Since 1995 the pathogens of genus Fusarium causing Root Rot, Snow Mold, Fusarium Head Blight of grain crops have been monitored in the Volga-Vyatka, Central, Central Chernozem and North Caucasian regions of the Russian Federation and in there were identified 15 Fusarium spp.: F. culmorum, F. heterosporum, F. sporotrichioides, F. oxysporum, F. nivale, F. graminearum, F. avenacеum, F. gibbosum, F. sambucinum, F. moniliforme, F. semitectum, F. poae, F. lateritium, F. solani, F. redolens. The high uniformity of Fusarium spp. has been revealed for the regions due to the susceptibility of crops to the soil-inhabiting micromycetes. Consistent long-term monitoring of the dynamics and frequency of occurrence of Fusarium spp. in a wide range of climatic areas has made it possible to characterize the state of the species of fungi in the regions and also to study their intraspecific and interspecific variability in toxicity and pathogenicity depended on biotic and abiotic factors. The prevalence of Fusarium spp. in the mycobiota has been determined by their plasticity and viability in the soil, on the weed roots and in the stubble of many crops and high competitive ability expressed pathogenicity and toxicity.