Insecticidal Effect of African Nutmeg (Monodora myristica) Oil on Sitophilus zeamais and Tribolium castaneum in African Breadfruit
Abstract
This study investigated insecticidal effect of African nutmeg (Monodora myristica Gaertn) oil against Sitophilus zeamais (Motsch) and Tribolium castaneun (Herbst) in African breadfruit during storage. Fruits (400g) of African nutmeg were milled into flour. Two hundred grams (200g) of flour was extracted for oil using 500ml of n-hexane. The fruit oil at 0.0, 0.25, 0.50, 0.75, 1.00ml per 1ml ethanol was dosed against 10 adults of either insects infested on 15-20g African breadfruit seeds during post-exposure (24h), contact (7-12 days) and fumigant (72h) toxicity tests at ambient conditions (33-39oC; 42-59% RH) in Lafia, Nasarawa State, Nigeria. The oil caused dose-dependent mortality (%) which increased with exposure time of the insects. Sitophilus zeamais (Motsch) had higher mortality than Tribolium castaneum (Herbst) within the same oil concentration and exposure time. In a glass vial filled to 70% column with African breadfruit, 1ml oil concentration caused 63% kill of T. Castaneum (Herbst), but 90% kill of S. zeamais (Motsch) in 7days exposure. The 1ml oil concentration on 72hour fumigation test killed 95% of S. zeamais (Motsch) and 62% of T. castaneum (Herbst). Monodora myristica (Gaertn) oil could replace synthetic insecticides to preserve this grain against the two insect pests under storage.
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