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

Abstract

We assessed the host stage preference and performance of the aphid parasitoidDiaeretiella rapae(McIntosh) on two aphid species,Brevicoryne brassicae(L.) andLipaphis 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 ofL. pseudobrassicae, and for the 3rd (40.0 ± 4.59%) instar ofB. brassicae. Across the host species, there was no significant difference in parasitoid preference between the 3rd and 4th instars, while 1st and 2nd instars ofL. pseudobrassicaewere 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 onB. brassicae, whereas this was highest on the 2nd, 3rd and 4th instars ofL. 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, femaleD. rapaereared onL. pseudobrassicaewere significantly larger than those reared onB. brassicae. We discuss the findings in the context of laboratory mass rearing ofD. rapaeand its potential as a biological control agent for both aphid pest species.