Possibility of biological control of the aphids on greenhouse komatsuna, Brassica rapa nothovar. III. Methods for mass producing Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae, Aphidiinae)

Abstract

We developed the mass production procedure of Diaeretiella rapae, a biological control agent against pest aphids. Twenty female adults of D. rapae were introduced into a cage containing Lipaphis erysimi on two plants of komatsuna Brassica rapa nothovar. kept at 20°C and a 15L-9D light cycle. Five treatments were used (i.e., 50-A, 100-A, 50-B, 75-B, 100-B); differing in the number of viviparous female adults provided (50, 75, 100) and interval between introduction of aphids and parasitoids (A: 0 day, B: 3 days). The newly mummified aphids (mummies) were counted and removed on days 7-9, 13-15 and 18-20 after aphid release, and the emergence rate and sex ratio of the parasitoids were assessed by rearing the mummies under the same conditions. From these results, the number of female parasitoids produced was calculated to be largest in 50-B (768), followed by 75-B (719), 100-A (584), 50-A (446) and 100-B (400). A simulation model for producing mummies developed from the life history traits of D. rapae and L. erysimi was used to analyze the present results.