Abstract
The Nakagawara strain of the green rice leafhopper is resistant to both carbamate and organophosphorus insectivides. Activity and sensitivity of cholinesterase, and toxicity of 10 substituted phenyl N-methylcarbamates for the resistant and susceptible strains were investigated and compared. Inter-strain difference in cholinesterase activity was found to be not significant, but the cholinesterase in the resistant strain was relatively insensitive to all the inhibitors tested as compared with the susceptible strain. Inter-strain ratio of I50 among inhibitors ranges from 5 to 120. Relationships of anticholinesterase activity and toxicity of carbamate insecticides tested for the two strains showed good correlations.Resistance spectrum showing especially high resistance to bulky alkyl or alkoxy phenyl carbamates were sufficiently well explained by the sensitivity of cholinesterase. Some considerations were given to the relationships between the structure of carbamates and the anticholinesterase activity in relation to resistance.
