Artificial Diet for Rearing Trichogramma Wasps (hymenoptera: Trichogrammatidae) with Emphasis on Protein Utilization

Trichogramma wasps are tiny hymenopterous egg parasitoids widely used in biological control programs worldwide. The huge quantities of insects necessary for inundative releases are mainly produced on factitious hosts like Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae), or on silkworms. In order to simplify production, increase its flexibility, and potentially reduce cost, studies on artificial media for the development of the parasitoids have been ongoing for many years. Some successes were obtained, mainly with artificial media containing insect extracts such as pupal hemolymph from Lepidoptera. To define new artificial media devoid of insect components or improve the performances of existing ones, a better knowledge of parasitoid nutrition would be useful. Proteins are key components in artificial media, and research was conducted on Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) to better understand the nutritional value of proteins by investigating to what degree they are assimilated by the insect. A method was developed for studying the assimilation of these nutrients by the preimaginal stages of T. pretiosum based on adding a mixture of free 14C-radiolabelled amino acids to the medium to be tested. The basic composition of the medium already included proteins, and proteins to be tested were also added. Amino acid analyses were performed on medium (for free and protein amino acids) and on T. pretiosum grown in the medium (for protein amino acids). For each radiolabelled amino acid, comparison of the specific activity in total amino acids in T. pretiosum pupae with the specific activity in free and protein amino acids in the medium, allowed us to determine the degree and the means by which the protein was utilized. We showed that the proteins included in the hemolymph-based medium, as well as casein added at final concentrations of 1.6 or 3.2 %, were completely assimilated. This protein, incorporated into the hemolymph-based medium to increase its protein content, led to im_______________________________________________ Artificial Diet for Rearing Trichogramma Wasps Second International Symposium on Biological Control of Arthropods 481 proved body composition and some development parameters of T. pretiosum. Even media containing hemolymph could be improved by protein addition because of the relatively low content of proteins in the hemolymph. The addition of 3.2% casein increased the protein content of T. pretiosum pupae by 25% and normal adult emergence yield by 40%.