Scottish barley growers should add some cheap and cheerful chlorothalinol to their T2 spray mix in order to prolong the effectiveness of two other major fungicide groups, Scotland’s Rural College warned yesterday.
With spring barleys now at the stage at which growers will be applying their key fungicide treatments when weather permits, the SRUC’s senior plant pathologist, Dr Neil Havis has, warned that ramularia resistant to both triazole and SDHI fungicides, first identified in Germany and Denmark, has been detected in crops in Scotland.
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And while the levels might still be low, the addition of a multi-site ingredient will reduce the selection pressures for the build up of spray-resistant disease.
Havis said that testing in Scotland by the college had revealed a significant shift in the sensitivity of the ramularia fungus between 2012 and 2016.
“Unless farmers take action there is a real risk fungicide resistant ramularia strains will build up causing major problems in future,” he said.
“But 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.”
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Havis said that a combination of chemicals, which include multi-sites, coupled with alternative strategies such as using varieties with known disease resistance, had proved best against infection from fungal diseases.
Relying on one mode of fungicide action could lead to a disease explosion “if not this year then next”.
“Biology means diseases are always evolving and we need every strategy to try to keep up,” warned Havis.