Abstract: As a potential alternative pest control agent on Ectropis obliqua Prout in the tea plantations, the E. obliqua nucleopolyhedrovirus Hubei strain (EcobNPV-HB) was tested in the lab, as well as in the field, to evaluate its virulence to the larvae of different generations of the moth. The bioassays showed that, at a temperature above 27℃, the pathogenicity of EcobNPV-HB toward the pest significantly declined. Under field conditions, the control effect with a viral treatment of 5×10⁶ polyhedral inclusion bodies (PIB)·mL^-1 on the 1^st to the 6^th generations of the larvae of the moth were 100%, 79.5%, 26.1%, 11.4%, 23.3%, and 72.4%, respectively. Thus, the maximum effect could be achieved with an application on the 1^st instar larva, whereas treatment on the 2^nd and 6^th generations would expect to receive somewhat reduced efficacies.