Growers would be wise to give more consideration to selecting barley varieties which have resistance to ramularia after trials in Scotland conducted separately by AHDB and SRUC showed isolates of the disease which were strongly resistant to azoles and SDHIs.
According to Dr Paul Gosling, AHDB crop protection scientist, who spoke at the AICC conference, the only fungicides having any effect were Bravo (chlorothalonil) and Treoris (penthiopyrad + chlorothalonil).
Dr Gosling said: “There are no results from England but it is not safe to assume the situation is different.”
In spring 2017 Bayer issued a statement, indicating their monitoring had detected field isolates with high levels of resistance to SDHIs and azole Proline (prothioconazole) in Germany.
However, the Scotland situation had arisen suddenly. Somewhat surprisingly, the Fungicide Resistance Action Committee (FRAC) had not reported anything concerning ramularia resistance in recent years, according to Dr Gosling. “This is why we need independent resistance testing in the UK.”
Regarding ramularia control, he said: “Think about including chlorothalonil at T2. For autumn 2018, think about avoiding susceptible varieties as we don’t want to just rely on chlorothalonil for ramularia control.”
A guide to ramularia identification has just been published by AHDB at www.cereals.ahdb.org.uk/ramularia.