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Ramularia and Spring Barley Risk in 2022

15 June 2022

Spring barleys look well in the main, although very rapid growth in the last few weeks has left some look a little stressed and with obvious signs of nutrient deficiency as they have struggled to shift nutrients in periods of rapid growth and dry conditions. Hopefully this will rectify as growth slows and after rain. A few of the early drilled crops look patchier than later drilled ones. The AHDB Strategic Farm in Fife has trials this year looking at optimum drilling dates and shows similar trends.

Early disease levels are very low and so T1 fungicides have had quite an easy time of it where they have been applied. The main concern moving forward is ramularia management which is still very reliant on azole fungicides as the pathogen has a terrible back record of developing fungicide resistance. This has rendered the strobilurins and SDHIs ineffective, although worth remembering that they retain good efficacy against other barley diseases so still have a place in programmes. Management of ramularia is based on two azole – the newer mefentrifluconazole (as in Revystar XE) and prothioconazole (as in Ascra Xpro or Siltra Xpro). The former is more effective but has an earlier cut off of GS 45 in malting crops. Adding in folpet gives variable results in SRUC trials but given the value of the crop this year there is enough evidence that it can help support ramularia management in strong programmes to make it worth including to support the azole component.

The optimum timing is just before the period of stress that triggers ramularia symptoms. That is frequently the stress of flowering so booting to ear emergence is a good catch-all timing to treat. Judging the risk of ramularia however remains something of a black art. Higher temperature and moisture levels from germination up to ear emergence increase the risk of ramularia symptoms. Stress is also a factor and is also out with our control, however some stresses such as complex tank mixes and nutrient deficiencies can be managed. Cooler drier conditions to date may have helped but that may have been countered by the stressy rapid growth we have seen and the nutrient stresses that are evident at the moment. Certainly, on sites where ramularia has been commonly observed, it should be carefully managed.

Fiona Burnett SRUC for the Farm Advisory Service

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