Arable Untreated Firefly.
Get fundamentals right to avoid firefight risk Go back twelve months, and few farmers thought they’d be firefighting 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 fill impairing final 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, especially with the safety net of CTL gone.
Compromised spray timings For NIAB’s Dr Aoife O’Driscoll (right) conditions were difficult 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 identification was particularly difficult 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 field 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 field. It will tick a box, but the aim is to hit the target leaf layer at the right time, otherwise yield and margins can suffer.” 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 flexibility, 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 insufficient 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 specific azoles and SDHIs together can be effective, 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 fluopyram 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 (mefentrifluconazole + fluxapyroxad) and Univoq (prothioconazole + fenpicoxamid) was difficult. “You have to put them under a lot of pressure to separate them apart. What Revystar and Univoq offer 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 offer some degree of flexibility 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 fluopyram. He also adds the formulation includes the most appropriate wetters and solvents for leaf adhesion and penetration of leaf surface.
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 figures showing a 10% margin increase over last season.” The exceptions could be Saki and Firefly. Despite robust programmes last spring, septoria found its way onto the flag leaf. continued over…
12 www.farmersguide.co.uk February 2022
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