Chemical Composition and Insecticide Efficacy of Essential Oils from Citrus medica L. var. sarcodactylis Swingle Against Tribolium castaneum Herbst in Stored Medicinal Materials

To develop botanical pesticides and repellents against stored-product insects, the chemical composition and insecticide properties of the essential oil from Citrus medica L. var. sarcodactylis Swingle were investigated. The essential oils from leaves and fruits of C. medica var. sarcodactylis were extracted by hydrodistillation and their chemical composition was analyzed by gas chromatography/mass spectrometry. The two essential oil samples as well as their major components were comparatively evaluated for fumigant, contact and repellent activities against adults of Tribolium castaneum Herbst. GC/MS results demonstrated that leaf essential oil of mainly consisted of monoterpenoids (63.6 %) and sesquiterpenoids (32.8 %). Fruit essential oil had large amounts of monoterpenoids (80.5 %) and aromatic compounds (15.2 %). Main components detected in the leaf essential oil were limonene (33.5 %), β-caryophyllene (18.2 %) and 3-carene (10.8 %), and in the fruit essential oil included limonene (38.7 %), γ-terpinene (28.0 %) and o-cymene (15.2 %). Results of bioassays indicated that the leaf essential oil and the fruit essential oil had strong fumigant effect, contact toxicity and repellency against T. castaneum. Notably, the fruit essential oil was highly effective and sustained a long duration in repellent assays at the concentration range of 78.63-3.15 nL/cm2. β-Caryophyllene exhibited good contact toxicity and repellency but failed to cause mortality of the target insects in fumigation. γ-Terpinene and o-cymene was potently toxic to T. castaneum in fumigant and contact assays while showed weak or even no repellency. This work confirmed the potent efficacy of C. medica var. sarcodactylis based on active substances in pest management and provided some evidence for its comprehensive development and utilization in bio- insecticides and repellents.