Temperature effects on the life history of the eulophid wasp Diglyphus isaea, an ectoparasitoid of leafminers (Liriomyza spp.), on tomatoes

The effect of constant and alternating temperatures on the life-history of Diglyphus isaea, as an ectoparasitoid of Liriomyza leafminers on tomato plants, was examined in the laboratory.
Parasitoid development and size were significantly affected by temperature and sex. Males showed a shorter development time and pupal size than female parasitoids. Both development time and pupil size in D. isaea differed according to the host species. Pupal size showed no consistent relationship with temperature. The lower thermal threshold for development and oviposition was determined. Fecundity with L. byroniae as host did not differ significantly between temperature regimes. Furthermore, larger females did not produce larger numbers of offspring. Development and reproduction under the alternating temperature regime did not differ from those at the comparable constant temperature, suggesting a rapid response to changes in temperature.
The intrinsic rate of increase (r_m) and net reproduction (R_o) of D. isaea nearly doubled from 15°C to 25°C and 20°C, respectively, and generation time at 25°C was less than half that at 15°C. Because the parasitoid's population growth is higher than that of these pest insects at all temperatures, D. isaea is a promising candidate for seasonal inoculative biological control of Liriomyza on tomato crops in Scandinavian and western European glasshouses. Possible constraints to its effectiveness are discussed.