Effects of Essential Oils of Vepris heterophylla (Rutaceae) and Xylopia aetiopica (Annonaceae) on Stage II and IV Larvae of Anopheles gambiae Sensu Stricto Giles 1902

Objective: In order to control malaria through the reduction of Plasmodium spp vector populations, a study of the sensibility of A. gambiae ss stage II and IV larvae to V. heterophylla and X. aetiopica essential oils was carried out as well as their combined effect evaluated in the University of Ngaoundere, Adamawa region Cameroon from january to february 2020. Methodology: The tests consisted in evaluating the mortality of A. gambiae ss larvae in the presence of diluted solutions of the essential oils following a WHO (2005) methodology. Results: Bioassays revealed that the essential oils of both plants have remarkable insecticidal properties. At 250ppm, essential oils of V. heterophylla and X. aetiopica induced 100% mortality of stage II larvae after 18h of exposure. In stage IV larvae, the same concentration killed 100% of the larvae after 24h of exposure. The combined effect of the essential oils of the two plants on stage II and IV larvae of A. gambiae ss varied according to the proportion of combination made. In stage II larvae, the combination of V. heterophylla 50% and X. aetiopica 50% essential oils showed better efficacy (LC₅₀=42.62ppm; LH₅₀=03hr23min27sec), followed by that of V. heterophylla 25% and X. aetiopica 75% (LC₅₀=44.24ppm; LH₅₀=03hr31min21sec) and that of V. heterophylla 75% and X. aetiopica 25% (LC₅₀=53.66ppm; LH₅₀=05hr07min59sec). A similar trend was observed in stage IV larvae. Conclusion and application: In sum, due to their proven insecticidal properties against A. gambiae ss, the combination of essential oils of V. heterophylla and X. aetiopica should be highly recommended for the development of natural biocides.