Chemical composition and bioactivity of essential oils against Ephestia kuehniella and their impact on beneficial parasitoid Bracon hebetor

Abstract

The present work aimed to evaluate the fumigant toxicity of essential oils extracted from five aromatic plants against Ephestia kuehniella (Zell.) and its impact on the parasitoid Bracon hebetor (Say). The chemical composition of all the essential oils showed that they were mainly composed of oxygenated monoterpenes. Among all the tested oils, Eucalyptus camaldulensis (Dehn.) oil was the most effective against both E. kuehniella larvae and adults with LC50 of 165.06 and 0.20 μL/L air, respectively. The next most toxic oil was Pelargonium graveolens (L.) oil. The mortality rate was affected by the exposure time and the concentration; E. camaldulensis reached 100% larval mortality at 300 μL/L air after 60 h. Oils had differential impact on B. hebetor, E. camaldulensis killed all the larvae within 24 h, while there was no mortality in Ocimum basilicum (L.) till day 5. The enzyme inhibitory effects of E. camaldulensis oil on acetylcholinesterase (AChE) and Glutathione S-transferase (GST) in E. kuehniella larvae were 64.46 and 51.45% respectively, which was the highest among the tested oils. These results imply that although E. camaldulensis and P. graveolens oils have potential as fumigants against E. kuehniella, their application could harm non-target beneficial insects. O. basilicum oil might be more
suitable for integrated pest management strategies because it had a potent effect on insect moths and was less toxic to B. hebetor.