Seasonal variation in chemical composition, insecticidal and repellent activities of Conioselinum smithii (Apiaceae) essential oils against stored-product insects
摘要
Widely used chemical insecticides pose significant risks to food safety through residue accumulation. Consequently, the development of safe and effective bio-insecticides has become a research priority. Essential oils (EOs) from medicinal plants have demonstrated notable insecticidal activity against stored-product pests. This study characterized the chemical composition of EOs from the aerial parts and roots of Conioselinum smithii (Apiaceae) collected from May to October and evaluated their insecticidal and repellent activities against Tribolium castaneum and Liposcelis bostrychophila. The highest EO yield was observed in September (root: 2.13%; aerial parts: 1.02%). Chemical analysis revealed that the aerial EOs were dominated by sesquiterpenoids and phthalides, whereas the root EOs primarily contained phthalides and monoterpenoids. Furanoeudesma-1,4-diene (23.52%–48.25%) and neocnidilide (30.30%–34.99%) exhibited the highest relative percentages in samples. The chemical compositions of the EOs collected in different months were correlated, with samples 7LD, 9LD, and 10LD exhibiting similar profiles, as did 6LG, 8LG, 9LG, and 10LG. A significant positive correlation was observed between 6LG and 22LG, 5LG, 8LG, and 9LG (p < 0.001). The EOs exhibited contact toxicity against both insects. For L. bostrychophila, the root EO collected in May showed the strongest toxicity (LC₅₀ = 17.68 µg/cm²). For T. castaneum, the aerial EO collected in May exhibited the strongest contact toxicity (LD₅₀ = 41.55 µg/adult). Certain C. smithii EO samples exhibited repellent activity superior to that of DEET: root EOs collected from June to September and aerial EOs from September showed enhanced repellency against T. castaneum, whereas root EOs collected in May, June, and August, along with the aerial EO from May, exhibited stronger repellent effects against L. bostrychophila. These findings indicate that C. smithii EOs exhibit promising insecticidal and repellent properties, supporting their potential as plant-based agents for stored-product pest management.