: Today’s agriculture is not only confronted with the production of food and animal food, but also with aspects of environmental protection. In today’s crop production, there is an increasing pressure to reduce the use of pesticides, to decrease the environmental impact and to lower potential production costs. It is therefore imperative that pesticides are only applied when and where needed. Disease control might be more efficient if disease patches within fields could be identified and fungicides applied only to infected areas. Recent developments in optical sensor technologies indicate the potential to enable direct detection of foliar diseases under field conditions ([We03]). In the context of this study different vegetation indices were evaluated for their potential to detect and identify different plant diseases. The influence of Erysiphe graminis (powdery mildew) and Septoria tritici (leaf blotch disease) on canopy refectance of winter wheat was analyzed in various field tria...