Costs of resistance to insecticides in the Maize Weevil,Sitophilus zeamais (Coleoptera: Curculionidae)

Sitophilous zeamais,the maize weevil is a main cause of infestation in stored maize throughout the tropical regions of the world. the attacked seeds are damaged badly,reduced their weight,nutritional values and market value. for the protection of maize crop,farmers usually use pyrethroid and organophosphate insecticides. the indiscriminate use of these insecticides resulted in the development of resistance in maize weevil and affected their growth rate. therefore for the determination of effect of insecticides on life history of sitophilous zeamais,two pyrethroid-resistant strains from fields of the counties juiz de fora (jf) and jacarezinho (ja) from state of parana were compared with one strain susceptible to both insecticides from the county of sete lagoas (sl),which were reared in an insectary,under the controlled condition. we tested whether individual-based life histories of two strains of the maize weevil s. zeamais resistant to pyrethroid insecticides showed fitness costs relative to a susceptible strain. none were detected,despite such costs having been shown in a mass-rearing experiment using the same strains.