Behavioural response of Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae) to kairomones

Bioassay with hexane extracts of male and female whole body wash of hosts viz, Earias vitella and Spodoptera litura with Trichogramma chilonis revealed their kairomonal activities. Whole body extracts of male and female moths were analysed separately by gas chromatography for determining their hydrocarbon profile, which showed the presence of straight chain saturated hydrocarbons ranging from C_g to C.,. Both the host insects showed variation in number and concentration of these chemicals, which were responsible for influencing the parasitoid activity, parasitism and emergence. The foraging activity of the parasitoid as indicated by parasitoid activity index (PAI) was highest (14. 17) in S. litura male body extract at concentration C_s (10, 000 ppm) followed by (11. 50) in E. vitella female body extract at C₄ (1000 ppm) by T. chilonis. Maximum percentage parasitism of (52. 22) and emergence (15. 00) was observed at highest concentration in S. litura male body extract followed by E. vitella female body extract. Highest overall response was recorded in egg cards treated with whole body wash of male and female of S. litura and E. vitella, respectively, which may be attributed to the presence of more number of favourable saturated hydrocarbons viz.; heneicosane, tricosane, pentacosane, hexacosane, octacosane, and nonacosane, as revealed by GC. Kairomonal interaction observed in the whole body extract of male and female of E. vitella were significantly different from male and female of S. litura as well as control. These favourable hydrocarbons at appropriate concentration of body extract of E. vitella female and S. litura male could be used for enhancing parasitization by T. chilonis.