The book describes diverse biological phenomena such as cold tolerance of snow mold fungi and plants and their interactions, occurring in an ecologically unique environment under the snow, which maintains constant low temperature and high humidity. Presented here are the unique strategies of snow mold fungi to survive in diverse habitats and the defensive mechanism in plants tolerant to snow mold fungi infection, as well as the conventional control methods using fungicide or cultural practice. Also contained in the book is speculation on the impact of a changing environment on snow mold diseasesand their effects on agricultural production.