Juvenomimetic and insecticidal activities of Senecio salignus (Asteraceae) and Salvia microphylla (Lamiaceae) on Spodoptera frugiperda (Lepidoptera: Noctuidae).
Plant extracts can be used as an alternative to synthetic insecticides for the control of insect pests. Based on this knowledge, juvenomimetic and insecticidal activities of n-hexane extracts of the aerial parts of Senecio salignus DC. (Asteraceae) and Salvia microphylla Kunth (Lamiaceae) collected in Mexico were evaluated against 1st instar larvae of Spodoptera frugiperda Smith & Abbot (Lepidoptera: Noctuidae). Senecio salignus extract showed insecticidal activity at 500 ppm, resulting in larval mortality of 52.5% and pupal mortality of 62.5%. Salvia microphylla extract at the same concentration caused larval mortality of 65.0% and pupal mortality of 82.5%. The LC50 was 440 ppm for S. salignus extract and 456 ppm for S. microphylla extract based on the total larval period. The juvenomimetic activity of S. salignus extract at 500 ppm increased the duration of the larval period to 17.3 d and of the pupal period to 1.4 d. It also reduced pupal weight by 34.7% with respect to the control (241 mg). For S. microphylla extract at 500 ppm, the duration of the larval and pupal periods were increased by 2.0 and 12.1 d, respectively, and the pupal weight was reduced by 14.1% with respect to the control (243 mg). The major compounds of S. salignus extract were γ-sitosterol, palmitic acid, lupeol, and β-amyrin, and those of S. microphylla extract were oleic acid, γ-sitosterol, (Z,Z,Z)-9,12,15-octadecatrien-1-ol, and palmitic acid. These results indicate that both extracts have potential to be used to control S. frugiperda due to their juvenomimetic and insecticidal activities.