The issues of microbiological indication of the forest ecosystem phyllosphere in Siberia are considered in the article. Microbial complexes serve as the tool for condition diagnostics and monitoring of the forest ecosystem. Number of the epiphytic microorganisms, correlation of the sporogenous and nonsporogenous forms and pigmented bacteria availability are the criteria of technogenic influence degree of the Nazarovskaya SREPP on the forest stands. The plant defoliation degree by Siberian silkworm is diagnosed by frequency of the Ophiostomataceae fungi complex occurrence, associated with the insects-xylophages.