Abstract: Previous lab report (Karim et al., 1999) had shown the efficacy of CAMB Bacillus thuringiensis preparation in potato field to control Helicoverpa armigera. In present study, CAMB Bt formulations based on locally isolated Bt strain were checked against 1st to 4th instar larvae of H. armigera by incorporating Bt proteins into artificial diet. Early instars showed significant susceptibility to Bt formulation. Laboratory assays of stored CAMB Bt formulations did not show any significant change in their toxicity towards H. armigera larvae in laboratory assays. Potency of stored Bt formulations for 12 and 24 months were also tested in small scale experiment conducted under contained conditions on tomato crop. All formulations were found effective to control H. armigera larvae in tomato crop. The present study shows that CAMB Bt formulation can be used in field applications to control target pests after long storage time.