Impact of extracts from three durable tropical woods from Côte d'Ivoire (Nauclea diderrichii, Mansonia altissima, Milicia excelsa) on Spodoptera frugiperda Smith, 1797 (Lepidoptera: Noctuidae) larvae in the laboratory

Abstract Maize, the staple food of many populations, is suffering major losses due to Spodoptera frugiperda. Chemical pesticides were being over-used to control this pest. But to preserve the ecosystem, it’s important to test products with a low ecological impact. Study aims to evaluate the impact of hydroalcoholic extracts of three tropical woods Badi (Nauclea diderrichii), Bete (Mansonia altissima) Iroko (Milicia excelsa) on the larvae of S. frugiperda, the main pest of maize. Different parameters be evaluate: larval mortality rate, LD50, pupation duration, rate of leaves consumed by the larvae, larval mortality rate. Young larvae were collected from untreated maize plants in field. Three doses evaluated (0.04; 0.08 and 0.1g/mL) of sapwood and heartwood extracts proved effective. Heartwood extracts were more effective than extracts from the sapwood at the 0.04g/mL dose. Contrarily, the sapwood extracts of Badi and Bete were significantly (p < 0.05) more effective than those of heartwood at the 0.08 and 0.1g/mL (100% death larvae at the first day). LD50 of sapwood extracts were 0.0535; 0.0419 and 0.0219 g/mL, respectively for Badi, Bete, Iroko. LD50 of heartwood extracts were 0.3535 (Badi) and 0.0283 g/mL (Bete). Pupation duration was longer for larvae exposed to sapwood (0.04g/mL) and shorter for those treated with duramen (0.08g/mL). Badi and Iroko sapwood (0.08g/mL) had the best antifeedant activity (0% leaves consumed). Insecticidal activity could be explained by the presence of secondary metabolites: alkaloids, flavonoids, polyphenols, tannins, observed in extracts. Studied wood extracts could be use in the formulation of bioinsecticides for sustainable control crop pests.