The variability in disease levels and yield potential in crops between seasons makes it very hard to judge the level of inputs that are right for Scottish cereal crops. If we look at the last four seasons we have rocked between extremely high levels of disease in 2012, record lows in 2013 and record highs in 2014. High disease levels in 2014 could be easily explained – we started the season with early drilling in the autumn before and then had a very mild autumn and winter combined. Disease therefore got in early and there was no winter clean up in cold conditions and disease just kept on climbing. The 2015 season, just past, started with exactly the same script, early drilling and a mild autumn and winter but the tables turned again and disease levels were not particularly high at all. The main reason for this was the exceptionally late and cold spring which really stalled disease progress.
In wheat, control with fungicide programmes was better than we saw in 2014. Septoria pressure was not as high and programmes in the early part were more robust which helped. There was more use of SDHIs at T1 (stem extension) which added to robust early treatments . Some crops suffered outbreaks of yellow rust and often this was where T1 sprays had been applied early because of the advanced state of crops coming out of the winter but the cold weather, particularly in May, meant that flag leaves were slow to emerge and gaps between sprays were overly long. There has also been another re-shuffling of yellow rust virulences, so varieties previously with better resistance were also affected in 2015. The late season and wet July also meant that sooty moulds and ear diseases were not uncommon. In both wheat and barley, mildew has been more common over the last two seasons.
In barley there was also quite high levels of disease at the start of the year in the winter crop but the cold spring also knocked this back and because emergence and growth of the spring crop was also slow in the cold weather, there wasn’t so much transfer of disease onto the spring crop. Ramularia levels were very variable with some crops affected, but it wasn’t a particularly severe year. Very late ripening meant that harvest often persisted into more changeable weather which drove higher levels of sooty moulds.
All this variability in disease levels means that accurate in season information on disease levels is crucial in helping to judge the need for fungicide inputs. Early decisions about the need for T0s will depend on your own crop walking information, and also wider intelligence on crop surveillance e.g. from the Adopt-a-crop information on the SRUC website and crop related publications such as the Crop Protection Report. This is gives you early warning on the approach of diseases such as yellow rust as it moves up the country, and an indication of the general disease pressure. Monitoring and surveillance are key parts of any integrated pest management plan and are easy wins when it comes to tailoring your inputs to the risk and also managing crop disease in a more sustainable way.
Fiona Burnett, Crop & Soil Systems, SRUC
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