Video: Septoria threat looms large in England’s wheat fields
The first Farmers Weekly and Bayer CropScience Crop Doctor helicopter tour has completed its first mission to assess winter wheat disease pressure around England.
Watch the video of two leading independent experts summarising the key wheat disease findings and read the full report below.
Cool, dry weather has slowed development of key wheat diseases, but septoria risk remains high and growers are advised to stamp down on the disease early this season.
See also: Photos of the helicopter tour
Last year, the Crop Doctor tour revealed the highest disease pressure in living memory during a spring that followed an open autumn and mild winter.
That had resulted in crops full of yellow rust and septoria, meaning sprayers went into fields early to apply fungicides and get on top of the problem to protect yields.
See also: Front load fungicides to boost wheat yields
Septoria
As we welcomed in the new year, it looked as if growers were heading into a similar scenario, with forward, lush wheat crops across the country carrying worrying levels of septoria, rusts and mildew.
However, a cool and dry period since January has checked the problem – particularly rusts and mildew – but the septoria threat remains according to two leading independent experts.
Principal research scientist at Adas, Jonathan Blake, was on board the Crop Doctor helicopter and says that up until a few weeks ago, it had almost been a rerun of 2014.
“The conditions have been enough to take out rust, but it hasn’t been sustained enough to stop septoria and that is the main focus early on this season,” says Mr Blake.
Actives
- Adexar – epoxiconazole + fluxapyroxad
- Aviator – bixafen + prothioconazole
- Bravo – chlorothalonil
- Cherokee – chlorothalonil + cyproconazole + propiconazole
- Proline – prothioconazole
- Tracker – boscalid + epoxiconazole
- Vertisan – penthiopyrad
Significant infection
Assessing plots at Bayer trial sites in Yorkshire, Herefordshire, Oxfordshire and Lincolnshire, Mr Blake and Scotland’s Rural College crop protection lead Fiona Burnett found the most damaging of wheat diseases on every site.
This was predominantly on the third last fully emerged leaf, with low levels on the second last leaf, indicating that there is already latent infection in the last emerged and emerging leaf.
Many growers will be applying T0s now, and Dr Burnett says that this should, in many cases, be well timed due to the cool and dry weather negating the need to go early.
“Without the rust pressure, we are back to a more normal situation and chlorothalonil with an alternative azole such as tebuconazole at T0 should suffice,” she adds.
Azole or SDHI?
With a well-timed T0 helping to get on top of septoria early, it may negate the need to use an SDHI at the GS 32 T1 timing, but Dr Burnett says there is a need to assess risk before making a decision.
It was clear from the tour that drilling date had a big influence on disease severity, as did variety; with infection on the second-to-last leaf to fully emerge ranging from 5-90% depending on resistance scores.
She explains that an early-drilled variety with a solid 5 or 6 for septoria on the HGCA Recommended List would still justify a product containing an SDHI. But the opposite could be true for that same variety drilled in late October.
“It is making sure that your programme is robust enough for the variety or sowing date and managing the gap to the flag leaf spray.
Early signs of eyespot
“If there is a concern, higher rates of an azole or an SDHI product would be much better than an extra spray, which only serves to drive fungicide resistance harder,” she says.
Universal threat
Mr Blake adds that the presence of septoria, irrespective of variety, could certainly cause growers a headache this season.
“The pressure isn’t as high as in 2014, but there is no difference between moderate or severe infection at this stage.
“It is there and if we get wet and warm weather during April and May, there is no reason why it can’t be as bad as last year,” he warns.
Stockbridge Technology Centre, Cawood, Yorkshire
‘Just add water’ for septoria explosion
Local Niab Tag crop consultant Julian Thirsk says that wheat crops are carrying low levels of disease across his area, but warns it only takes a spell of wet weather for septoria to escalate.
Except for a spell of rain in October that delayed drills on many farms, the back end of the year was kind and crops came out of the winter in good shape and numerous frosts have helped to hold back both crop and disease development.
“Septoria has been kept static and old leaves have died, so are no longer in the canopy and there is no yellow rust at all in commercial crops. The frosts also took out any mildew too,” he explains.
The trial site at Stockbridge Technology Centre has HGCA Recommended List variety trials drilled in the last week of September and Bayer trials drilled in the last week in October.
Julian Thirsk, Niab Tag crop consultant
Disease levels between the two drilling dates were contrasting, with the early-drilled plots carrying more severe septoria symptoms than the later sown.
Mr Thirsk says his commercial crops fall into the same two camps and plans a solid programme on early-drilled crops, starting with an azole/chlorothalonil mix at T0.
“We just need to add water and if rain arrives to spread septoria and throw timings out we could be in for a bad year. I’ll use two SDHIs, unless we get a drought after the first T1 Aviator/Bravo application.
“The later-drilled crops behind roots are further behind and clean at present, so they won’t have a T0 and an azole-based T1 will suffice,” he adds.
He sees Adexar as his product of choice for the flag leaf spray as it has better curative activity that is not thought to be compromised by the addition of the multisite product.
“I also like to have a good mix of azoles in the sequence. Where eyespot is a risk, Tracker or SDHI Vertisan will be used at T1 to control the stem-based disease.”
Mr Thirsk adds that despite the good fungicide technology, timings are crucial and if any products are applied too early or late, growers could come unstuck.
“We saw last year what can happen, so it’s essential to target the right leaf.”
Hinton Waldrist, Oxfordshire
Timings need to be spot-on
Despite a cold and dry spell dampening disease, local AICC member Sam Clarke hasn’t changed his mindset as his fungicide programmes kick off this week with a T0.
He says crops across his area of Oxfordshire, Buckingamshire and Wiltshire are relatively clean, but septoria is present and rain could soon splash it up his wheat crops.
“It’s far too early to start second-guessing what weather and disease pressure is going to do, so we are sticking to the T0 plan of chlorothalonil and, depending on variety, some will get the addition of a triazole.
“I’ve tried to steer away from that to ease the build-up of resistance if I can. A strobilurin will be added on second wheats for some take-all cover,” says Mr Clarke.
Sam Clarke, AICC Oxfordshire
He believes that the timing of his T0s will be just right this year, estimating that it should be no more than 22-27 days between the early spray and the T1 application.
Mr Clarke favours a “front-loading” approach, applying an SDHI/azole co-formulation at T1 to get on top of any disease present early in the crop’s development.
“Septoria is like a fire in a building: if you let it get away, it is very hard to get under control. So we will apply Adexar plus Bravo to all our wheats and then see where we are.
“We might be able to save some money at T2 if it stays dry, but otherwise Aviator will be my choice at T2, but without the Bravo. I don’t think it is worth the risk of reducing its curative activity,” says Mr Clarke.
He adds that he will be out dissecting plants to monitor growth stages and alerting his clients to when they should be spraying. “We need to get timings spot on.”
Long Sutton, Lincolnshire
Usual suspect absent in The Wash
Yellow rust can’t be found at Bayer’s Long Sutton trial site, according to its Lincolnshire commercial technical manager, Darren Adkins.
Situated on former UK wheat yield record holder David Hoyles’ 600ha of deep silt land, the area is notorious for yellow rust as the prevailing conditions favour the disease.
However, Mr Adkins hasn’t seen any signs of it yet, even on susceptible varieties, but expects the disease to appear once temperatures start to rise.
“We still need protect crops against yellow rust, so fast-acting azoles or strobilurins should feature early on in fungicide programmes. But at the moment septoria is the focus,” says Mr Adkins.
UK world wheat yield record holder David Hoyles
Mr Hoyles notes a similar story in his commercial crops that surround the site. No rust has been found so far, but septoria has been present in his early-drilled Santiago since November.
Recent cold and dry weather has prevented it from progressing in the crop, but Mr Hoyles has applied a T0 fungicide of Cherokee to his most forward wheat to keep it in check ahead of an unsettled forecast.
“The more average crops will be getting a T0 too, but the backward wheat may not be getting one at all, depending on what the weather does in the next week or so.
“I try to delay the T0 applications for as long as I can to manage the gap to the T1 timing, which helps to optimise the performance of that spray,” he explains.
With very high yield potential of between 12-14t/ha, fungicide budget is not much of a concern for Mr Hoyles, who prefers to look after the crop early than play catch-up later.
“We will give the crop what it needs now and apply a more risk-based approach later once we know how the season is panning out. If it comes warm and wet, disease could romp away.
“There is a long way to go, but I’m pretty happy with how things are at the moment,” adds Mr Hoyles.
Callow, Herefordshire
Septoria a ‘natural problem’ in West
On the Bayer trial site at Callow, Herefordshire, commercial technical manager Gareth Bubb says that septoria pressure is similar to last year’s high levels.
Despite the fact that frosts have increased this winter, they haven’t been sustained enough and, as is the norm in western areas, plenty of rain has fallen to keep the wet weather disease active.
“The inoculum is there, but much will depend on the rainfall we get in the coming weeks,” he says.
Independent agronomist Malcolm Williams, who covers Gloucestershire, Herefordshore and Wales, says that, locally, septoria levels were high at the turn of the year.
Despite the pressure being dampened since, he still expects the disease to be an issue if and when rain arrives, with septoria a “natural problem” across his patch.
Independent agronomist Malcolm Williams
“We don’t help ourselves to a certain extent, growing susceptible varieties and drilling them in September.
“I was seeing the odd fleck of yellow rust before Christmas, but that has disappeared and the low levels of mildew will be easily controlled by our prothioconazole-based fungicide programme,” says Mr Williams.
In early-sown wheats, Mr Williams is seeing stem-based browning, which could be the early signs of eyespot and includes azole prochloraz in his T0 recommendations.
“We get eyespot in most years here, so it gives us some early suppression. Getting the product to the base of the stem is more of an issue at T1,” he explains.
His T1 plans are predominantly based on an application of Proline, along with multisite Bravo, except on crops that are more advanced or susceptible to disease.
“I’m confident that will be enough on some varieties, but on high-biomass crops sown in early September, we will use an earlier SDHI.
“At flag leaf, much will depend on the pressure at the time and we will tailor a programme based on the various strengths and weaknesses of the available products, but an SDHI such as Aviator is planned,” he says.
