Topping up foliar disease control, rather than ear diseases, should be the target of T3 sprays this season, ADAS plant pathologist Bill Clark told growers at the organisation’s Boxworth open day.
“Ear sprays are going to be crucial this year, with the debate surrounding the weather.
If it stays hot for another week or 10 days, then the risk of ear blights will be much lower,” he said last Thursday (8 June).
“But the temperatures really favour brown rust, which could be bad in the eastern region.”
Luckily, the hot weather should dry up yellow rust infections that had become prominent, at least in untreated areas of Robigus.
Product choice in the eastern counties needed to take brown rust into account, he said.
“It would tend to steer away from Proline, with its weakness on brown rust.
The standard Amistar + Folicur treatment would be fine, although in pockets of high septoria pressure I am advising Opus.”
High septoria pressure in the west meant growers in that region needed to top up for that disease primarily, he advised.
It has been a difficult season for septoria control, he noted.
“Heavy rains [around flag leaf emergence] and now the hot weather have really pushed septoria.
I’ve never seen it this high in the first week of June at Boxworth.”
Because of the poor weather around flag leaf emergence, sprays had typically been delayed.
“Ours were 10 days later than usual.”
But the gap between T1 and T2 was irrelevant to the spread of disease this season, he suggested.
“Septoria hasn’t spread up the plant from leaf three like usual – it is all rain splash from lower down the plant.
The issue is how long leaf two was out before the flag leaf spray was applied.”
The likelihood was leaf two was infected for too long a period before the flag leaf was applied for the curative kickback from the triazoles to have any effect.
“We’ll know more in a week’s time.”
But already some leaf twos were showing infection, he noted.
“Growers might lose 10-15% yield because of leaf two infection, although the flag leaf should be OK.”