Coexistence of two effective parasitoids of the white peach scale Pseudaulacaspis pentagona (Hemiptera: Diaspididae): the role of host stage and temperature.

Encarsia berlesei (Howard) and Pteroptrix orientalis (Silvestri) are endoparasitoids of Pseudaulacaspis pentagona (Targioni Tozzetti), that are sympatric in Campania (Italy). The influence of host stages on several components of E. berlesei fitness and the effect of mating status on the production of Pteroptrix orientalis progeny were evaluated at 25°C. Parasitization of earlier host stages resulted in an increase in the development time and a decrease in progeny number of E. berlesei, Adult parasitoids were largest when young female stages were parasitized. Pupal mortality did not differ among host stages. Mated female P. orientalis produced a greater number of progeny and proportionally fewer sons (13.6% of the total progeny) than did virgin females (21.7%). The reproductive potential of both parasitoids was also evaluated at four regimes of constant temperature (20, 24, 26 and 30°C). Encarsia berlesei attained rm values nearly double those of P. orientalis at 20, 24 and 26°C, whilst at 30°C the two parasitoids achieved the same rm value, since at this temperature E. berlesei suffered a high pupal mortality. Sex ratio of P. orientalis, expressed as proportion of males, varied significantly between 20 and 24°C only.