Insecticidal effects of substances from cinnamon bark – eugenol, trans-cinnamaldehyde and cinnamaldehyde on Tenebrio molitor (Coleoptera: Tenebrionidae)
Aleksandra Dzięgelewska, Jan Lubawy, Zbigniew Adamski
Abstract
The use of synthetic pesticides is increasingly limited due to their environmental impact, development of pest resistance, and confirmed negative effects on human health. At the same time, the demand for food grown in accordance with the principles of organic farming is increasing. Integrated Pest Management (IPM) promotes the use of biopesticides - natural substances with low toxicity to nontarget species as alternatives to synthetic pesticides. These substances include, among others, compounds found in the bark of the Ceylon cinnamon tree ( Cinnamomum verum J. Presl, Lauraceae), such as eugenol, trans -cinnamaldehyde and cinnamaldehyde. However, the mechanism of their action has not been sufficiently researched . Therefore, this study compared the effects of these substances and various modes of their application on important pests of cereal crops and food stores and on a model organism, Tenebrio molitor beetle (Coleoptera: Tenebrionidae). The tested compounds were administered by injection, inhalation, food, by immersing the tested larvae or by contacting them with substratum soaked in the tested compound. The results allowed us to determine the LT 50 parameter, and the probit analysis estimated the LC 20/30/50/95 values. The results showed that the most effective route for administering cinnamon bark compounds is contact and injection, and the most effective compound is eugenol, with an LC 50 value of 2.01 μl/ml (contact). The lowest LC 50 values for trans -cinnamaldehyde and cinnamaldehyde were 6.28 μl/ml (injection) and 15.66 μl/ml (contact), respectively. Second, cinnamaldehyde and trans -cinnamaldehyde (filter paper tests at 200 μl/ml) and eugenol (immersion test at 300 μl/ml) had the lowest LT 50 values. The test results also indicate that all the tested compounds cause morphological malformations in T. molitor larvae in the concentration range of 50–300 μl/ml. This research highlights the insecticidal potential of eugenol and cinnamaldehydes, indicating that cinnamon bark-derived pesticides could effectively control T . molitor populations. These compounds are promising for developing eco-friendly biopesticides. • Substances from cinnamon bark are promising biopesticides for pest management. • Contact and injection are the best ways to apply eugenol and cinnamaldehydes. • Trans -cinnamaldehyde is the most effective by injection, eugenol is stronger overall. • Cinnamon bark-derived substances cause morphological malformations in tested larvae.