Repellent efficacy of essential oils and plant extracts against Tribolium castaneum and Plodia interpunctella

This study was conducted to investigate the repellent efficacy of essential oils (Origanum vulgare,Pimpinella anisum, andTanacetum cinerariifolium) and four plant extracts (Agastache rugosa,Capsicum annuum,Citrus reticulata, andGinkgo biloba) againstTribolium castaneum(adults and larvae) andPlodia interpunctella(larvae). Gas chromatography/mass spectrometry analysis revealed the presence of carvacrol, anethole, and jasmolin I as the predominant constituent inO. vulgare,P. anisum, andT. cinerariifolium, respectively. Furthermore, ethyl hexopyranoside, 9,12-octadecadienoic acid, cyclopentanol, and 2-cresol were identified inA. rugosa,C. annuum,C. reticulata, andG. biloba, respectively. The repellent efficacy of each essential oil, plant extract, and the combination of oils was evaluated using a specially designed cylinder trap for 120 h. Among the three oils,O. vulgareandT. cinerariifoliumhad greatest repellent efficacy againstP. interpunctellalarvae.T. cinerariifoliumexhibited effective repellence against the adults and larvae ofT. castaneum. Therefore,O. vulgare(O) andT. cinerariifolium(T) were selected for further investigation of combined effects. Two essential oils were mixed in three different ratios of OT1 (1:3), OT2 (1:1), and OT3 (3:1). The repellent efficacies of OT1 and OT2 against the adults ofT. castaneumwere significantly greater than that of OT3. OT1 was effective against the larvae ofT. castaneum, whereas OT2 was effective against the larvae ofP. interpunctella. OT1 enhanced the repellent efficacy by approximately five times against larvae ofT. castaneum, compared with that ofT. cinerariifolium. Overall, OT1 was selected as the best repellent substance against all the tested insects.