Technical Abstract: Field surveys were conducted from 2008 to 2011 in southern Khabarovskiy Kray (Khabarovsk area) and Primorskiy Kray (Vladivostok area) to investigate the occurrence of the emerald ash borer (EAB), Agrilus planipennis Fairmaire, and mortality factors affecting its immature stages. Survey findings indicate that EAB commonly occurred in both Khabarovsk and Vladivostok areas on the introduced North American green ash (Fraxinus pennsylvanica Marshall) trees, and to much lesser extent on oriental ash (F. mandshurica Rupr. and F. rhynchophylla Hance) trees. In both regions, EAB densities (larvae / m2 of phloem area in Khabarovsk) were several-fold higher on green ash (11.3 to 76.7 in Khabarovsk area and 77 to 245 in Vladivostok area) than on artificially stressed Manchurian ash (2.2) or Oriental ash (10 – 59). Mortality rate of EAB larvae caused by different biotic factors (woodpecker predation, host plant resistance and/or undetermined diseases, and parasitism) varied with survey time, sites and ash species. Except for one site at one sampling time in the Khabarovsk area, low woodpecker predation of EAB larvae was observed in both study areas between 2008 and 2011. While low rates (3 – 27 percent) of EAB larval mortality caused by undetermined biotic factors were observed on green ash logs in both Khabarovsk and Vladivostok between 2009 and 2011, much higher rates (26 – 95 percent) of EAB larval mortality caused predominantly by putative plant resistance were observed in Oriental ash species in both regions. Few (less than 1 percent) parasitism of EAB larvae was observed in Khabarovsk; however, three hymenopteran parasitoids (Spathius nsp, Atanycolus nigriventris and Tetrastichus planipennisi) were observed attacking late (3rd to 4th) instars of EAB larvae in Vladivostok area, resulting in greater 63 percent EAB larval parasitism (primarily by Spathius nsp.) in two of the three study sites. Relevance of these findings to classical biological control of EAB in newly invaded regions is discussed.