| Insect nuclear polyhedrosis virus (NPV) are invertebrate-specific pathogens that have been shown to be important in controlling populations of insects in natural epizootics and after application as biological insecticides, which play an important role in the integrated pest management (IPM) because of the virtues mentioned above.The toxicity of Heliothis armigera nuclear polyhedrosis virus (HaNPV) to the third instar larvae was tested in the laboratory. The lethal medium dose (LD50) and concentration (LC50) are 1.99×103 polyhedron inclusion bodies(PIB) and 3.44×104PIB/ml.The lethal medium time (LT50) is varied with different infection concentrations, the more the larvae infected, the earlier they will die.Heliothis armigera larvae are infected with concentrations of LC90,LC70,LC50,and LC30. Survivors are respectively gathered to rear in the laboratory. Mortality ,pupation ration,emergence ration and average weight of a pupa were observed in the progeny. The results are as follows: (1) Mortality in the first generation (F1) and second generation (F2) is much higher (12.22-50.42%) than that of the controls (7.50-8.33%). There is no significant distinction in larval mortality of the other generations except for treatment LC30 in the third generation (F3), whose mortality is 17.78%, significantly higher than that of control (8.83%). (2) significant distinction was observed in pupation in parent generation (F0) and the first generation (F1) in the all treatments, the pupation ration is much lower than that of the controls, especially in the treatment LC90, whose pupation ration is only 32.14% while control 96.63%.There is no significant difference in the other generations between the treatments and the control.(3) There is significantly different in emerging ration between all the treatments and controls in parent generation (F0).Treatments in parent generation (F0), such as LC90 and LC70 ,whose emerging rate are 50.00% and 51.52% respectively, much lower than that of the control (85.99%).In the second generation (F2), only the treatment LC70(67.00%) is significantly different from the control(83.93%) while the others are no difference compared with the controls. In the other generations, no distinction was observed between treatments and controls. (4)As far as average weight of a pupa is concerned, all the treatments (0.1996-0.2356g) are significant distinction with controls (0.3036g) in the parent generation(F0). In the first generation (F1) and second generation (F2), only treatments LC70 and LC50 are significantly distinct with controls, while the others have no difference, furthermore, no distinction was observed in the other generations between all the treatments and controls.Specific Primers were designed according to sequence of polyhedrin gene of HaNPV,polymerase chain reaction(PCR) technology was employed to detect Heliothis armigera nucleopolyhedrovirus DNA sequences from viral polyhedral inclusion bodies(PIB).The level of sensitivity by the technology was as low as 10fg.polymerase chain reaction amplification of polyhedrin gene sequences demonstrated that the virus was present in eggs and pupae whose parents infected with HaNPV.This method may provide a better understanding of HaNPV epizootics as well as proved the vertical transmission of the virus at molecular level.
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