The effect of Zingiber officinale and Allium sativum against adult rice weevil (Sitophilus oryzae) was conducted using dried powdered bulbs and rhizomes of garlic and ginger to ascertain its effectiveness in preservation of stored rice grains. The samples include ginger treated rice grains, garlic treated rice grains, and ginger and garlic treated rice grains at concentrations of 2g, 4g and 6g of the powdered experimental plant materials. The ginger and garlic treated rice grains was prepared at the ratio of 50%Zo : 50%As and the control sample was preserved without treatment. Mortality rate of adult S. oryzae was determined daily for a period of 21 days and compared with the control. The results shows that mean mortality of adult S. oryzae treated with two plant powders (Z. officinale and A. sativum) at various concentrations ranged from 1.22±1.093 to 1.44±0.882, 1.56±0.726 to 2.56±1.014 and 1.56±0.726 to 2.22±1.481 for ginger treated rice grains, garlic treated rice grains, and ginger and garlic treated rice grains, respectively. The lethal effect at 7 days interval was also determined and the result revealed that the mortality was highest at 21 days and least at 7 days of post treatment for Z. officinale; while A. sativum treated sample revealed that the mortality effect of was highest at 7 and 21 days and least at 14 days of post treatment. When the lethal effect was compared, A. sativum powder caused higher mortality of adult S. oryzae than Z. officinale. These results suggest that these plants are suitable for possible exploitation in protecting stored rice from damage by storage insects.
Keywords: Eco-Friendly, bio-pesticide, lethal effect, mean mortality, rice weevil
