Compatibility of HaNPV and SBM combinations and its effects on the mortality and biological activities of cotton bollworm Helicoverpa armigera HubnerMany ways to increase the effectiveness of //aNPV against insect pests. Combination of //aNPV and other control method, namely using neem seed powder (SBM) which reduced the insect immunity system, was one way to increase the effectiveness of//aNPV. Synergistic combination of SBM to //aNPV not only increased the effectiveness of insect control but SBM itself could also substitute //aNPV which was unavailable commercially. The study was caried out in the Entomology Laboratory of Indonesian Tobacco and Fiber Crops Research Institute (ITOFCRI) in Malang rom March to July 2002. The objective was to ind out the compatibility and efficacy of //aNPV+SBM combination against cotton bollworm and its impacts to larval motality and biological activities. The treatment tested were combinations of //aNPV+SBM based on both sublethal (LCjj) and lethal (LC50) concentrations, viz. (1) Control (untreated), (2) SBM(LC2!), (3) SBM(LCjo), (4) //aNPV(LC23), (5) //aNPV(LC50), (6) //aNPV(LC25) 4 SBM(LC25), (7) //aNPV(LC2J) + SBM(LCso),(8) //aNPV(LC3o) + SBM(LC2S), (9) //aNPV(LCj0) + SBM(LCjo). Each treatment was arranged in a randomized block design (RBD) with four replications Results showed that the combinations of HaNPV and SBM at different concentrations proved to be additive and synergistic interaction. The synergistic interaction was signiicant when //aNPV(LC,o) was combined with + SBM(LC50) with caused ± 80% of larval motality. Reducing in larval weight and prolong the larval age were effectively influenced by HaNPV and SBM either alone or combination.