Novel <scp> <i>Enterobacter</i> </scp> strains applied as entomopathogenic insecticides against <scp> <i>Plutella xylostella</i> </scp> (Lepidoptera: Plutellidae)

Abstract BACKGROUND Identifying environmentally friendly entomopathogenic microorganisms and using them as alternatives to chemical insecticides is crucial for advancing green agriculture. RESULTS Three culturable Enterobacter bacterial strains (S‐18, S‐22, and S‐30) with insecticidal activity against 3rd‐instar diamondback moth (DBM, Plutella xylostella ) were isolated from the gut of field‐collected Spodoptera eixuga larvae. The lethal concentration 50 (LC 50 ) values of S‐18, S‐22, and S‐30 for the 3rd‐instar DBM larvae were 747.92, 833.54, and 422.02 mg bacteria/L (at 96 h), respectively. After ultrasonic fragmentation, the LC 50 values were reduced to 141.50, 182.84, and 90.75 mg bacteria/L, respectively. The median lethal time (LT 50 ) values of S‐18, S‐22, and S‐30 for the third‐instar DBM larvae ranged from 1.56 to 1.81 days at a concentration of 5000 mg L −1 . When 3rd‐instar DBM larvae were exposed to a sublethal dose of the three bacteria, larval growth and diet consumption were significantly inhibited. When the three Enterobacter sp. were applied to laboratory‐potted white radish sprouts, all showed insecticidal rates similar to that of the reference insecticide (emamectin benzoate, EB) at the manufacturer's recommended concentration, and all caused approximately 100% mortality at 72 h after spraying. Field trials applying the three Enterobacter spp. to cabbage and cauliflower demonstrated that their efficiency in controlling pests was comparable to that of EB. CONCLUSION Three insect gut‐resident bacterial strains with high larvicidal activity were identified in this study, and these strains have the potential to effectively manage DBM and reduce the reliance on chemical insecticides. © 2026 Society of Chemical Industry.