Insecticidal Activity of Tithonia diversifolia Extract Against the Fall Armyworm (Spodoptera frugiperda): Laboratory and Semi-Field Evaluations

Abstract

Spodoptera frugiperda (Lepidoptera: Noctuidae) is a globally significant pest, causing considerable economic damage, particularly in maize crops. Botanical derivatives present promising alternatives for its management. This study evaluated the insecticidal activity of tagitin C-enriched extract obtained from Tithonia diversifolia leaf trichomes using dichloromethane as the extraction solvent by: (i) determining the most susceptible larval stage of S. frugiperda, (ii) assessing its toxicity to larvae, (iii) evaluating pest mortality on treated maize plants and (iv) determining phytotoxicity to the crop. The extract was applied at a concentration of 0.1 mg L⁻¹. Exposure resulted in 100% mortality of newly hatched larvae by the pupal stage and reduced larval weight by 91.3%. The median lethal concentration (LC₅₀) and effective concentration (EC₅₀) were 7.42 and 16.31 mg L⁻¹, respectively, while the LC₉₀ and EC₉₀ values were 32.52 and 70.02 mg L⁻¹. In maize plants treated with the extract at 325 mg mL⁻¹ (LC₉₀), newly hatched larvae reached 100% mortality within 4 days. These findings demonstrate that the dichloromethane-derived tagitin C-enriched extract from T. diversifolia has strong insecticidal activity, particularly against neonate larvae, and shows potential for development as a botanical tool for lepidopteran pest management.