Abstract: Beauveria bassiana isolated locally from the larvae of Bombyx mori was evaluated at different concentrations viz. 1x108, 1x106, 1x104 and 1x102 spore mL-1 against white grub (Holotrichia sp.) for dose optimization of this fungus. It was observed that among these concentration 1x108 spore mL-1 was the most promising one, showing initial mortality very early and cent per cent in a shorter period of time. The mortality in general in each treatment was recorded in the order of 1x108, 1x106, 1x104 and 1x102 spore mL-1. This spore concentration viz. 1x108 of B. bassiana was tested against different stages of white grub (Holotrichia sp. ) to determine the comparative susceptibility of different stages to this fungus. It was observed that initial (56.66%) mortality occurred on 4th day and cent percent on the 10th day, respectively in case of 1st instar. The initial mortality (46.66 and 43.33%) in 2nd and 3rd instars was recorded on 4th and 6th day and 100% mortality on 12th and 16th day, respectively. These results showed that 1st stage grubs were more susceptible followed by 2nd and 3rd instar grubs.