Ramularia collo-cygni, a new pathogenic fungus of barley

Leaf spot constitutes a threat to barley cultivation, leading to significant quantitative and qualitative yield losses. Although these symptoms can be due to physiological stress, they are primarily caused by infestation with the Ramularia collo-cygni fungus. In the absence of sporulation, these two types of leaf necrosis are practically impossible to tell apart. In order to control the pathogen Ramularia collo-cygni, Agroscope has launched a major study to learn more about its biology. The fungus was monitored by molecular analysis from the earliest stages of cultivation, allowing us to ascertain that it can be transmitted by seed. New forms of transmission of the disease have also been discovered whose roles in the epidemiology and survival of the fungus have yet to be determined. Fungicide trials have been conducted with different application strategies. These have shown that, in the absence of other leaf diseases in the crop, a single treatment from the BBCH 37 (flag-leaf) stage onwards is sufficient for the effective control of barley leaf spot.