Comparative bioefficacy of different insecticides against fruit and shoot borer (Leucinodes orbonalis Guenee) of brinjal and their effect on natural enemies

Background: Brinjal (Solanum melongena Linn.) is the fourth most important vegetable grown after potato, onion, and tomato in India. This vegetable crop is primarily grown by small and marginal farmers and it is an important source of income for them. Brinjal production faces a number of problems which cause enormous yield losses. Fruit and shoot borer (Leucinodes orbonalis Guenee) is the most devastating insect pest of brinjal, which causes 60-70% yield loss, besides deteriorating product quality. Due to increasing levels of resistance of L. orbonalis to different insecticides, there is an urgent need to test new chemicals. Objective: An experiment was carried out at Instructional Farm of Uttar Banga Krishi Viswavidyalaya to evaluate the efficacy of four insecticides, viz., carbosulfan 25 EC, emamectin benzoate 5% SG, lamda-cyhalothrin 5% EC, and fenpropathrin 30% EC at different doses during rabi season 2013 and 2014. Materials and Methods: The research design was followed in the present investigation is randomized block design with four treatments at different doses including an untreated check. There were three replication were taken for each treatment. Result: On the basis of pooled means, the result revealed that the application of carbosulfan 25 EC at 375 g a.i./ha was found most economical, resulting in minimum shoot and fruit infestation 7 days after application (2.00% and 5.93%) and 15 days after application (3.33% and 11.67%), respectively, with a highest marketable yield (9.23 q/ha) followed by fenpropathrin 30% EC at 100 g a.i./ha with the shoot and fruit infestation 7 days after application (3.33% and 8.15%) and 15 days after application (5.33% and 12.89%), respectively. The insecticides also offered good protection against the borer but both were found highly toxic and unsafe for natural enemies. An account of natural enemies was also taken from the plots and highest population was recorded from the control plot (Coccinellid - 8.07, Syrphid fly - 2.21, Dragonfly - 0.74, Damsel fly - 0.57, Spider - 0.62/plant, respectively). However, shoot and fruit infestation was brought down and marketable yield increased to some extent. Conclusion: It is, therefore, suggested that the spray of carbosulfan 25 EC, being the most effective and economically viable insecticides, can be utilized as a valuable chemical component in integrated pest management to manage the L. orbonalis in brinjal crop.