Abstract: Acetylcholinesterase insensitivity is an important mechanism of resistance of diamondback moth (Plutella xylostella (L.)) to organophosphorus and carbamate insecticides, which has been widely recognized and documented. A dot-blot on nitrocellulose membranes technique for identification of insensitive AChE in single insect provides the opportunity for early detection and subsequent monitoring of resistance in field population. The technique is simple, sensitive and inexpensive. The percentages of inhibition of AChE activi ties in resistant strain (GBR) and field population (DG) were 50.97% and 43.96 % respec tively in the presence of propoxur and were 63.76% and 35.87% respectively in the presence of paraoxon. The results showed the GBR and DC, had a higher degree of AChE insensitivity to OP and carbamate than did the susceptible strain.

Key words: Plutella xylostella (L.), resistance, acetylcholinesterase, organophosphorus, carbamate