Chemical compositions and insecticidal activities of Tetradium ruticarpum essential oils against Lasioderma serricorne

Abstract

Stored products are susceptible to insect infestation. Many plant essential oils (EOs) have been used to control various pests, and compared to conventional pesticides, these natural products generally pose lower risks to humans and the environment. This study aimed to evaluate the insecticidal and repellent properties of EOs extracted from Tetradium ruticarpum (formerly Euodia rutaecarpa) fruits at different collection times against Lasioderma serricorne. EOs were obtained through hydrodistillation and analyzed using gas chromatography-mass spectrometry (GC-MS). The oil yield was 1.18 v/w. A total of 41 compounds were identified, with monoterpenes dominating in most samples. Except for the TRF-7 sample, where the main compound was 1,3-dicyclohexylpropane (45.9%), the predominant compound in all other EOs was 3-carene, with contents exceeding 87%. According to Principal Component Analysis (PCA), the composition of TRF-7 EO differed significantly from the other EOs due to the different collection times. The bio-assays showed that EOs demonstrated strong contact toxicity and repellent effects against L. serricorne, but fumigant toxicity was relatively weak. Among the tested samples, TRF-2 and TRF-4 exhibited the highest contact toxicity, with LD₅₀ values of 2.76 mg/L air and 4.08 mg/L air, respectively. Repellency was effective at higher concentrations but diminished with lower doses and extended exposure. These results suggest that EOs from T. ruticarpum fruits hold potential as botanical insecticides for protecting stored products.