Resistance of Plutella xylostella(L.)to three new insecticides in field of different areas in Guangxi

【Objective】The susceptibility of larval field population of Plutella xylostella in six vegetable areas in Guangxi against chlorantraniliprole,flubendiamide and metaflumizone were evaluated to provide a theoretical basis for application of pesticide in Plutella xylostella and their resistance monitoring to these pesticides.【Method】Comparative analysis on the LC50 value of the three pesticides between susceptible strains and field populations of Plutella xylostella,which employed the leaf dipping method(IRAC Method No.7)to measure the toxicity of chlorantraniliprole,flubendiamide and metaflumizone against the larva of strain and the six field populations of Plutella xylostella,respectively,was used to determine the relevant resistance ratio.【Result】The sensitivity of the field population in Tiandong County to chlorantraniliprole was the lowest,its LC50 value was 0.00423 mg/L,and its resistance ratio was 7.6 fold,while that in Lipu County was the highest,its LC50 value was 0.00735 mg/L,and its resistance ratio was 1.3 fold.The sensitivity of the field population in Liujiang County to flubendiamide was the lowest,its LC50 value was 0.366 mg/L,and its resistance ratio was 2.27 fold,while that in Anji aera was the highest,its LC50 value was 0.168 mg/L,and its resistance ratio was 1.04 fold.The sensitivity of the field population in Liujiang County to metaflumizone was the lowest,its LC50 value was 4.692 mg/L,and its resistance ratio was 2.96 fold,while that in Lipu County was the highest,its LC50 value was 1.622 mg/L,and its resistance ratio was 1.02 fold.【Conclusion】In Tiandong County the field population had the resistance ratio of 7.61 fold,which meant low resistance,therefore adequate attention should be given.The resistance ratio to three pesticides of Plutella xylostella was less than 5 fold compared with the susceptible strain,except Tiandong population.Plutella xylostella of six field populations was still pretty sensitive to the three new insecticides.Consequently,these insecticides must be used in rotation to delay the resistant forming and growth.