Performance and parasitism rate of Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae), a larval parasitoid of diamondback moth (Plutella xylostella) on brassica genotypes: a life table analysis

The performance, life history, and parasitism rate of Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae) on Plutella xylostella (Linnaeus, 1857) (Lepidoptera: Plutellidae) reared on six different cruciferous cultivars (Broccoli, Cabbage, Canola, Cauliflower, Chinese cabbage and PakChoi) was evaluated under controlled conditions (25 +/- 2 degrees C, 65 +/- 5% RH, and 16 L: 8 D photoperiod). The life history parameters were compared using the age -stage and two -sex life table theory. Significant variations were observed in different life stages of D. insulare on its host, P. xylostella, reared on different cruciferous genotypes. The adult duration of D. insulare ranges from 7.70 day on Pak Choi to 6.65 day on Cabbage. The maximum (19.83 offspring) and minimum (9.23 offspring) net reproductive rates of D. insulare were observed on cultivars Pak Choi and Cabbage, respectively. The increase in intrinsic rate ranged from the highest (0.1970 day -1) on Broccoli to lowest (0.1471 day -1) on Cabbage. The maximum (0.2814 host) finite predation rate was recorded on Broccoli, and was the minimum (0.2112 hosts) on Cabbage. The values of stable predation rate increased from 0.1824 (host/ parasitoid) to 0.2308 (host/ parasitoid) with changes in host diet. All tested brassica cultivars affected the life performance of D. insulare. The results confirmed that D. insulare showed better performance on Broccoli genotype when compared to other tested genotypes. Hence, Broccoli can be used for the rearing of D. insulare on a large scale for mass releases of this parasitoid in the brassica fields to get effective suppression in the population of P. xylostella.