Biochemical identification and comparative insecticidal activity of nucleopolyhedrovirus isolates pathogenic for Heliothis armigera (Lep., Noctuidae)larvae

Three Nucleopolyhedrovirus (NPVs) originally isolated from Heliothis armige ra larvae, collected from Portugal (HearNPV-PO) and two places in Spain (He arNPV-SP1 and HearNPV-SP2), and three previously described NPVs were compar ed biochemically and biologically. Restriction endonuclease analysis of the virus genome with several enzymes revealed that isolates HearNPV-SP1 and H earNVP-SP2 are unique but closely related genotypes which represent two new strains of the NPVs of H. armigera. The DNA fragment profiles of HearNPV-P O were distinct from those of the HearNPV-SP1 and HearNPV-SP2, with all the enzymes used, while they were identical to the Mamestra brassicae NPV stra in present in the commercial product MAMESTRIN(R). Bioassays in third-insta r H. armigera larvae showed that the LD50 value obtained for HearNPV-SP1 (6 8 occlusion bodies/larva) was about two- and six-times lower than those of HearNPV-SP2 and a Russian isolate, HearNPV-RU; respectively. The correspond ing LT50 values were not found to differ significantly between these three virus isolates at comparable doses.