Evaluation of plant extracts as botanical insecticides for controlling <i>Spodoptera frugiperda</i> (Lepidoptera: Noctuidae)

The increasing incidence of Spodoptera frugiperda resistance and the adverse effects of excessive synthetic insecticide use emphasize the need to develop safer and more environmentally sustainable alternative control strategies. One promising alternative is the use of botanical insecticides. This study aimed to evaluate the bioactivity of five plant extracts, namely spiked pepper (Piper aduncum), African marigold (Tagetes erecta), Mexican sunflower (Tithonia diversifolia), sugar apple (Annona squamosa), and soursop (Annona muricata), as candidates for botanical insecticide formulations against S. frugiperda. The experiments assessed toxicity, antifeedant, and ovicidal activities. Toxicity was tested using the leaf-dipping method with five concentration levels, equivalent to LC15, LC35, LC55, LC75, and LC95. Antifeedant activity was tested using the choice method with three concentration levels, equivalent to LC15, LC35, and LC55. Moreover, ovicidal activity was tested by spraying the extract on eggs with concentrations equivalent to LC95 and 2×LC95. The results showed a positive correlation between increasing test concentrations and higher larval mortality, antifeedant activity, and ovicidal activity. P. aduncum extract showed the highest toxicity, with LC50 and LC95 values of 0.11% and 0.70%, respectively. Among the tested extracts, T. diversifolia showed the highest antifeedant activity with moderate to strong effects, while the other showed very weak to moderate effects. In terms of ovicidal activity, all extracts showed strong inhibitory effects (>75%), particularly at a concentration of 2×LC95, with P. aduncum being the most effective extract due to its highest inhibition rate. These findings indicate that each extract exhibited bioactivity in at least one parameter, supporting its potential as a botanical insecticide. P. aduncum emerged as the most promising candidate, with strong toxicity and ovicidal effects despite relatively weak antifeedant activity.