Get fundamentals right to avoid re ght risk

Untreated Fire y.

Get fundamentals right to avoid firefight risk

Go back twelve months, and few farmers thought they’d be re ghting disease late in the 2020/21 season. But that’s how it was after prolonged weather volatility – so what plan of action should be made this year?

The 2020/21 season was a season to forget, with disease levels rocketing in June and then dull weather during grain ll impairing nal yields.

Bayer’s National Snapshot data makes interesting reading. Farm partners saw rapid qPCR testing deliver low Septoria tritici results throughout March, April and May – typically in the region of 0–4.0ng/µl levels (picograms per million). But by early June, these jumped – with many results over 20.0ng/µl. At one Herefordshire site, September-drilled Extase held 30.710ng/ul in leaf 4.

February 2022 looks a lot better. Crops are more even, and many are well forward. However, experts believe there are lessons from the 2020/21 season which are worth remembering this season.

One is the importance of application timing, One is the importance of application timing, especially with the safety net of CTL gone. especially with the safety net of CTL gone.

Compromised spray timings

For NIAB’s Dr Aoife O’Driscoll (right) conditions were di cult right from the beginning. The cold start to spring compounded the impact of the wet autumn and winter. With growers primed for typical T1 calendar dates, highly variable leaf emergence meant GS32 identi cation was particularly di cult and resulted in compromised spray timings. “In many cases, T1 applications were too early or a bit light, leaving some crops slightly unprotected,” she notes.

Indigro agronomist Damian McAuley (right) agrees and always looks to dissect plants to check for leaf 3 emergence. “We had some eld areas racing ahead and others that hadn’t established properly. The temptation is to take advantage of a good weather window and get the sprayer into the eld. It will tick a box, but the aim is to hit the target leaf layer at the right time, otherwise yield and margins can su er.” If the gap to T2 had remained short the damage wouldn’t have been so great, but this got stretched. Without the bolster of CTL, and many growers opting to reduce azole and SDHI T1 rates, it was a ‘double whammy’. Mr McAuley wants growers to make the most of fungicide dose exibility, but adhere to manufacture and FRAC guidance. He understands the pressure to retain farm margins but says growers have to be realistic about what is possible. “Last season it was feasible to ease rates for resilient varieties but excessive dose reduction is possibly creating a problem further down the line. Risking chemistry exposure for what could be as little as £5/ha isn’t worth it.”

Bayer’s Greg Hanna points out that farm data from last season has shown fungicide rates were insu cient to meet FRAC stewardship recommendations in some situations.

Dr O’Driscoll considers this strategy high risk if not done with appropriate experience and data to back it up. “There is data which shows that adding low rates of speci c azoles and SDHIs together can be e ective, if put together in the right stack and sequences. The question is how low do you go? And very low rates are something that is not currently permitted, given recommended use.”

Mr Hanna says the combination of two SDHIs is one reason why Ascra has remained a consistent protectant since launch. “Bixafen and uopyram are two separate SDHI classes and we see incomplete cross-resistance between them. Where we see a shift with one, we don’t see it with the other.”

Mr McAuley notes that, in AICC trials, pulling apart Ascra, Revystar (mefentri uconazole + uxapyroxad) and Univoq (prothioconazole + fenpicoxamid) was di cult. “You have to put them under a lot of pressure to separate them apart. What Revystar and Univoq o er is a little bit more kickback if needed.”

He also feels co-forms are the obvious answer to avoid exposing any active. “A well-formulated azole + SDHI combination is designed to deliver the right ratio of actives when used at recommended rates. Straights o er some degree of exibility but you have to know what you’re doing to avoid an imbalance and exposure of an active,” he says. Mr Hanna agrees, and points out that even at the 1-litre/ha rate, Ascra is delivering a 65% dose of prothioconazole to help support bixafen and uopyram. He also adds the formulation includes the most appropriate wetters and solvents for leaf adhesion and penetration of leaf surface.

highly variable leaf emergence meant di cult and resulted in compromised looks to dissect plants to check for leaf 3 emergence. “We had some eld areas and margins can su er.” If the gap to T2 had remained short the damage wouldn’t have been so great, but this got stretched. Without the bolster of CTL, and many growers opting to reduce azole and SDHI T1 rates, it was a ‘double whammy’. to make the most of fungicide dose exibility, but adhere active,” he says. Mr Hanna agrees, and points out that even at the 1-litre/ha rate, Ascra is delivering a 65% dose of prothioconazole to help support

Stick to disease control fundamentals

For the 2020/21 season, Mr McAuley’s policy of adhering to timing and rate worked, helping deliver respectable yields and margins for Indigo customers, so he says why change it.

Especially with his upgraded gross margin forecasts showing a 10% increase over last season. He has reworked margin planning forecasts with N at £600/t and a grain price of £220/t. “Growers are in a good place right now, with my gures showing a 10% margin increase over last season.”

The exceptions could be Saki and Fire y. Despite robust programmes last spring, septoria found its way onto the ag leaf.

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Dr O’Driscoll’s suggestion for growers with varieties with Cougar parentage is to design your fungicide programme based on the new one-year rating which sits alongside the three-year rating from the AHDB Recommended List trials. This, has seen Fire y’s septoria score fall from 6.8 to 4.6.

Mr McAuley wants one-year lists to continue, and urges growers to gather as much variety data as possible. He points out that RL ratings are an accumulation of trial results, so the more data the better, particularly local trials data. 2021 was the rst season without CTL, and Mr McAuley sees little choice but to rely on alternative multisites like folpet. It is likely to feature in most T1 mixes, but he feels the T2 timing might be too late. However, if septoria pressure is high or where he has highly susceptible varieties in the ground then it is an option. He does point out that early drilled, wellestablished crops could be carrying higher septoria pressure this season.

Dr O’Driscoll feels the addition of folpet is useful in high disease pressure situations. She would prefer to go twice rather than once, and use it at the full rate. But she agrees disease control bene ts might not be realised, especially in the east where yellow rust could be the greater problem.

She also has concerns with growers relying on just one or two varieties – a trend of recent seasons. She considers it a potential ‘red ag’ this season. “We saw septoria break out in Extase last season and could trace some of the reasons right back to the previous autumn. Early drilling large areas of Extase into fertile soils is a potential management problem in the spring. With lots of wheat drilled in September 2021, we could see a similar problem this year.

“Time is one thing few farmers have, and the bene t of growing a wider portfolio of varieties with di ering disease ratings and maturity dates might be a little overlooked,” she adds.

This season, Mr McAuley’s general approach is likely to be a broad-spectrum SDHI product such as Ascra at the T1 followed by Revystar or Univoq at T2. “Ascra is a good septoria protectant, so an option at T1 or in lower risk T2 situations. With a high loading of prothioconazole, it’s active against the stembased complex and Fusaria, making it a good T1 t. I can then come back with the most potent o erings for the T2. For susceptible yellow and brown rust varieties Elatus might be an option.”

Mr Hanna says Ascra’s stem-based activity could be welcome this season. He points out reduced eyespot pressure over recent seasons has been down to weather patterns. “Autumn rain has delayed wheat drilling which has been followed by cool, dry weather during March and April.

“This season, some crops have gone into the ground early. Early drilling alone isn’t enough to trigger an eyespot threat, but a wet spring could see the disease emerge. Few varieties have strong resilience and, in such situations, Ascra’s prothioconazole loading will be useful.”

However, he says don’t overlook the bene ts of Ascra at the T2. He points to trials at Callow and Hinton Waldrist with an Aviator (prothioconazole + bixafen) T1 followed by Ascra at the T2, with Ascra delivering a strong yield response and ROI.

He acknowledges Revystar and Univoq are potent septoria options but feels they may be better suited to where the disease is established or for the most susceptible varieties. Where rusts are an issue, Ascra has the edge. “At the rates used, some potent septoria products o er little protection against rusts The combination of two SDHI sub-groups with prothioconazole’s broad spectrum activity makes it suitable for so many situations,” he notes.

This season, Dr O’Driscoll says growers need to be driven by what is in front of them. “Growers know variety rating, drilling date, soil type and the weather to date, and can also get further information via rapid qPCR testing. In today’s digital world there’s plenty of opinions aired but growers should only be in uenced by the situation for that eld. It will always come back to matching your spray to what’s in front of you.”

Mr Hanna agrees, and points out what happened in previous seasons might not apply this season. “Growers need to keep an open mind with risk management. We see shifts in septoria populations which is re ected in chemistry performance. This year we’ve seen some wheat go into the ground early – that means a variety rated at 6.5 is more likely to perform as one rated a point below.”

Mr McAuley concludes: “What last season has taught is how quickly any situation can change and the same could apply this season. We need to bear this in mind when thinking about our disease control strategies.” FG