Fifth instar larvae of the new bivoltine hybrid (CSR2 ${ imes}$ CSR5) were reared under different temperature and humidity viz., $20^{circ}C$ and 85 ${pm}$ 5% R.H (T1), $25^{circ}C$ and 70 ${pm}$ 5% R.H (T2-Optimum), $30^{circ}C$ and 80% ${pm}$ 5 R.H (T3) and $35^{circ}C$and 50 ${pm}$ 5% R.H (T4). The cocoon yield, cocoon characters and disease incidence were studied in normal (non infectious source, i.e control) rearing as well as in 1% infectious source of rearing. The results indicated that V instar larval duration was prolonged and cocoon weight was improved in T1. ERR and shell ratio were significantly improved and disease incidence was minimised in T2. Further significant difference was observed among the treatments with regard to spread of diseases.