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

<title>Abstract</title> Maize, the staple food of many populations, is suffering major losses due to <italic>Spodoptera frugiperda</italic>. 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 (<italic>Nauclea diderrichii</italic>), Bete (<italic>Mansonia altissima</italic>) Iroko (<italic>Milicia excelsa</italic>) on the larvae of <italic>S. frugiperda</italic>, 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 (<italic>p &lt; 0.05</italic>) 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.