Parasitism and sex ratio of Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae) against Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) on cruciferous cultivars under different temperatures

Abstract

Background: Diadegma insulare (Cresson) is the most efficient parasitoid of Plutella xylostella (L.) in cruciferous crops. Considering its effectiveness, the present study was performed to investigate the impacts of cauliflower and cabbage cultivars under 3 different temperature regimes on the parasitism efficiency and offspring sex ratio of D. insulare. Main body: This study revealed that D. insulare remained active at all the 3 temperatures (i.e., 19, 23, and 27 °C) and on all selected cruciferous cultivars. However, 23 °C (along with 65±5% RH and 16L: 8D hours) was the most suitable temperature, whereas relatively preferred host plant cultivars were the “White marble” (cauliflower) and “Asha” (cabbage) at which comparatively higher parasitism rates (79.39 and 73.31%, respectively) were recorded. Moreover, non-significant differences were observed in the offspring sex ratios of the parasitoid at different temperature regimes; however, minute differences were found among studied cruciferous cultivars. Conclusion: Overall, “White marble” (cauliflower) and “Asha” (cabbage) were recommended to be used as potential host plant cultivars for mass rearing of D. insulare.