Assessment of Fall Armyworm through Combined Plant Extracts and Microbial Biocontrol Agents

The fall armyworm [Spodoptera frugiperda (Lepidoptera: Noctuidae)] is the most destructive pest of maize, and nonchemical insecticide control is required. In this study, the ethanolic extracts of neem (Azadirachta indica) and moringa (Moringa oleifera), as well as maize-associated bacterial isolates, were assessed for direct fumigant toxicity against FAW. GC-MS analysis revealed tissue-specific chemical diversity with eight important bioactive compounds, namely trimethyl fluorosilane and hexadecanoic acid from neem, whereas ethyl oleate and octadecanoic acid were detected in moringa. Eighty-nine bacterial isolates were tested for extracellular enzyme activities (cellulase, chitinase, glucanase, and protease) and siderophore production, among which 4 strains designated as DR-55 (Bacillus subtilis), HL-7 (Bacillus cereus), HL-37 (Bacillus cereus), and DR-63 (Enterobacter sp.) expressed >50% biocontrol activity under greenhouse conditions. Larval mortality of FAW varied depending on the stage, being higher (80-88%) in larvae, moderate (15-17%) in pupae, and low (6-7%) in adults, with LC₅₀ values of 2.16, 1.28, and 1.85, respectively. High relationships were found between in vitro antagonism and the efficacy under field conditions (r = 0.73-0.88), confirming the predictive performance of laboratory screening methods. These findings suggest that the addition of plant bioactive extracts to maize-associated microbial isolates offers a strong and non-hazardous stage-targeted integrated pest management practice, which can effectively suppress FAW while maintaining the good health of the maize plant, even with reduced application of synthetic insecticides.