Screening of bacterial strains for potential biopesticidal activity against the forest pest Jacobson’s spanworm (Geometridae, Erannis jacobsoni Djak.)

<jats:p>This study focused on developing a biological control agent targeting Jacobson's spanworm (Erannis jacobsoni Djak.), a major forest pest in Mongolia. The  aim of the research was to isolate and identify Bacillus thuringiensis strains capable of producing toxic crystal proteins, with the goal of contributing to biopesticide development. Samples were collected from dead insects showing symptoms of bacterial infection in order to isolate and screen bacterial strains with activity against Jacobson’s spanworm. Among them, isolate MNL 78-4 demonstrated the highest effectiveness, causing 100% mortality of target insects within 8 days. This result suggests that MNL 78-4 is a promising candidate for further development as a biological control agent for managing Jacobson’s spanworm in Mongolia. These findings indicate that eco-friendly microbial pesticides may provide a sustainable alternative to synthetic chemical insecticides, contributing to forest health, biodiversity conservation, and ecosystem balance.</jats:p>