Abstract: To reduce the use of chemical pesticides for control of seedling aphids, combination of Metarhizium anisopliae CQMa421 OD with reduced-dosages of chemical pesticides were evaluated in field trials. The results showed that the recommended dosage of the M. anisopliae CQMa421 OD (900 mL/hm²) alone achieved a control of 5.36%-15.46% and the three chemical pesticides had good control of seedling aphids. Especially, afidopyropen DC 50 g/L achieved the best field efficacy, with quick action and long persistence; the control effects of sulfoxaflor 50% WG and flonicamid 10% WG were relatively stable at 3 days after application. The combined application of 25% dosage of chemicals with M. anisopliae showed control equivalent to chemical pesticides alone. Among them, the control of the combined application of flonicamid 10% WG with M. anisopliae was the highest, being 34.76%, 7.02%, 3.25% and 5.49% higher at 1, 3, 7, 14 days after combined application than the control with the recommended dosage of flonicamid 10% WG alone, respectively. The rates of plants with aphids and leaf rolling could be reduced by the use of the chemical pesticides and Metarhizium anisopliae, 5.47%, 5.51%, 4.82%, and 12.78% of leaf-rolling plants were observed with the recommended dosage, the combined use of M. anisopliae with the recommended dosage, the 25% dosage, and the 50% dosage of afidopyropen 50g/L DC, respectively. To sum up, the control effect of M. anisopliae CQMa421 OD used alone is low and needs to be improved, the combined application of M. anisopliae with 25% or 50% dosage of some chemical pesticides has significant synergistic effects.

Key words: Metarhizium anisopliae, chemical pesticides, seeding aphids, reduced dosages and combined application