Management of rice weevil, Sitophilus oryzae using essential volatile oils
Effect of four essential volatile oils viz., clove (Syzygium aromaticum L.), cinnamon (Cinnamomum zeylanicum Blume), lemon grass (Cymbopogon flexuosus (Nees ex steud)) and pepper (Piper nigrum L.) on mortality of rice weevil, Sitophilus oryzae L. in stored rice was studied under laboratory conditions. Preliminary toxicity bioassays (without food and with food) were carried for fixing the concentrations of these oils. Percentage mortality of weevils by volatile essential oils increased with increase in concentration and period of exposure. Pepper oil @ 200 μl/500 cm-3 volume caused cent per cent mortality without any progeny emergence whereas cinnamon oil @ 30 μl 500 cm-3 caused 95.55 per cent mortality of weevils with 98.81 inhibitions on progeny emergence. The highest concentration (30 μl 500 cm-3) of clove oil caused 76.67 percentage mortality of weevils while lemon grass oil (200 μl 500 cm-3) caused 68.89 percentage mortality.