Mechanism of dichlorvos-resistance of striped flea beetle, Phyllotreta striolata(Coleoptera:Chrysomelidae)

Conventional insecticide control became less effective and the beetle's insecticide resistance increased.This study screened the SFB populations by exposing the insects to dichlorvos two consecutive times to obtain high resistance individuals.The insecticide susceptibility,activities of carboxylesterase(CarE),acetylcholinesterase(AChE) and glutathione-S-transferase(GST),as well as the kinetic constants of screened(SP) and control populations(CP) were determined.The results indicated that LC50 value of SP was slightly higher than CP.The maximum velocity(Vmax) and Michaelis constant(Km) of CarE in SP were much less than that in CP.The AchE activity of SP was 0.0074 OD412insect-1min-1,significantly lower than that of CP(0.009 6 OD412 insect-1min-1).And,the GST activity of SP was 0.0050 OD340insect-1min-1,significantly higher than that of CP(0.0036 OD340insect-1min-1).Our study suggested that the resistance of SFB to dichlorvos might relate to the decreased activity of AChE as well as the increased activities of CarE and GST.