Kairomonal effect of host body washing on the egg parasitoid Trichogramma brasiliensis (Ashmead) (Hymenoptera: Trichogrammatidae)

Abstract

Bioassay with hexane extracts of male and female whole body wash of host insects viz., Earias vittella and Spodoptera litura with Trichogramma brasiliensis 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 C8 to C35. The concentration of these hydrocarbons ranged from 0.02 µg/g to 2579 µg/g of insect extract. 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 (12.00) in S. litura male body extract at concentration C4 (1000 ppm) followed by (10.83) in E. vittella female body extract at C5 (10,000 ppm) by T. brasiliensis. Maximum percentage parasitism of (45.55) and emergence (12.50) was observed at concentration C4 in S. litura male body extract followed by E. vittella 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. vittella, 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. These favourable hydrocarbons at appropriate concentration of body extract of E. vittella female and S. litura male could be used for enhancing parasitization by T. brasiliensis