Ramularia spotting on leaves

Scottish barley growers are being warned that signs of fungicide resistance to ramularia have been seen and they are being urged to make sure chlorothalonil fungicide is used in their sprays.

Earlier this year, agrochemicals giant Bayer said ramularia leaf spot disease was not being controlled by SDHI and azole fungicides in Germany and Denmark, and now Scottish growers face a similar threat.

Scotland’s Rural College (SRUC) confirmed it has seen a significant shift in sensitivity of the ramularia fungus to both these types of fungicides between 2012 and 2016.

See also: Angus mixed farm trials undersown grass in spring barley

Ramularia poses a particular threat to spring-sown barley crops, but can also affect autumn-sown crops.

Neil Havis, senior plant pathologist at the SRUC, said there is a real risk that  fungicide-resistant ramularia strains will build up and cause major problems in the future.

“But our research shows the fungus is still sensitive to chlorothalonil, so we are recommending farmers add chlorothalonil to their spraying programme,  particularly at the T2 spray timing,” Dr Havis said in a disease update note.

With many spring-sown barley due to have their T2 fungicide sprays soon, the SRUC recommends that growers consult their adviser or agronomist to decide on the most effective treatment.