| Pesticides are important agrochemicals and play an important role in control of crop diseases and pests and protecting the safety of agricultural production.However,the pesticide formulations currently used have limitations such as low utilization of crop target and pest target,which is also easy to cause environmental pollution.At present,most pesticide compounds have low solubility and poor dispersion in aqueous media,which restricts the development of the effective formulation.At the same time,the low melting point pesticide compound is easy to soften during the processing and Ostwald ripening is easy to occur during the heat storage process,which increase the difficulty of the preparation of pesticide formulations.New nano-pesticide formulations are currently developed using nanomaterials and nanotechnology.It is of great significance to improve the water solubility and dispersibility of poorly soluble pesticides,increase the deposition rate of crop targets,improve the stability of low melting pesticides,fully exert the biological activity of active ingredients,and reduce residual pollution.In this paper,two low melting point and poorly soluble pesticides were studied.The development of new formulations of water-based nano-pesticides were developed using nano-granularization preparation method,which overcome the dispersibility of poorly soluble pesticides,eliminate the use of harmful solvents and additives,and promote the absorption and utilization of pesticide ingredients.The mechanism of nano-pesticides on improving drug dispersion,wettability and stability was explored,and the mechanism of synergistic effect of nano-pesticides delivery system on insecticidal and bactericidal activity was elucidated,which provide new ideas and methods for water-based dispersion of low melting point and insoluble pesticides and provide a theoretical basis for development of high-efficiency and environmentally friendly new nano-pesticides formulations.1.The lambda-cyhalothrin nanosuspension was prepared by melt-shearing emulsification method.The nanoparticles with uniform particle size and smooth surface can be obtained by optimizing the process.The average particle size was 12 nm and PDI was 0.279.Compared with commercial suspension concentrates,LCNS exhibited better wettability,retention and deposition properties after dispersion.The particle size of the nanoparticles increased to 39 nm and 24 nm after different storage conditions,respectively.The nanoparticles do not aggregate substantially,the particle size changes little,and the particle size distribution is uniform.The decomposition rate of the sample under different storage conditions is below 5%,showing good physicochemical stability.Mustard aphid was used as the test object.The results demonstrate that the virulence effect of the nanosuspension is 2-3 times that of commercial suspension concentrates.2.The lambda-cyhalothrin nano water dispersible granule was developed by self-emulsifying carrier solidification method.L25（56）blank orthogonal experiment design with six factors and five levels was carried out to optimize the process formula.The pesticide nanoparticles showed a smooth spherical surface and a uniform size with an average particle size of 18 nm and PDI of0.200.Nano water dispersible granule exhibited good wettability after dispersion compared with traditional solid formulations.The particle size of the nanoparticles changes small and particle distribution is uniform.The crystal structures of the sample under different storage conditions were consistent with the structure of the initial sample by X-ray diffraction,and the decomposition rate of samples was below 1%,showing good physicochemical stability.Aphis gossypii and Myxus persicae were used as the test objects.The results demonstrate that the virulence effect of the nanoformulation on Myxus persicae is 1.2 times that of water dispersible granule and the virulence effect of the nanoformulation on Aphis gossypii is 2 times that of water dispersible granule.3.The pyraclostrobin nano water dispersible granule was developed by self-emulsifying carrier solidification method.In this experiment,L9（34）blank orthogonal experiment design with four factors and three levels was carried out to optimize the process formula.The average particle size of the nanoparticles is 15 nm,the PDI is 0.225,and the zeta potential is-29.3 mV.The water dispersible granule exhibited good dispersion and wettability.The particle size of the nanoparticles increased to 38 nm and 36 nm after different storage conditions,respectively,which means that particle size changes little.The nanoparticles don’t aggregate and particle size distribution is uniform.The decomposition rate of the solid nanodisperison under different storage conditions is below 1%,showing good physicochemical stability.The EC50 of nanoformulation was 0.743μg/mL.Toxicity regression analysis showed that the toxicity effect of the solid nanodispersion experimental group was 4.5 times that of water dispersible granule treatment group.As concentration of the pyraclostrobin increased from 1 to 20μg/mL,more ROS was produced in F.oxysporum.In addition,compared with other control group,the nanoformulation treatment group had a higher level of ROS,and therefore,the oxidative damage of the fungi is more serious.As the incubation time prolongs,the oxidative system and the antioxidant system of the fungi in the nanoformulation group are unbalanced.The degree of oxidation in the fungi exceeded its antioxidant capacity,and superoxide dismutase and catalase activity were lower.Therefore,the oxidation damage of fungi tissue was more serious.In conclusion,the effects of pyraclostrobin on antioxidase activity levels in F.oxysporum were consistent with release of ROS.Pyraclostrobin nano water dispersible granule has stronger antifungal activity against F.oxysporum. |
