Investigation on bio-efficacy, LD50 and LT50 of Steinernema carpocapsae against Spodoptera litura

Bio-efficacy of S. carpocapsae was studied against Tobacco caterpillar under laboratory conditions. The per cent mortality of insect larvae was recorded after every 12 hrs up to 168 hrs at different inoculum levels viz., 100, 200, 300, 400 and 500 IJs per Petri plate (5 larvae/Petri plate). The experimental results revealed that maximum (100.00) per cent mortality of S. litura was recorded within 72 hrs of exposure at an inoculum level of 500 IJs of S. carpocapsae. While, minimum 50 per cent mortality of S. litura was observed after 72 hrs at 100 IJs per Petri plate. After 132 hrs 100 per cent mortality of S. litura was recorded at all inoculum levels viz., 500, 400, 300, 200 and 100 IJs per Petri plate, respectively. The LD50 values after 12, 24, 36, 48, 60, 72, 84 and 96 hrs of exposure were 959.4, 469.9, 325.1, 219.8, 152.1, 77.8, 49.09 and 16.26 IJs per Petri plate (5 larvae/ Petri plate), respectively and the LT50 values recorded were 68.2, 50.23, 40.83, 31.7 and 23.04 hrs, at inoculum levels of 100, 200, 300, 400 and 500 IJs per Petri plate, respectively. S. litura was found highly susceptible to S. carpocapsae and the mortality of insect larvae further increased with an increase in the inoculum levels and period of exposure.