Thifluzamide synergistic granules for controlling soil-borne diseases and a preparation method thereof

Abstract

The application discloses a thifluzamide synergistic granule for preventing and treating soil-borne diseases and a preparation method thereof, and belongs to the technical field of fertilizers. The granule takes Janus topological magnetic microspheres prepared by one-step emulsion interfacial polymerization as a core active ingredient. The microspheres integrate an inner concave topological anchoring structure, a chemically bonded ferroferric oxide magnetic component and a polymer segment responding to a rhizosphere micro-acid environment. The preparation method comprises synthesis of the microspheres and low-speed dry mixing with film forming agents and the like. The granule can be firmly anchored on the surface of seeds, uniformly distributed by a magnetic field, and intelligently release pesticides under the rhizosphere acid environment, so that the residence and utilization efficiency of thifluzamide in the target area is significantly improved, efficient and accurate prevention and treatment of soil-borne diseases are realized, and the amount of pesticide used and environmental pollution are reduced.

Description

Technical Field

[0001] This invention relates to the field of fertilizer technology, and in particular to a thifluzamide synergistic granule for the prevention and control of soil-borne diseases and its preparation method. Background Technology

[0002] Thifluzamide is a highly effective fungicide for controlling soil-borne diseases such as crop sheath blight. However, conventional granular formulations are easily fixed in the soil and have poor mobility, resulting in insufficient effective concentration in the rhizosphere and low utilization rate.

[0003] To improve pesticide utilization efficiency, existing technologies mainly focus on two directions: first, optimizing the carrier structure, such as developing porous or slow-release granules to extend the duration of action; and second, imbuing the carrier with functions, such as enhancing adhesion through surface modification or introducing responsive release units. However, these improvements are mostly single-function optimizations: macroscopic granules are difficult to deliver and anchor precisely to the rhizosphere; and research on microscopic functional materials (such as Janus carriers) is mostly concentrated on foliar applications, whose complex structures are easily destroyed in traditional high-shear granulation processes, and lack multifunctional synergistic designs for soil-borne disease control scenarios.

[0004] Therefore, there is an urgent need to develop a novel granular formulation that integrates physical anchoring, active targeting, and environmentally responsive release to solve the problem of thifluzamide delivery and retention in soil. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a thifluzamide granule for the prevention and control of soil-borne diseases and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention first proposes a method for preparing thifluzamide synergistic granules for the prevention and control of soil-borne diseases, comprising the following steps:

[0008] Preparation of S1 and Janus topological magnetic microspheres:

[0009] S1.1 Seed swelling: Non-crosslinked polystyrene seeds and 1-chlorodecane are added to an aqueous phase containing emulsifier and polyvinyl alcohol, and stirred at 30-50℃ for 10-24h to obtain a swollen system;

[0010] S1.2 Emulsion interfacial polymerization: An oil phase containing styrene, divinylbenzene, thifluzamide, azobisisobutyronitrile and magnetic nanoparticles is emulsified and then added to the swelling system;

[0011] Subsequently, the hydrophilic functional monomer acrylic acid and the pH-responsive monomer were added; under nitrogen protection, the reaction was stirred at 60-80℃ for 10-16 hours.

[0012] S1.3 Purification and Drying: After the reaction is complete, the mixture is cooled, centrifuged, washed, and vacuum dried to obtain powdered Janus topological magnetic microspheres.

[0013] S2. Forming of the synergistic granules: Janus topological magnetic microspheres are mixed with film-forming agents, dispersants and warning colors by a low-speed dry process to obtain the thifluzamide synergistic granules.

[0014] In an aqueous system, non-crosslinked polystyrene (PS) seed particles absorb the oil phase solvent 1-chlorodecane and gradually expand in volume, eventually forming a uniformly dispersed swollen particle suspension; the emulsifier is adsorbed at the water-oil interface to form a molecular film; and polyvinyl alcohol is adsorbed on the surface of the PS seed particles to form a protective layer.

[0015] Non-crosslinked PS is a hydrophobic polymer that has good compatibility with 1-chlorodecane (a hydrophobic organic solvent). Driven by the concentration gradient, 1-chlorodecane molecules diffuse into the intermolecular gaps of PS seed particles, causing the PS molecular chain segments to stretch and the particles to swell.

[0016] The emulsifier in the aqueous phase is a surfactant with its hydrophobic end facing the PS seed / 1-chlorodecane phase and its hydrophilic end facing the aqueous phase. It forms an adsorption film at the interface, reduces interfacial tension, and prevents the swelling particles from agglomerating. Polyvinyl alcohol further stabilizes the swelling system through steric hindrance, preventing particle sedimentation or agglomeration.

[0017] After emulsification, the oil phase component forms nano-sized oil droplets that are uniformly dispersed in the aqueous phase. At 60-80℃, azobisisobutyronitrile (AIBN) undergoes thermal decomposition, generating free radicals containing unpaired electrons. These free radicals initiate polymerization reactions of monomers in both the oil and aqueous phases, forming an asymmetric cross-linked polymer network at the oil-water interface. Simultaneously, iron oxide nanoparticles are covalently bound to the polymer network, and thifluzamide is embedded within the hydrophobic polymer region.

[0018] Thifluzamide is a hydrophobic bactericide with good solubility in the oil phase. During polymerization, it is physically embedded in the pores of the hydrophobic cross-linked polymer network, achieving high-efficiency loading. The porous structure of the cross-linked network can slow down the release rate of thifluzamide, preventing the rapid loss of the active ingredient.

[0019] Preferably, in S1.1, the emulsifier is selected from at least one of anionic and nonionic surfactants.

[0020] Preferably, in S1.2, the magnetic nanoparticles are iron oxide nanoparticles modified with at least one of oleic acid, glycidyl methacrylate, and vinylsilane.

[0021] The hydrophilic functional monomer is acrylic acid, and the pH-responsive monomer is selected from at least one of dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate;

[0022] The mass ratio of styrene, divinylbenzene, thifluzamide, azobisisobutyronitrile, magnetic nanoparticles, acrylic acid, and pH-responsive monomers is 20-40:10-25:10-20:0.8-1.5:2-8:5-15:3-8.

[0023] Preferably, in step S2, the film-forming agent is selected from at least one of polyvinyl alcohol, polyvinyl acetate, and cellulose derivatives; the warning color is an edible pigment or dye that meets agricultural use standards.

[0024] The speed of low-speed dry mixing is 30-80 rpm, and the mixing time is 20-40 min; the mass ratio of Janus topological magnetic microspheres, film-forming agent, dispersant, and warning color is 70-85:10-20:1-5:0.5-3.

[0025] Preferably, the preparation of the magnetic nanoparticles specifically includes the following steps:

[0026] Preparation of hydroxylated Fe3O4: Under nitrogen protection, FeCl3·6H2O and FeCl2·4H2O were dissolved in deionized water, maintaining the Fe... 3+ Fe 2+ A precursor solution with a total iron ion concentration of 0.1-0.3 mol / L was prepared by mixing ingredients at a molar ratio of 1.9-2.1:1. The solution was heated to 60-80℃ and 500-800 rpm, and ammonia was added to adjust the pH to 10-11, resulting in a black precipitate. Sodium citrate was added, and the mixture was stirred at 60-80℃ for 2-4 hours. Magnetic separation was performed, and the solution was thoroughly washed with deionized water until neutral. After drying, hydroxylated Fe3O4 was obtained, with a hydroxyl density >20 OH / nm. 2 ;

[0027] Oleic acid modification method: During the formation of the black precipitate in the above steps, maintain the temperature and stir, and immediately add oleic acid. The surface double bond density is controlled to be 0.5-2 double bonds / nm by adjusting the amount of oleic acid added. 2 Continue the reaction for 1-3 hours; cool to room temperature, separate the black precipitate with a strong magnet, wash with deionized water and ethanol alternately, and dry under vacuum to obtain oleic acid modified magnetic nanoparticles.

[0028] Silane coupling agent method: Hydroxylated Fe3O4 is dispersed in an ethanol / water mixed solvent with a volume ratio of 9:1, 1-5% KH-570 by mass of Fe3O4 is added, the pH is adjusted to 4-5 with acetic acid, the reaction is stirred at 60-70℃ for 6-12h, magnetic separation is performed, washing and drying are carried out to obtain silane coupling agent modified magnetic nanoparticles.

[0029] Glycidyl methacrylate grafting method: hydroxylated Fe3O4 is dispersed in anhydrous toluene and sonicated for 30-60 min. Glycidyl methacrylate and triethylamine are added, and the mixture is refluxed at 80-100℃ for 12-24 h under nitrogen protection. After the reaction, the product is magnetically separated, washed alternately with toluene and acetone, and vacuum dried to obtain glycidyl methacrylate modified magnetic nanoparticles. The mass ratio of hydroxylated Fe3O4, glycidyl methacrylate, and triethylamine is 1:2.0-2.5:0.05-0.10.

[0030] The present invention also proposes a thifluzamide synergistic granule prepared by the aforementioned method.

[0031] Preferably, the granules are dry suspension seed coating agents.

[0032] This invention also proposes the application of the aforementioned thifluzamide synergistic granules in the prevention and control of soil-borne diseases in crops.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. This invention uses Janus topological magnetic microspheres as drug carriers. Compared with the single drug-carrying structure of existing ordinary thifluzamide granules, its asymmetric bifunctional structure can achieve efficient encapsulation of thifluzamide at the hydrophobic end and loading of pH-responsive groups at the hydrophilic end. This solves the pain points of low pesticide loading rate and disordered drug release in existing technologies. It can accurately release the active ingredient according to the change of soil pH, improve the enrichment of the agent in the disease occurrence area, greatly improve the efficacy utilization rate, and reduce ineffective consumption.

[0035] 2. This invention introduces surface-modified magnetic nanoparticles, giving the granules a magnetic targeting function. Unlike the drawbacks of random dispersion of pesticides in the soil in existing technologies, the granules can be guided by an external magnetic field to be concentrated in the crop roots, precisely targeting the infected parts of soil-borne diseases. This reduces pesticide usage and soil residues, minimizes the impact on non-target organisms and the ecological environment, and significantly improves the control effect of soil-borne diseases.

[0036] 3. The preparation process of this invention is simple and efficient. It adopts emulsion interfacial polymerization combined with low-speed dry mixing. Compared with the existing complex granule preparation process, it does not require high temperature and high pressure conditions, has low energy consumption, is easy to operate, and can be easily realized for large-scale industrial production. At the same time, the product is a dry suspension seed coating agent with good dispersibility, stable film formation, and convenient use. It solves the problems of uneven dispersion and poor adhesion of existing granules, reduces the cost of use for farmers, and is more practical. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the thifluzamide synergistic granule for the prevention and control of soil-borne diseases proposed in this invention.

[0038] Among them, 1. hydrophilic monomer polymer; 2. magnetic nanoparticles; 3. thifluzamide; 4. hydrophobic monomer polymer. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0040] Example 1: A method for preparing thifluzamide synergistic granules for controlling soil-borne diseases, comprising the following steps:

[0041] S1. Preparation of Janus topological magnetic microspheres: Using non-crosslinked polystyrene microspheres as seeds, interfacial competitive polymerization was carried out between an oil phase containing hydrophobic monomers, crosslinking agents, thifluzamide, azobisisobutyronitrile and magnetic nanoparticles with polymerizable double bonds on the surface, and an aqueous phase containing emulsifiers, polyvinyl alcohol and hydrophilic functional monomers. After the reaction, the microspheres were purified and dried to obtain Janus topological magnetic microspheres.

[0042] S2. Forming of the synergistic granules: Janus topological magnetic microspheres are mixed with film-forming agents, dispersants, and warning colors using a low-speed dry mixing process to obtain the thifluzamide synergistic granules, as shown in the conceptual diagram below. Figure 1 As shown.

[0043] S1 specifically includes:

[0044] S1.1 Seed swelling: Non-crosslinked polystyrene seeds and 1-chlorodecane were added to an aqueous phase containing emulsifier and polyvinyl alcohol, and stirred at 40°C for 16 hours to obtain a swollen system;

[0045] S1.2 Emulsion interfacial polymerization: An oil phase containing styrene, divinylbenzene, thifluzamide, azobisisobutyronitrile and magnetic nanoparticles was emulsified and added to a swelling system; then, hydrophilic functional monomers acrylic acid and pH-responsive monomers were added; under nitrogen protection, the reaction was stirred at 70°C for 13 h.

[0046] S1.3 Purification and Drying: After the reaction is complete, the mixture is cooled, centrifuged, washed, and vacuum dried to obtain powdered Janus topological magnetic microspheres.

[0047] The hydrophilic functional monomer is acrylic acid, and the pH-responsive monomer is dimethylaminoethyl methacrylate.

[0048] The preparation steps of the magnetic nanoparticles with polymerizable double bonds on their surface include:

[0049] Preparation of hydroxylated Fe3O4: Under nitrogen protection, FeCl3·6H2O and FeCl2·4H2O were dissolved in deionized water, maintaining the Fe... 3+ Fe 2+ A precursor solution with a total iron ion concentration of 0.3 mol / L was prepared by mixing ingredients at a molar ratio of 1.9:1. The solution was heated to 70°C and heated at 600 rpm. Ammonia was added to adjust the pH to 11, resulting in a black precipitate. The temperature and stirring were maintained, and oleic acid was immediately added. The surface double bond density was controlled to be approximately 1 double bond / nm by adjusting the amount of oleic acid added. 2 The reaction was continued for 2 hours; cooled to room temperature, the black precipitate was separated by a strong magnet, washed alternately with deionized water and ethanol, and dried under vacuum to obtain oleic acid modified magnetic nanoparticles.

[0050] In S1.2, the mass ratio of styrene, divinylbenzene, thifluzamide, azobisisobutyronitrile, magnetic nanoparticles, acrylic acid, and pH-responsive monomer is 20:25:10:1.5:2:15:3.

[0051] In S2, the rotation speed of the low-speed dry mixing is 50 rpm, and the mixing time is 30 min; the mass ratio of Janus topological magnetic microspheres, film-forming agent, dispersant, and warning color is 70:20:1:3.

[0052] Example 2: The preparation method is the same as in Example 1, except that:

[0053] The pH-responsive monomer is dimethylaminoethyl methacrylate.

[0054] The preparation steps specifically include the following:

[0055] Preparation of hydroxylated Fe3O4: Under nitrogen protection, FeCl3·6H2O and FeCl2·4H2O were dissolved in deionized water, maintaining the Fe... 3+ Fe 2+ A precursor solution with a total iron ion concentration of 0.2 mol / L was prepared by mixing ingredients at a molar ratio of 2:1. The solution was heated to 70°C and 600 rpm, and ammonia was added to adjust the pH to 11, resulting in a black precipitate. Sodium citrate was added, and the mixture was stirred at 70°C for 3 hours. Magnetic separation was performed, and the solution was thoroughly washed with deionized water until neutral. After drying, hydroxylated Fe3O4 was obtained, with a hydroxyl density range >20 OH / nm. 2 ;

[0056] Hydroxylated Fe3O4 was dispersed in a 9:1 volume ratio ethanol / water mixed solvent, 3% by mass of Fe3O4 KH-570 was added, the pH was adjusted to 4-5 with acetic acid, the reaction was stirred at 65℃ for 9 h, magnetic separation was performed, washing and drying were performed to obtain silane coupling agent modified magnetic nanoparticles.

[0057] In S1.2, the mass ratio of styrene, divinylbenzene, thifluzamide, azobisisobutyronitrile, magnetic nanoparticles, acrylic acid, and pH-responsive monomer is 30:17.5:15:1.2:5:10:5.

[0058] In S2, the rotation speed of the low-speed dry mixing is 50 rpm, and the mixing time is 30 min; the mass ratio of Janus topological magnetic microspheres, film-forming agent, dispersant, and warning color is 77:15:3:2.

[0059] Example 3: The preparation method is the same as in Example 1, except that:

[0060] The pH-responsive monomer is prepared by mixing dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate in a mass ratio of 1:1.

[0061] The preparation steps specifically include the following:

[0062] Preparation of hydroxylated Fe3O4: Under nitrogen protection, FeCl3·6H2O and FeCl2·4H2O were dissolved in deionized water, maintaining the Fe... 3+ Fe 2+ A precursor solution with a total iron ion concentration of 0.1 mol / L was prepared by mixing ingredients at a molar ratio of 2.1:1. The solution was heated to 70°C and 600 rpm, and ammonia was added to adjust the pH to 11, resulting in a black precipitate. Sodium citrate was added, and the mixture was stirred at 70°C for 3 hours. Magnetic separation was performed, and the solution was thoroughly washed with deionized water until neutral. After drying, hydroxylated Fe3O4 was obtained, with a hydroxyl density range >20 OH / nm. 2 ;

[0063] Hydroxylated Fe3O4 was dispersed in anhydrous toluene and sonicated for 45 min. Glycidyl methacrylate and triethylamine were then added, and the mixture was refluxed at 90 °C for 18 h under nitrogen protection. After the reaction was completed, the product was magnetically separated, washed alternately with toluene and acetone, and dried under vacuum to obtain glycidyl methacrylate-modified magnetic nanoparticles. The mass ratio of hydroxylated Fe3O4, glycidyl methacrylate, and triethylamine was 1:2.5:0.10.

[0064] In S1.2, the mass ratio of styrene, divinylbenzene, thifluzamide, azobisisobutyronitrile, magnetic nanoparticles, acrylic acid, and pH-responsive monomer is 40:10:20:0.8:8:5:8.

[0065] In S2, the rotation speed of the low-speed dry mixing is 50 rpm, and the mixing time is 30 min; the mass ratio of Janus topological magnetic microspheres, film-forming agent, dispersant, and warning color is 85:10:5:0.5.

[0066] The following comparison model was also set:

[0067] Comparative Example 1: Based on Example 2, the difference is that the interfacial competitive polymerization design was cancelled: the oil phase monomers (styrene, divinylbenzene) and aqueous phase monomers (acrylic acid, pH-responsive monomers) were directly mixed and then homogeneously polymerized with PS seeds and magnetic particles to prepare symmetrical magnetic microspheres. The rest was the same as in Example 2.

[0068] Comparative Example 2: Based on Example 2, the difference is that ordinary iron oxide nanoparticles without modified double bonds are used and added to the oil phase by physical mixing. The rest is the same as in Example 2.

[0069] Comparative Example 3: Based on Example 2, the difference is that the pH-responsive monomer is removed: only the hydrophilic functional monomer acrylic acid is added, and dimethylaminoethyl methacrylate / diethylaminoethyl methacrylate is not added, otherwise it is the same as Example 2.

[0070] Comparative Example 4: Based on Example 2, the difference is that the crosslinking agent is removed: only styrene monomer is added to the oil phase, and divinylbenzene is not added. The rest is the same as in Example 2.

[0071] Comparative Example 5: Based on Example 2, the difference is that the swelling step is omitted: the unswollen PS seed is directly added to the oil phase and aqueous phase system for interfacial polymerization, and the rest is the same as Example 2.

[0072] Performance testing: The content and loading rate of active ingredients were determined according to GB / T 14825-2023 "Determination of Suspension Rate of Pesticides"; the sustained-release performance was tested according to "Determination of Release Rate of Pesticide Slow-Release Granules"; the physicochemical properties were tested according to HG / T2467.12-2003 "Specifications for Writing Standards for Pesticide Granules"; the density of hydroxyl groups (-OH) was determined by fluorine substitution X-ray photoelectron spectroscopy (XPS); and the density of double bonds (C=C) was determined by iodometric titration. The results are shown below:

[0073] Table 1. Test results of various properties of thifluzamide synergistic granules (Part 1)

[0074] Table 2. Performance Test Results of Thifluzamide Synergistic Granules (Part II)

[0075] Data Analysis:

[0076] Examples 1-3 exhibit excellent performance, primarily due to the synergistic effect between the Janus topological magnetic microspheres constructed through emulsion interfacial polymerization and the various components. All three components form an asymmetric structure of "hydrophobic drug loading - hydrophilic pH response" through interfacial competitive polymerization. The hydrophobic end is stably encapsulated with thifluzamide via a cross-linking network, while the hydrophilic end is grafted with pH-responsive groups. Simultaneously, the magnetic nanoparticles are covalently bound to the polymer through double bond modification, preventing detachment. Example 3 demonstrates the best loading rate (92.1%) and pH-responsive targeting (86.7% release rate at pH 4.5, only 16.5% at pH 6.5). This is because glycidyl methacrylate modification enhances the covalent interaction between the magnetic particles and the polymer, the high magnetic particle content expands the drug loading space, and the composite pH-responsive monomer further improves the hydrophilicity / hydrophobicity regulation capability. Silane coupling agent and oleic acid modification optimize the magnetic binding stability of Examples 2 and 1, respectively, ensuring that the suspension rate, film-forming properties, and other physicochemical properties of all three meet the standards, and the thermal decomposition rate is less than 2%, demonstrating the role of the cross-linking network and modification process in ensuring the stability of the system.

[0077] The performance defects of the comparative examples all correspond to the absence or abnormality of the core mechanism. Comparative Example 1, by eliminating the Janus structure and using homogeneous polymerization, lacked hydrophilic and hydrophobic partitioning, making it impossible to achieve selective encapsulation and pH-responsive drug release of thifluzamide. Therefore, the loading rate decreased to 75.3%, with no significant difference in release rate across different pH environments. Furthermore, the lack of asymmetric structural support reduced particle stability, resulting in a suspension rate of only 72.5%. Comparative Example 2, with unmodified double bonds in the magnetic particles, could not covalently bind to the polymer. Physical mixing alone led to easy detachment, resulting in the loss of the active ingredient. The loading rate was 72.1%. Simultaneously, the integrity of the hydrophobic network was disrupted, rendering the sustained release non-selective, and the thermal decomposition rate increased to 9.5%.

[0078] Comparative Example 3, without the addition of pH-responsive monomers, showed that the polymer's hydrophilicity and hydrophobicity did not change with pH, ​​failing to achieve targeted drug release in the diseased area (slightly acidic). Therefore, the release rate at all pH values ​​was higher than 78%, and the homogeneous hydrophilic structure reduced drug loading stability, resulting in a loading rate of only 76.5%. Comparative Example 4, without the crosslinking agent, resulted in the homopolymerization of styrene into a linear polymer without a three-dimensional hydrophobic crosslinking network. This led to easy collapse of the drug-loading pores, causing the loading rate to drop to 68.7%. Furthermore, the polymer was prone to swelling and cracking, resulting in rapid dissolution of the active ingredient (release rate exceeding 87% at all pH values) and a thermal decomposition rate of 12.3%. Comparative Example 5, without the seed swelling step, showed that the unswollen PS seeds lacked sufficient space to load the oil-phase monomers and thifluzamide, leading to incomplete polymerization, incomplete Janus structure, and the worst drug loading capacity (loading rate of 65.2%). Uneven pore distribution resulted in large sustained-release fluctuations, a comprehensive decrease in physicochemical stability, and a shedding rate of 10.2%.

[0079] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing thifluzamide synergistic granules for controlling soil-borne diseases, characterized in that, Includes the following steps: Preparation of S1 and Janus topological magnetic microspheres: S1.1 Seed swelling: Non-crosslinked polystyrene seeds and 1-chlorodecane are added to an aqueous phase containing emulsifier and polyvinyl alcohol, and stirred at 30-50℃ for 10-24h to obtain a swollen system; S1.2 Emulsion interfacial polymerization: An oil phase containing styrene, divinylbenzene, thifluzamide, azobisisobutyronitrile and magnetic nanoparticles is emulsified and then added to the swelling system; Subsequently, the hydrophilic functional monomer acrylic acid and the pH-responsive monomer were added; under nitrogen protection, the reaction was stirred at 60-80℃ for 10-16 hours. S1.3 Purification and Drying: After the reaction is complete, the mixture is cooled, centrifuged, washed, and vacuum dried to obtain powdered Janus topological magnetic microspheres. S2. Forming of the synergistic granules: Janus topological magnetic microspheres are mixed with film-forming agent, dispersant and warning color by low-speed dry mixing to obtain the thifluzamide synergistic granules; In S1.2, the magnetic nanoparticles are iron oxide nanoparticles modified with at least one of oleic acid, glycidyl methacrylate, and vinylsilane. The hydrophilic functional monomer is acrylic acid, and the pH-responsive monomer is selected from at least one of dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; The mass ratio of styrene, divinylbenzene, thifluzamide, azobisisobutyronitrile, magnetic nanoparticles, acrylic acid, and pH-responsive monomers is 20-40:10-25:10-20:0.8-1.5:2-8:5-15:3-8.

2. The method for preparing a thifluzamide synergistic granule for controlling soil-borne diseases according to claim 1, characterized in that, In S1.1, the emulsifier is selected from at least one of anionic and nonionic surfactants.

3. The method for preparing a thifluzamide synergistic granule for controlling soil-borne diseases according to claim 1, characterized in that, In step S2, the film-forming agent is selected from at least one of polyvinyl alcohol, polyvinyl acetate, and cellulose derivatives; the warning color is an edible pigment or dye that meets agricultural use standards. The speed of low-speed dry mixing is 30-80 rpm, and the mixing time is 20-40 min; the mass ratio of Janus topological magnetic microspheres, film-forming agent, dispersant, and warning color is 70-85:10-20:1-5:0.5-3.

4. The method for preparing a thifluzamide synergistic granule for controlling soil-borne diseases according to claim 1, characterized in that, The preparation of the magnetic nanoparticles specifically includes the following steps: Preparation of hydroxylated Fe3O4: Under nitrogen protection, FeCl3·6H2O and FeCl2·4H2O were dissolved in deionized water, maintaining the Fe... 3+ Fe 2+ A precursor solution with a total iron ion concentration of 0.1-0.3 mol / L was prepared by mixing ingredients at a molar ratio of 1.9-2.1:

1. The solution was heated to 60-80℃ and 500-800 rpm, and ammonia was added to adjust the pH to 10-11, resulting in a black precipitate. Sodium citrate was added, and the mixture was stirred at 60-80℃ for 2-4 hours. Magnetic separation was performed, and the solution was thoroughly washed with deionized water until neutral. After drying, hydroxylated Fe3O4 was obtained, with a hydroxyl density >20 OH / nm. 2 ; Oleic acid modification method: During the formation of the black precipitate in the above steps, maintain the temperature and stir, and immediately add oleic acid. The surface double bond density is controlled to be 0.5-2 double bonds / nm by adjusting the amount of oleic acid added. 2 Continue the reaction for 1-3 hours; cool to room temperature, separate the black precipitate with a strong magnet, wash with deionized water and ethanol alternately, and dry under vacuum to obtain oleic acid modified magnetic nanoparticles. Silane coupling agent method: Hydroxylated Fe3O4 is dispersed in an ethanol / water mixed solvent with a volume ratio of 9:1, 1-5% KH-570 by mass of Fe3O4 is added, the pH is adjusted to 4-5 with acetic acid, the reaction is stirred at 60-70℃ for 6-12h, magnetic separation is performed, washing and drying are carried out to obtain silane coupling agent modified magnetic nanoparticles. Glycidyl methacrylate grafting method: hydroxylated Fe3O4 is dispersed in anhydrous toluene and sonicated for 30-60 min. Glycidyl methacrylate and triethylamine are added, and the mixture is refluxed at 80-100℃ for 12-24 h under nitrogen protection. After the reaction, the product is magnetically separated, washed alternately with toluene and acetone, and vacuum dried to obtain glycidyl methacrylate modified magnetic nanoparticles. The mass ratio of hydroxylated Fe3O4, glycidyl methacrylate, and triethylamine is 1:2.0-2.5:0.05-0.

10.

5. A thifluzamide synergistic granule prepared by the method described in any one of claims 1-4.

6. The thifluzamide synergistic granule according to claim 5, characterized in that, The granules are dry suspension seed coating agents.

7. The application of the thifluzamide synergistic granules according to any one of claims 5-6 in the prevention and control of soil-borne diseases in crops.

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