Abstract: In the present paper,the natural fungal epizootic in the overwintering larvae of Dendrolimus tabulaeformis and D, spectabilis was extensively investigated and studied. Infective dynamics of overwintering larvae and its relation to soil temperature, humidity and precipitation under the function of P.farinosus were studied. The effectiveness of P.farinosus in controlling the overwintering larvae of the pine caterpillar on a large area was compared to that of Beauveria bassiana in the same conditions. The main results are as follows:1.The natural mortality of overwintering larvae of Dendrolimus tabulaeformis and D.spectabis is mainly caused by fungal epizootic, in which P. farinosus play an important role.2.Using P.farinosus and B,bassiana to control overwintering larvae of the two kinds of pine caterpillar are all effective, but P.farinosus is more effective. The precipitation in general years is content with the infecting overwintering larvae for P.farinosus. Therefore, the result of control can be stable, the results are always over 70%.3.The period from the end of autumn to the beginning of winter (October to December) is very fuitabls for the infection of P.farinosus to the pine caterpillar, and so do spring, but there is less infection in winter. 4.There are some larvae died after going up the tree from the soil. The phenomenon that ihe death lags infection is caused by infective latent period. when we count the mortality, this part should be added.5.The main cause which effect the protection of larvae through winter by P.farinosus is not moisture but temperature, so the effect of south slope is better than that of north slope

Key words: epizootic, Dendrolimus tabulaeformis, Paecilomyces farinosus, overwintering larvae