Efficacy of Bacillus thuringiensis var. kurstaki and NPV against tea looper, Hyposidra infixaria Walk. (lepidoptera: Geometridae)

Effect of Bacillus thuringiensis var kurstaki on 3^rd instar larvae of H. infixaria was studied. On 7^th day after treatment lowest (50%) and highest (96.43%) mortality were provided by Bt kurstaki @ 0.5 g/lit and 2 g/lit, respectively. On 10^th day after treatment Bt kurstaki @ 2 g/lit provided cent percent mortality, whereas, 94.64%, 89.29% and 82.14% mortality were given by Bt kurstaki @ 1.5 g/lit, 1 g/lit and 0.5 g/lit, respectively. Pathogenicity tests were positive. bioassay study with nuclear polyhedrosis virus on H. infixaria was carried out. the lc₅₀ value of 2.7 × 10 PIb/ml concentration at 9^th day termination of experiment was observed against 7 day old larvae. At 11^th day the lc₅₀ value was observed to be 8.32 × 10⁴ PIb/ml. Similarly in case of 11 day old larvae higher lc₅₀ value of 7.81 × 10⁵ PIb/ml was recorded at 9^th day termination of experiment in comparison to the lc₅₀ value of 1.44 × 10⁵ PIb/ml at 11^th day termination of experiment.