AbstractThe use of insecticide mixtures is generally considered to result in the simultaneous development of resistance to the components. However, experiences with leaf and planthoppers do not necessarily support this opinion and indicate that theN‐methylcarbamate/N‐propylcarbamate combination can overcome the resistance of the green rice leafhopper (GRLH) by synergism between the two components. It was found that theN‐methylcarbamate/oxadiazolone combination gave a similar but more remarkable synergism than the former combination. The mechanism of synergism was studied by the analysis of acetylcholinesterase (AChE) inhibition using the logv‐tplot. AChE from the resistant population is provided with two active sites, one being sensitive toN‐methylcarbamate and oxadiazolone compounds and the other being insensitive toN‐methylcarbamates but highly sensitive to oxadiazolones. The overall results indicate that the biochemical mechanism of action of theN‐methylcarbamat/oxadiazolone combination is essentially the same as that of theN‐methylcarbamate/N‐propylcarbamate combination. Selection of susceptible GRLH by aN‐methylcarbamate developed the cross‐resistance to the wholeN‐methylcarbamate group; but the population became more susceptible toN‐propylcarbamates. When further selected by theN‐methylcarbamate/N‐propylcarbamate combination, no further resistance developed to the combination or its components. Thus, certain combinations of insecticides may be useful in resistance manag