1Biotechnology Centre, Punjab Agricultural University, Ludhiana-141 004, Punjab (India).
2Department of Plant Breeding, Punjab Agricultural University, Ludhiana-141 004, Punjab (India).
Spore-crystal (SC) preparations from 7 out of 9 Bacillus thuringiensis (BT) strains exhibited more than 90 per cent mortality in Chilo partellus (Swinhoe) larvae. The dose vs. mortality curve suggested that SC-preparation from BT strain HD-1 (94% mortality at 0.05 mg/ml level) proved to be the most effective bioinsecticide with lowest LD50 (7.62 x 10−4 mg/ml) for the control of C. partellus. Two other BT strains, viz., HD-73 and HD-263 with 97 and 99% larval mortality at 0.1 mg/ml level and LD50 values of 1.69 x 10−3 and 1.85 x 10−2 mg/ml, respectively also proved promising. The susceptibility of C. partellus Larvae declined with the age. Younger larvae (up to 56 h in age) exhibited high susceptibility to HD-1 SC-preparation. However, sharp decline in mortality was observed with ageing of larvae beyond 72 h.
