Control of Ramularia leaf spot in barley crops

Ramularia leaf spot is a major economic disease of barley crops across temperate areas of the globe. The disease continues to expand its geographical spread as the recognition of symptoms becomes more widespread. Symptoms are a characteristic square spot, bounded by the leaf veins, necrotic through the leaf with a chlorotic halo. The disease reduces yield in barley crops primarily through the late season reduction in green leaf area in the canopy. Control has relied heavily on the use of fungicides. However, the fungus developed resistance to the strobilurin fungicides rapidly following their introduction and in the last 2 years the fungus has developed resistance to both the triazole and succinate dehydrogenase inhibitor groups. This has increased the reliance on the multisite fungicide chlorothalonil, which is already under threat from legislation in some countries and is already banned in others. In this paper we will report on the resistance status of the fungus to a range of fungicides and the potential of Integrated Pest Management measures, e.g. mixing of varieties, use of resistance elicitors, potential of risk forecasts to control and alleviate Ramularia leaf spot damage in barley.