Effect of Probiotics Lactobacillus Plantarum and Sporobolomyces Roseus on rhe Growth, Cocoon Parameters and Survival of Silkworm Bombyx Mori (L.) and Tolerance to Bombyx Mori Nuclear Polyhedrosis (Bmnpv) K.K.Singh, R.M.Chauhan, A. B. Pande and S. B. Gokhale Abstract Use of probiotics is recognized in preventing selective infections in human beings and animals and also for improving economic characters in the silkworm Bombyx mori. In sericulture industry, major economic losses are due to a viral epidemic Nuclear Polyhedrosis Virus (BmNPV). Present study deal with understanding the role of probiotics namely Lactobacillus plantarum and Sporobolomyces roseus with respect to economic parameters of Bombyx mori (L.) and tolerance to BmNPV infection. Individual supplementation of probiotics (namely L plantarum and S roseus) to silkworm larvae (4th instar) before and after (24hrs respectively) infection with BmNPV showed increase in larval weight, cocoon wt. and shell wt. as compared to control groups (BmNPV and non-infected).Significantly, prior supplementation (24hrs before) with probiotics L plantarum to the group showed highest tolerance (in terms of survival of larvae, cocoon and pupae formation) to BmNPV infection. Interestingly, group of larvae supplemented with S.roseus didn’t show marked difference in pupae formation after infecting with BmNPV. The group of larvae supplemented with mixed culture (L.plantarum + S.roseus) showed adverse effect on survival of larvae and pupae with respect to control (BmNPV and non-infected) groups. Results indicated that the supplementation probiotics L.plantarum is not only useful for improving the economic characters but also increasing the tolerance level of silkworm B.mori during BmNPV infection. The probiotics may influence the host native microbiota (directly or indirectly) leading to modulation of gut micro-flora, and innate immunity leading to tolerance to BmNPV. Key words: Probiotics, Lactobacillus plantarum, Sporobolomyces roseus Cocoon production, survival of larva and pupae, Bombyx mori (L.) and nuclear polyhedrosis virus