Abstract. Tan spot caused by the necrothrophic pathogen Drechslera tritici repentis (Died.) Shoemaker becomes an important disease of winter wheat worldwide under a changing global climate and new resource conserving technologies. Beside the positive impact of minimum tillage and no-tillage systems on the soil physical and chemical properties as well as soil erosion reduction, soil moisture conservation, productivity of labor and machinery, energy conservation, environmental benefits (reduced Greenhouse gas emissions) and increased crop yields, practicing minimum tillage and no-tillage systems with residues have a major impact on the risk of Drechslera tritici repentis in wheat comparatively with conventional tillage system without residues, due to the pathogen`s ability to survive in the previous year`s crop residues especially if those crops are bread wheat, durum wheat or triticale. Under both minimum and no-tillage systems with residues the onset of tan spot epidemic occurs earlier than under conventional tillage and higher levels of disease severity are recorded during grain filling stage. Thus, an adequate management of crop residues is required because they are an important source of inoculum for Tan spot and it is also important to introduce additional control measures beside chemical ones, biological control and host resistance as a part of an integrated disease management. Considerable reduction in disease severity has been observed on those plots where it is practiced crop rotation in all tillage systems. Thus, lower percent of area with leaf tan spots have been assessed in wheat after non cereal crops than in continuous monoculture demonstrating the benefits of alternative crops preceding wheat for both minimum and no-tillage systems with residues. Even crop rotation and an efficient residue management are effective tools for reducing tan spot in winter wheat, farmers should not rely on few management practices to minimize tan spot risk, but rather to develop a sustainable long-term strategy for disease management to protect their crops and conserve natural resources.

Key words: Drechslera tritici repentis, management, residue, tillage, wheat, tan spot

Presentation: oral