The hymenopterous parasitoids of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), on cruciferous vegetables in Delhi, India

Abstract Background The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a serious and economically important pest of crucifers in Delhi, India. Larvae and pupae of the pest were collected from the cabbage, cauliflower and broccoli crops grown in vegetable fields at the farm of ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi-110012, from December 2021 to June 2022. The larvae and pupae of the pest were transferred to the laboratory and reared for emergence of parasitoids’ adults at 25 ± 0.5 °C and RH 70 ± 5%. Results Four parasitoid species were emerged, viz. Apanteles mohandasi Sumodan & Narendran 1990, Cotesia vestalis (Haliday, 1834), Diadegma insulare (Cresson, 1865) and Diadromus collaris (Gravenhorst, 1829). Among them, A. mohandasi , C. vestalis and D. collaris were reported for the first time in Delhi, whereas D. insulare (Hymenoptera: Ichneumonidae) is recorded here for the first time in India. Additionally, the first record of parasitism by A. mohandasi on P. xylostella from Delhi was established. The highest parasitism percentage was that of C. vestalis and D. collaris . Moreover, higher parasitism rate was recorded during May 2022 in organically cultivated fields. The parasitism percentage by A. mohandasi , C. vestalis , D. insulare and D. collaris was 7.5, 22.5, 12.5 and 15%, respectively. Conversely, in conventionally farmed fields, the parasitism rates were 3.57, 16.67, 10 and 13.33%, respectively. Conclusion The use of biological control agents particularly the parasitoids in the IPM program of P. xylostella should be considered, thereby reducing reliance on insecticides and increasing the efficacy of hymenopteran parasitoids.