Abstract: The codling moth, Cydia pomonella, a destructive pest whose larvae bore into fruits, poses a severe threat to the sustainable development of apple, pear, and walnut industries in Xinjiang, China. This study evaluated the toxicity of Bacillus thuringiensis G033A (Bt G033A), emamectin benzoate, matrine, and Beauveria bassiana against first-instar larvae of C. pomonella using direct spray assays under laboratory conditions. Furthermore, the combined toxicity and field control efficiency of Bt G033A paired with the other three agents were assessed. Laboratory bioassays revealed LC₅₀ values are 1.17×10⁶ IU/L (Bt G033A), 0.02 mg/L (emamectin benzoate), 38.35 mg/L (matrine), and 6.25×10⁹ spores/L (B. bassiana), respectively. The most significant synergism was observed in the 1:1 LC₅₀ combination of Bt G033A and B. bassiana, with a synergistic toxicity index (CF) of 100.02. Field trials (spray volume: 40 L/667 m²) showed that single application of 200 g/667 m² Bt G033A achieved control of 53.79%—64.02% at 7 days post treatment. The combination B. bassiana (100 g/667 m²) with Bt G033A (100 g/667 m²) improved control to 89.98%—92.24%. These findings indicate that the combined application of Bt G033A and B. bassiana significantly enhances insecticidal activity and field control of C. pomonella.

Key words: Bacillus thuringiensis G033A, Beauveria bassiana, insecticidal activity, pesticide combination, field control efficacy