Biological studies of Diaeretiella rapae (McIntosh) on cabbage aphid (Brevicoryne brassicae) infesting cole crops

Abstract

The present study discovered that the third instar nymphs of cabbage aphid, Brevicoryne brassicae, were found as most preferred host for parasitism by primary parasitoid, Diaeretiella rapae, on cole crops. A single mated pair of endoparasitoid killed a total of 24.20 aphids over a period of five days, follwed by the fourth instar nymphs recording 21.80 aphids/mated endoparasitoid. Time taken from egg to adult emergence of D. rapae was observed as 11.32 ± 0.92 days. This included 5.32 ± 0.27 days from parasitism to mummification and 6.00 ± 0.23 days after mummification to adult emergence. On an average adult emergence was 84.00 ± 0.84%. The present study revealed a female biased sex ratio of 1.62:1. The average longevity of female and male parasitoids was 4.10 ± 0.64 and 3.35 ± 0.62 days, respectively.