The aphid species are major insect pests of many plants, mainly crucifers, in several parts of the world. It is not admissible to use chemical pesticides to control such pests especially on the edible crops which are consumed as a human food. The routine application of these pesticides to control aphids has two adverse impacts, firstly they are mostly non selective and kill aphid natural enemies, which causes further disturbance of the ecosystem. Secondly, as in other species, resistant strains of aphids can be expected to develop soon.The present study aims to throw some light on the following objectives: Host suitability and host stage preference of certain aphid species for Diaeretiella rapae , Mass-rearing of the parasitoid , D. rapae insects on natural pests and evaluation the role of aphid parasitoid Diaeretiella rapae in the field on certain aphid species.