Optimierte Strategien zur Krankheitsbekämpfung in der Gerste unter Berücksichtigung neuer Erkenntnisse zur Epidemiologie des Blattfleckenkomplexes

The leaf spot complex constitutes an increasing challenge for integrated pest control in barley. The complex consists of biotic and abiotic factors causing early ripening after a rapid loss of green leaf area, in particular in upper, exposed leaves. Severe symptoms appear late in the growing season after heading. The experience from recent years shows that the control of the leaf spot complex improves yield. Best control is achieved by new, effective fungicides. Efficiency is improved by late fungicide application and is dose-dependent. In contrast, late treatments provide poor control of early appearing diseases. For a successful disease control in barley good efficiency in the control of the leaf spot complex appears based on a sufficient control of the other diseases. For optimization of disease control, we require improved knowledge of the epidemics of the leaf spot complex and of the contribution of individual biotic and abiotic factors. Besides the weather, the fungal pathogen Ramularia collo-cygni and its photodynamic toxins play a mayor role in symptom development. By combination of conventional and molecular diagnostics we aim at a better understanding of the complex as a basis for early and reliable prediction of epidemics. Because non fungicidal factors like the physiological plant age play a significant role in the occurrence of the leaf spot complex, they should be taken into account for integrated control.