Fungicide strategies for disease-free wheat

With the all-important flag leaf about to emerge in winter wheat crops, the focus will be on keeping it disease-free to boost yields. David Jones looks at the fungicide strategies of two wheat growers in Nottinghamshire and Essex







Sleep easier with a full fungicide focus

Robert-GashThe price of two-thirds of a tonne of feed wheat is a good insurance premium to pay to keep disease at bay in high-yielding crops on a Nottinghamshire farm.

David Gash and his brother Robert spent £116/ha on a comprehensive four-spray fungicide programme last season to prevent an invasion of septoria and rusts, and a similar approach is planned this year.

With plenty of local horror stories of poor yields and pinched grains in 2012’s wet harvest, the plan came up trumps, highlighting that fungicide yield responses can be greatest in high disease years.

“It was money well spent last year as – with wheat at current prices – it only takes a small response to pay for the fungicide treatment,” says David Gash.

Yields were down on their predominantly heavy land farm at about 8.6t/ha against an average of 10t/ha, but with feed wheat prices more than £180/t, the spray programme easily paid its way.

“Keeping crops clean is key when growing susceptible varieties and it only take an extra two-thirds of a tonne to pay for the fungicide programme,” says Robert Gash.

Planned wheat fungicide programme for 2013 at Grange Farm
  • T0 – Capalo (triazole epoxiconazole + morpholine fenpropimorph + benzophenone metrafenone)
  • T1 – Proline (triazole prothioconazole) and Vertisan (SDHI penthiopyrad)
  • T2 – Seguris (triazole epoxiconazole + SDHI isopyrazam), plus chlorothalonil if wet
  • T3 – Proline + Amistar (strobilurin azoxyatrobin) plus chlorothalonil if wet.

This year they are growing Santiago, Conqueror and Kielder feed wheat varieties as part of a four-year wheat, oilseed rape, wheat and linseed rotation.

Although winter wheat crops on the farm are three to four weeks behind normal, there is little sign of serious disease developing so far this spring.

The brothers operate about 280ha of arable land after giving up beef cattle some years ago at Grange Farm, Cotham, about five miles south of Newark.

Independent agronomist Adrian Farley has devised a four-spray programme for this year, with septoria and mildew only seen on the lower dying wheat leaves.

As wheat rushes through its growth stages this spring, fungicide timings are likely to be compressed, giving potentially better disease control with narrower spray gaps, he adds.

Mr Farley recommended a T0 Capalo fungicide spray, a triazole-based mix containing two mildewicides for early April, and the T1 treatment in mid-May was a triazole and SDHI mix using Proline and Verista.

Mixing the triazole and SDHI on farm gave flexibility in altering rates of both rather than using a pre-mixed product, says Mr Farley.

He anticipates the gap between T1 and T2 sprays will be three weeks this spring rather than four weeks in a more normal year, meaning the T1 treatment is unlikely to “run out of steam”.

The T2 spray is the most important fungicide treatment as it protects the emerging flag leaf and 45% of yield comes through photosynthesis from this top leaf, so Mr Farley says growers need to protect the flag leaf, even if the yield potential is low.

“Disease does not distinguish between high- and low-yielding crops, so whatever the yield potential, you still need to protect,” he adds.

He is planning on a similar triazole-SDHI combination at T2 and is opting for Seguris, with the addition of chlorothalonil if the weather turns very wet.

Mr Farley says the SDHI in Seguris is not as good in a curative knock-down disease mode as other SDHIs, but if used in a full fungicide protective approach it does have advantages.

He adds the product can save growers about £6/ha over other triazole/SDHI combinations and the SDHI component is more persistent in terms of disease control than other competitors.

The T3 ear spray is likely to be a Proline and Amistar mix with chlorothalonil added if the weather is wet, with the aim to control fusarium and other ear diseases as well as septoria and rusts.

Ian Hamilton, field technical manager for Seguris maker Syngenta, says the product is best used as a protectant fungicide rather than curative when disease is seen.

He points out that septoria is the biggest disease threat to wheat and rainfall is the key driver of this wet-weather-loving disease.

“There is a strong link between rainfall in April and May and septoria development between the T1 and T2 fungicide timing,” says Mr Hamilton.

He adds 2012 was the worst septoria year since 2006, and all SDHIs, when used as part of a full fungicide programme, gave a 2.5t/ha yield boost compared with untreated crops.

Once fungicides are applied in a curative mode the crop is already losing yield, so the long-lasting effects of SDHIs are best seen when applied at the early stages of disease, Mr Hamilton says.

With the effectiveness of the triazoles declining, he argues it is crucial growers use these fungicides along with SDHIs and chlorothalonil to prevent resistance building up.

He advises that the best strategy is to use a protective approach and keep fungicides intervals to less than four weeks to give good control of yellow and brown rusts, as well as septoria.

The wheat grower who gave up on rotations

Stephen-GravesStephen Graves grows wheat and has grown nothing but wheat for the past 13 years, learning to live with the added weed and disease problems on his Essex farm.

He ploughs the whole farm to stay on top of a blackgrass weed invasion and has seen off the worst of the yield decline from take-all disease during the first few years.

As he grows all feed wheat there is no problem in keeping harvest grain separate and no cleaning of the farm sprayer between crops, so he has created a simple management system for his 130ha.

“I can get some of the economies of scale that a big farmer gets as a smaller farmer,” he says.

With average yields of 8.75t/ha, fungicide costs less than £100/ha and no pigeons to chase off oilseed rape crops in the winter and early spring, he believes he has found a sustainable system.

He does not get a yield boost from first wheats after oilseed rape, and has little residual soil nitrogen in the autumn, but foliar disease problems are similar to his neighbours.

Some costs he can not escape such as seed treatments to control take-all and a comprehensive herbicide programme, although he has kept a firm grip on spring fungicide costs.

He turned to continuous wheat in 2000 when subsidies were cut for field beans and linseed, and after three poor years with oilseed rape he concluded his neighbours were better at keeping pigeons away than him.

He chooses vigorously tillering varieties with good eyespot resistance such as JB Diego and Relay for most of his chalky boulder clay land at Hill Farm, Radwinter, some five miles east of Saffron Walden.

Ploughing the whole farm still gives him time to create a stale seed-bed and then spray off any emerging blackgrass with glyphosate before drilling in late September.

He takes the precaution of using seed dressing such as Galmano and Kinto to control take-all and a “beefy” pre-emergence spray of Crystal and Twister for weed control.

The lack of nitrogen from a break crop and the full herbicide treatment does hold the crop back in the autumn, but he still has the advantage of not having to chase off pigeon all winter.

Planned fungicide strategy at Hill Farm
  • T0 – omitted
  • T1 – Tracker (triazole epoxiconazole+SDHI boscalin) plus chlorothalonil
  • T2 – Adexar (epoxiconazole+SDHI fluxapyroxad) or Aviator (triazole prothioconazole+SDHI bixafen) plus chlorothalonil if Adexar is used
  • T3 – Proline (prothioconazole) or another triazole tebuconazole

“Crops come out of the winter on the backfoot, and never as thick as first wheats, and that is why we are looking at Relay for its good tillering,” he says.

His thinner crops helped in 2012 when many thick crops around the country failed to yield to their potential due to the lack of sunlight through the summer, which caused low grain numbers in wheat ears and grains not filling well.

His yields were down to about 8t/ha across the farm in 2012, a good performance for such a poor year, while he kept his four-spray fungicide programme cost to £90/ha.

This year he believes disease control costs will be trimmed to about £85/ha, as he has already omitted his early T0 fungicide spray due to low disease pressure, with only a little septoria seen on the lower leaves.

His T1 spray in mid-May was the triazole-SDHI mix Tracker with chlorothalonil. This was chosen for its good eyespot control but it was slightly cheaper than products with newer SDHIs.

The T2 flag-leaf approach will again be a triazole/SDHI approach, but he has not yet decided between competing products with new SDHIs, Adexar or Aviator.

He used Adexar last year with good disease control results, and if used this year, he will likely add chlorothalonil for added protectant control.

Septoria is the big wheat yield robber, but there has been little rain since the start of April, signalling a lower threat from the wet-weather disease so far this season.

Steve Dennis, agronomy team manager at BASF, says any delay in the key T2 fungicide timing can be very critical, as sprays delayed by seven days can cost growers a loss in yield and margin.

Mr Graves’ planned T3 application is likely to be Proline to control fusarium and other ear diseases when the wheat head is fully emerged, although a less expensive option could be a another triazole such as tebuconazole.

An advantage of his focus on just wheat is that Mr Graves can spray the whole farm in just two days, with no sprayer cleaning needed between different crops.

In his thirteenth year of continuous wheat, the only problem on the horizon is if his blackgrass problem exacerbates and then he could consider a break from autumn drilling.

“If blackgrass does become a bigger problem I would go for spring cropping – either wheat or barley – to give me more time to control the weed,” he says.

But the system works well for him, although there is a heavy workload through August, September and October, especially with his commitment to ploughing.

“The only downside is that when I go down to the pub after harvest my neighbours claim an extra 1t/acre in yield after oilseed rape,” he says.

But then he is getting his yield from across the whole farm and not just a headline yield figure from first wheats.

 

JULY
14

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