Novel Enterobacter strains applied as entomopathogenic insecticides against Plutella xylostella (Lepidoptera:...

Identifying environmentally friendly entomopathogenic microorganisms and using them as alternatives to chemical insecticides is crucial for advancing green agriculture.

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 (LC₅₀) 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 LC₅₀ values were reduced to 141.50, 182.84, and 90.75 mg bacteria/L, respectively. The median lethal time (LT₅₀) 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.

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.