Biodiversity of Insect Pest Complex Infesting Okra (Abelmoschus esculentus (L.) Moench) Ecosystem

A field experiment was conducted during kharif and rabi seasons, 2016 and 2017 respectively at Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat (Assam) to study the diversity of herbivores and their natural enemies in okra ecosystem. Altogether 20 species herbivores and 20 species of predators were recorded in rabi season (February to May) as against 21 species of herbivores with 20 species of predators found during kharif season (July to October) in this ecosystem. Six species of herbivores were identified as “major”, based on relative abundance and they were Aphis gossypii (Glover), Amrascabiguttulabiguttula (Ishida), Bemisiatabaci (Gennadius), Syleptaderogata (Fabricius), Dysdercuscingulatus (Fabricius) and Eariasvittella (Fabricius), in both the seasons. Among the natural enemies, Coccinella transversalis (Fabricius) and Menochilussexmaculatus (Fabricius) were recorded as the most predominant species in okra. A. gossypii, A. biguttulabiguttula, B. tabaci and S. derogata were comparatively more abundant in vegetative stage, while D. cingulatus and E. vittella in reproductive stage of okra. It was observed that, species richness (R), species diversity (H’) and evenness (E) of herbivores was more in kharif season (7.37, 2.14 and 0.74) and least in rabi season (6.90, 2.16 and 0.72) respectively. As regards to the predators, maximum species richness, species diversity and evenness of predators were found in kharif season (4.75, 2.82 and 0.89) as against rabi season (4.96, 2.74 and 0.89) respectively.