Specificity of response to sex pheromones among sweetpotato weevils, Cylaspuncticollis and C-brunneus

Trapping experiments were carried out in Uganda and Indonesia with decyl (E )-2-butenoate and dodecyl (E)-2-butenoate, previously identified as compone nts of the female sex pheromones of the African species of sweetpotato weev il, Cylas puncticollis and C. brunneus, respectively. In Uganda, decyl (E)- 2-butenoate attracted only C. puncticollis males, but dodecyl (E)-2-butenoa te attracted males of both C, brunneus and C. puncticollis. Catches of C. p uncticollis with both compounds were higher when they were dispensed from p olyethylene vials rather than rubber septa, while dodecyl (E)-2-butenoate d ispensed from rubber septa gave higher catches of C. brunneus and was more selective for this species. Release rates of the two compounds from the two types of dispenser were measured in the laboratory and possible explanatio ns for differences in dispenser performance considered. Lures containing de cyl (E)-2-butenoate were as attactive to male C. puncticollis as 10 live vi rgin female C. puncticollis weevils, but lures containing dodecyl (E)-2-but enoate were not always as attractive to male C, brunneus as the conspecific virgin female weevils. Dose-response relationships with the synthetic pher omones varied between repeat experiments and with the type of dispenser. Ad dition of dodecyl (E)-2-butenoate to decyl (E)-2-butenoate either did not a ffect or increased catches of C. puncticollis males, but adding 1% or more of decyl (E)-2-butenoate to dodecyl (E)-2-butenoate significantly reduced a ttractiveness to C. brunneus. Traps baited with synthetic lures captured ma le C. brunneus weevils mostly early in the evening while the majority of ma le C. puncticollis were trapped between 01:00 hr and 03:00 hr. This clear t emporal separation of activity of males of the two species helps to ensure species specificity of mating in these sympatric species. In Indonesia. dod ecyl (E)-2-butenoate but not decyl (E)-2-butenoate attracted C, formicarius males, but this attractiveness was less than 0.4% that of the pheromone of C. formicarius, (Z)-3-dodecenyl (E)-2-butenoate.