The use of chemical insecticides has had several side-effects, such as environmental contamination, foodborne residues, and human health threats. The utilization of plant-derived essential oils as efficient bio-rational agents has been acknowledged in pest management strategies. In the present study, the fumigant toxicity of essential oil isolated from Satureja intermedia was assessed against cosmopolitan stored-product insect pests: Trogoderma granarium Everts (khapra beetle), Rhyzopertha dominica (Fabricius) (lesser grain borer), Tribolium castaneum (Herbst) (red flour beetle), and Oryzaephilus surinamensis (L.) (saw-toothed grain beetle). The essential oil had significant fumigant toxicity against tested insects, which positively depended on essential oil concentrations and the exposure times. Comparative contact toxicity of S. intermedia essential oil was measured against Aphis nerii Boyer de Fonscolombe (oleander aphid) and its predator Coccinella septempunctata L. (seven-spot ladybird). Adult females of A. nerii were more susceptible to the contact toxicity than the C. septempunctata adults. The dominant compounds in the essential oil of S. intermedia were thymol (48.1%), carvacrol (11.8%), p-cymene (8.1%), and γ-terpinene (8.1%). The high fumigant toxicity against four major stored-product insect pests, the significant aphidicidal effect on A. nerii, and relative safety to the general predator C. septempunctata make terpene-rich S. intermedia essential oil a potential candidate for use as a plant-based alternative to the detrimental synthetic insecticides.
Keywords: Aphis nerii; Coccinella septempunctata; Oryzaephius surinamensis; Rhyzopertha dominica; Tribolium castaneum; Trogoderma granarium; plant-based insecticide.