Field Efficacy of Selected Synthetic and Botanical Insecticides against Lepidopterous Borers, Earias vittella and Helicoverpa armigera (Lepidoptera: Noctuidae), on Okra (Abelmoschus esculentus (L.) Moench)

Okra (Abelmoschus esculentus (L.) Moench) is an important summer vegetable in many tropical and subtropical countries of Africa and Asia. However, okra production is hampered by the incidence of many insect pests. Particularly, okra shoot and fruit borer (Earias vittella) and okra fruit borer (Helicoverpa armigera) cause substantial quantitative and qualitative losses to okra crop. In this study, 18 pesticides including conventional and new-chemistry synthetic insecticides and different botanical extracts were screened against these pests on okra variety 'Pusa Sawani' under field conditions during 2015 and 2016 in a randomized complete block design. The average number of lepidopterous larvae in plots treated with the synthetic insecticides was 1.87 and 2.12 larvae/plant in 2015 and 2016, respectively, compared with 6.5 larvae/plant in untreated control plots. For the botanicals, an average of 2.57 and 2.92 larvae/plant was recorded in 2015 and 2016 respectively, compared with 4.12 in untreated control plots. Among the synthetic insecticides tested, emamectin benzoate and indoxacarb caused the most significant reduction of okra borers, followed by abamectin and lambda-cyhalothrin. While among the botanicals, Azadirachta indica, Citrullus colocynthis and Nicotiana tabacum caused the most significant reduction of okra borers in both years, followed by Curcuma longa and Corymbia citriodora. These synthetic insecticides and botanicals on average reduced okra fruit infestation by 20 to 56% and by 18 to 10%, respectively, and increased okra fruit yield up to 45%. We therefore recommend their integration in biorational IPM programmes against lepidopterous borers of okra and other vegetables.