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A perfect storm of late-drilled fields, susceptible varieties and the mild winter means yellow rust is now lurking in many winter wheat crops. With... Yellow rust is ‘lurking’ in late-drilled wheat

A perfect storm of late-drilled fields, susceptible varieties and the mild winter means yellow rust is now lurking in many winter wheat crops.

With its potential to reduce yields by as much as 50%, it is important to tackle yellow rust early – before it has the chance to spread up the plant, says Syngenta cereal disease expert Joe Bagshaw.

“Unlike septoria tritici, which is favoured by earlier drilling, yellow rust tends to be more of a problem in later-drilled winter wheat,” explains Mr Bagshaw.

“Clearly, later drilling has been commonplace this season because of the washout weather. But several key varieties that are suited to later drilling also have low yellow rust resistance ratings,” he adds.

On top of that, winter temperatures simply haven’t been cold enough to kill off the lower leaves where yellow rust is lurking, says Mr Bagshaw.

Final yield

“All this means later drilling has been commonplace in the base of many wheat crops. This will need controlling before it spreads up to the top three leaves, because these leaves contribute about three-quarters of final yield.”

With yields already likely to be depressed to some degree because of later drilling, Mr Bagshaw says it will be vital to do the best possible job of safeguarding remaining yield potential, but to do so cost-effectively.

“Understandably, growers will be looking for cost-effective fungicides in the early part of the season. But it’s important to ensure these fungicide also provide proven yellow rust activity wherever this is a threat.”

Growers are advised to consult the fungicide dose response curves on the AHDB website. These curves show the results achieved by different spray strategies on reductions in yellow rust and yields.

Protecting crops

Solatenol (benzovindiflupyr), which is the SDHI fungicide in Elatus Era, has given top-level results in yellow rust situations. “It also provides excellent value for money for protecting crops at the important T1 fungicide timing,” says Mr Bagshaw.

Following a wet spring, it’s also important to stay on top of septoria tritici.

“Where later-drilled wheat crops contain lower levels of septoria tritici, they should be in a more preventative situation than earlier-drilled fields. This again makes Elatus Era a good option to consider at T1 in these later-drilled situations.”

In addition, Mr Bagshaw says tank-mixing a multi-site fungicide with an SDHI is always an important consideration for resistance management in Septoria tritici situations, to help protect the activity of SDHIs for the future.

“An SDHI which offers good value for money makes it an easier decision to include a multi-site in the tank mixture, and to apply that SDHI at a suitably robust dose for better disease control.”