ارزیابی سمیت تدخینی نانوکپسول بارگذاری شده با اسانس آویشن ‌دنایی (Thymus daenensis) روی شته مومی کلم، Brevicoryne brassicae (L.)

Botanical pesticides based on plant essential oils are biocompatible agents that control insect pests. However, the low solubility in water, oxidation, and instability in the presence of light, humidity, and heat are the main obstacles to the practical application of essential oils. Encapsulation of essential oils could improve the stability and efficiency, overcome some limitations, and make the application more useful. Therefore, in this study, the essential oil of Thymus daenensis Celak (Lamiales: Lamiaceae) was obtained by hydrodistillation and then analyzed using gas chromatography (GC) and GC/mass spectrometry (MS). In situ polymerization technique was used to prepare nanocapsules of urea-formaldehyde loaded with essential oil extracted from T. daenensis. Transmission electron microscopy (TEM) was performed to determine the morphology of the nanocapsules. Also, nanocapsules' diameter and poly-dispersity index (PDI) were determined through the dynamic light scattering (DLS) technique. Subsequently, the fumigant toxicity of T. daenensis essential oil and oil-loaded nanocapsules was assessed against Brevicoryne brassicae (L.) (Hemiptera: Aphididae). The adult aphids were exposed to different concentrations of the mentioned compounds at the standard environmental conditions (25±1℃, 65±5% RH, and a photoperiod of 16:8 h L:D). Chemical composition of T. daenensis essential oil was measured and totally 126 components were identified by gas chromatography and mass spectroscopy. Thymol (56.61%) and carvacrol (17.02%) were the major components of the essential oil. Characterization of nanocapsules using dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed that the nanocapsules were spherical with sizes of between 8.30 to 17.61 nm, the median diameter (x50) of 12.10 nm, and a PDI of 0.098. Based on the relative toxicity ratios, there were significant differences between non-formulated and oil-loaded nanocapsules of T. daenensis. After 96 h., the LC50 and LC90 values of fumigant toxicity of nanocapsulated formulation (10.55 and 32.31 µl/l air, respectively) were smaller than non-formulated essential oil (18.66 and 45.65 µl/l air, respectively). The results showed that the nanoformulation of T. daenensis essential oil can effectively control the cabbage aphid. Moreover, further studies are recommended to prove the efficiency of the compound under field conditions.