Due to economic importance of diamondback moth pest and
resistance to conventional insecticides, it is necessary to use novel and
suitable compounds in control programs. Therefore, we evaluated the toxicity of
Bacillus thuringiensis to four instars larvae of diamondback moth, Plutella
xylostella (L.). In this study 1st, 2nd, 3rd and 4th instars larvae were
exposed to different concentrations of Bacillus thuringiensis. The
exposure times were 24, 48 and 72 h for oral trials. Experiments were performed
in complete randomized block design with four replications. After treatment the
samples were held under constant conditions in laboratory rearing room (25±2^oC,
50±5% RH and 14 and 10 hrs. L: D  photoperiod).
The maximum mortality rate for 1st, 2nd, 3rd and 4th instars larvae in 90, 140,
200 and 250 ppm of Bacillus thuringiensis was achieved 98.33, 97.67, 96.67
and 90% after 72 h, respectively. Our results suggest Bacillus
thuringiensis could be an important agent in control of larval instars
of Plutella xylostella.