Entomopathogenic Bacillus cereus impairs the fitness of the spotted‐wing drosophila, Drosophila suzukii.

<italic>Drosophila suzukii</italic> is a notorious pest which causes devastating damage to thin‐skinned fruits, and the larvae feed on the fruit, causing extensive agricultural economic loss. The current application of insecticides to manage this pest results in serious resistance and environmental hazards, so an alternative strategy for <italic>D. suzukii</italic> biocontrol is urgently needed. Here, we reported that entomopathogenic <italic>Bacillus cereus</italic> has the potential to biocontrol <italic>D. suzukii</italic>. We isolated and identified the bacterial strain, <italic>B. cereus</italic> H1, that was detrimental to the fitness of both <italic>D. suzukii</italic> progenies and parents. <italic>D. suzukii</italic> was robustly repelled to depositing eggs on the halves with metabolites of <italic>B. cereus</italic> H1. Both males and females of <italic>D. suzukii</italic> were susceptible to <italic>B. cereus</italic> H1. <italic>B. cereus</italic> H1 significantly arrested larval development with at least 40% lethal larvae. The median lethal time (LT50) of males and females of <italic>D. suzukii</italic> challenged with <italic>B. cereus</italic> H1 was 3 and 2 d, respectively. Moreover, <italic>B. cereus</italic> H1 disrupted the intestinal integrity and pH value of <italic>D. suzukii</italic> and resulted in an increase in bacterial load of guts and hemolymph. Mechanistically, infection of <italic>B. cereus</italic> H1 led to the activation of the dual oxidase (DUOX)‐ROS‐Jun N‐terminal kinase (JNK) pathway. The findings showed that the entomopathogen <italic>B. cereus</italic> H1 could potentially act as a biological control agent against <italic>D. suzukii</italic>, advancing fundamental concepts of integrated pest management programs against <italic>D. suzukii</italic>. [ABSTRACT FROM AUTHOR]