Disease control in thin winter cereals this late spring will be top priority once the weather warms up as growers try and maximise yields from backward crops.

The level of disease is generally low, but with warmer temperatures forecast for next week, at long last, crops could start growing rapidly and so could disease.

“This is a year to throw the calendar out of the window as when things warm up crops could go quickly through their growth stages,” says marketing and technical director Tony John at adviser ProCam.

Dr John argues with more thin and open crops this year, it will be even more essential to stop disease going up into the canopy and keeping the top three leaves as clean as possible

He advises looking to spray a fungicide when the third leaf on the main stem of winter cereals emerges as 95% of yield comes from the top three leaves.

Agronomists say few winter cereals crops are mature enough for a first T0 fungicide spray, which might well be delayed up to mid-April compared with a more normal March timing.

“We would advise growers to wait for a bit of growth and not to dismiss a T0 spray just because it is a late season,” says Christine Lilly, technical manager at adviser Frontier.

In this late and difficult year, a T0 spray may be delayed well into April and so a T1 spray might not be until the first week of May.

There is a low level of septoria disease in winter wheat, while some early hot spots of yellow rust have largely disappeared due to the recent cold weather.

“We would advise growers to wait for a bit of growth and not to dismiss a T0 spray just because it is a late season.”
Christine Lilly, technical manager at Frontier

But Ms Lilly warns yellow rust could quickly return with warmer temperatures, especially with susceptible wheat varieties such as Oakley and Torch.

Peter Gladders, plant pathologist at crop consultant ADAS, reports little disease pressure in cereal crops due to cold days and frosty nights, but urges growers to be on the alert.

“There will be forward crops where a T0 spray will be necessary to control septoria and yellow rust, but I expect these to be in the minority,” says Dr Gladders.

He advises that septoria is the number one risk to wheat followed by yellow rust, although mildew could become a threat if lush growth is combined with dry weather.

Dr Gladders recommends using a triazole fungicide to control yellow rust and chlorothalonil for protection against septoria in an early spray, and would look to save the newer SDHI products for a later flag leaf T2 spray.

ProCam’s Dr John adds if there is similar warm and wet weather through April and May, such as last year, then these are ideal conditions for rapid septoria development.

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