Evaluation of Bacillus thuringiensis Berliner subsp. kurstaki for management of lepidopteran pests of lac insect

摘要

Field trials were conducted to evaluate the commercial formulation of Bacillus thuringiensis Berliner subsp. kurstaki against two key lepidopteran predators viz., Eublemma amabilis Moore and Pseudohypatopa pulverea Meyr of lac insect on rainy season crop of rangeeni lac insect culture reared on the trees of Butea monosperma (palas). Bt formulations with all the concentrations tried (0.008, 0.017, 0.034, 0.05, 0.07, 0.085 per cent) significantly reduced the incidence of predators and increased the yield of broodlac over control. Two sprays of Bt formulation (0.05%) at an interval of one month (30 and 60 days of inoculation) significantly reduce the incidence of both the lepidopteran predators and increased the yield of broodlac significantly. However, single spray of Bt formulation at a concentration of 0.07% will also reduce the incidence of lepidopteran predators and increase the broodlac yield significantly. In order to get the desired efficacy of biopesticide as with chemical pesticides in suppressing the predators population, the application of Bt formulation at a concentration of 0.07% was found to be effective. The increase in broodlac yield amongst various treatments of biopesticide varied to the tune of 4.2-10.2 fold with single spray and3.2-11.8 fold with double spray of Bt formulation.