Purpose To investigate the control effect of Mucor hiemalis, azadirachtin, and their combination against Ceracris kiangsu.
Methods The leaf-dipping method was used to determine the indoor toxicity of different densities of M. hiemalis strain YAFGDT01, different mass concentrations of azadirachtin, and their combination against the 3rd instar nymphs of C. kiangsu, as well as the greenhouse control effect on adult insects.
Results The mortality of C. kiangsu nymphs was positively correlated with the spore suspension density of M. hiemalis. When the spore density was 1.0×108 mL−1, the 7-day mortality of nymphs reached the maximum of 76.67%; when the spore density was 1.0×104 mL−1, the 7-day mortality was the lowest at 46.67%. The mortality of C. kiangsu nymphs was also positively correlated with the mass concentration of azadirachtin. When the effective mass concentration of azadirachtin was 2.5 mg/L, the 7-day mortality was as high as 80.00%; when the mass concentration was 2.5×10−3 mg/L, the 7-day mortality was only 33.33%. When M. hiemalis was mixed with azadirachtin at volume ratios of 9∶1, 4∶1, 1∶1, 1∶4, and 1∶9, the median lethal concentrations were 3.50×10−3, 9.42×10−3, 12.62×10−3, 25.52×10−3, and 14.39×10−3 mg/L, respectively. The co-toxicity coefficients (CTC) varied among different combination groups. Among them, the CTC of the mixture of M. hiemalis and azadirachtin in a volume ratio of 9∶1 was greater than 120, indicating a significant synergistic effect, and its 7-day greenhouse control effect was significantly higher than that of a single insecticide.
Conclusion The effect of the combination of M. hiemalis and azadirachtin on the C. kiangsu is affected by the proportion of combination, and the effect is better when the volume ratio is 9∶1. The combination of the two insecticides has good development and application prospects for the prevention and control of Acridodea pests.
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