Host stage preference and performance of the aphid parasitoid Diaeretiella rapae (Hymenoptera: Braconidae) on Brevicoryne brassicae and Lipaphis pseudobrassicae (Hemiptera: Aphididae)

We assessed the host stage preference and performance of the aphid parasitoid Diaeretiella rapae (Mcintosh) on two aphid species, Brevicoryne brassicae (L.) and Lipaphis pseudobrassicae (Davis). Although the parasitoid parasitized all nymphal instars of both aphid species, it showed a higher oviposition preference for 2nd (48.2 ± 7.74%) and 3rd (41.0 ± 7.82%) instars of L. pseudobrassicae , and for the 3rd (40.0 ± 4.59%) instar of B. brassicae . Across the host species, there was no significant difference in parasitoid preference between the 3rd and 4th instars, while 1st and 2nd instars of L. pseudobrassicae were significantly more preferred than their counterparts ( B. brassicae ). Days to mummification among different instars of the same host was not significantly different when the parasitoid was reared on B. brassicae , whereas this was highest on the 2nd, 3rd and 4th instars of L. pseudobrassicae . Number of mummies was also significantly different among the nymphal instars of both host species and between the two host species for the 1st and 2nd instars. In terms of body size, female D. rapae reared on L. pseudobrassicae were significantly larger than those reared on B. brassicae . We discuss the findings in the context of laboratory mass rearing of D. rapae and its potential as a biological control agent for both aphid pest species.