Abstract: To clarify the control efficacy of the combined application of Beauveria bassiana with reduced-dose chemical pesticides against strawberry red spider mites, a field experiment was conducted by combining Beauveria bassiana with reduced doses of 20% etoxazole and 30% cyenopyrafen. The control effects of different treatments against strawberry red spider mites, as well as their influences on the activities of strawberry leaf defense enzymes, plant growth, fruit quality and yield, were systematically compared. The results showed that the control effects of Beauveria bassiana combined with a 25% reduced dose of 20% etoxazole (T3) and with a 25% reduced dose of 30% cyenopyrafen (T7) reached 82.17%, 86.74% and 83.30%, 87.36% at 14 and 20 days after application, respectively, all of which were higher than those of the recommended full dose of 20% etoxazole alone (T2) and 30% cyenopyrafen alone (T6). The control effects of Beauveria bassiana combined with a 50% reduced dose of 20% etoxazole (T4) and with a 50% reduced dose of 30% cyenopyrafen (T8) reached 85.15% and 84.14%, respectively, at 20 days after application, which were also higher than those of T2 and T6. The activities of leaf peroxidase, catalase, superoxide dismutase, and polyphenol oxidase in T3 and T7 at 3, 7, 14, and 21 days after application were all higher than those in T2 and T6. Similarly, the activities of these enzymes in treatments T4 and T8 were also higher than those in T2 and T6 at 20 days after application. Plant height, stem diameter, maximum leaf area, and SPAD values in T3, T4, T7, and T8 were all higher than those in T2 and T6. Moreover, the contents of soluble sugar, soluble solids, vitamin C and fruit yield in T3, T4, T7, and T8 were significantly higher than those in T2 and T6.

Key words: Beauveria bassiana, chemical pesticide, reduced doses and combined application, strawberry, red spider mites, control effect