Insecticidal and repellent activities of Cananga odorata leaf essential oil against Sitotroga cerealella, a post-harvest pest of rice

Rice in storage is increasingly attacked by Sitotroga cerealella, a highly destructive and economically important pest. The use of plant extracts, especially essential oils, is a natural alternative to synthetic insecticides in crop pest control. This study determined the chemical composition of the essential oil of Cananga odorata leaves and evaluated its biological properties, the insecticidal and insect repellent effect of the oil against Sitotroga cerealella. The essential oil was obtained by hydro-distillation, and analyzed by gas chromatography-mass spectrometry (GC-MS). Fumigation tests were carried out to evaluate the ovicidal, larvicidal, insecticidal and anti-oviposition properties of the oil on the insect and its insect repellent effect was determined using an olfactometer. The analysis showed that the oil contains 32 main compounds, the major ones being α-pinene (7.0 %), lavandulyl acetate (7.2 %), caryophyllene (30.3 %), α-humulene (13.4 %) and germacrene D (9.0 %). C. odorata essential oil showed high adulticidal toxicity with values CL50 of 0.094 µl/mL/L air and CL90 of 0.46 µl/mL. This oil has ovicidal and larvicidal or egg development retardant properties. It also caused strong oviposition inhibition activity with an insect repellency rate of 75.7 %. Its insecticidal effects preserved grain weight, with weight losses of no more than 0.38 % and a germination rate of paddy rice seeds of over 80 %. The essential oil from the leaves of the C. odorata can be used as an alternative to modern toxic synthetic chemicals, for protection against Sitotroga cerealella.