Exploring Syzygium aromaticum essential oil and its bioactive compounds against Ulomoides dermestoides: insecticidal insights into respiratory integrity

Abstract

Although synthetic chemical insecticides are widely used for controlling stored-product pests, increasing efforts have been directed toward identifying environmentally friendly alternatives. Essential oils (EOs) are considered novel alternatives to pesticide use due to their insecticidal properties. This research characterized the Syzygium aromaticum EO by GC-FID × GC-MS and investigated the effects of this EO and its major compounds on lethality, survival, behavioral activity, and respiratory physiology of Ulomoides dermestoides. Chemical characterization of S. aromaticum EO showed that its principal compounds were eugenol (60.3%), eugenyl acetate (24.1%), β-caryophyllene (5.23%), α-humulene (3.53%), and caryophyllene oxide (2.23%). Toxicological assays demonstrated that S. aromaticum EO (LD₅₀ = 3.66 μg insect⁻¹), eugenol (LD₅₀ = 3.37 μg insect⁻¹), and eugenyl acetate (LD₅₀ = 3.85 μg insect⁻¹) were highly toxic to U. dermestoides, with negligible mortality in the control group. Time–mortality analyses indicated significant reductions in insect survival at both LD₅₀ and LD₉₀, with eugenol producing the strongest lethal effect. Exposure to lethal doses significantly altered the respiration rate of U. dermestoides, with treated insects showing a progressive decline in CO₂ production over time, particularly at higher doses. Additionally, reduced walking distance and increased resting time on surfaces treated with S. aromaticum EO (129 cm and 92 s), eugenol (389 cm and 250 s), and eugenyl acetate (127 cm and 198 s) indicate a clear repellent effect. These findings suggest that S. aromaticum EO affects multiple physiological functions in this insect, opening new avenues for pest control and contributing to the development of innovative insecticides.