Toxic potential of some indigenous plant oils against the rice weevil, Sitophilus oryzae (Linnaeus)
2019
Khan, Hafiz Azhar Ali | Akram, Waseem | Lee, Sumi | Ahmad, Taskeen | Maqsood, Kamran | Khan, Hassan Ali | Nazir, Muhammad Waqas | Javaid, Muhammad Faisal
The present study was conducted to evaluate the toxic potential of five indigenous plant oils: black pepper (Piper nigrum), Chinese cinnamon (Cinnamomum cassia), garlic (Allium sativum), river red gum (Eucalyptus camaldulensis), and yellow oleander (Thevetia peruviana), against laboratory reared Sitophilus oryzae adults. The bioassays were done by the diet incorporation method with concentrations ranging from 50 ppm to 500 ppm. Based on lethal concentrations to kill 50% (LC₅₀) of the subjected weevils, T. peruviana proved to be the most toxic having the lowest LC₅₀ values, 414.58, 201.94, and 129.52 ppm, after 7, 14, and 21 days of exposure, respectively, followed by E. camaldulensis (475.51, 366.65, and 251.28 ppm, respectively). The rest of the plant oils also showed toxic potential, but these were less toxic compared with T. peruviana and E. camaldulensis. With respect to the time taken to cause 50% mortality (LT₅₀) of the exposed weevils, T. peruviana had LT₅₀ at 14.54 days followed by P. nigrum (22.09 days), E. camaldulensis (24.29 days), and C. cassia (28.71 days). Whereas, A. sativum took the longest time (44.47 days) to cause 50% mortality of the exposed weevils. In conclusion, the result revealed toxic potential of tested plant oils, and suggests further studies under simulated‐field conditions should be included in the management plan for S. oryzae.
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