Pathogenic complex and recovery of cereal agrocenoses in the Steppe of Ukraine

Topicality. Changes in weather and climatic conditions affect the formation of pathogenic complexes of grain agrocenoses and the species composition of pathogens, which are typical for the Steppe zone of Ukraine. At the same time, changes in cultivation technologies accompanying the transition to new forms of management also play a significant role in the formation of pathogenic complexes. It is necessary to find out the features of the pathogenic mycoflora formation and plant immunity in order to scientifically substantiate measures to stabilize the phytosanitary state of agro-cenoses at the current stage of grain production. Purpose. To divide into appropriate groups of grain crop diseases in the Steppe zone in terms of the nature of development, harmfulness and hy-drothermal dependence of their pathogens. Materials and Methods. In 1999–2019, we conducted surveys of wheat (winter and spring), rye, barley (winter and spring), oats and maize for disease in-festation in the Northern Steppe of Ukraine according to generally accepted methods of phytopathological research. Results. Over the years of research, we identified 123 pathogens, which caused 135 diseases in grain crops. The most diverse composition of pathogens was observed on wheat and maize, 64 and 55 pathogens, and, 33 and 41 diseases, respectively. It should be noted a wide range for specialization of the widespread pathogens in the Northern Steppe of Ukraine. The pathogens of smut infects generally a certain type of grain crops, rusts are somewhat less specialized. Less specialized parasites, such as fungi from the genera Fusarium, Helminthosporium, Alternaria cause the same type of diseases in several plant species, and some of them affect different plant organs. Thus, among the pathogens of Fusarium root rot of wheat, rye, barley and maize, the fungus Fusarium moniliforme Sheld. was identified. On the maize, in particular, this pathogen caused seedling mold, root and stem rot, cob rot, and grain mold. Conclusions. It was established that the hydrothermal regime can affect the development of diseases not only due to its compliance with the pathogen's requirements, but also affect the resistance of plants. The problem of agrocenosis recovery can be successfully solved by adapting modern intensive technologies of growing grain crops that aimed to optimally utilized ecological resources by plants in the Steppe of Ukraine, and prevent the spread of harmful organisms. Key words: winter wheat, maize, pathogens, diseases, hydrothermal conditions, harmfulness