High spring temperatures mean the disease, which was present throughout the winter – especially in Alchemy – has kept going and has taken-off in a number of varieties over the past fortnight, he said.
The severity of the epidemic in Robigus is particularly concerning, but growers could see it in many other varieties, he said. “Brown rust is rarely talked about with regard to T1 spray decisions, but this year is a worrying exception.
“People are going to have to change their fungicide plans quickly. Even where T0 and T1 sprays have been applied, the brown rust has jumped up onto newly emerged leaves.”
In these cases, yellow rust has been reasonably well controlled, but brown rust on newly emerged leaves is very active, Mr Clark added. The planned flag leaf spray is over two weeks away for many crops, so treatment with a slightly late T1 or pre-T2 spray may be needed, he said.
“It could be an expensive season keeping on top of this disease which is traditionally only of concern late in the season.”
Yellow rust has also been a concern in many areas and some experts regard the current problems as the worst for several years. See Farmers Weekly (20 April) for the latest advice on what to do about it.