and Aims: The Cydia pomonella granulovirus (CpGV) is a baculovirus and very effective biological control agent against apple pest, codling moth, Cydia pomonella L. especially for healthy organic apple production and protection. Not only, screening of CpGV isolates via biochemical variation, but also their biological variation is practically necessary. However, the bioassay methods and biological activity parameters, such as LC50, LD50 and LT50 are different, sensitive and usually time and

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... e consuming; the right chosen method of bioassay can show differences and variation for applied screening purposes. Materials and Methods: In this study, an appropriate double bioassay method have been successfully set to express biological variation of CpGV isolates on neonate larvae under laboratory conditions (26±0.2 ˚C, RH: 60%±2, 16:8 L: D). The diet incorporation bioassays (LC50) with 0 to 16000 occlusion bodies/ml usually determine the rate of larval mortality on 7th day. Results: The LC50 of CpGV isolates were evaluated 4454 to 2277 occlusion bodies (OBs) per ml of artificial diet. Conclusions: Tthat show the double bioassay method have been successfully set and comparable with other results that can enhance biocontrol of codling moth especially in organic apple orchards.