Control Efficiency of Three Pesticides Combined with Beauveria Bassiana against Melanaphis Sacchari
The synergistic relationship of neonicotinoid pesticides with Beauveria bassiana,the compatibility of imidacloprid,thiamethoxam,and dinotefuran with B.bassiana,and their combined control efficiency against the sorghum aphids,Melanaphis sacchari were investigated in this study.Mortality of M.sacchari exposed to different concentrations of B.bassiana(strain GZGY-1-3)and the three chemical pesticides was determined using bioactivity assay.The results showed that the corrected mortalities of M.sacchari subjected to B.bassiana at different concentrations(1.6×105―1×109 conidia/mL)were 34.22%―89.90%.Th three chemical pesticides ranked according to the mortalities of the treated M.sacchari from high to low were imidacloprid,dinotefuran,and thiamethoxam.The effects of pesticide concentration and mixing time on conidial germination of B.bassiana were investigated.The results showed a positive correlation between the pesticide concentration,and the treatment time and the effect on conidial germination.When treated with 1/8 and 1/10 concentration of the recommended pesticide dose,the B.bassiana showed high compatibility,with conidial germination rate of over 90%.Based on the previous test results,the control efficiency of the combination of fungus and pesticide against aphids was determined.The combinations were characterized by co-toxicity coefficients of over 80 and resulted in significantly higher mortality rates of the sorghum aphids,showing additive or synergistic effects.Among the combinations,B.bassiana(4×107 conidia/mL)mixed with dinotefuran was the most virulent,with a mortality rate of 97.67%and a co-toxicity coefficient of 135.37.Therefore,the compatibility of B.bassiana with the three nicotinic chemical pesticides are high when the chemical pesticides are diluted by a factor of 8-fold and the mixed treatment time is less than 4 h.The best mixture is between B.bassiana(4×107 conidia/mL)and dinotefuran.
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