Effect of okra plant architecture and semiochemicals on parasitism of Helicoverpa armigera eggs by Trichogramma species

A series of experiments were conducted during 2013 at College of Horticulture, Bidar, University of Horticultural Sciences, Bagalkot, India to understand the effect of the host plant okra (Abelmoschus esculentus) and fruit borer (Helicoverpa armigera) on parasitism by Trichogramma species. Okra cultivars, Parbhani Kranti and Shakti-303 with glabrous surface permitted higher parasitism on fruit borer eggs, i.e 36.4% and 33.7%, respectively, compared to hirsute cultivars, Ankur (AROH-10), Mahalaxmi Amisha, which recorded 31.1% and 29.6% parasitism, respectively. Among the different species of Trichogramma, Trichogramma chilonis (41.0%) and Trichogramma brasiliense (34.6%) recorded significantly higher parasitism. Further, among the different plant parts, leaf extract of Parbhani Kranti cultivar attracted the highest number of T. chilonis (6.5 individuals). To know the attraction of T. chilonis to okra fruit borer with and without host plant, T. chilonis was exposed to H. armigera eggs on Parbhani Kranti okra leaf T. chilonis made higher number of encounters of eggs on leaves (9.36 eggs were searched) compared to eggs on filter paper (6.45 eggs searched). Among the different species, T. chilonis was observed to be the most active with 5.55 individuals getting attracted to the frass mixture of H. armigera larvae.