Biological fungicide for controlling crop root-knot nematode and preparation method thereof

Abstract

The application belongs to the technical field of agricultural fungicides, and discloses a biological fungicide for preventing and treating crop root-knot nematodes and a preparation method thereof. The biological fungicide is prepared from furfural, abamectin, deionized water, sodium phytate, sodium lignosulfonate, C8-10 alkyl glycoside, tea saponin, polysaccharide dispersion paste, citric acid, sodium citrate and sodium pyrosulfite. In the preparation, the furfural is used to dissolve the abamectin to obtain an organic cold oil phase, then a water phase containing sodium phytate and a surfactant component is prepared, the polysaccharide dispersion paste, an acidity adjusting component and sodium pyrosulfite are added to form a polysaccharide buffer, and the finished product is obtained after high-shear cooling emulsification and low-speed aging. The application is helpful to improve the dispersion and storage stability of the finished product, reduce the loss of volatile components under open conditions, and improve the effect of the biological fungicide on the soil at the roots of crops, and is suitable for treating crops harmed by root-knot nematodes by root irrigation or water application.

Description

Technical Field

[0001] This application relates to the field of agricultural fungicide technology, specifically to a bio-based fungicide for controlling crop root-knot nematodes and its preparation method. Background Technology

[0002] Root-knot nematodes are a type of harmful organism that infects the roots of crops. They commonly infect the roots of various crops, forming nodular root knots that hinder the normal absorption of water and nutrients. In daily production, when dealing with this type of underground disease, naturally extracted bio-based substances are often used to prepare fungicides. These bio-based fungicides mainly rely on plant active ingredients or microbial metabolites to exert their disease-suppressing effects. They are easily degraded in natural soil and do not easily cause long-term residue accumulation, giving them certain advantages in reducing environmental burden and meeting the requirements of low-carbon planting.

[0003] In conventional pesticide application, the above-mentioned formulations are usually applied to the farmland surface through root irrigation or flushing with water. The treatment solution needs to penetrate downwards with the help of water, passing through the shallow topsoil and reaching the root-dense area, and then contacting the target for control through fumigation or contact. To ensure good dispersion of the treatment solution in water, traditional processes often add surfactants or macromolecular thickeners during formulation.

[0004] However, the complex pore structure of soil means that during the infiltration process of traditional water-based fungicides, the high molecular weight substances they contain can easily cross-link or flocculate with free metal ions in the pore water of shallow soil layers. This often leads to premature flocculation of the treatment solution at the surface soil and its retention in shallow layers. Even if some of the treatment solution infiltrates to deeper layers, without suitable local retention methods, the active ingredients often leak further into deeper, non-target soil layers with the water, resulting in a lower actual drug concentration in the soil around the roots. In addition, some natural ingredients with fumigation activity have high saturated vapor pressures, leading to rapid volatilization and loss during surface application and initial infiltration stages. This significantly limits the utilization rate of the active ingredients and the duration of their effect on diseases.

[0005] Therefore, this application proposes a bio-based fungicide for controlling crop root-knot nematodes and its preparation method to address the shortcomings of the prior art. Summary of the Invention

[0006] To address this, this application provides a bio-based fungicide for controlling crop root-knot nematodes and its preparation method, which solves the problems of existing crop application processes where fungicides are easily physically trapped in the soil surface or leaked into non-target deep areas, and bio-based fungicides containing volatile nematicidal components are rapidly lost in the early stages of surface application, resulting in insufficient concentration of effective ingredients in the soil around the roots and low fungicide utilization.

[0007] To address the above problems, this application provides the following technical solution: In a first aspect, this application provides a bio-based fungicide for controlling root-knot nematodes in crops, employing the following technical solution: A bio-based fungicide for controlling root-knot nematodes in crops, the bio-based fungicide being prepared from the following raw materials in parts by weight: furfural 10.0-20.0 parts; abamectin 1.0-3.0 parts; deionized water 49.2-78.1 parts; sodium phytate 0.3-1.0 parts; sodium lignosulfonate 3.0-7.0 parts; C8-10 alkyl glycoside 4.0-8.0 parts; tea saponin 0.5-2.0 parts; polysaccharide dispersion 1.1-4.8 parts; citric acid 0.5-1.5 parts; sodium citrate 0.5-1.5 parts; sodium metabisulfite 1.0-2.0 parts.

[0008] By adopting the above technical solution, the interaction of various components in the formulation helps to adjust the distribution characteristics of the treatment solution in the soil and reduce the rate of volatile substance loss. During actual application, the treatment solution often penetrates the soil. At this time, sodium phytate dissolved in the aqueous phase can combine with some free divalent cations in the shallow soil pore water. This combination can, to some extent, reduce the premature cross-linking or flocculation of these cations with the polysaccharide dispersion and sodium lignin sulfonate. Combined with the surface-active effects of C8-10 alkyl glycosides and tea saponins, the treatment solution can usually penetrate the topsoil layer relatively smoothly.

[0009] As the infiltration process progresses into the soil around the crop roots, the concentration of the treatment solution decreases due to soil pore water, thus reducing the effect of sodium phytate on cation binding. Residual divalent cations such as calcium and magnesium in deeper soil layers can interact with sodium alginate, thereby increasing the retention of bio-based fungicides in localized soil layers. This makes it easier for emulsion droplets containing abamectin and furfural to maintain a certain distribution in the soil around the crop roots, reducing the proportion lost to deeper, non-target soil layers.

[0010] Furthermore, citric acid and sodium citrate provide a weakly acidic environment in the formulation solution, under which sodium metabisulfite provides a source of bisulfite and forms a reversible addition relationship with furfural. This transformation helps reduce the volatilization loss of some free furfural. After the bio-based fungicide is applied to the crop root zone, this reversible relationship helps maintain the retention level of furfural in the soil, thereby ensuring the relatively sustained effect of the active ingredient within the soil.

[0011] Preferably, the raw materials are present in the following proportions by weight: 15.0 parts furfural; 2.0 parts abamectin; 64.3 parts deionized water; 0.6 parts sodium phytate; 5.0 parts sodium lignosulfonate; 6.0 parts C8-10 alkyl glycoside; 1.2 parts tea saponin; 2.4 parts polysaccharide dispersion; 1.0 part citric acid; 1.0 part sodium citrate; 1.5 parts sodium metabisulfite.

[0012] By employing the above-mentioned technical solution, this specific ratio typically matches the ion-binding amount of sodium phytate with the number of cross-linking sites of polysaccharides. While maintaining adequate surface penetration, this helps to improve the distribution ratio of the active ingredient in the soil around the crop roots, thus balancing fungicide flowability and the deposition ratio of the active ingredient in the target area.

[0013] Preferably, the polysaccharide dispersion is composed of sodium alginate and propylene glycol, and the weight ratio of sodium alginate to propylene glycol is 1:(5-10).

[0014] By employing the above technical solution, propylene glycol is used as a non-aqueous polar medium to disperse sodium alginate powder. When introduced into the aqueous phase, the propylene glycol on the powder surface diffuses outward due to concentration differences. This process slows down the rate at which water penetrates into the powder, largely preventing the rapid absorption of water and clumping of the particle surface. The sodium alginate particles then hydrate in a relatively loose state in the aqueous phase, which helps improve the uniformity of the dispersed phase within the emulsion and has a positive impact on the centrifugal and static stability of the finished drug.

[0015] Preferably, the method for preparing the polysaccharide dispersion includes the following steps: Add the sodium alginate to the mixing tank, start the stirrer and set the speed to 50-100 rpm. Under the condition of 20-25℃, add the propylene glycol dropwise to the sodium alginate over 2-4 minutes. After the addition is complete, continue stirring for 10-15 minutes to obtain the polysaccharide dispersion.

[0016] By employing the above technical solution, and with appropriate stirring at specific temperatures and feeding times, propylene glycol can be uniformly adhered to the outer surface of sodium alginate particles. Suitable stirring duration typically facilitates the formation of a relatively uniform solvent isolation layer between particles, thereby reducing powder agglomeration during subsequent hydration operations.

[0017] Secondly, this application provides a method for preparing a bio-based fungicide for controlling crop root-knot nematodes, using the following technical solution: A method for preparing a bio-based fungicide for controlling crop root-knot nematodes includes the following steps: S1: Pump the furfural into the organic batching vessel, add the abamectin and stir to obtain an organic cold oil phase; S2: The deionized water is injected into the main reactor and heated. Sodium phytate is added and stirred to obtain a pre-complexed aqueous solution. Sodium lignin sulfonate, C8-10 alkyl glycoside, and tea saponin are added sequentially to the pre-complexed aqueous solution and stirred continuously to obtain a surfactant aqueous solution. S3: The polysaccharide dispersion slurry is poured into the surfactant aqueous solution at a uniform speed and stirred to obtain a polysaccharide gel solution; citric acid and sodium citrate are added to the polysaccharide gel solution and the pH value is controlled to obtain a constant acid gel solution; sodium metabisulfite is added to the constant acid gel solution and stirred to obtain a polysaccharide buffer solution; S4: Start the high-shear disperser and pump the organic cold oil phase into the polysaccharide buffer solution at a uniform rate to form a mixed liquid. During the pumping process, the mixed liquid is cooled to obtain the initial water emulsion. S5: Turn off the high-shear disperser, switch the stirring mode, and control the temperature of the initial water emulsion. Continue stirring and aging to obtain the bio-based bactericide.

[0018] By employing the above technical solution, this method utilizes a stepwise phase transfer approach. In the initial stage of preparation, avermectin is dissolved in the organic phase, while complexing and surfactant components are introduced stepwise into the continuous aqueous phase. When the dispersion containing polysaccharide materials is added, it provides a reaction environment for the subsequent reversible addition between sodium metabisulfite and furfural at a specific pH. Subsequently, under the shearing action of the dispersion equipment, the oil phase containing the active substances enters the aqueous phase and is dispersed into droplets. Combined with cooling operations, this helps reduce the loss of volatile components during emulsification and improves the emulsion dispersion state. Subsequent low-speed aging further stabilizes the finished product, which plays a role in maintaining the physical stability of the final product.

[0019] Preferably, in step S1, the liquid phase temperature in the organic mixing vessel is controlled at 15-18°C, the stirring speed is 100-200 rpm, and the stirring time is 30-40 minutes.

[0020] By adopting the above technical solution, since furfural has a high saturated vapor pressure, controlling the liquid phase temperature within a lower range helps to control the natural loss of volatile components during the batching stage. Stirring at the aforementioned specific rotation speed allows avermectin technical material to dissolve in furfural, thereby obtaining a liquid phase mixture, providing liquid material for subsequent phase transfer.

[0021] Preferably, in step S2, the water temperature in the main reactor is controlled to rise to 40-45°C, the stirring speed after adding the sodium phytate is 150-250 rpm, and the stirring time is 10-15 minutes; the stirring speed after adding the sodium lignosulfonate, the C8-10 alkyl glycoside, and the tea saponin is 150-250 rpm, and the stirring time is 20-30 minutes.

[0022] By employing the above-mentioned technical solution, sodium phytate is first added to heated deionized water and stirred. Its properties allow it to pre-complex trace amounts of free divalent cations present in the water. This pretreatment reduces the impact of these cations on the hydration process of subsequently added substances. Subsequently, sodium lignosulfonate, C8-10 alkyl glycosides, and tea saponins are added in steps, maintaining appropriate stirring times to ensure uniform dispersion of various surfactants in the continuous phase, resulting in an aqueous solution with suitable dispersion properties.

[0023] Preferably, in step S3, the temperature of the main reactor is maintained at 40-45°C, and the pH of the polysaccharide solution is controlled to be 5.3-5.8 using the added citric acid and sodium citrate.

[0024] By employing the above technical solution, citric acid and sodium citrate are used to limit the pH value of the adhesive solution to this weakly acidic range, aiming to ensure that the subsequently added sodium metabisulfite remains in a properly dissociated state. Under this acid-base environment, the dissociated bisulfite ions are ready to undergo an addition reaction, and can reversibly add to free furfural in subsequent processes.

[0025] Preferably, in step S4, the rotation speed of the high-shear disperser is set to 3000-3500 rpm, and the mixed liquid is cooled to 23-27°C within 20-30 minutes by cooling circulating water during pumping.

[0026] By employing the above technical solution, the shearing action generated during the operation of the disperser disperses the pumped cold oil phase into smaller droplets. During the mixing of the two-phase fluids, cooling water is introduced externally to reduce the overall temperature of the mixture. This cooling process, to some extent, reduces the tendency of the initial droplets to coalesce due to changes in surface tension, which is beneficial for maintaining the stability of the dispersed droplet size.

[0027] Preferably, in step S5, the stirring mode is switched to an anchor mixer and the speed is set to 30-60 rpm, the temperature of the initial water emulsion is controlled to be 23-27°C, and the continuous stirring and aging time is 40-50 minutes.

[0028] By adopting the above technical solution, switching from high shear to lower-speed anchor stirring reduces the internal shearing effect of the material. Continuous stirring under relatively constant temperature conditions allows for the redistribution of components at the oil-water interface. This aging process allows time for the reversible addition relationship between furfural and bisulfite ions to stabilize, promoting a more stable finished product state and positively impacting the long-term storage physical properties of the finished product.

[0029] Compared with the prior art, this application has at least the following beneficial effects: 1. This application introduces sodium phytate and polysaccharides, utilizing the binding capacity of sodium phytate for cations to reduce premature cross-linking or flocculation of polysaccharides in shallow soil, thus facilitating the smooth penetration of this bio-based fungicide into the topsoil. As the bio-based fungicide continues to infiltrate, the binding effect of sodium phytate on cations gradually decreases, and some ions in the soil can interact with the polysaccharides, allowing the fungicide components to be retained to a certain extent in the soil around the crop roots, thereby helping to increase the distribution ratio of effective components in the underground target area.

[0030] 2. This application utilizes citric acid and sodium citrate to provide a weakly acidic environment and sodium metabisulfite to provide a source of bisulfite, enabling a reversible addition relationship between these ions and furfural. This reduces the volatilization loss of some free furfural under open conditions. When the bio-based fungicide is applied to the root zone of crops, this reversible relationship helps maintain furfural retention levels. Combined with the contact action of abamectin, this enhances the persistence of action when used as a fungicide to control root-knot nematodes.

[0031] 3. This application utilizes a non-aqueous medium to pre-disperse polysaccharide powder, thereby delaying water penetration through medium diffusion and reducing the likelihood of powder clumping upon contact with water, thus improving the initial dispersion uniformity of the bio-based solution. In the preparation process of this fungicide, the incorporation of cooling and aging operations helps reduce droplet aggregation during emulsification and stratification after storage. This process helps maintain the physical stability of the fungicide after storage, thus providing a more uniform fungicide base for subsequent application to crops to control root-knot nematodes.

[0032] To more intuitively illustrate the prior art and this application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0033] Figure 1 This is a flowchart illustrating the preparation method of the bio-based fungicide for controlling crop root-knot nematodes according to this application. Detailed Implementation

[0034] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] In the description of this application: unless otherwise stated, "a plurality of" means two or more. The terms "first," "second," "third," etc., in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (e.g., they should not be construed as an emphasis on importance or order). Expressions such as "including," "comprising," and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0036] The terms used in this application, such as "upper," "lower," "left," "right," and "middle," are generally used to indicate the general relative positional relationship for the purpose of intuitive understanding by referring to the accompanying drawings, and are not absolute limitations on the positional relationship in the actual product.

[0037] The main raw materials and reagents used in the following preparation examples, examples, comparative examples and test examples are as follows. Unless otherwise specified, all reagents are commercially available analytical grade or higher grade products.

[0038] Avermectin, CAS No. 71751-41-2, commercially available industrial grade, purity ≥95wt%; furfural, CAS No. 98-01-1, commercially available industrial grade, purity ≥98wt%; C8-10 alkyl glycoside, CAS No. 68515-73-1, commercially available industrial grade, specification APG0810; tea saponin, CAS No. 8047-15-2, commercially available industrial grade, purity ≥80wt%; sodium lignosulfonate, CAS No. 8061-51-6, commercially available industrial dispersant grade, weight average molecular weight 10,000 to 50,000; sodium metabisulfite, CAS No. 7681-57-4, commercially available industrial grade; sodium phytate, CAS No. 14306-25 -3, commercially available industrial grade hydrate; sodium alginate, CAS number 9005-38-3, commercially available industrial grade, its dynamic viscosity at 20℃ is 20 mPa·s to 50 mPa·s for a 1 wt% aqueous solution; propylene glycol, CAS number 57-55-6, commercially available industrial grade, water content ≤0.1 wt%; citric acid, CAS number 77-92-9, commercially available analytical grade; sodium citrate, CAS number 68-04-2, commercially available analytical grade anhydrous.

[0039] Preparation Example 1: This preparation example provides a method for preparing a polysaccharide dispersion, including the following steps: Add 0.4 parts by weight of sodium alginate to the mixing tank, start the stirrer, set the speed to 75 rpm, and add 2.0 parts by weight of propylene glycol to the sodium alginate dropwise over 3 minutes at 25°C. After the addition is complete, continue stirring for 12 minutes to obtain the polysaccharide dispersion.

[0040] Preparation Example 2: This preparation example provides a method for preparing a polysaccharide dispersion, including the following steps: Add 0.1 parts by weight of sodium alginate to the mixing tank, start the stirrer, set the speed to 50 rpm, and add 1.0 part by weight of propylene glycol to the sodium alginate dropwise over 2 minutes at 20°C. After the addition is complete, continue stirring for 10 minutes to obtain the polysaccharide dispersion.

[0041] Preparation Example 3: This preparation example provides a method for preparing a polysaccharide dispersion, including the following steps: Add 0.8 parts by weight of sodium alginate to the mixing tank, start the stirrer, set the speed to 100 rpm, and add 4.0 parts by weight of propylene glycol to the sodium alginate dropwise over 4 minutes at 25°C. After the addition is complete, continue stirring for 15 minutes to obtain the polysaccharide dispersion.

[0042] Reference Figure 1 Examples 1 to 3 below provide a method for preparing a bio-based fungicide for controlling crop root-knot nematodes. The preparation method includes the following steps: S1: preparing an organic cold oil phase; S2: preparing an aqueous surfactant solution; S3: preparing a polysaccharide buffer solution; S4: preparing a primary water-in-oil emulsion; S5: preparing the bio-based fungicide. Example

[0043] This embodiment provides a method for preparing a bio-based fungicide for controlling crop root-knot nematodes, including the following steps: S1: Pump 15.0 parts by weight of furfural into an organic batching vessel with a refrigerated brine circulation jacket, control the liquid phase temperature in the vessel to 16°C, start the stirrer and set the speed to 150 rpm, add 2.0 parts by weight of abamectin, and continue stirring for 35 minutes to obtain an organic cold oil phase. S2: Inject 64.3 parts by weight of deionized water into the main reactor, turn on the jacket heating to raise the water temperature to 42°C, add 0.6 parts by weight of sodium phytate, and stir at 200 rpm for 12 minutes to obtain a pre-complexed aqueous solution; add 5.0 parts by weight of sodium lignosulfonate, 6.0 parts by weight of C8-10 alkyl glycoside, and 1.2 parts by weight of tea saponin to the pre-complexed aqueous solution in sequence, maintain 42°C and stir continuously at 200 rpm for 25 minutes to obtain a surfactant aqueous solution; S3: Maintain the temperature of the main reactor at 42℃ and the stirring speed at 200 rpm. Pour 2.4 parts by weight of the polysaccharide dispersion prepared in Preparation Example 1 into the surfactant aqueous solution at a uniform rate within 4 minutes, and continue stirring for 12 minutes to obtain a polysaccharide gel solution. Add 1.0 parts by weight of citric acid and 1.0 parts by weight of sodium citrate to the polysaccharide gel solution, and control the pH to 5.5 to obtain a constant acid gel solution. Add 1.5 parts by weight of sodium metabisulfite to the constant acid gel solution and stir for 10 minutes to obtain a polysaccharide buffer solution. S4: Start the high shear disperser and set the speed to 3200 rpm. Pump the 16°C organic cold oil phase into the 42°C polysaccharide buffer solution at a uniform speed. During the pumping process, cooling circulating water is introduced through the jacket of the main reactor to control the temperature of the mixed liquid to drop to 25°C within 25 minutes to obtain the initial water emulsion. S5: Turn off the high-shear disperser, switch to the anchor mixer and set the speed to 45 rpm, control the temperature of the mixed liquid to 25℃, and continue stirring and aging for 45 minutes to obtain the bio-based bactericide. Example

[0044] This embodiment provides a method for preparing a bio-based fungicide for controlling crop root-knot nematodes, including the following steps: S1: Pump 10.0 parts by weight of furfural into an organic batching vessel with a refrigerated brine circulation jacket, control the liquid phase temperature in the vessel to 15°C, start the stirrer and set the speed to 100 rpm, add 1.0 parts by weight of abamectin, and continue stirring for 30 minutes to obtain an organic cold oil phase. S2: Inject 78.1 parts by weight of deionized water into the main reactor, turn on the jacket heating to raise the water temperature to 40°C, add 0.3 parts by weight of sodium phytate, and stir at 150 rpm for 10 minutes to obtain a pre-complexed aqueous solution; add 3.0 parts by weight of sodium lignosulfonate, 4.0 parts by weight of C8-10 alkyl glycoside, and 0.5 parts by weight of tea saponin to the pre-complexed aqueous solution in sequence, maintain 40°C and stir continuously at 150 rpm for 20 minutes to obtain a surfactant aqueous solution; S3: Maintain the temperature of the main reactor at 40°C and the stirring speed at 150 rpm. Pour 1.1 parts by weight of the polysaccharide dispersion prepared in Preparation Example 2 into the surfactant aqueous solution at a uniform rate within 3 minutes, and continue stirring for 10 minutes to obtain a polysaccharide gel solution. Add 0.5 parts by weight of citric acid and 0.5 parts by weight of sodium citrate to the polysaccharide gel solution, and control the pH to 5.3 to obtain a constant acid gel solution. Add 1.0 part by weight of sodium metabisulfite to the constant acid gel solution and stir for 10 minutes to obtain a polysaccharide buffer solution. S4: Start the high shear disperser and set the speed to 3000 rpm. Pump the 15°C organic cold oil phase into the 40°C polysaccharide buffer solution at a uniform speed. During the pumping process, cooling circulating water is introduced through the jacket of the main reactor to control the temperature of the mixed liquid to drop to 23°C within 20 minutes to obtain the initial water emulsion. S5: Turn off the high-shear disperser, switch to the anchor mixer and set the speed to 30 rpm, control the temperature of the mixed liquid to 23℃, and continue stirring and aging for 40 minutes to obtain the bio-based bactericide. Example

[0045] This embodiment provides a method for preparing a bio-based fungicide for controlling crop root-knot nematodes, including the following steps: S1: Pump 20.0 parts by weight of furfural into an organic batching vessel with a refrigerated brine circulation jacket, control the liquid phase temperature in the vessel to 18°C, start the stirrer and set the speed to 200 rpm, add 3.0 parts by weight of abamectin, and continue stirring for 40 minutes to obtain an organic cold oil phase. S2: Inject 49.2 parts by weight of deionized water into the main reactor, turn on the jacket heating to raise the water temperature to 45°C, add 1.0 parts by weight of sodium phytate, and stir at 250 rpm for 15 minutes to obtain a pre-complexed aqueous solution; add 7.0 parts by weight of sodium lignosulfonate, 8.0 parts by weight of C8-10 alkyl glycoside, and 2.0 parts by weight of tea saponin to the pre-complexed aqueous solution in sequence, maintain 45°C and stir continuously at 250 rpm for 30 minutes to obtain a surfactant aqueous solution; S3: Maintain the temperature of the main reactor at 45°C and the stirring speed at 250 rpm. Pour 4.8 parts by weight of the polysaccharide dispersion obtained in Preparation Example 3 into the surfactant aqueous solution at a uniform rate within 5 minutes, and continue stirring for 15 minutes to obtain a polysaccharide gel solution. Add 1.5 parts by weight of citric acid and 1.5 parts by weight of sodium citrate to the polysaccharide gel solution, and control the pH to 5.8 to obtain a constant acid gel solution. Add 2.0 parts by weight of sodium metabisulfite to the constant acid gel solution and stir for 10 minutes to obtain a polysaccharide buffer solution. S4: Start the high shear disperser and set the speed to 3500 rpm. Pump the 18°C ​​organic cold oil phase into the 45°C polysaccharide buffer solution at a uniform speed. During the pumping process, cooling circulating water is introduced through the jacket of the main reactor to control the temperature of the mixed liquid to drop to 27°C within 30 minutes to obtain the initial water emulsion. S5: Turn off the high-shear disperser, switch to the anchor mixer and set the speed to 60 rpm, control the temperature of the mixed liquid to 27°C, and continue stirring and aging for 50 minutes to obtain the bio-based bactericide.

[0046] Comparative Example 1: Compared with Example 1, the difference is that polysaccharide dispersion slurry is not used in S3. Instead, 0.4 parts by weight of sodium alginate powder and 2.0 parts by weight of propylene glycol are added to the surfactant aqueous solution at a uniform rate within 4 minutes, respectively. All other aspects are the same.

[0047] Comparative Example 2: Compared with Example 1, the difference is that sodium phytate is not added in S2, and the amount of deionized water is increased from 64.3 parts by weight to 64.9 parts by weight, while the rest are the same.

[0048] Comparative Example 3: Compared with Example 1, the difference is that the polysaccharide dispersion prepared in Example 1 is not used in S3. Instead, 2.0 parts by weight of propylene glycol are added to the surfactant aqueous solution at a uniform rate within 4 minutes, and the amount of deionized water in S2 is increased from 64.3 parts by weight to 64.7 parts by weight. All other aspects are the same.

[0049] Comparative Example 4: Compared with Example 1, the difference is that sodium metabisulfite is not added in S3, and the amount of deionized water in S2 is increased from 64.3 parts by weight to 65.8 parts by weight, while the rest are the same.

[0050] Comparative Example 5: Compared with Example 1, the difference is that tea saponin is not added in S2, and the amount of deionized water is increased from 64.3 parts by weight to 65.5 parts by weight, while the rest are the same.

[0051] Comparative Example 6: Compared with Example 1, the difference is that the order of adding raw materials in S2 is changed. After the water temperature is raised to 42°C, 5.0 parts by weight of sodium lignosulfonate, 6.0 parts by weight of C8-10 alkyl glycoside, and 1.2 parts by weight of tea saponin are added in sequence. The temperature is maintained at 42°C and the mixture is stirred continuously at 200 rpm for 25 minutes. Then, 0.6 parts by weight of sodium phytate is added and the mixture is stirred continuously at 200 rpm for 12 minutes to obtain the surfactant aqueous solution with sodium phytate added later. All other steps are the same.

[0052] Test Example 1: Experimental steps: 1. In the preparation process of Examples 1 to 3 and Comparative Example 1, the feed amount was scaled up to 1 kg per part by weight. After the preparation in step S3 of each group was completed, all the polysaccharide buffer solutions prepared in the corresponding batch were slowly poured into a pre-weighed 60-mesh stainless steel standard test sieve for atmospheric pressure filtration. The sieve surface was rinsed with room temperature deionized water until the filtrate flowing out was colorless, clear, and no longer viscous.

[0053] 2. Place the entire test sieve with surface residue in an 85℃ forced-air drying oven and dry it to constant weight. Weigh the final mass and subtract the weight of the test sieve itself to obtain the mass of the dried agglomerate on the sieve. Divide the mass of the dried agglomerate on the sieve by the total theoretical mass of sodium alginate powder input for this batch and multiply by 100% to obtain the agglomeration rate of the powder on the sieve for the corresponding test object.

[0054] 3. Take 400 ml of each of the finished bactericides prepared in Examples 1 to 3 and Comparative Example 1, and divide them into two equal portions. Measure 200 ml of each portion and place it into a 250 ml sealed glass reagent bottle. Thus, each test subject will have two reagent bottles containing equal amounts of sample, labeled as the cold storage group and the hot storage group, respectively. Place the reagent bottles of the cold storage group in a low-temperature incubator set to 0°C for 14 days for cold storage testing, and place the reagent bottles of the hot storage group in a constant-temperature drying oven set to 54°C for 14 days for hot storage testing.

[0055] 4. After the storage period, remove all reagent bottles and allow them to stand and return to an ambient temperature of 25°C. Transfer 50 ml of each sample into a graduated centrifuge tube and centrifuge at 3500 rpm for 15 minutes. After centrifugation, read the volume of the upper oil phase and the lower clear aqueous phase. Divide the volume of the upper oil phase by the total volume of the sample in the centrifuge tube (50 ml) and multiply by 100% to obtain the corresponding group's cold-stored or hot-stored centrifugation oil separation rate; divide the volume of the lower aqueous phase by the total volume (50 ml) and multiply by 100% to obtain the corresponding group's cold-stored or hot-stored centrifugation water separation rate.

[0056] The experimental results are shown in Table 1: Table 1: Data on powder dispersion and storage stability of Examples 1 to 3 and Comparative Example 1 Example 1 0.7 0.4 ＜0.1 1.3 0.4 Example 2 1.1 0.8 0.2 1.7 0.8 Example 3 1.4 0.6 ＜0.1 1.5 0.5 Comparative Example 1 18.2 4.6 1.5 9.4 3.8 Test conclusion: According to the data in Table 1, after using polysaccharide dispersions in Examples 1 to 3, the agglomeration rate of polysaccharide powder on the sieve was 0.7% to 1.4%; in Comparative Example 1, sodium alginate dry powder and propylene glycol were added simultaneously, and the agglomeration rate on the sieve was 18.2%. These results indicate that pre-dispersing sodium alginate with propylene glycol is beneficial in reducing agglomeration and sieve retention after sodium alginate enters the aqueous phase. After sodium alginate wetted with propylene glycol is added to the aqueous phase, the contact process between water and the surface of the sodium alginate dry powder is more gradual, which can reduce the formation of a gel-like coating after rapid water absorption on the outer layer of the particles, thereby improving the dispersion uniformity of sodium alginate in the aqueous phase.

[0057] Centrifugation results after storage showed that the centrifugal water separation rate and centrifugal oil separation rate of Examples 1 to 3 were lower than those of Comparative Example 1 after cold and hot storage. This result indicates that adding sodium alginate to the aqueous phase after pre-dispersion is beneficial for its participation in the thickening and emulsification dispersion process of the aqueous phase, and helps improve the phase stability of the finished product after low and high temperature storage. Comparative Example 1 used sodium alginate dry powder and propylene glycol for simultaneous direct addition. After S3, the powder sieving rate was relatively high, indicating that some sodium alginate was not fully dispersed into the aqueous phase; correspondingly, its centrifugal water separation rate and centrifugal oil separation rate after cold and hot storage were higher than those of Examples 1 to 3. The above data indicate that the non-aqueous pre-dispersion process helps improve the uniformity of preparation and enhances the physical stability of the finished product after storage.

[0058] Test Example 2: Experimental steps: 1. Take 200 grams each of the finished bactericides prepared in Examples 1 to 3 and Comparative Example 4 as test objects. Divide each test object into open volatilization test samples and closed original sample determination samples. The closed original sample determination samples are stored in a sealed container until furfural determination is performed.

[0059] 2. For the open-air evaporation test, prepare three clean glass petri dishes with an inner diameter of 10 cm for each test object, for a total of 12 petri dishes. Accurately weigh and record the mass of each empty petri dish. Add 20.0 g of test sample to each petri dish, weigh and record the total mass again, and subtract the mass of the empty petri dish from the total mass to obtain the initial mass of each group of samples. Place all petri dishes containing samples in an environmental test chamber set at 35℃ and 45% relative humidity, and leave them in an open state for 48 hours to examine the mass loss under open conditions. After the standing period, remove the petri dishes and allow them to cool to room temperature, then accurately weigh the remaining total mass. Subtract the mass of the empty petri dish from the remaining total mass to obtain the remaining mass of each group of samples after standing. Subtract the remaining mass after standing from the initial mass of the sample, divide the difference by the initial mass of the sample, and finally multiply by 100% to obtain the open-air evaporation mass loss rate of the corresponding test sample. For each test subject, the average value of the open evaporation mass loss rate of three parallel petri dishes was calculated and used as the open evaporation mass loss rate of that test subject; the initial mass and the remaining mass after placement of the sample were also averaged from three parallel petri dishes.

[0060] 3. Determine the furfural content of the samples after open-air storage in step 2. Collect the remaining sample from each petri dish and transfer it to an iodine flask. Add 50 mL of anhydrous ethanol for extraction, then dilute with deionized water to bring the furfural in the sample into a state that can be measured by the reaction with hydroxylamine hydrochloride. Add 100 mL of 0.5 mol / L hydroxylamine hydrochloride solution, and shake the reaction at room temperature for 30 minutes. Titrate the generated free hydrochloric acid with bromophenol blue as an indicator using 1.0 mol / L sodium hydroxide standard solution until the solution changes from yellow to blue-purple. Record the volume of sodium hydroxide standard solution consumed and calculate the furfural mass in the open-air stored sample accordingly. Calculate the furfural mass in the open-air stored sample of the same test subject using the above method for three parallel petri dishes. Take the average of the three parallel petri dish calculations as the furfural mass in the open-air stored sample of that test subject.

[0061] 4. Perform furfural determination on the sealed original sample. Take 20.0 g of the sealed original sample from each test subject and determine the volume of sodium hydroxide standard solution consumed using the same titration method as in step 3. Calculate the mass of furfural in the sealed original sample based on this. Divide the mass of furfural in the open sample calculated in step 3 by the mass of furfural in the sealed original sample calculated in this step, and then multiply by 100% to obtain the furfural retention rate for the corresponding test subject.

[0062] The experimental results are shown in Table 2: Table 2: Open-air volatilization and furfural retention test data of Examples 1 to 3 and Comparative Example 4 Example 1 20.02 18.75 6.34 64.6 Example 2 20.05 18.66 6.93 61.8 Example 3 19.98 18.38 8.01 59.3 Comparative Example 4 20.01 17.12 14.44 42.5 Test conclusion: According to the data in Table 2, the open-air volatilization mass loss rate of Examples 1 to 3 after being exposed to the open at 35°C for 48 hours was 6.34% to 8.01%, and the furfural retention rate was 59.3% to 64.6%. The open-air volatilization mass loss rate of Comparative Example 4, without the addition of sodium metabisulfite, was 14.44%, and the furfural retention rate was 42.5%. These results indicate that under the test conditions, Examples 1 to 3 with the addition of sodium metabisulfite exhibited a lower open-air volatilization mass loss rate and a higher furfural retention rate compared to Comparative Example 4.

[0063] In this fungicide, sodium metabisulfite, when added to a polysaccharide buffer solution with a pH of 5.3 to 5.8, provides a source of bisulfite. During emulsification and aging, a reversible addition relationship can be formed between bisulfite and the aldehyde groups in furfural, thereby reducing some of the volatilization loss of free furfural under open conditions. Comparative Example 4, without the addition of sodium metabisulfite, showed a higher mass loss rate and lower furfural retention rate under the same open storage conditions. These results indicate that the addition of sodium metabisulfite helps to improve the furfural retention level of this fungicide after open storage.

[0064] Test Example 3: Experimental steps: 1. Eighteen rigid polyvinyl chloride (PVC) pipes with an inner diameter of 10 cm and a length of 45 cm were used as test soil columns, with three parallel soil columns set up for each test object. A layer of nylon mesh with a pore size of 2 mm was laid at the bottom of the soil column, and then a layer of quartz sand with a thickness of 2 cm was laid on the mesh. Neutral loam soil taken from the topsoil of farmland was naturally air-dried and crushed, and after passing through a 2 mm standard sieve, it was measured at 1.2 g / cm³. 3 The bulk density of the solution is evenly filled into each soil column to a height of 40 cm. Deionized water is slowly dripped onto the surface of the soil column until the soil moisture content reaches 60% of the field capacity. The column is then left to stand for 24 hours to reach equilibrium before use.

[0065] 2. Take 10.0 g of each of the finished bactericides prepared in Examples 1 to 3 and Comparative Examples 2, 3, and 6 as test subjects, and add them to 1990 g of deionized water, stirring evenly to prepare a 200-fold dilution treatment solution. Accurately measure 100 ml of the corresponding diluted treatment solution for each parallel soil column of each test subject, and slowly and evenly add it to the surface of the test soil column using a peristaltic pump at a flow rate of 2 ml / min. Record the initial total mass of abamectin contained in the 100 ml of diluted treatment solution added to each test soil column.

[0066] 3. After the treatment solution has completely penetrated the soil surface, lay a layer of quantitative filter paper on the surface of the soil column. Measure 250 ml of deionized water and add it dropwise to the top of the soil column at the same flow rate for leaching treatment. After the leaching operation is completed, let the soil column stand vertically at room temperature for 48 hours.

[0067] 4. Break the wall of the test soil column and cut it vertically according to depth. Collect all soil from a depth of 0 to 5 cm as the topsoil sample, and collect all soil from a depth of 15 to 30 cm as the deepsoil sample. Mix each soil sample thoroughly and accurately weigh the total weight of each layer. Weigh 50.0 grams from each soil sample and place it in a stoppered Erlenmeyer flask.

[0068] 5. Add 100 mL of methanol to the Erlenmeyer flask and extract by shaking in a constant-temperature shaker for 2 hours. Filter and collect the extract. Determine the concentration of abamectin in the extract using high-performance liquid chromatography (HPLC). Calculate the mass of abamectin in 50.0 g of soil sample using this concentration, and then calculate the total mass of abamectin in each soil layer based on the total weight of the corresponding soil layer. Divide the total mass of abamectin in the 0-5 cm soil layer by the initial total mass of abamectin, and then multiply by 100% to obtain the percentage of abamectin content in the 0-5 cm topsoil of the corresponding test soil column. Divide the total mass of abamectin in the 15-30 cm soil layer by the initial total mass of abamectin, and then multiply by 100% to obtain the percentage of abamectin content in the 15-30 cm deep soil of the corresponding test soil column. Subtract the sum of the percentages of the 0-5 cm topsoil content and the 15-30 cm deep soil content from 100%, and the remaining portion is counted as the percentage of soil layers not included in the calculation and the percentage of leachate in the corresponding test soil column. For each test soil column, the percentage of topsoil content (0-5 cm), percentage of deep soil content (15-30 cm), and percentage of soil layers and leachate not included were calculated using the above method. After calculating the percentages for three parallel soil columns of the same test object, the average value was taken as the test result for that test object.

[0069] The experimental results are shown in Table 3: Table 3: Distribution data of abamectin in soil layers in Examples 1 to 3 and Comparative Examples 2, 3, and 6 Example 1 18.6 58.2 23.2 Example 2 20.4 54.6 25.0 Example 3 19.7 56.8 23.5 Comparative Example 2 42.8 28.6 28.6 Comparative Example 3 13.5 31.8 54.7 Comparative Example 6 34.6 39.5 25.9 Test conclusion: According to the data in Table 3, the content of abamectin in Examples 1 to 3 ranged from 18.6% to 20.4% in the 0-5 cm topsoil and from 54.6% to 58.2% in the 15-30 cm deep soil. Comparative Example 2, without the addition of sodium phytate, had a content of 42.8% in the 0-5 cm topsoil and 28.6% in the 15-30 cm deep soil. Comparative Example 3, without using the polysaccharide dispersion prepared in Preparation Example 1, had a content of 13.5% in the 0-5 cm topsoil and 31.8% in the 15-30 cm deep soil, with 54.7% excluding soil layers and leachate. Comparative Example 6, with a change in the order of sodium phytate addition, had a content of 34.6% in the 0-5 cm topsoil and 39.5% in the 15-30 cm deep soil. The above results indicate that the content of abamectin in Examples 1 to 3 in soil layers 15 to 30 cm deep was higher than that in Comparative Examples 2, 3 and 6.

[0070] In Examples 1 to 3, after adding sodium phytate, polysaccharide dispersion, and surfactant, the content of avermectin in the 15-30 cm deep soil layer was relatively high, while the content in the soil layer and leachate was relatively low. Comparative Example 2, without the addition of sodium phytate, showed a higher proportion of avermectin in the 0-5 cm topsoil layer, indicating that the addition of sodium phytate helps reduce the retention of avermectin in the topsoil. Comparative Example 3, without using the polysaccharide dispersion prepared in Preparation Example 1, showed a higher proportion of avermectin in the soil layer and leachate, indicating that the addition of the polysaccharide dispersion helps reduce the proportion of avermectin that continues to migrate with leachate. In Comparative Example 6, after changing the order of sodium phytate addition, the proportion of avermectin in the 0-5 cm topsoil layer was higher than in Example 1, while the proportion of avermectin in the 15-30 cm deep soil layer was lower than in Example 1, indicating that the order of sodium phytate addition affects the distribution of avermectin in the soil layer. The above results indicate that the preparation methods of Examples 1 to 3 help to improve the distribution ratio of abamectin in soil layers 15 to 30 cm deep.

[0071] Test Example 4: Experimental steps: 1. Prepare healthy tomato seedlings at the 3-leaf-1-heart stage and transplant them into plastic pots filled with high-temperature sterilized nutrient soil, planting one seedling per pot. This test included 10 treatment groups, corresponding to the commercially available fungicides used in Examples 1-3 and Comparative Examples 1-6, respectively, and a blank control group without the commercially available fungicide. Each treatment group was replicated three times, with five pots per replicate, for a total of 15 pots of tomato seedlings used in each treatment group. After transplanting and survival, holes were made in the soil around the roots of the tomato seedlings, and each pot was inoculated with 2 ml of an aqueous suspension containing southern root-knot nematode eggs and second-instar larvae, with the inoculation amount controlled to approximately 2000 nematodes per pot.

[0072] 2. Apply the pesticide on the 3rd day after nematode inoculation. Take the finished fungicide from Examples 1 to 3 and Comparative Examples 1 to 6, and dilute it 500 times with deionized water to prepare working treatment solutions. Apply the working treatment solution to the flowerpots of the corresponding treatment groups using the root drenching method, with each plant receiving 100 ml. The blank control group is drenched with 100 ml of deionized water.

[0073] 3. All experimental potted plants were placed in a greenhouse for uniform cultivation. The greenhouse temperature was controlled between 25℃ and 28℃, and the relative humidity was maintained between 65% and 75%. Routine light, water, and fertilizer management were carried out. The cultivation cycle was set at 45 days.

[0074] 4. After the cultivation period, use a measuring tape to measure the distance from the base of the stem to the apical growing point of each tomato plant from the soil surface. Add the measured distances of 15 plants in each group and divide by 15 to obtain the plant height of the corresponding group. Then cut the plant above the cotyledon node, collect the above-ground parts, and weigh the total fresh weight of 15 plants in each group on a balance. Divide the total fresh weight by 15 to obtain the fresh weight of the above-ground parts of the corresponding group.

[0075] 5. After completing the measurement of plant height and above-ground fresh weight, remove the root system of each treatment group and rinse the soil attached to the root system with clean water. Observe the root knot formation of tomato roots and record it according to the 0 to 9 grade standard. Grade 0 indicates no root knot; Grade 1 indicates that the proportion of root knot in the root system is between 1% and 24%; Grade 3 indicates that the proportion is between 25% and 49%; Grade 5 indicates that the proportion is between 50% and 74%; Grade 7 indicates that the proportion is between 75% and 99%; Grade 9 indicates that the proportion reaches 100%. Record the number of plants belonging to each grade in each group of 15 plants. Multiply the number of plants in each grade by the corresponding grade value and sum them up. Divide the sum by the product of the total number of investigated plants (15 plants) and the highest grade (9), and then multiply by 100 to obtain the disease index corresponding to each group. Subtract the disease index of the corresponding treatment group from the disease index of the blank control group, divide the difference by the disease index of the blank control group, and then multiply by 100% to obtain the control efficacy of the corresponding treatment group's finished fungicide.

[0076] The experimental results are shown in Table 4: Table 4: Test data of potted plant efficacy and growth indicators of Examples 1 to 3, Comparative Examples 1 to 6 and blank control group Example 1 5.9 89.6 54.3 42.1 Example 2 8.1 85.8 52.6 39.4 Example 3 7.4 87.0 53.8 41.2 Comparative Example 1 15.6 72.6 48.1 33.6 Comparative Example 2 27.4 51.9 45.2 29.5 Comparative Example 3 25.9 54.6 46.4 30.2 Comparative Example 4 21.5 62.3 46.9 31.8 Comparative Example 5 24.4 57.2 44.8 28.7 Comparative Example 6 28.1 50.7 45.1 29.1 Blank control group 57.0 — 38.6 23.5 Note: — indicates that the blank control group was not treated with the finished bactericide and the efficacy was not calculated.

[0077] Test conclusion: According to the data in Table 4, the disease index of Examples 1 to 3 ranged from 5.9 to 8.1, with a control efficacy of 85.8% to 89.6%. The control efficacy of Comparative Examples 1 to 6 ranged from 50.7% to 72.6%. The disease index of the blank control group was 57.0, indicating that root-knot nematode inoculation of tomatoes resulted in root-knot disease symptoms in this test. Regarding crop growth indicators, the plant height and above-ground fresh weight of Examples 1 to 3 were higher than those of the comparative examples and the blank control group. No yellowing or wilting of leaves was observed under the test conditions.

[0078] Based on the data from the aforementioned test examples, Examples 1 to 3 showed different results compared to the comparative example in terms of powder dispersion, storage stability, open-air volatilization mass loss rate, furfural retention rate, and abamectin distribution in the soil layer. Examples 1 to 3 used polysaccharide dispersions in their preparation, resulting in better physical stability of the finished products. Furthermore, Examples 1 to 3 exhibited a higher proportion of abamectin in the 15-30 cm deep soil layer, and a higher furfural retention rate than the comparative example 4, which did not contain sodium metabisulfite. These factors correspond to the lower disease index and higher control efficacy observed in the pot test.

[0079] Comparative Example 2, without the addition of sodium phytate, showed a pot control efficacy of 51.9%; Comparative Example 3, without using the polysaccharide dispersion prepared in Preparation Example 1, showed a pot control efficacy of 54.6%; Comparative Example 6, with a change in the order of sodium phytate addition, showed a pot control efficacy of 50.7%. The control efficacies of the above three comparative examples were lower than those of Examples 1 to 3. Comparative Example 4, without the addition of sodium metabisulfite, showed a pot control efficacy of 62.3%, lower than that of Examples 1 to 3. Comparative Example 5, without the addition of tea saponin, showed a pot control efficacy of 57.2%, lower than that of Examples 1 to 3. The plant height and above-ground fresh weight of Examples 1 to 3 were higher than those of the blank control group, indicating that under the test conditions, Examples 1 to 3 did not show an inhibitory effect on the growth of tomato seedlings. The above test results show that the bio-derived fungicide of this application, when used to control crop root-knot nematodes, can reduce the root-knot disease index of tomatoes and maintain the normal growth of tomato seedlings.

[0080] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

Claims

1. A bio-based fungicide for controlling root-knot nematodes in crops, characterized in that, The bio-based bactericide is prepared from the following raw materials in parts by weight: Furfural 10.0-20.0 parts; Avermectin 1.0-3.0 parts; Deionized water 49.2-78.1 parts; Sodium phytate 0.3-1.0 parts; Sodium lignosulfonate 3.0-7.0 parts; C8-10 alkyl glycosides 4.0-8.0 parts; Tea saponin 0.5-2.0 parts; Polysaccharide dispersion 1.1-4.8 parts; Citric acid 0.5-1.5 parts; Sodium citrate 0.5-1.5 parts; Sodium metabisulfite 1.0-2.0 parts.

2. The bio-based fungicide for controlling crop root-knot nematodes according to claim 1, characterized in that, The weight parts of the raw materials are: 15.0 parts furfural; 2.0 parts abamectin; 64.3 parts deionized water; 0.6 parts sodium phytate; 5.0 parts sodium lignosulfonate; 6.0 parts C8-10 alkyl glycoside; 1.2 parts tea saponin; 2.4 parts polysaccharide dispersion; 1.0 part citric acid; 1.0 part sodium citrate; 1.5 parts sodium metabisulfite.

3. The bio-based fungicide for controlling crop root-knot nematodes according to claim 1, characterized in that, The polysaccharide dispersion is composed of sodium alginate and propylene glycol, and the weight ratio of sodium alginate to propylene glycol is 1:(5-10).

4. The bio-based fungicide for controlling crop root-knot nematodes according to claim 3, characterized in that, The preparation method of the polysaccharide dispersion includes the following steps: Add the sodium alginate to the mixing tank, start the stirrer and set the speed to 50-100 rpm. Under the condition of 20-25℃, add the propylene glycol dropwise to the sodium alginate over 2-4 minutes. After the addition is complete, continue stirring for 10-15 minutes to obtain the polysaccharide dispersion.

5. A method for preparing a bio-based fungicide for controlling crop root-knot nematodes as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Pump the furfural into the organic batching vessel, add the abamectin and stir to obtain an organic cold oil phase; S2: The deionized water is injected into the main reactor and heated. Sodium phytate is added and stirred to obtain a pre-complexed aqueous solution. Sodium lignin sulfonate, C8-10 alkyl glycoside, and tea saponin are added sequentially to the pre-complexed aqueous solution and stirred continuously to obtain a surfactant aqueous solution. S3: The polysaccharide dispersion slurry is poured into the surfactant aqueous solution at a uniform speed and stirred to obtain a polysaccharide gel solution; citric acid and sodium citrate are added to the polysaccharide gel solution and the pH value is controlled to obtain a constant acid gel solution; sodium metabisulfite is added to the constant acid gel solution and stirred to obtain a polysaccharide buffer solution; S4: Start the high-shear disperser and pump the organic cold oil phase into the polysaccharide buffer solution at a uniform rate to form a mixed liquid. During the pumping process, the mixed liquid is cooled to obtain the initial water emulsion. S5: Turn off the high-shear disperser, switch the stirring mode, and control the temperature of the initial water emulsion. Continue stirring and aging to obtain the bio-based bactericide.

6. The method for preparing the bio-based fungicide for controlling crop root-knot nematodes according to claim 5, characterized in that, In step S1, the liquid phase temperature in the organic mixing vessel is controlled at 15-18℃, the stirring speed is 100-200 rpm, and the stirring time is 30-40 minutes.

7. The method for preparing the bio-based fungicide for controlling crop root-knot nematodes according to claim 5, characterized in that, In step S2, the water temperature in the main reactor is controlled to rise to 40-45℃, the stirring speed after adding sodium phytate is 150-250 rpm, and the stirring time is 10-15 minutes; the stirring speed after adding sodium lignosulfonate, C8-10 alkyl glycoside and tea saponin is 150-250 rpm, and the stirring time is 20-30 minutes.

8. The method for preparing the bio-based fungicide for controlling crop root-knot nematodes according to claim 5, characterized in that, In step S3, the temperature of the main reactor is maintained at 40-45°C, and the pH of the polysaccharide solution is controlled to be 5.3-5.8 using the added citric acid and sodium citrate.

9. The method for preparing the bio-based fungicide for controlling crop root-knot nematodes according to claim 5, characterized in that, In step S4, the rotation speed of the high shear disperser is set to 3000-3500 rpm, and the mixed liquid is cooled to 23-27°C within 20-30 minutes by cooling circulating water during pumping.

10. The method for preparing the bio-based fungicide for controlling crop root-knot nematodes according to claim 5, characterized in that, In step S5, the stirring mode is switched to an anchor mixer and the speed is set to 30-60 rpm. The temperature of the initial water emulsion is controlled to be 23-27℃, and the continuous stirring and aging time is 40-50 minutes.

Images