Contact toxicity and ovicidal activity of Spinacia oleracea plant extract and their nano emulsion formulation on Tetranychus urticae
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Tetranychus urticae widely known as one of the most important pests causes economic losses in many crop products. The harmful effects of chemical pesticides on the environment and human health, highlights use of biopesticide compounds as a suitable method to remove the high risk pesticides in integrated pest management programs. During the last few decades the nanoformulasion has emerged as a feasible and effective solution to the problems faced by the high percentage of poorly water-soluble compounds with the large size of particles. Decreasing the size of such compounds to the nanoscale, can significantly change their physical properties and leads to higher efficiency of the formulated compounds. In this study, contact toxicity and ovicidal activity of methanolic extracts and their nano-formulated extract of Spinacia oleracea have been studied on T. urticae under the laboratory conditions. The emulsion containing spinach extract particles forming micelles with hydrophilic and hydrophobic suspended in water (O/W) was prepared which in aquatic phase self-assembled and converted to nano particles. The spherical nano emulsified spinach extract was revealed by Transmission Electron Microscopy (TEM). The average size of particles was estimated 48.42 nm. The experiments were carried out in five replications under laboratory conditions at 25±1℃, 65±5% RH and 16:8 (L: D) h. 20 female mites placed on bean leaf discs then, 1 ml of each solution was sprayed on mites (1 bar) and the mortality was recorded after 24 hours. Statistical analysis was done by using SPSS 23 software. Our Results showed that the LC50 values of Unformulated and formulated spinach extracts was 2678.86 and 234.29 ppm respectively. Moreover, supplementary studies were done on the ovicidal activity of the extracts. Hatched eggs were exposed with 8333 and 434 ppm concentration for about 12 days. The LC80 value of contact toxicity test, revealed that nano emulsion formulation causes a significant increase in egg mortality (88) in comparison with unformulated extract (43). Based on our findings, after nonoformulation of the spinach seed extracts, compound toxicity significantly increased, so contact LC50 was almost 11 times decreased. Nanoemulsion has a high efficiency with beneficial properties including viscosity, penetrance, crystallization, thermal constancy, solubility and biodegradability. Our results revealed that the methanol extract of spinach seed has a positive effect on the mortality of different life stages of two-spotted spider mite. So, this compound can be considered as a potential factor to use in the integrated pest management programs.
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