Role of rice plant volatiles on the orientation of leaf folder larval parasitoids, Trichomma cnaphalocrocis (Uchida) (Ichneumonidae: Hymenoptera) and Cotesia angustibasis (Gahan) (Braconidae: Hymenoptera)

Orientation of the hymenopteran parasitoids to the volatiles emanating from leaf folder damaged and healthy rice plants of resistant Ptb 33, moderately resistant IR 72 and highly susceptible TN1 rice was studied under laboratory condition using multichoice glass olfactometer. Orientation of the T. cnaphalocrocis and C. angustibasis were more to the leaf folder damaged leaves than to the healthy leaves of Ptb 33, IR 72 and TN1. However, maximum number of visits was to the leaf folder damaged TN 1 leaves when compared to the resistant Ptb 33 and moderately resistant IR 72 and they differed significantly among themselves. In the GC-MS studies on volatile profile, arrays of volatile compounds have been identified. The leaf folder damaged plants of resistant and moderately resistant emitted less number of volatile compounds, while highly susceptible emitted more volatile compounds. Particularly, the volatile Docosane, was more in highly susceptible genotype TN 1 when compared to resistant Ptb 33 and moderately resistant IR 72 genotypes. It could be responsible in the attraction of T. cnaphalocrocis and C. angustibasis.