The relative susceptibility of Diamondback moth, Plutella xylostella L. to Bacillus thuringiensis Berliner was studied in larval population of three locations viz., Oddanchatram, Nilgiris and Coimbatore of Tamil Nadu. The studies showed that population from Oddanchatram required a higher level of LC50 for endosulfan, quinalphos and fenvalerate than that of Nilgiris and Coimbatore population, but these population were equally susceptible to B. thuringiensis. The differential susceptibility may be attributed to the differences in the pesticide use patten, intensity and temperature conditions.
