Yellow rust piled on the pressure at Yorkshire trials site

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Across the UK, 2020 winter wheat crops were pressured with yellow rust following a season of mixed weather. This was particularly evident at the Frontier 3D Thinking site at Haywold, Yorkshire, where trials provided valuable data on tolerance to this key disease.

“Although this year the average yields at Haywold appear to surpass the average tonnage across the rest of the UK, it’s important to note it is a very fertile, high-yielding site with a long growing season, so we always expect to see high yields. In fact, it was the only Frontier 3D Thinking site in 2020 to maintain its usual yield levels,” explains Christine Lilly, Frontier research and technical support manager.

“Yield performance has been consistent with previous years, with varieties such as SY Insitor, RGT Saki, RGT Gravity, Gleam, KWS Colosseum and KWS Kerrin all yielding well.”

However, Christine notes several of these varieties are very susceptible to disease, with septoria tritici usually presenting the biggest issue, but this season was dominated by yellow rust. 

“The weather patterns from early establishment through the growing season meant we saw unusually high cases of yellow rust, so we were able to truly see how varieties coped under disease pressure and the value of a targeted fungicide programme.”

She explains the disease was present from February through to July, with higher levels than previously seen at the site.

“Ordinarily you would expect to see infection on the leaves, but we saw disease present on the ear of some varieties, even when a robust fungicide programme had been applied.

“The magnitude of disease presence across the site is most likely down to weather conditions and an increased number of susceptible varieties, including some where yellow rust had not been widespread in the past, such as KWS Extase.

So, as we move into the new season, we can reflect on this season’s results.

“Those varieties that gave high responses to fungicides in 2020 included KWS Kerrin, KWS Kinetic, Gleam, Shabras, RGT Wolverine (Europe’s first BYDV-resistant variety), KWS Zyatt and Skyfall,” notes Christine.

“These should be varieties that are monitored closely for onset of yellow rust and may require treatment in early spring, typically with a triazole.”

It is important to check product labels for the earliest application timing, she adds, and notes that 2021 will be the last season for epoxiconazole use – a very rust active triazole.

“This means yellow rust control will become more challenging in future seasons,” she continues.

However, at the other end of the spectrum some varieties were much less responsive to fungicides. 

“These included KWS Colosseum, RGT Saki, Graham, KWS Extase and Costello, and are varieties which provide more flexibility in spray timings but still require a decent programme to get the optimum returns. Observations from other trials showed that follow-up fungicides needed to be prompt, as long gaps allowed fresh rust infection to develop. This is worth considering when planning timings next season.”

Christine concludes, “2020 was challenging for all sorts of reasons; however, it did provide us with a much-increased database on yellow rust susceptibility. This data has highlighted the value of a comprehensive fungicide regime for supporting yield in many of our key varieties and will enable us to fine tune decision-making for 2021.”

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