In nature, the population of Nosema bombycis (Microsporidia) causing pebrine disease is small and their development is extremely slow and only few ultimately producing spores. Pebrine infected silkworm, Bombyx mori larvae collected from sericulture field were alive till $3^{rd}$ generation though the concentration of N.bombycis spore was very high ($2.4-3.0{ imes}10^8$ spores. $mL^{-1}$). All larvae were died during $4^{th}$ generation with extremely high concentration of pebrine spores ($3.0-4.0{ imes}10^9$ spores. $mL^{-1}$) and mostly contain long polar tube (LT). Alternately, all larvae were died immediately (at $3^{rd}$ stage of $1^{st}$ generation) when it was artificially inoculated with same concentration of N.bombycis spores harvested from field ($2.4-3.0{ imes}10^8$ spores. $mL^{-1}$) though concentration of spores harvest was very less ($3.0-4.0{ imes}10^6$ spores. $mL^{-1}$) and mostly contain short polar tube (ST). Artificially pebrine infected male moth when mated with healthy female moth took six generations to develop pebrine disease and all larvae were died at the $2^{nd}$ stage with very less spore harvest ($3.0-10.0{ imes}10^6$ spores. $mL^{-1}$). Survival percentage was increased in all generations (~92.0% at $4^{th}$ generation) when silkworm rearing was conducted under new integrated disease management system.