Sustaining rice revolution through the use of Essential Oils (EOs) of plants' extracts for postharvest protection of stored rice against Sitophilus oryzae in Nigeria

Bioassay experiments were conducted to test the efficacy of essential oils (EOs) of two spice plants in controlling S. oryzae in stored rice. 50g of X. aethiopica and D. tripetala seeds were separately washed, dried and pounded into powder. Essential oils were extracted from each of the spice plants through a vacuum distillation apparatus connected to high vacuum pump. The EOs were held separately for use in the laboratory bioassay to test their repellence against S. Oryzae in stored rice. The bioassay was conducted using a 4-way Olfactometer in which some rice grains were kept side by side with each of the EOs impregnated into filter paper. The rice grains and the filter paper were placed in one arm of the Olfactometer as test arm, while the other three arms were used as control. The insect pest was placed at the center of the Olfactometer and was allowed to respond to the emissions of Semiochemicals from the rice and the volatiles from the EOs. The number of entries and time spent by the insect in each arm of the Olfactometer were recorded. All data generated were subjected to analysis of variance (ANOVA) and the means separated by Tukey’s simultaneous means separation. The number of entries was analyzed using t-test. The result showed a significant (p<0.05) repellency of the EOs to the insect pests, with EO of X. aethiopica more repellent than D. tripetala. It was therefore recommended amongst others that EOs of the two spice plants can be applied in small quantities on stored grains to serve as repellents and protectants against S. Oryzae.