Abstract: To ascertain the key factors influencing the natural population dynamics of the emerald ash borer (EAB), Agrilus planipennis Fairmaire, the natural population life tables of EAB populations in Tianjin, Beijing and Liaoning were constructed by specific time (autumn in 2000 and  spring in 2011) sampling method. The results indicated that population density would increase in the three areas in the following years. The host plant of Beijing and Tianjin populations was Fraxinus velutina, but that of the Liaoning population was F. mandshurica. The population density of EAB had the fastest growth rate (index of population trend, I=12.9997 and I=12.4388, respectively) in Beijing and Tianjin, but had the slowest growth rate in Liaoning (I=3.6394).  The main lethal factors for EAB were Spathius agrili Yang (the exclusion index of population control, EIPC=1.5382) and woodpecker (EIPC=1.4515) in Tianjin and Beijing, respectively, but was Oobius agrili Zhang et Huang in Liaoning (EIPC=1.4701). It is concluded that the difference of host plants is the major factor influencing natural population density of EAB, and the parasitoid S. agrili Yang also plays an important role in its population density. Therefore, breeding resistant host species and artificially rearing dominant natural enemies will be effective methods to control the pest in practical application.

Key words: Agrilus planipennis, natural population life table, index of population trend, death factors, parasitization