Insecticidal effects of substances from cinnamon bark – eugenol, trans-cinnamaldehyde and cinnamaldehyde to yellow mealworm

Abstract

Abstract The use of synthetic pesticides is limited due to increasing environmental pollution and developing pest resistance, as well as the increasingly confirmed negative impact of these compounds on human health. At the same time, the demand for food grown in the spirit of organic farming is increasing. Therefore, as part of Integrated Plant Protection (IPM), biopesticides are used, i.e., substances of natural origin that are characterized by low toxicity to non-target species and easy availability. Such substances include, among others, compounds found in the bark of the Ceylon cinnamon tree (Cinnamomum verum J.Presl), such as eugenol, trans-cinnamaldehyde and cinnamaldehyde. However, the mechanism of their action has not been sufficiently researched. Therefore, this study presents the results of the impact of these compounds on the important pest of cereal crops and food stores, and - at the same time - a model organism - Tenebrio molitor beetle. The tested compounds were administered by injection, inhalation, with food or one of two contact routes: by immersing the tested larvae or by contacting them with substratum soaked in an appropriate solution of the tested compound. The results allowed us to determine the LT50 parameter, and the probit analysis carried out the LC20/30/50/95 values. The obtained results also allowed to conclude that the most effective route of administering cinnamon bark compounds is contact and injection, and the most effective is eugenol. The impact of the tested compounds on the morphological malformations of T. molitor larvae was also documented and discussed.