Nanoemulsion of Calotropis gigantea L. Extract: A Prospective Nanopesticide against Spodoptera frugiperda (Fall Armyworm)

Abstract

Spodoptera frugiperda (fall armyworm, FAW) is an invasive pest associated with substantial losses in maize production in Indonesia, while effective and environmentally compatible control options remain limited. This study formulated a nanoemulsion of Calotropis gigantea leaf extract (NEC) and evaluated its lethal, sublethal, and antifeedant effects against third-instar FAW larvae. NEC was prepared by homogenisation, ultrasonication, and centrifugation. Six concentrations (0, 0.4, 0.8, 1.6, 3.2, and 6.4%) were evaluated using leaf-dip and no-choice methods. Larval mortality, feeding inhibition, pupation, adult emergence, and particle size were assessed. Larval mortality was recorded 96 h after application, while feeding inhibition was assessed at 24 and 48 h. NEC showed concentration-dependent insecticidal activity, with an LC₅₀ of 1.79% and an LC₉₀ of 5.92%. At 6.4%, NEC caused 90% larval mortality, while pupation and adult emergence were reduced to 10% and 3.75%, respectively. Feeding inhibition also increased with concentration and observation time, reaching 50.02% at 48 h at the highest concentration. Particle-size analysis showed an average particle size of 266.1 nm and a polydispersity index of 1.22, indicating a relatively broad size distribution. These findings show that NEC has insecticidal and antifeedant activity against FAW under laboratory conditions. Further formulation optimisation, stability assessment, non-target testing, and field validation are required before practical application.