Attention is focused on the fact that phytopathogenic bacteria, in particular, the components of the automicrobiota are extremely h armful and are directly involved in epiphytotic dieback of forests. For the study of bacterial diseases of Pinus sylvestris, Quercus robur, Fraxinus excelsior, Betula pendula, we used reconnaissance and detailed methods of forest pathological examinations and phytopathological studies, as well as methods commonly used in experimental microbiology, in particular the selection of diseased organs and tissues, isolation of mico-and microorganisms into pure culture, verification of the pathogenic properties of isolated microorganisms and their identification, etc. The results of long-term experimental studies of the bacterial pathology of forest woody plants in Ukraine are presented. From Pinus sylvestris we isolated Pseudomonas syringae, Pectobacterium carotovorum, Enterobacter nimipressuralis, Pseudomonas fluorescens, Paenibacillus polymyxa, Pantoea agglomerans, Bacillus subtilis, B. pumilus and various systematic and functional groups of micromycetes. We have investigated the interaction of the components of mycobacteria and microorganisms of the types" bacteria-bacteria"," bacteria-fungus" and preparations based on Bacillus subtilis in the laboratory and in the natural environment. It was established that the causative agent of bacterial dropsy of Silver birch in Ukraine is the polybiotroph Enterobacter nimipressuralis, the pathogenicity of which was proved in the experiment, and Xanthomonas campestris, P. agglomerans, B. subtilis associated with it, mycomicetes from Zygomycota, Ascomycota, Deuteromyta. From tuberculosis of Common ash we isolated and identified P. syringae pv. savastanoi, P. fluorescens, P. syringae, Pseudomonas sp., Erwinia herbicola, E. horticola, Xanthomonas sp. Currently, episodic dieback of Common oak is taking place. From pathology of oak trees we isolated bacterial pathogens on vegetative and generative organs, in particular P. carotovorum, E. nimipressuralis, E. quercina, E. rhapontici, P. fluorescens, Pseudomonas sp. and other systematic and functional groups of myco-and microorganisms associated with them. It is noted that it is necessary to deepen the research on automicrobiotа, in particular its pathogenic components, in the context of understanding the general biological problems of pathology, and in order to develop forest protection measures, including biological ones.