Improving the knowledge of Aphytis melinus biology to optimize its mass production: influence of food source, host and parasitoid densities

Abstract

The purpose of this work is to study the influence of several factors on fecundity and proportion of female parasitoids in the mass rearing of Aphytis melinus DeBach (Hymenoptera Aphelinidae). Its mass-rearing can be influenced by both host and parasitoid densities and by the available food source. In this study, host density did not influence the number of observed offspring per female per day (1.14 ± 0.15) or the sex ratio (0.32 ± 0.07 ♂) of A. melinus. Parasitoid density, on the other hand, did influence offspring production, with the higher parasitoid densities resulting in the lowest number of offspring (0.41 ± 0.07 per female per day). Medium and low parasitoid densities, meanwhile, produced similar numbers of offspring (0.83 ± 0.18 and 0.77 ± 0.13 per female per day, respectively). Sex ratio (0.43 ± 0.03 ♂) was not influenced by parasitoid density. The highest survival for A. melinus was achieved with honey (14.1 ± 1.2 days), but no statistical difference was observed with 10% honey. A mixture of honey, sugar and agar was not as good food source (only 3.0 ± 0.6 days of survival). Observed parasitoid host feeding was not continuous in the honey and 10% honey treatments, occurring only during 11.9 and 20.4% of the life-span, respectively. Maximum efficiency in offspring production per female was achieved when the host/parasitoid ratio was 5 to 10 hosts per female parasitoid per day. To maintain the lowest male bias of the offspring, female parasitoids should be in contact with the host for a period of no more than 3-4 days.