| Summary: | Crocidolomia binotalis larvae is important insect pests on cabbage plants that can damage the crop of cabbage resulting reduce crop yields. Controlling of C. binotalis larvae using microbial agent have been developed to replace synthetic chemical insecticides. In C. binotalis dead larvae were found during rearing maintenance at the Entomology Laboratory, Faculty of Biology, Gadjah Mada University, allegedly use were contained potentially pathogenic bacteria for insect. Therefore, it is necessary to screening, isolation, and doing pathogenicity test to obtain an alternative control agents against C. binotalis. The use of second and third instar larvae of C. binotalis were done in Entomology Laboratory, Faculty of Biology, Gadjah Mada University in August 2013 - May 2014. The method was done using completely randomized design with four concentration series and three replication. The method used for pathogenicity test was leaf deep method. The mortality of tested larvae was observed for 72 hours after treatment. The mortality data obtained was analyzed statistically by using ANOVA and DMRT. The lethal concentration of 50% death larvae (LC50) and 95% death larvae (LC95) were analyzed by using Probit analysis. The results showed that the two isolates bacteria obtained are pathogenic to the second and third instar larvae of C. binotalis, were isolates SmLIIIR and SmMI1. Both isolates were more pathogenic against third instar larvae of C. binotalis than second instar larvae with the value of LC50 respectively were 7,32 x104 cells/ml and 3,58 x105 cells/ml, while the value of LC95 respectively were 1,02 x 109 cells/ml and 7,20x1016 cells/ml.
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