A comparative study of the parasitization behaviour of Encarsia formosa with the greenhouse whitefly (Trialeurodes vaporariorum) and the sweetpotato whitefly (Bemisia tabaci) on poinsettia

The objectives of this study were two-fold: (1) to elucidate, in the light of the optimal foraging theory, how host species selection operates when Encarsia formosa is exposed simultaneously to both whitefly species and (2) to predict the potential of E. formosa to control the sweetpotato whitefly in a poinsettia crop infested with the two whitefly species.;Observations of the parasitization behaviour of E. formosa under two foraging scenarios ((1) with either Trialeurodes vaporariorum or Bemisia tabaci, (2) with both whitefly species in mixed patches) and preliminary studies of the development of E. formosa when reared on B. tabaci were made.;The encounter rate of E. formosa with B. tabaci was lower than with T. vaporariorum. The wasp appeared to follow the same stereotyped sequence in her oviposition behaviour with both whitefly species. However, E. formosa took longer to examine and lay an egg in B. tabaci than in T. vaporariorum. The acceptance-rejection pattern of B. tabaci changed when this whitefly was in a mixed patch, such that it was accepted less often.;Detrimental changes in behaviour and quality as well as higher larval mortality of E. formosa were observed when reared on the sweetpotato whitefly compared to the commercial parasite reared on T. vaporariorum.;Frequent introductions of E. formosa, in high enough numbers, are suggested as potential control of B. tabaci in a poinsettia crop infested with both whitefly species. (Abstract shortened by UMI.).