Abstract
The development of insecticide resistance in rice brown planthoppers and its mechanism were studied. The susceptibility of malathion- and MTMC-selected strains to malathion decreased to 1/39 and 1/25 of the initial level after 45 selections, respectively, while that to MTMC decreased to 1/2.5 and 1/4.2. These selected strains were more susceptible to synthetic pyrethroids than the parent strain. K1 and K2 showed high synergism to the selected strains, and also inhibited the decomposition of malaoxon. Malathion resistance in the malathionor MTMC-selected strains was suggested to be caused by high degradative activity to malathion and malaoxon. The mechanism of MTMC resistance in the MTMC-selected strain was presumed to be caused by low sensitivity of acetylcholinesterase.
