Evaluating the Lethal and Repellent Activities of Eucalyptus camaldulensis Essential Oil Against the Adults of Oryzaephilus surinamensis on Date Palm Fruits

Abstract

Date palm fruits are commonly infested by saw-toothed grain beetle, Oryzaephilus surinamensis, which can cause substantial damage. Botanical insecticides are gaining attention as a cost-effective and low-risk alternative to chemical insecticides. In this study, we analyzed the volatile compounds of the essential oils of the leaves and seeds of Eucalyptus camaldulensis using gas chromatography mass spectroscopy and evaluated the toxicity of these oils against O. surinamensis. Two exposure methods were applied, including contact and fumigation. The GC-MS analysis detected many terpene compounds in both of the leaves and seeds essential oil such as eucalyptol, which acts as a respiratory toxicant against insects. The contact method was more effective in controlling adult insects than the fumigation method. The mortality rate reached 76.50 % when the adults were exposed to 1000 mg/L of the leaves essential oil using the contact method. However, in the fumigation method, the same concentration gave 61.00 % mortality. The concentration of 1000 mg/L of the seeds essential oil gave 65.00 % mortality by using the contact method and 52.00 % mortality by using the fumigation method. Effective repellent activity of the essential oil was achieved and continued for 24 h, indicating that the essential oil effect is not reversible. Because of their high activity, these essential oils could be used to control stored products insects, and can be used as a component in integrated pest management programs in combination with microbial insecticides, traps, and beneficial insects.

Keywords:

Aromatic plants, date palm, eucalyptol, fumigation, stored products insect, toxicity.