Individual and Synergistic Effects of the Acetonic Extract of <em>Jatropha curcas </em>L. (Euphorbiaceae)<em> </em>Seeds and the Enzymatic Extract of <em>Serratia marcescens </em>Strain 81 on <em>Spodoptera frugiperda </em>(J.E. Smith)

We evaluated the individual and combined insecticidal and insectistatic activities of the acetonic extract of Jatropha curcas seeds (JcAE) and the enzymatic extract of Serratia marcescens (SmEE) against the fall armyworm Spodoptera frugiperda. An ingestion bioassay was performed using 0 ppm, JcAE (100, 250, 1000, and 2500 ppm), SmEE (40, 80, 150, and 300 ppm), or JcAE+SmEE (1000+150, 1000+300, 2500+150, and 2500+300 ppm). We determined the weight, development, and mortality of S. frugiperda larvae and pupae, identified the major components of JcAE, and evaluated the chitinolytic activity of SmEE. Mortality was compared via Fisher’s exact test, whereas continuous variables were compared via the Kruskal‒Wallis test followed by Dunn’s test. The percentage difference was also evaluated using 0 ppm as a baseline. The two highest concentrations of JcAE (1000 and 2500 ppm) and SmEE (150 and 300 ppm) resulted in significant insecticidal and insectistactic activity because they increased the cumulative larval and pupal mortality between 77.33% and 86.67%, decreased the weights of the larvae (range, -63.02% to -80.23%) and pupae (range, -8.45% to -22.72%), and retarded their development for up to 10 and 4 days, respectively. Additionally, 1000+300 and 2500+300 ppm JcAE+SmEE increased the cumulative mortality by 93.33% and 90.0%, reduced larval and pupal weights, and prolonged larval development. Seven major fatty acids were identified as the main components of JcAE, and SmEE showed exo- and endochitinase activity. JcAE and SmEE, either individually or in combination, are alternatives for sustainable biological control of S. frugiperda.