author(s)
K Devaki, T Murali Krishna and KV Hariprasad

abstract
A total of 203 B. thuringiensis strains were collected from 925 soil samples covering different soil environments of Chittoor, Kadapa and Nellore districts of Andhra Pradesh. These strains were bioassayed against Spodoptera litura in laboratory studies and identified 28 potential strains which were developed into solid and liquid formulations to test against S. litura under field studies. The results revealed that, S. litura larval population ranged from 7.0 to 22.5 No/metre row and it was low in three strains F493 (7 larva/m row), F504 (7.5 larva/m row), C33 (7.5 larva/ m row) which were superior over the other strains as well on par with standard check HD-1 (7.5 larva/m row). In untreated control a larval population 22.5 larva/m row was recorded. The defoliation at 7 days after spray was low in F493 (14.93%) and HD-1 (16.87%) which were superior over the other treatments, whereas, in untreated control the damage was 40.15%. The same strains were effective in liquid formulations which were equivalent with HD-1. Highest pod yield was recorded in HD-1, F493 and F504 treated plots. From the present studies, it is again proved that, B.thuringiensis based biopesticides are effective in controlling S.litura and solid formulations were effective compared to liquid formulations.