Comparative Study of the Insecticidal Activity of Essential Oils Obtained by Hydrodistillation of Dried Leaves From Two Myrtaceae Species Callistemon Viminalis and Melaleuca Leucadendra Against Sitophilus Zeamais (Motschulsky, 1855)

Background: Post-harvest maize storage is threatened by Sitophilus zeamais, a major pest in sub-Saharan Africa, traditionally controlled using synthetic insecticides with recognized toxicological concerns. Aim: This study compared the bioinsecticidal potential of essential oils (EOs) from dried leaves of Callistemon viminalis and Melaleuca leucadendra, obtained by hydrodistillation and characterized by GC/MS. Methods: Insecticidal activity was evaluated against adult S. zeamais at four doses (D1-D4), with corrected mortality monitored over 29 days. Data were analysed using three-factor ANOVA (Plant × Dose × Time) followed by Tukey’s test. Results: EO yield was significantly higher in C. viminalis (5.032 ± 0.014%) than in M. leucadendra (1,684 ± 0,210%). GC/MS revealed contrasting chemical profiles: C. viminalis contained phenylpropanoids (eugenol, meta-eugenol and methyleugenol; 16.94%) and phytol (12.21%), whereas M. leucadendra was dominated by hydrocarbon sesquiterpenes, mainly β-humulene and aromadendrene (53.01%), with no phenylpropanoids detected. C. viminalis produced rapid and pronounced insecticidal activity, reaching 99-100% mortality within 24 h, with an overall mean mortality of 81.00%. In contrast, M. leucadendra showed lower efficacy (40.7%) and a marked dose-dependent response. The difference was highly significant (F = 154.84; p < 0.001). Conclusion: C. viminalis appears more promising for botanical protection of stored maize, potentially due to the combined effects of its major bioactive constituents.