The Fifth Five-Year Plan laid the foundation for a new stage of growth in all sectors of the national economy of the Soviet Union, including agriculture. One of the central tasks in the further development of agriculture was the substantial increase in the yields of all crops. An important factor in achieving high yields is the timely development and implementation of scientifically sound systems of crop disease control, a responsibility entrusted to plant protection specialists. Considerable attention is currently being devoted to the training of specialists in plant protection, and the principal purpose of this textbook is to provide students, the future specialists in this field, with the fundamental knowledge required for crop protection. More than ten years have passed since the publication of the first edition. During this period, the science of plant disease control has achieved significant advances, and these achievements have been incorporated into the second edition. Several new chapters have been added, including a chapter devoted to diseases of tree species used in shelterbelts and protective forest plantations. The textbook provides basic information on the most important and widely distributed crop diseases. It describes the causes of each disease, the characteristics of the causal pathogens, the degree of plant resistance, and the influence of environmental conditions on the occurrence and development of diseases. All of this information forms the basis for developing appropriate disease-control measures. Information on methods and means of disease control is presented in separate chapters. In addition, the principal chapters of the textbook have been supplemented with specialized material that examines particular aspects of parasite biology in greater detail, explores their relationships with plants under changing environmental conditions, and illustrates the specific features of disease control through a series of practical examples. The material contained in the specialized chapters is necessary not only for students specializing in plant protection but is also useful for students of agronomy. As for the material presented in the general section, in the authors' opinion and in accordance with the curriculum requirements, it is intended primarily for students of plant protection. Unless otherwise indicated and properly cited, the illustrations in the book are based on the authors' own drawings and photographs.