Bionomics of the parasitoid Apanteles taragamae as influenced by different diets fed to its host, Maruca vitrata

The parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) has been introduced into Benin by the International Institute of Tropical Agriculture (IITA-Benin station) from Taiwan in an attempt to control the cowpea pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), a serious pest of flowers and pods of cowpea Vigna unguiculata Walp. (Leguminosae: Fabaceae). Both the pest and its parasitoid are currently mass-reared using a cowpea and maize flour-based meridic diet. In this study, the suitability of germinating seeds from three cowpea varieties, Kpodji-guèguè, Tawa and TVX3236, as substrates, was tested for rearing A. taragamae under laboratory conditions. The seeds that were soaked for 48 h were the most suitable for M. vitrata larval rearing with up to 87 % survival. The highest parasitism rate of M. vitrata larvae by A. taragamae was observed on the local variety Tawa. Compared to meridic diet, the development cycle of the parasitoid was shorter on Tawa sprouts which also lead to the highest lifetime fecundity. The parasitoid sex ratio varied significantly between feeding substrates with a higher proportion of female wasps on the improved varieties TVX2336 and local variety Kpodji-guèguè. Rearing M. vitrata larvae on germinating cowpea grains is 4.38 times cheaper than on meridic diet. The data are discussed with emphasis on the effects of feeding substrates quality on life history parameters of insect pests and their parasitoids.