By Professor Fiona Burnett,
Head of SRUC Crop
and Soil Systems

WE ARE well used to reading about fungicide resistance problems in wheat, but researchers at SRUC are concerned that while attention has been on wheat, barley diseases are becoming more and more problematic.
Emerging information from Germany about disease control failures there in 2016 point to severe issues with ramularia resistance to two key groups that are widely used in Scotland – the SDHIs and the azoles.
This potentially bad news about ramularia needs to be taken seriously this year by growers, given that it also comes on top of a growing catalogue of other resistance issues in the crop.
Our data shows a gradual decline in the efficacy of azoles against ramularia but nothing as catastrophic as the failures being described by Bayer in Germany. Last year, in Scotland, field control was good where SDHIs and azoles were used, especially where the multi-site, chlorothalonil, was applied.
That’s really the key action for growers this year when managing the disease – we can’t assume that the German problem won’t spread. In fact, in time it almost certainly will.
Don’t rely on the SDHI and azole you use – but boost it with chlorothalonil. This will improve disease management anyway, but will also serve as an anti-resistance strategy and, hopefully, preserve the useful lifespan of the SDHI and azole products in Scotland.
It is worth highlighting that ramularia in Scotland is already completely resistant to the strobilurin fungicide group, so they should not be counted on to manage ramularia leaf spotting either.
We hope that the period of dry weather has reduced the risk a bit in the winter crops for this year, but it is early days for the spring crop and if conditions are lush and wet, this will help to increase the risk of the disease passing up the crop and into the upper leaves where the severe speckling that emerges around flowering with ramularia can really reduce yield and quality.
We have been lucky in recent seasons to have a choice of very effective fungicides to help manage the package of disease risks in barley and groups such as the azoles, the SDHIs, and the strobilurins have all helped to increase average yields. But a number of resistance issues have bubbled up.
We know that net blotch has evolved partial resistance to SDHIs and strobilurins. Rhynchosporium has evolved resistance to older azoles and a mutation conferring resistance to strobilurins has also been detected but fortunately at low levels to date.
This backdrop of issues is worrying for barley growers, but there is merit in some of the newer varieties which have better disease resistance and a reduced reliance on fungicides.
If you compare the disease ratings of Laureate with those of Concerto, for example, it really is an upswing. That’s really the best route forward for the industry.
Therefore, improved varieties will be one of the key subjects of interest for growers over summer open events and trial tours.