Nanoemulsions are particularly suitable as a platform in the development of delivery systems for lipophilic functional agents. Current research describes the formation of oil-in-water (O/W) diazinon nanoemulsions using synthetic and natural additives by adopting a high-energy (ultrasound) emulsification method. The diazinon nanoemulsions were spontaneously formed by adding dropwise a mixture of diazinon, solvent and co-solvent in an aqueous solution containing a surfactant (tween or lecithin) with continuous stirring. The nanoemulsions were then formed by ultra-sonication. The effects of three levels of active ingredient, solvent, co-solvent, surfactant, sonication time and sonication cycle and power were performed by Minitab software to design the experiment. Effects of these factors on droplet size, polydispersity index (PDI), viscosity and pH of nanoemulsions were investigated. The results of the modeling showed that the experimental data could be adequately adapted in a second-order polynomial model with a multiple regression coefficient r of 0.821 for the prediction of particle size, PDI and viscosity. The long-term and thermodynamic stability of the prepared nanoemulsions were tested. The droplet size and morphology of the nanoemulsions were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM). On this basis, a water-insoluble insecticide diazinon was incorporated into 26 optimized nanoemulsion systems to demonstrate potential applications in pest control. The results of DLS and TEM measurements showed that most of prepared nanoemulsions had an almost monodisperse droplet size distribution (PDI < 200 nm). Incorporation of diazinon had no significant effect on the size and stability of the nanoemulsions and the formulated nanoemulsion remained stable after four months of storage.
The present study was conducted to determine the effect of baits containing nano particles of silica against the fourth instar larvae of Agrotis ipsilon (Hufn.) along sequential daily intervals post treatment under laboratory conditions. The determined percentages of larval mortality due to the admixed baits with SiNPs increased up to 100% after 15 days of application. The admixing of nanoparticles of silica in the bait during the sensitive period of larval development caused morphological abnormalities that are generally irreversible and often lead to death, beside certain biochemical changes of some inorganic elements in the haemolymph of the treated insects. It could be concluded that the tested nanoparticles of silica were most effective and indicated the highest concentration reductions of inorganic constituents in larval haemolymph, especially calcium, sodium and potassium. Therefore, more attention must be directed towards the inorganic constituents in the larval haemolymph as biomarkers for SiNPs efficacy.
Field trials were carried at El-Ashartalaf feddan region, Behaira government, Egypt during two successive seasons of 2016 and 20117 to evaluate four insecticides and three of their mixtures against the tomato leafminer Tuta absoluta under field conditions. The seven evaluated insecticidal treatments were applied in three consequent sprays within an interval of 10 days between each in addition to the treatment of untreated check. The lonely or individually evaluated insecticides included chlorantraniliprole, thiamethoxam, lufenuron and chlorpyriphos which have been sprayed according to the recommendations of the Egyptian Ministry of Agriculture. Meanwhile, their evaluated mixtures: chlorantraniliprole + thiamethoxam, chlorantraniliprole+ lufenuron and thiamethoxam + lufenuronwere were applied at the rate of half recommended dose of each insecticide within the tested mixture. The obtained results showed a more or less toxic efficiency of the individually and/or admixed insecticides against the insect throughout both the seasons of 2016 and 2017. In the first season of 2016, the mixture of chlorantraniliprole + lufenuron was comparatively high effective during the elapsed period after the 1 st and 2 nd spray; furthermore it was proved to be the utmost superior efficient post the 3 rd spray achieving complete infestation reduction (100%) of larvae. During the second season of 2017, chlorpyriphos was the most effective tested individual insecticide. The mixture of chlorantraniliprole + lufenuron was proved again to be superior achieving reduction level of 100% after the 3 rd spray. Therefore, this mixture would be recommended for achieving efficient control of T. absoluta in the growing tomato plants under field conditions. It is also better to use chlorpyriphos alone in IPM program to reduce the costs and slow down the development of resistance of this insect-pest to other involved compounds in the mixtures.Keywords: Tomato plants, the tomato leafminer Tuta absoluta, insecticidal treatments, mixture of insecticides and infestation reduction percentage.
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