SUMMARY
An investigation using Bacillus thuringiensis H-14 local strain which was kept in coconuts during the days 4, 7, 14, 21 and 28 and its efficacy test toward malaria (Anopheles spp), filaria (Culex quinquefasciatus) and Dengue Haemmoraghic Fever (Aedes aegypti) which were conducted in the microbiology laboratory in Vector Control Research and Reservoir Unit Salatiga. The efficacy test of B. thuringiensis H-14 local strain was conducted according to the 1989 WHO procedure of to obtain the survival death of concentration vector larvae test. The result showed that B. thuringiensis H-14 local strain, which was kept in coconuts during the days 4, 7, 14, and 28, was still effective to kill various of vector mosquito larvae test even though at different concentration. The smaller concentration of B. thuringiensis H-14 local strain for controlling 50% and 90% 3rd instar larvae Cx. quinquefasciatus (from 5 species which were tested) was 0.002 ml/100 ml (LC50) and 0.003 ml/100 ml (LC90) with a Total Viable Cell (IVC) and a Total Viable Spore Count (IVSC) of 6.8x106 cells/ml and 7.1x106 Spores/ml at day 14th after an exposure of 24 hours respectively. After an exposure of 48 hours, the concentration needed to kill the larvae, which was mentioned above, was 0.001 ml/100 ml (LC50) and 0.027 ml/100 ml (LC90). The investigation should be developed further by using local media for formulating the local strain of B. thuringiensis H-14. Keywords: Lethal Concentration (LC), mosquito, B. thuringiensis H-14