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Background: Nowadays, the fall armyworm, Spodoptera frugiperda (J.E. Smith) FAW, is the most *destructive crop pest invading maize in different countries. Objective: This study holds significant implications for the field of pest management. It aims to assess the efficacy of crude algal extract of Chlorella vulgaris and Bacillus thuringiensis strain against the 2nd and 4th larval stages of the fall armyworm, a pest currently causing significant damage to maize crops. Methods: A rigorous research process was followed, using serial concentrations of bioagents to determine the mortality percent and LC50 values via a feeding technique. Results: Regarding the effect on the biological aspects, LC50 values were fed to the 2nd and 4th larval instar. In addition, histological investigations were checked. The results indicated that the high mortality percents were 90% and 60 % at the concentrations of 20000 ppm of algal extract, recording LC50 values of 10027.42 and 15805.06 ppm for the 2nd and 4th larval instar, respectively. Furthermore, bacterial strains induced 100% and 60 % mortality at the concentrations of 1000 ppm with LC50 values of 232.50 and 883.46 ppm for the 2nd and 4th larval instar, respectively. Moreover, feeding these compounds caused alterations in the mid-gut tissue and disturbances in the life cycle of the fall armyworm. Conclusions: The algal extract and the bacterial strain have demonstrated a significant toxic impact on the fall armyworm and could be involved in the integrated management protocol of this pest. [ABSTRACT FROM AUTHOR]