Apple scab Venturia inaequalis (Cooke) is one the most serious disease of apples. It occurs in all regions where apples are cultivated. Protection against this disease demands 8 to 12 sprayings. Elaboration of warning bases of scab occurrence by Mills and La Plante was a great achievement in plant pathology development. Criteria of infection periods by V. inaegualis had been and also still are under continuous verification and complementation. The results of studies conducted by Butt and Xu , MacHardy and Gadoury , Roosje [27, 28], Schwabe et al. [29, 30, 31], Trapman  and Triloff  concerning new directions in apple scab prediction seem to be of special importance.