Evaluation of Moringa Oleifera (Lam) (Moringaceae) Seed Oil For Larval Control of Aedes Aegypti L. (Diptera: Culicidae)

Abstract

Comparative bioassays were carried out with 1^st and 4^th instar larvae of Aedes aegypti L. (Diptera: Culicidae) using Moringa oleifera seed oil. This was to investigate whether the oil extract would show lethal effects on the mosquito larvae and to further establish at which point during the larval growth the oil would be effective. The larvae were exposed at ambient laboratory temperatures of 28 ± 2⁰C, 80 ± 5% r.h and photoperiod of 12:12 light and dark hours. Seven dosages of 200, 100, 50, 25, 12.5, 6.25 and 3.125 µl of oil dissolved in acetone per millilitre of water and control treatments with ordinary acetone were included in the trials. These were arranged on the laboratory bench in a Completely Randomised manner. Larval mortality was recorded at 3, 6, 9, and 12 hours post treatment. Mortality data were subjected to analysis of variance and log-probit regression, accordingly. Results showed that significant (P<0.05) dosage-related morality responses were noted for both instars. Thus, Moringa oil showed significant (P<0.05) toxic action against all larval instars of Ae. aegypti tested. Higher concentrations of the oil resulted in higher kill of the larvae within 12 hours, while sublethal dosages gave low mortality rates. The LD₅₀ values determined were 208.35 µl/ml and 62.94 µl/ml for the 4^th and 1^st instar larvae, respectively. The present studies therefore, demonstrate that moringa seed oil exhibits significant toxic action against all larval instars of Ae. aegypti especially the 1^st instar. Higher levels of toxicity with increasing larval mortality were achieved with increasing dosage levels and longer exposure time.