Use a T0 on Susceptible Wheats to Prevent Rust Escape, Advise Experts
While you may not be able to see yellow rust on susceptible wheats a T0 fungicide remains a key spray this season.
According to ADAS plant pathologist, Jonathan Blake, it simply isn’t worth the risk on Solstice, Oakley, Viscount and Robigus.
“Despite little visual evidence of yellow rust at present, if I had a crop of one of these varieties, I wouldn’t take the chance. Use your T0 to protect your T1 performance,” he says.
Mr Blake’s advice comes after a winter period that has curtailed yellow rust disease development, but to what extent remains unclear.
“We know that around 40% of the UK wheat area is down to these higher risk varieties, but just how much at risk IT is difficult to say.”
This view is backed by KWS consultant agronomist, Bob Simons, who advises growers that crop inspection in an effort to find yellow rust can be misleading and probably pointless.
“My view is that there is no point rushing out there to check your crops as there’s little sporulation occurring,” he says. “Just because you can’t see the disease it doesn’t mean it is not there.
“Don’t make a similar mistake to that of three years ago when a lack of symptoms meant many opted to drop a T0 for brown rust on Alchemy, with the result that they were left fighting a rear-guard action to get the disease under control.
“Far better to base your yellow rust spray decisions on risk and experience: A low cost insurance spray at T0 on susceptible wheats is a must, this year,” says Mr Simons.
Mr Blake’s advice is that T0’s need to be applied 3 weeks prior to true T1 timing, when leaf 3 has emerged. “The temptation could be, if you missed out on the T0, to pull the T1 forward as a result of any subsequent disease expression. This though would stretch the gap between the T1 and T2.
“All the evidence shows that important to leave no more than a 4 week gap between the T1 and T2; you mustn’t let yellow rust in before this, hence the importance of the T0 on at risk varieties, he says”
In terms of spray timing, Mr Blake reckons that the cold start to the year will mean that the T0 sprays will be needed at the end of March or first week of April. However, he would be prepared to go earlier if disease is seen.
“It is better to try and keep the crop clean rather than let infection in and the use of a rust-active T0 triazole is prudent,” he says. “This should do the job before a properly timed leaf 3 T1.”
