Objective Beauveria bassiana is widely used to control agricultural and forestry arthropod pests, but the slower and unstable efficacy limit its application. Pyrethrins is a natural botanical insecticide commonly used in organic agriculture for pest control, but it is expensive and has a short persistence period. This study was aimed to mix Beauveria bassiana and pyrethrins together, develop effective and low-cost mixing combinations and appropriate preparations.

Method Under indoor conditions, the conidia of B. bassiana BbPs01 strain, natural pyrethrins and their mixtures against cotton aphid, Aphis gossypii were tested by spray method. To screen the synergistic combinations of BbPs01 and pyrethrins, the joint virulence of mixtures was evaluated with cotoxicity factor (c. f.). The 1.0% dispersible oil suspension of BbPs01-pyrethrins (1.0% BbPy OD) was prepared and applied in fields to investigate the control efficacy.

Result The results from toxicity tests in lab showed that after 3 days of treatment, the mixture of BbPs01 and pyrethrins in the mass ratios of 0.8∶0.2, 1.8∶0.2, 0.7∶0.3, 0.6∶0.4, 0.5∶0.5 showed an synergistic effect on A. gossypii. A comprehensive combination of B. bassiana and pyrethrins in mass ratio of 0.7∶0.3 was selected to prepare 1.0% BbPy OD. The LC₅₀ of 1.0% BbPy OD against aphids was 1.98 mg/L, which is lower than the positive control (the LC₅₀ of 1.5% pyrethrins EW is 5.05 mg/L). In field trials, it was found that 1.0% BbPy OD had good efficacies to control A. gossypii on cucumber, Bemisia tabaci on tomato and Phyllotreta striolata on Chinese flowering cabbage.

Conclusion B. bassiana and pyrethrins has synergistic effect on aphids, and their binary mixed dispersible oil suspension shows good control effect on aphids and other pests. This study provides a new insight for expanding the application technology of myco- and botanical insecticides.