Renu Kumaria & Prabha Rania*
*aDepartment of Zoology, Patna University, Patna, Bihar, India
Received 9th June, 2012; Revised:5th August, 2012
Abstract : The tobacco caterpillar (Spodoptera litura) is a polyphagous insect attacking a number of plants, is also one of the most serious common pests of cauliflower crop. All the 1st to 4th instar larvae infesting plant of cauliflower by eating leaves and curds, but, the 5th instar larva spoiled the curd with excreta. It has developed resistance to several synthetic insecticides. So, the biopesticide named Bt. formulation has used for pest control. They are not only effective against pests but, are also safer to environment. Bacillus thuringiensis commonly known as Bt. is one of the promising biopesticides, useful for the control of insect pests. So many registered formulations of Bt. have been developed under different trade names such as bioasp, biobit, biolep, dipel, halt, thuricide etc., of which bioasp is one of the most prominent formulation effective against lepidopteron pests. Therefore, experiment were concerned to study the effect of Bt. formulation (Bioasp) as biopesticide on the rate of mortality of all 1st to 5th instar larvae of S. litura. For these five treatments of following concentration like, 0.05%, 0.1%, 0.2%, 0.3% and 0.4% were taken along with untreated control measure. After experiment it was observed that almost all the Bt. treatments were effective in varying degree and were significantly different from the control measure. The larva of 1st instar showed cent percent mortality % of Bt. gave 85% and 90% mortality respectively. In 2nd instar larvae, within 48 hours at the concentration ranging from 0.2 to 0.4% while 0.05 and 0.1appreciable reduction was noticed only at 0.2% to 0.4% of Bt., wherein, 0.4% gave cent percent mortality of 2nd and 3rd instar larvae. The remaining stages of Spodoptera litura exhibited poor response to low concentration of Bt. and their mortality rate increased with concentration.
Key words: polyphagous, Spodoptera litura, Bt. formulation, biopesticides, Bacillus thuringiensis and cauliflower.