Growers are being urged to prioritise cost-effective early control of yellow rust, which is “lurking in wheat”, according to Syngenta.

Syngenta cereal disease expert, Joe Bagshaw, said a perfect storm of late-drilled fields, susceptible varieties and the mild winter means yellow rust is now lurking in many winter wheat crops.

Yellow rust has the potential to inflict as much as 50% yield loss, so it will be important to tackle this early before it has chance to spread up the plant, Bagshaw said.

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

“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.”

Joe Bagshaw. Image: Syngenta

On top of that, Bagshaw said winter temperatures have not been cold enough to kill off the lower leaves where yellow rust is lurking.

“All this means we now have a bank of infection in the base of many wheat crops,” he said.

“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, Bagshaw said 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,” he said.

“But it’s important to ensure these fungicide also provide proven yellow rust activity wherever this is a threat.”

“Consult the fungicide dose response curves on the AHDB website, which show results on the reductions in yellow rust and yields achieved with different fungicides.”