust, like prothioconazole, and also keeping an eye on brown rust,” she says.

Even if there is dry weather from the T0 application up to T1 timing in late April, growers will still need a strong septoria programme because of the high risk and the high levels of septoria inoculum.

We will be looking at a robust approach at T1, to cover septoria and also yellow rust and eyespot, with prothioconazole covering the latter two

“Septoria is already touching the emerging leaves and all we need is some heavy dews for the septoria to move up onto the main leaves,” she adds.

Chloe adds that in such a high pressure septoria year she would encourage the use of multisite protectant fungicides, such as folpet or sulphur, at the T1 and T2 stages.

These will help with disease control and also with resistance management as multisites have not shown any signs of developing resistance, unlike single site fungicides such as SDHIs, azoles and strobilurins.

Gareth Bubb, Bayer’s commercial technical manager for west England and based in Herefordshire, says the trial site was well established, but is now under high septoria pressure from the heavy rains from November onwards and early drilling which has produced a high biomass crop.

“The risk is already there for T1s from the septoria pressure, while I have never seen yellow rust come into crops so early as this season,” he says.

He is already planning to use Bayer’s Plaxium at the T1 stage for this crop while for other later-drilled crops in the area he might opt for Ascra.

His area is dominated by feed wheats, such as Dawsum and Typhoon, which have suffered from a fall in yellow rust resistance scores.

Experts suggest growers may use SDHI-azole combinations such as Plaxium, Ascra or Revystar at T1, and leave more focused septoria products such as Miravis, Univoq and  Jessico Fusion for the flag leaf T2 stage.

Antony Wade, technical manager for agronomy group Agrovista in western England, says most of his crops have had a T0 spray aimed at rust control.

With high septoria pressure and the potential for the disease to climb up the crop, he is also aiming for a comprehensive T1, which may come slightly earlier this year than his traditional target date of 23 April.

“We will be looking at a robust approach at T1, to cover septoria and also yellow rust and eyespot, with prothioconazole covering the latter two,” he says.

Further east, agronomist Paul Gruber from agronomy group ProCam says disease pressure is also very high in his area of Oxfordshire.

“There is more septoria than I have seen for a long time, encouraged by early drilling and the fact that we have not really had a winter,” he says.

Key wheat fungicide actives
Amistar	strobilurin azoxystrobin
Ascra	SDHIs bixafen and fluopyram plus azole prothioconazole
Comet	strobilurin pyraclostrobin
Jessico Fusion	Picolinamide fenpicoxamid (Inatreq) plus SDHI isoflucypram (Iblon)
Miravis Plus+Era	SDHI pydiflumetofen (Adepidyn), in a twin pack with azole prothioconazole (Era)
Plaxium	SDHIs isoflucypram (Iblon) and fluopyram, plus azole prothioconazole
Revystar	SDHI fluxapyroxad (Xemium) plus azole mefentrifluconazole (Revysol)
Univoq	Picolinamide fenpicoxamid (Inatreq) plus azole prothioconazole
Vivalis	SDHI isoflucypram (Iblon) plus azole prothioconazole
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