The potency of the green algae Chlorella vulgaris and Bacillus thuringiensis as biocides against Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae).

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 2^nd and 4^th 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 2^nd and 4^th 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 2^nd and 4^th 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 2^nd and 4^th 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]