Cereal mildew may well need closer attention this season, given the increasing susceptibility of varieties to the disease and the unusually mild winter so far.
As much as a fifth of the wheat area, mainly Solstice and Claire, is at high risk, warns the HGCA’s Graham Jellis. He notes that the resistance of some varieties is slipping as new mildew races emerge. “Robigus was rated nine at first. Last year it was an eight, and now it’s been downgraded to a seven.”
Altogether 13 wheats on the Recommended List have had their ratings dropped by a point, adds UAP’s Chris Bean. “We also know that in the field the ratings may effectively be different depending on fertility and the weather.”
This season’s lush crops, encouraged by warm soils and higher than normal nitrogen release through mineralisation, are especially vulnerable, he says.
Recent frosts may have helped check the disease, but the threat remains high, says ProCam’s David Ellerton.
“We’ve also got resistance to the morpholines and occasionally to quinoxyfen in the UK.” That means growers seeking to control the disease should consider alternatives, such as Cyflamid (cyflufenamid) or Talius (proquinazid), he suggests. “There’s no known mildew resistance to either of them.”
Proquinazid is more persistent and protectant, whereas cyflufenamid has good curative action and so could be more appropriate where the disease has already taken hold, says Dr Ellerton.
UAP trials have confirmed French findings that cyflufenamid is also useful against septoria in wheat and rhynchosporium in barley, says Mr Bean.
The active has also performed well against mildew in the HGCA’s appropriate dose research work, says Prof Jellis. “It’s in the top three at half dose.”