The Press and Journal (Aberdeen and Aberdeenshire)
SRUC warning over disease threat to Scots barley crop
Arable: Ramularia leaf spot strains proving resistant to fungicides
Scotland’s Rural College (SRUC) has issued a warning to barley growers of fungicide resistance in a key crop disease.
Early this year crop protection company Bayer announced that crops infected with the ramularia collo-cygni fungus in Germany and Denmark were not responding to normal fungicide treatments containing triazole and SDHI fungicides.
Now SRUC has urged growers to check their spraying programmes and make adjustments to treatments after studies indicated Scottish barley faces a similar threat.
Ramularia collo-cygni causes ramularia leaf spot disease, which not only poses a problem in springsown crops but also affects production in autumnsown crops. The established protection regime is based on triazole and SDHI fungicides, but SRUC has revealed a significant shift in the sensitivity of the fungus to both of these chemicals between 2012 and 2016.
Senior plant pathologist Neil Havis said that unless farmers took action there was a risk that the fungicontinue cide resistant ramularia strains would build up causing major problems in future.
He said: “Our research shows that the fungus is still sensitive to cholorothalonil, so we are recommending farmers add cholorothalonil into their spraying programme, particularly at the T2 spray timing.”
However SRUC experts to warn against over reliance on one set of substances when they are suspected to be at risk. Combinations of chemicals, which include multisites, coupled with alternative strategies such as using varieties with known disease resistance, have proved best against infection from fungal diseases.
“Few treatments are guaranteed fully effective on their own,” said Mr Havis.
“Using just one fungicide with one mode of action risks resistant strains to multiply and gather strength without the competition from other isolates. If those are also resistant to the other chemicals in our armoury we risk a disease explosion, if not this season next season. Biology means diseases are always evolving and we need every strategy to try to keep up.”
“The fungus is still sensitive to cholorothalonil”