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Arable

Growers underestimate septoria threat – survey According to a survey carried out by BASF last season, many wheat growers underestimated the threat of septoria in their wheat crops. “Leaf samples were taken from 132 fields just prior to T2,” says BASF agronomy manager for the South of England, Andrew Clune (left). “All fields had already received T0 and T1 fungicides, so generally looked clean.” Two sets of samples were collected, one a random selection of the top two leaves (flag leaf and leaf 2), and the other of the bottom two leaves (leaf 3 and 4). “The results showed that 90 per cent of leaves 3 and 4 had latent or advanced infection, and, perhaps more surprisingly, that 64 per cent of leaves 1 and 2 were also infected, mainly with latent disease.” However, 6out of 10 growers taking part in the study believed their crops were clean from top to bottom. This is perhaps not surprising given they had already applied two fungicide treatments, Mr Clune adds, but the analysis clearly shows no matter how green a crop looks, the chances are septoria is present. “Just because a crop looks clean doesn’t mean it is. The results clearly show that even in a relatively lowor late-disease year like 2017, the majority of wheat crops are in a curative situation when it comes to septoria, at T1 and T2.”

Well-timed fungicide The findings underline the importance of using a strong, well-

A BASF survey suggests growers underestimate the threat of septoria in their wheat crops.

timed fungicide programme that offers good kick-back against latent septoria and as strong protective activity, says BASF agronomy manager for West Midlands and Wales, Robin Rose (left). Eight years of independent and BASF trials shows that Xemium, which is present in Adexar (Xemium + epoxiconazole) and Librax (Xemium + metconazole), is the most curative of the SDHIs, says Mr Rose. Over the past 4 very different seasons, in 123 comparisons, Adexar delivered on average an extra 0.2t/ ha over Aviator in conventional plot trials. New work shows the molecule is maintaining a lead over newer products such as Ascra Xpro and Elatus Era, says Mr Rose. In three independent trials carried out by ADAS, NIAB TAG and SRUC in 2017 on Santiago, Adexar applied at T1 and again at T2 delivered the biggest margin compared with other SDHI combinations tested. The Adexar sequence produced a yield of 11.21t/ha and a margin over input cost of £225/ha, while the best of the other sequences were 0.1–0.2t/ha adrift and produced margins over input costs that were £20–30/ ha lower. Librax showed even better curative properties than Adexar against septoria last year, and is now the standard recommendation at

T2, at 1.25-litres/ha + CTL, following Adexar at 1-litre/ha + CTL, he adds.

Real Results This T1/T2 Adexar/Librax programme was tested in BASF’s Real Results initiative last year in field conditions on 50 farms and compared with sequences chosen by the farmer. “There was a yield benefit to the BASF programme in the statistically significant trials, but in the wider dataset it ended up in a draw,” says Mr Rose. “However, this was not the most responsive year. We are repeating the exercise this year and are hoping for a more testing season.” Charlton Park Farms farm manager, Robin Aird (left), based near Malmesbury, took part in Real Results. In his trial, the BASF sequence outyielded two applications of Variano at 1.25-litres/ha by 0.78t/ha. He was surprised at the size of the Real Results yield difference,

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although the BASF-treated crop had looked greener and less stressed. “Last year wasn’t a proper South-West disease year, so I’m not sold yet. But if the result is repeated this season I’ll have no choice but to change to the BASF programme across all my acreage.” He grows 310ha of winter wheats on varying soils types and is well aware of the need to control septoria. “We know we’ll need four sprays, including two SDHIs backed up by azoles and multi-sites. This gives us the best chance of keeping ahead of disease.” Such combinations of chemistry are vital, says Mr Rose. “SDHIs have the strongest curative activity on septoria but are single-site and need to be protected at all costs. “We are not seeing any drop off in performance in the field where they are used at appropriate dose and with appropriate chemistry. “We need to protect the tools we have in the tool box, because new chemistry is still not here yet,” he concluded. ■

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