Genetic aspects of insecticide tolerance in Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae) strains

Trichogramma genus is one of the most important groups of biotic agents employed for the control of several lepidopterous pests. However, these parasitoids are also subjected to environmental stress such as insecticides, temperature etc. in the agricultural field. Selection of parasitoids tolerant to insecticides has been recognized as a potent method for enhancing their performance. In this regard, the present study was carried out to know insecticide tolerance level and the kind of inheritance in Trichogramma chilonis Ishii., strains on commonly used insecticides in the agricultural fields. Endosulfan, spinosad and lamda cyhalothrin tolerant strains along with a susceptible one were selected to carryout the crossing experiments. The LC₅₀ values of endosulfan, spinosad and lamda cyhalothrin tolerant strains were found to be 278.03, 9.84 and 6.23 ppm respectively. This is in contrast to the respective susceptible strains to these insecticides which have exhibited LC₅₀ values of 106.03, 4.78 and 3.45 ppm respectively. The endosulfan tolerance appeared to be recessive for the cross involving tolerant male parent and semi dominant for the tolerant female parent. The spinosad tolerance was found to be semi dominant for crosses involving both male and female tolerant parents. In contrast, the lamda cyhalothrin tolerance was completely dominant for crosses with the tolerant male and female parents.