Analysis of the Susceptibility of Maruca testutalis Geyer to Abamectin

The susceptibility of Maruca testutalis Geyer to abamectin was studied by leaf immersion method and spectrophotometry. The results showed that Maruca testutalis in different areas had different susceptibility to abamectin; the resistance of Maruca testutalis increased 3.5701-fold in Dingan and 2.8650-fold Dongfang based on the results of the LC50 of Maruca testutalis in Liangyuan LC50,the bioassay of carboxylesterase indicated that carboxylesterase activity in Maruca testutalis significantly increased after treated by abamectin 18,9,4.5,3,0.225 mg/kg. The results above all showed that the susceptibility of Maruca testutalis to abamectin declined mainly because of carboxylesterase activity in Maruca testutalis significant increase.