The role of insect cell lines in an artificial diet for the parasitoid wasp, Trichogramma pretiosum

Abstract

Trichogramma species are mass-produced for biological control using host eggs. Artificial diets have been developed to reduce production costs, however, most include insect haemolymph as a major component, which still results in a significant expense. Medium conditioned with insect cell lines has produced some success as a haemolymph replacement in artificial diets for several parasitoid wasp species. Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae) was the first species to develop successfully to the adult stage on diets containing concentrated Heliothis zea (Boddie) (Lepidoptera: Noctuidae) cells. Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) was subsequently grown to the adult stage on a similar cell line diet. This success encouraged a systematic investigation into the use of insect cell lines in Trichogramma artificial diets. We compared the effect of diets containing insect cells with diets containing conditioned cell line media. Diets containing insect cells produced significantly more pupae than diets containing conditioned medium and, although not significant, produced a higher number of adults. Second, we compared the effect of diets containing cell lines established from ovary-associated tissue of H. zea and embryo tissue of Aedes albopictus (Skuse) (Diptera: Culicidae) on T. pretiosum development. Trichogramma pretiosum development was not significantly different on diets containing cells from the two origins and tissue types. Third, the effect of cell storage on T. pretiosum development was observed. Heliothis zea cells in medium were stored at 4 °C and room temperature (22 °C) for one, two, four and seven days before addition to artificial diets. Cell viability was calculated for these storage treatments. Heliothis zea cells could be stored at 4 °C for up to seven days with no detrimental effect on T. pretiosum development. Trichogramma pretiosum development did not depend on cell viability. The use of insect cell lines as a haemolymph replacement has the potential to significantly reduce production costs and simplify Trichogramma artificial diets with the eventual aim of replacing host production in mass rearing facilities.