Susceptibility to insecticide and detoxifying enzymes activity of rice water weevil,Lissorhoptrus oryzophilus in Liaoyang

Three field populations of rice water weevil, Lissorhoptrus oryzophilus Kuschel,were collected in Liaoyang,Liaoning province during 2010-2011 and their susceptibility to six insecticides were investigated.The LD50s of the same insecticide to different populations varied from 4.2- to 49.4-fold.The susceptibility of Dashiqiao population to abamectin,triazophos and spinosad decreased slightly in 2011 compared to that in 2010.To control this beetle effectively,five insecticide mixtures that showed significant synergism were screened out through indoor bioassays,and the mixtures are abamectin mixed with triazophos at 1∶1 and 1∶3(m/m),chlorantraniliprole mixed with triazophos at 1∶1 and 1∶3(m/m),and spinosad mixed with phoxim at 1∶3(m/m).The specific activity of acetylcholinesterase,carboxylesterase and glutathione S-transferase were analyzed among the three field populations and possible reasons for the difference in susceptibility were discussed.The results of the present work would be helpful for controlling the rice water weevil in Liaoyang area.