Baker, S.Z., S.M. Ismail and K.F. Saeed. 2023. Effect of Some Surfactants on the Expired Bioformulation Belthirul® and Evaluation of its Efficacy Against Fig Moth Larvae, Ephestia cautella (Walker). Arab Journal of Plant Protection, 41(2): 119-126. https://doi.org/10.22268/AJPP-041.2.119126 A laboratory study was conducted to evaluate the effect of two surfactants Neutrafol-pH and Inex-A compared to the expired Belthirul® formulation (Bacillus. thuringiensis var kurstaki) on the larvae of the fig moth Ephestia cautella (Walker). Tests were conducted to determine the time required for wetting, stability of the suspension under normal conditions and compatibility between the entomopathogen and surfactants. Expired formulation, fresh formulation and treated expired formulation were bio-assayed on third instar larvae of the fig moth E. cautella to evaluate its efficacy. The results obtained showed that the two surfactants Neutrafol-PH and Inex-A were highly efficient in reforming the expired bioformulation Beltirul®, improved its physical specifications and increased its biological activity on fig moth larvae, and Neutrafol-PH was more effective in increasing the activity and vitality of B. thuringiensis var. kurstaki in the expired bioformulation. The number of bacterial colonies was 17.3×1010 CFU/g, whereas it was 8.0×1010 colonies/g in the expired bioformulation treated with Inex-A surfactant, compared with non-treated expired bioformulation which reached 3.9×1010 CFU/g. The treated expired bioformulation with Neutrafol-PH and Inex-A increased its efficacy by increasing mortality rate 82.08 and 74.38%, respectively, on the third instar larvae of the fig moth at the concentration of 1 g/L. Keywords: Efficacy, Belthirul®, surfactants, fig moth, Ephestia cautella.