Positive ramularia identification
Barley spotting disease ramularia appears to be a much bigger problem for English growers than previously thought, according to agchem manufacturer Syngenta.
The firm sent 28 samples from either commercial fields or field trials across England to SAC, who tested for the presence of ramularia using its new PCR diagnostic test.
“All but one tested positive,” according to SAC’s plant pathologist Neil Havis.
In a way it shouldn’t be a surprise, he suggests.
“At Cereals events in the past we’ve had growers looking at our displays on ramularia saying they had seen it in their own crops.”
In addition Syngenta monitored a further 21 field trials sites from Lincs to Cornwall either through the PCR test or visually.
Ramularia was positively identified at eight of the sites, the firm’s David Ranner says.
Importantly ramularia was found in all the regions tested, including the south and south-west of England.
The results confirm ramularia and abiotic spotting is not just a Scottish problem, TAG agronomist Ben Freer says.
“It is more widespread than that.
It appears to be environmental rather than varietal and appears to occur most when the plant is under some sort of stress, such as getting too much sun.”
The issue for growers is whether to put some suntan lotion in with the second spray on barley crops, in the form of chlorothalonil, he says.
“We’ve found putting a litre on sorts the problem out – it is curable.”
Syngenta trials with TAG show adding chlorothalonil gives the highest levels of green leaf retention, Mr Ranner says.
“My advice would be to keep an eye out for spotting and where it is an issue to apply Amistar Opti which in trials has been a consistent performer.”
Prothioconazole also has good activity against spotting, Mr Freer says.
“It comes down to cost, and whether you want to use prothioconazole as the second spray in barley.”
Both winter and spring barley can be at risk from barley spotting.
SAC crop monitoring has shown even in lower disease years 12% of winter crops had up to 25% leaf spotting on the flag leaf, while 8% of spring crops had 25-100% spotting.
“I’d be considering it for both winter and spring crops,” Mr Freer says.
“If you’ve seen it in the past, whether it is ramularia or abiotic spotting, you can do something about it.”
