Repellency, Toxicity and Chemical Composition of Different Clove (Syzygium aromaticum) Parts Against Rice Weevil (Sitophilus oryzae)

The post-harvest loss of rice during storage due to insect infestation, particularly by rice weevil ( Sitophilus oryzae ), and the utilization of synthetic insecticides for pest management are two major concerns in the current world. Therefore, this study aimed to evaluate the potential of clove ( Syzygium aromaticum ) part formulations as alternatives to S. oryzae management. The contact repellent activity of clove part essential oils was tested by the filter paper impregnated method. The fumigation mortality of essential oils was tested, and mortality percentage & LD 50 values were computed. Further, the composition of essential oils was analyzed using Gas Chromatography–Mass Spectrometry. The yield of clove stem essential oil (5.52%) was significantly higher than leaf essential oil (3.92%). Among two essential oils, stem oil with a 100 µL dose showed the highest repellency (100.00±0.00%) and mortality (96.67±3.33%) while 50 and 75 µL doses caused similar mortality (83.30±3.33%) after 5 days. The lowest LD 50 (28.06 µLL -1 ) was observed on day 5, indicating the higher toxicity of stem oil. Eugenol (73.73 & 82.56%), β-caryophyllene (24.84 & 16.67%), α.-humulene (0.82 & 0.33%) and 1S, CIS-calamenene (0.14 & 0.03%) were detected as the major components responsible for the repellent and insecticidal potential of stem and leaf essential oils. Hence, clove parts could be potential biopesticides, and clove stem essential oil could be the most effective alternative for rice weevil management.