Foliar diseases pose a major challenge to barley (Hordeum vulgare L.) production, particularly in no-till farming systems, where pathogens thrive in crop residues and persistent soil moisture. This study investigates the epidemiology of barley leaf diseases under no-till conditions and assesses the associated yield losses during the 2023-2024 cropping season. The experiment was conducted in Ouled Boughadi-Beni Khirane on a 2-hectare plot, using a local six-row barley variety. Foliar treatment with a systemic fungicide containing three molecules was applied to half of the plot at the early heading stage. Disease severity and Normalized Difference Vegetation Index (NDVI) measurements were taken at different growth stages (tillering, end of stem elongation, end of booting, early heading, and milk stage). The results showed a low overall foliar disease severity (13%), with powdery mildew at 5.5%, net blotch at 4.1%, and scald at 3.2%. While fungicide treatments reduced the disease severity, there was no significant impact on grain yield, thousand-kernel weight, or biomass. This suggests that climatic conditions, particularly drought stress, had a more substantial effect on the yield than disease pressure. In conclusion, this study reveals that foliar treatments are not cost-effective under low disease pressure and in no-till systems. Additionally, the NDVI was not a reliable indicator of disease severity in this context, as changes in the NDVI were primarily influenced by growth stages rather than disease progression. An integrated approach that considers both disease management and environmental factors is crucial to optimizing crop productivity in no-till systems. Further research is needed to explore the complex interactions between diseases, agricultural practices, and environmental conditions.