Insecticidal potential of terpenes and phenylpropanoids: natural solutions and nanotechnology for agricultural pests control

Abstract

Agriculture is one of the main economic activities in Brazil. Annually, productivity suffers losses due to various factors, including the action of pest insects. The primary control method is the use of synthetic chemical insecticides, which is often done abusively and without awareness, causing issues such as contamination of natural resources, selection of resistant individuals, and posing risks to ecosystem integrity and human health. As an alternative to these compounds, natural products have gained attention, especially terpenes and phenylpropanoids, which are constituents of essential oils from plant species. Natural products are considered environmentally friendly and are used in sustainable production practices. This study aimed to evaluate the insecticidal activity of terpenes and phenylpropanoids on pest insects Drosophila suzukii and Sitophilus zeamais; to use the most potent compounds in nanoparticle synthesis to overcome limitations imposed by the physicochemical properties of these molecules. Additionally, the effects of sublethal doses on target organisms and non-target species, such as Doru luteipes, Palmistichus elaeisis, and Tetrastichus howardi, were assessed. For D. suzukii, L-(-)-carvone, carvacrol, (E)-anethole, and (E)-cinnamaldehyde caused high mortality and deformities in adults. These compounds also altered the activity of detoxifying enzymes, such as catalase (CAT), superoxide dismutase (SOD), and glutathione-S-transferase (GST), and induced histological changes in the exoskeleton, intestines, and fat body of this pest. Nanoparticled compounds showed prolonged insecticidal effects, especially PCL-carvacrol. The compounds did not significantly affect natural enemies D. luteipes and P. elaeisis, suggesting biological selectivity. For S. zeamais, carvacrol was the most effective compound, followed by (E)-cinnamaldehyde and p-anisaldehyde. Furthermore, (E)-anethole demonstrated strong synergy in binary mixtures. The compounds activated antioxidant enzymes and increased lipid peroxidation, promoting oxidative stress. They also inhibited digestive enzymes, such as α-amylase, and reduced muscle fiber and intestinal thickness, as well as lipid reserves and carbohydrates in the fat body. (E)-cinnamaldehyde showed the greatest compatibility with T. howardi, a pest parasitoid. The results indicate that these natural compounds are potential selective biopesticides with promising applications for the sustainable control of agricultural pests.