A mefenoxam-ipconazole combined seed treatment agent, preparation method and use thereof

Abstract

This invention discloses a compound seed treatment agent containing metalaxyl-M and tebuconazole, its preparation method, and its uses, belonging to the technical field of seed treatment agents. The suspension of this invention uses metalaxyl-M, tebuconazole, and sodium selenite as the main components, supplemented with emulsifying and dispersing agents, wetting and dispersing agents, antifreeze agents, suspending agents, film-forming agents, and warning colors, and is prepared by adding deionized water to a sufficient volume. Metalaxyl-M targets and inhibits ribosomal RNA polymerase I of oomycete pathogens, while tebuconazole targets and inhibits sterol 14α-demethylase. The two have complementary fungicidal spectra, synergistically controlling maize stalk rot and maize head smut. Sodium selenite, by inhibiting the oxidative stress defense system of pathogenic fungi involving glutathione and thioredoxin, promotes the effects of the two main components and simultaneously remediates selenium-deficient soils. This invention is suitable for the green and efficient control of maize stalk rot and head smut, and also has the function of ecological restoration of selenium-deficient soils.

Description

Technical Field

[0001] This invention relates to the field of seed treatment agent technology, specifically to a compound seed treatment agent of metalaxyl-mancozeb, its preparation method, and its uses. Background Technology

[0002] Corn stalk rot and corn head smut are two important soil-borne diseases that harm corn production, often occurring together and causing significant yield losses in major corn-producing areas of northern my country. The former is mainly caused by pathogens of the genus *Pythium* (Oomycetes), while the latter is mainly caused by *Ustilago maydis* (Basidiomycetes). These two pathogens have different taxonomic positions and fundamentally different sensitivities to existing fungicides, making it difficult for a single fungicide to effectively control both diseases simultaneously. Therefore, in production practice, there is an urgent need for compound seed treatment agents with complementary fungicidal spectrums. Metalaxyl is a phenylamide systemic fungicide that exerts selective fungicidal activity by inhibiting ribosomal RNA polymerase I in Oomycete pathogens. It has good control efficacy against stalk rot caused by *Pythium*, but its activity against *Ustilago maydis* is extremely weak. Iprodione is a triazole systemic fungicide that blocks ergosterol synthesis by inhibiting sterol 14α-demethylase, exhibiting high activity against *Ustilago maydis*, but its control efficacy against stalk rot caused by Oomycetes is insufficient. Neither of these two agents can achieve simultaneous and effective control of the two diseases when used alone, but their combination creates a natural complementarity in their fungicidal spectrum. However, there are currently no registered binary compound formulations of metalaxyl and cymoxanil. Existing ternary compound products contain quinoline copper, a heavy metal copper preparation, which poses a risk of copper accumulation in the soil with continuous use and may cause potential irreversible damage to the soil microbial community.

[0003] Pathogens are prone to developing adaptive resistance under long-term selective pressure from single fungicides, which is one of the important reasons for the shortened effectiveness of pesticides. When pathogens are simultaneously exposed to multiple antimicrobial components with different mechanisms of action, the probability of developing tolerance mutations to multiple mechanisms is significantly reduced, which helps to delay the development of resistance. Large areas of land in the main maize-producing areas of northern my country are geologically selenium-deficient or low-selenium areas. Under long-term cultivation conditions, the soil selenium pool is continuously depleted, affecting maize's absorption of selenium nutrients and quality formation. Existing research shows that adequate selenium can activate plant acquired resistance-related signaling pathways, upregulate the activity of defense enzymes, and enhance the plant's natural resistance to soil-borne pathogens. Furthermore, selenite ions have direct inhibitory activity against various fungi and oomycete pathogens. Therefore, designing seed treatment products that integrate soil selenium deficiency remediation and disease control functions is of great significance. Summary of the Invention

[0004] To address the problems existing in the background art, the present invention provides a metalaxyl-mancozeb-sodium compound seed treatment agent, which, by weight, consists of the following components:

[0005] The mixture comprises 10-20 parts of metalaxyl-M, 30-60 parts of tebuconazole, 0.2-2.0 parts of sodium selenite, 10-30 parts of phenethylphenol polyoxyethylene ether, 10-20 parts of calcium lignosulfonate, 30-60 parts of ethylene glycol, 1-3 parts of polydimethylsiloxane, 1-2 parts of sodium benzoate, 0.5-1.5 parts of xanthan gum, 5-20 parts of polyvinyl alcohol, 0.3-0.5 parts of rhodamine B, and deionized water to a balance of 1000 parts; the mass ratio of metalaxyl-M to tebuconazole is 1:2 to 1:4.

[0006] In the preferred embodiment, the dosage of metalaxyl is 15 parts, the dosage of cymoxanil is 45 parts, and the mass ratio of metalaxyl to cymoxanil is 1:3; the dosage of sodium selenite is 0.8 to 1.2 parts.

[0007] This invention also provides a method for preparing a compound seed treatment agent of metalaxyl-methyl and cymoxanil, comprising the following steps:

[0008] S1: Raw material preparation; Sodium selenite is dissolved alone in deionized water to prepare an aqueous solution of sodium selenite; Xanthan gum is mixed with deionized water and swollen to prepare a xanthan gum dispersion; Polyvinyl alcohol is dissolved in hot deionized water and cooled for later use;

[0009] S2: Mixed pre-dispersion; Metalaxyl, cymoxanil and various adjuvants are mixed with deionized water and pre-dispersed by high-speed shearing to obtain pre-dispersed material;

[0010] S3: Grinding and refining; Grind the pre-dispersed material obtained in S2 to a particle size D. 90 ≤5μm, remove the grinding media to obtain the finished sand-milled material;

[0011] S4: Post-processing molding; Add sodium selenite aqueous solution, polyvinyl alcohol aqueous solution and rhodamine B solution obtained in S1 to the sand-milled material obtained in S3 in sequence, add deionized water to 1000 parts, stir evenly, and the product is obtained.

[0012] Furthermore, step S1 includes the following specific steps:

[0013] S11: Add sodium selenite solid to deionized water and stir until completely dissolved to obtain a clear, colorless solution. The mass ratio of sodium selenite to deionized water is 1:99 to 1:199. Add dilute hydrochloric acid dropwise to the obtained solution, monitoring the pH in real time with a pH meter. Stop adding dilute hydrochloric acid when the pH of the solution stabilizes in the range of 6.5 to 7.5. Seal and store for later use. The obtained solution is an aqueous solution of sodium selenite.

[0014] S12: Take solid xanthan gum, add it to deionized water, stir evenly, and let it stand to swell until the system is a uniform semi-transparent colloidal dispersion with no dry powder particles or lumps. This is the xanthan gum dispersion for later use.

[0015] S13: Add solid polyvinyl alcohol with a degree of hydrolysis of 88% to hot deionized water and stir continuously until the system is clear and transparent with no insoluble particles. After cooling to room temperature, seal and store for later use. The resulting solution is the polyvinyl alcohol aqueous solution for later use.

[0016] Furthermore, step S2 includes the following specific steps:

[0017] S21: Add the remaining deionized water to the mixing container, and add sodium benzoate, xanthan gum dispersion obtained in S12, ethylene glycol, calcium lignosulfonate, and phenylethylphenol polyoxyethylene ether in sequence while continuously stirring. Stir until visually uniform after each addition before adding the next component.

[0018] Subsequently, metalaxyl-M technical solid and cymoxanil technical solid were added simultaneously and stirred until the solid technical solids were initially wetted and dispersed in the liquid phase. Then, polydimethylsiloxane was added and stirred evenly. The resulting material was a coarsely dispersed suspension containing large particle agglomerates, which is the premix.

[0019] S22: Place the premix obtained in S21 into a high-shear disperser and shear it until there are no visible agglomerates of the original drug in the material and the whole material has a uniform suspended appearance. Stop shearing. The resulting material is the pre-dispersed material.

[0020] Furthermore, step S3 includes the following specific steps:

[0021] S31: Transfer the pre-dispersed material obtained in S2 into a sand mill, and add zirconium beads with a diameter of 0.8 to 1.0 mm into the sand mill. The ratio of the volume of zirconium beads to the volume of the material is 6:4 to 7:3.

[0022] Start the sand mill and take samples every 30 minutes to measure the particle size D using a laser particle size analyzer. 90 ;

[0023] When D 90 Stop milling when the zirconium beads are ≤5μm. Open the mill outlet to allow the material to flow out and be separated by a screen.

[0024] The collected uniform and fine suspension is the material after sand milling.

[0025] Furthermore, step S4 includes the following specific steps:

[0026] S41: Slowly add the sodium selenite aqueous solution obtained in S11 to the sand-milled material obtained in S3 under continuous stirring, and stir until the material is visually uniform in color and without layering or streaks.

[0027] Add the polyvinyl alcohol aqueous solution obtained from S13, stir evenly, and obtain a uniform suspension containing each active ingredient;

[0028] S42: Dissolve Rhodamine B solid in a small amount of deionized water to prepare a 0.1% (w / w) Rhodamine B solution; add the Rhodamine B solution to the homogeneous suspension obtained in S41 and stir until the color distribution is uniform; add deionized water until the total mass of all components reaches 1000 parts, stir again until homogeneous, and obtain the product to be tested; test the product to be tested item by item, including the mass fraction of metalaxyl and tebuconazole, and the sodium selenite content; simultaneously meet the following requirements: pH 6.0–8.0; suspension rate ≥90%; particle size D 90 ≤5μm; after all the above tests are passed, the compound seed treatment agent is obtained.

[0029] This invention also provides the use of metalaxyl-methyl-fungicide-ammonium compound seed treatment agent in the prevention and control of corn stalk rot and / or corn smut.

[0030] Furthermore, the compound seed treatment agent is applied by seed coating; the application amount is 100-300 ml of the compound seed treatment agent per 100 kg of corn seeds; the application operation is as follows: the compound seed treatment agent is mixed and rotated with the corn seeds in a seed coating machine until a uniform and continuous film is formed on the seed surface, and then the seeds are naturally dried before sowing.

[0031] This invention also provides the use of metalaxyl-methyl-fungicide-ammonium compound seed treatment agent in remediating selenium-deficient soil.

[0032] The beneficial effects achieved by this invention are as follows:

[0033] In this invention, metalaxyl and tebuconazole have natural complementarity in their fungicidal spectrum. Metalaxyl selectively controls corn stalk rot caused by Pythium by inhibiting ribosomal RNA polymerase I of oomycete pathogens, while tebuconazole specifically controls corn head smut caused by Ustilago maydis by inhibiting sterol 14α-demethylase. The combination of the two has good control efficacy against both diseases. Furthermore, the introduction of sodium selenite further enhances the control efficacy against both diseases through a dual pathway of direct fungicide application and plant resistance induction. Field efficacy is significantly improved compared to the binary system without sodium selenite, and it achieves superior overall control efficacy compared to commercially available ternary products containing quinoline copper without introducing heavy metal copper formulations. This avoids the risk of soil heavy metal accumulation and soil microbial community damage caused by continuous copper ion application. The selenite ions in sodium selenite can selectively inhibit glutathione synthase and thioredoxin reductase in pathogenic fungi, causing the pathogens to lose their oxidative stress defense system function, thereby eliminating the molecular basis for the pathogens to develop adaptive resistance to metalaxyl and tebuconazole. At the same time, the increased permeability of fungal cell membranes caused by tebuconazole promotes the more effective entry of selenite ions into the fungal cells, forming a self-reinforcing closed-loop synergistic effect. The combined fungicidal activity against Pythium is significantly higher than the theoretical value calculated based on the toxicity of each single agent.

[0034] This invention achieves an organic combination of pesticide formulation and soil trace element remediation functions by introducing sodium selenite. After application with seed coating agents, sodium selenite ions migrate and accumulate in the rhizosphere region of maize along with soil moisture. After being partially reduced to organic selenium by rhizosphere microorganisms, its bioavailability is further improved. It can gradually increase the effective selenium content in the rhizosphere of selenium-deficient soil from the level of selenium deficiency and maintain it within the range of adequate selenium. With continuous use, it can improve the selenium nutritional quality of maize, realizing the integration of disease prevention and treatment and ecological restoration of selenium-deficient soil.

[0035] The preparation method of this invention adopts a strategy of separately preparing sodium selenite solution and introducing it later. The sodium selenite aqueous solution is added after the organic active ingredient has been sand-milled. This effectively avoids the risk of oxidative degradation of highly oxidizing selenite ions in direct contact with the organic active ingredient under the high temperature and high shear conditions of sand milling. It ensures the long-term coexistence stability of the three active ingredients, metalaxyl, cymoxanil and sodium selenite, in the formulation. The thermal storage stability meets the registration requirements. The suspension rate and particle size index both meet the quality standards of suspension seed coating agents. The formulation has good safety and no significant adverse effect on seed germination rate after coating treatment. Attached Figure Description

[0036] Figure 1 This is a comparison chart of the CTC (Combined Toxic Toxicity) index between Examples 1 to 4 and Comparative Example 1;

[0037] Figure 2 The above are field control efficacy comparison charts of Examples 1 to 4 and Comparative Examples 1 to 4, where (a) is a comparative bar chart of the control efficacy of each treatment against maize stalk base rot, and (b) is a comparative bar chart of the control efficacy of each treatment against maize head smut.

[0038] Figure 3 This is a comparison chart of the changes in available selenium content in the rhizosphere soil with sowing time between the treatment group and the blank control group in Example 1.

[0039] Figure 4 This is a comparison chart showing the changes in the content retention rates of the three active ingredients—methamidophos, tebuconazole, and sodium selenite—in the product of Example 1 during heat storage over time.

[0040] Figure 5 This is a flowchart of a method for preparing a compound seed treatment agent of metalaxyl-mancozeb according to the present invention. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The formulation of the metalaxyl-mancozeb-sodium compound seed treatment agent of the present invention uses the following components:

[0043] Metalaxyl-M (chemical formula) (CAS No. 70630-17-0, molecular weight 279.33 g / mol) is a phenylamide systemic bactericide. Its target is ribosomal RNA polymerase I of oomycete pathogens. By competitively inhibiting the activity of this enzyme, it blocks the biosynthesis of rRNA in oomycete pathogens, thereby inhibiting cell protein synthesis and cell division. It has highly selective bactericidal activity against oomycete pathogens such as Pythium ultimatum.

[0044] Ipconazole (chemical formula) (CAS No. 125225-28-7, molecular weight 333.86 g / mol) is a triazole systemic fungicide. Its target is sterol 14α-demethylase (CYP51) in the ergosterol biosynthesis pathway of fungi. By inhibiting CYP51, it blocks the synthesis of ergosterol and disrupts the structural integrity and function of fungal cell membranes. It has high activity against Ustilago maydis, a basidiomycete.

[0045] Sodium selenite (chemical formula) (CAS No. 10102-18-8, molecular weight 172.94 g / mol) is an inorganic selenium compound, whose selenite ion... It exists in ionic form in aqueous solution and has direct antibacterial activity against a variety of fungi and oomycete pathogens. It also has the function of activating acquired resistance in plants and remediating selenium-deficient soils.

[0046] Phenethylphenol polyoxyethylene ether (ethoxylation degree EO=10, i.e., 10 ethylene oxide addition units per molecule) is a nonionic emulsifying dispersant; calcium lignosulfonate is an anionic wetting and dispersing agent; ethylene glycol (chemical formula...) (CAS No. 107-21-1) is an antifreeze; polydimethylsiloxane is a defoamer; sodium benzoate (chemical formula...) (CAS No. 532-32-1) is a preservative; xanthan gum is an anionic polysaccharide suspending agent; polyvinyl alcohol (PVA) with a degree of alcoholysis of 88% is a film-forming agent; rhodamine B (chemical formula...) (CAS No. 81-88-9) is a red alert dye used to prevent the accidental ingestion of treated seeds. In the following examples and comparative examples, all parts are by weight, totaling 1000 parts.

[0047] Example 1: This example describes the preparation of a 6% metalaxyl-mancozeb-sodium selenite seed treatment agent. The mass ratio of metalaxyl-mancozeb to soyzaprobamate is 1:3, and the amount of sodium selenite is 1.0 part. The dosage of each component is shown in Table 1.

[0048] Table 1. Formulation composition of Example 1 (based on 1000g of finished product)

[0049]

[0050] The preparation process of the seed treatment agent in this embodiment is as follows: Figure 5 As shown, the specific steps are as follows: Step S1 involves raw material preparation. S11: Take 1.00g of sodium selenite solid and add it to 99g of deionized water. Stir with a magnetic stirrer at room temperature for about 10 minutes until the solid is completely dissolved, resulting in a clear, colorless solution. Then, add 0.1mol / L dilute hydrochloric acid dropwise to the solution using a syringe, while monitoring the pH in real time with a calibrated pH meter. After adding about 0.3mL of dilute hydrochloric acid, the pH of the solution stabilizes at 7.0. Stop adding acid, seal and store in the dark to obtain a sodium selenite aqueous solution with a concentration of about 10g / kg. S12: Slowly sprinkle 1.0g of xanthan gum solid into 80g of deionized water, gently stir with a glass rod, and let it stand to swell for 2 hours. After swelling, the system is a uniform, semi-transparent colloidal dispersion that can be stretched into threads without any dry powder particles or lumps, resulting in a xanthan gum dispersion. S13: Take 15.0g of polyvinyl alcohol solid with a degree of hydrolysis of 88% and add it to 150g of deionized water. Place it in an 85℃ water bath and stir continuously for about 40 minutes until the system is clear and transparent with no insoluble particles. After cooling to 25℃, seal and set aside for later use to obtain a spare polyvinyl alcohol aqueous solution with a mass fraction of about 9.1%.

[0051] Step S2 involves pre-dispersion mixing, comprising the following two specific steps: S21: Add approximately 600g of deionized water to a 500mL beaker. While continuously stirring with an electric stirrer at approximately 400rpm, add 1.5g of sodium benzoate, the total volume of xanthan gum dispersion obtained in S12, 40.0g of ethylene glycol, 15.0g of calcium lignosulfonate, and 20.0g of phenethylphenol polyoxyethylene ether one by one, stirring until visually uniform after each addition before adding the next. Subsequently, add 15.79g of metalaxyl technical solid and 45.92g of cymoxanil technical solid, stirring until the solid technicals are initially wetted and dispersed in the liquid phase, and the particle surface is coated with liquid. Then add 2.0g of polydimethylsiloxane and stir evenly. The resulting premix appears as a coarse suspension containing large agglomerated particles. S22: Transfer the premixed material into a high-shear disperser and shear it at 3500 rpm for 10 minutes until there are no visible agglomerates of the original drug in the material and the material has a relatively uniform suspended appearance. Then stop shearing to obtain the pre-dispersed material.

[0052] Step S3 involves sand milling for finer refining. S31: Pour the pre-dispersed material into the sand mill jar of a vertical sand mill, add 350g of 0.8 to 1.0mm diameter zirconium beads (approximately 65% ​​of the material volume), and start the mill at 2000rpm. Take samples every 30 minutes, dilute with deionized water 100 times, and measure the particle size D using a laser particle size analyzer. 90 D at 30 minutes 90 =12.3μm, D at 60min 90 =7.6μm, D at 120min 90 =4.6μm, satisfying D 90 If the particle size is ≤5μm, stop grinding; filter the material through a matching stainless steel screen (0.2mm aperture) to remove zirconium beads, collect the ground material, which will appear as a uniform and fine suspension.

[0053] Step S4 involves post-processing and molding, comprising the following two specific steps: S41: Place the milled material in a beaker, and slowly pour in the full volume of the sodium selenite aqueous solution obtained in S11 under electric stirring. Stir for approximately 5 minutes until the material appears visually uniform in color, without layering or streaks. Then, add the full volume of the polyvinyl alcohol aqueous solution obtained in S13 and stir until homogeneous, obtaining a uniform suspension containing all active ingredients. S42: Dissolve 0.4g of Rhodamine B solid in approximately 4g of deionized water to prepare a Rhodamine B solution with a mass fraction of approximately 9.1%. Add the Rhodamine B solution to the above uniform suspension and stir until the red color is evenly distributed. Add deionized water until the total mass of all components reaches 1000g, and stir again until homogeneous, obtaining the product to be tested. Test results showed: Metalaxyl-M mass fraction 1.51% (HPLC), tebuconazole mass fraction 4.49% (HPLC), sodium selenite content 0.098% (Hydroxygenation atomic fluorescence spectrometry, HG-AFS), pH 7.1, suspension rate 93.8%, particle size D... 90 =4.6μm, the germination rate of the seeds after coating treatment was 1.8 percentage points lower than that of the blank control, and all indicators were qualified, which is the product of Example 1.

[0054] Example 2: This example prepares a low-content formulation product containing 10 parts of metalaxyl-M, 30 parts of tebuconazole, and 0.2 parts of sodium selenite. The ratio of metalaxyl-M to tebuconazole remains 1:3. The amounts of adjuvants are: 10.0 parts of phenethylphenol polyoxyethylene ether, 10.0 parts of calcium lignosulfonate, 30.0 parts of ethylene glycol, 1.0 part of polydimethylsiloxane, 1.0 part of sodium benzoate, 0.5 parts of xanthan gum, 5.0 parts of polyvinyl alcohol, and 0.3 parts of rhodamine B, with the remaining amount of deionized water to 1000 parts. The preparation steps are completely consistent with those of Example 1, with the only differences being: in S11, 0.20 g of sodium selenite is added, along with 19.8 g of deionized water to adjust the pH to 6.8; in S12, 0.5 g of xanthan gum is added; in S13, 5.0 g of polyvinyl alcohol is added; and in S21, 10.53 g of metalaxyl-M technical grade and 30.61 g of tebuconazole technical grade are added. Grinding to D 90 Stop when the particle size reaches 4.8 μm. Testing revealed: metalaxyl-M mass fraction 1.02%, cymoxanil mass fraction 3.01%, sodium selenite content 0.019%, pH value 6.8, suspension rate 91.2%, particle size D... 90 =4.8μm, the seed germination rate differed from the control by 2.3 percentage points, and all items were qualified.

[0055] Example 3: This example prepares a high-content formulation product containing 20 parts of metalaxyl-M, 60 parts of tebuconazole, and 2.0 parts of sodium selenite. The ratio of metalaxyl-M to tebuconazole remains 1:3. The amounts of adjuvants are: 30.0 parts of phenethylphenol polyoxyethylene ether, 20.0 parts of calcium lignosulfonate, 60.0 parts of ethylene glycol, 3.0 parts of polydimethylsiloxane, 2.0 parts of sodium benzoate, 1.5 parts of xanthan gum, 20.0 parts of polyvinyl alcohol, 0.5 parts of rhodamine B, and deionized water to a final volume of 1000 parts. The preparation steps are completely consistent with Example 1, with the only difference being: in S11, 2.00 g of sodium selenite is added to 198 g of deionized water to adjust the pH to 7.2; in S21, 21.05 g of metalaxyl-M technical grade and 61.22 g of tebuconazole technical grade are used. The mixture is then milled to D... 90 Stop when the particle size reaches 4.3 μm. Testing revealed: metalaxyl-M mass fraction 2.03%, cymoxanil mass fraction 6.02%, sodium selenite content 0.198%, pH value 7.2, suspension rate 94.6%, particle size D... 90 =4.3μm, the seed germination rate differed from the control by 3.1 percentage points, and all items were qualified.

[0056] Example 4: In this example, 15 parts of metalaxyl-M, 30 parts of tebuconazole, and 1.0 part of sodium selenite were prepared, with a metalaxyl-M to tebuconazole ratio of 1:2. The amount of adjuvants was exactly the same as in Example 1. The preparation steps were exactly the same as in Example 1, with the only difference being: in S21, 15.79g of metalaxyl-M technical grade and 30.61g of tebuconazole technical grade were used. The mixture was milled to D... 90 Stop when the particle size reaches 4.9 μm. Testing revealed: metalaxyl-M mass fraction 1.50%, tebuconazole mass fraction 2.99%, sodium selenite content 0.099%, pH 7.0, suspension rate 92.7%, particle size D... 90 =4.9μm, the seed germination rate differed from the control by 2.0 percentage points, and all items were qualified.

[0057] Comparative Example 1: This comparative example prepared a binary metalaxyl-methyl·tebuconazole seed treatment agent without sodium selenite. The formula was exactly the same as in Example 1, except that sodium selenite and its corresponding water volume were removed and replaced with an equal amount of deionized water. Step S11 was omitted, and the remaining steps were the same as in Example 1. Testing revealed: metalaxyl-methyl mass fraction 1.50%, tebuconazole mass fraction 4.48%, pH value 7.0, suspension rate 93.5%, particle size D... 90 =4.7μm, all parameters are within acceptable limits. This comparative example serves as a direct control to verify the synergistic effect of sodium selenite.

[0058] Comparative Example 2: This comparative example uses a commercially available 6% metalaxyl seed treatment agent as a single agent, which was purchased directly and used without being prepared separately. It was used to compare the single-agent efficacy with the examples and to verify the effect of metalaxyl in controlling corn smut.

[0059] Comparative Example 3: This comparative example used a commercially available 5% tebuconazole seed treatment agent as a single agent, which was purchased and used directly to verify the effect of tebuconazole in the prevention and control of corn stalk rot.

[0060] Comparative Example 4: This comparative example uses a commercially available 20% metalaxyl-methyl·quinoline copper·fungicide seed treatment agent, wherein quinoline copper (chemical formula C...) 18 H 12 CuN2O2 (CAS No. 10380-28-6) is a copper-based formulation. This product is registered for the control of corn stalk rot and corn head smut, and serves as a commercially available positive control closest to this invention. It can be purchased directly for use without further preparation.

[0061] Example 1: Indoor Bioactivity Determination and Co-toxicity Coefficient Analysis; This example refers to NY / T1154.7-2006 Pesticide Indoor Bioassay Test Guidelines, Part 7, Fungicides, and uses the toxic medium method to determine the effective median concentration (EC50) of each test sample against *Pythium ultimum* (representing the oomycete pathogen causing corn stalk rot). 50 The cotoxicity coefficient (CTC) was calculated based on Sun Yunpei's method (1960).

[0062] The experimental method was as follows: Each test sample was dissolved in dimethyl sulfoxide (DMSO) and diluted with sterile distilled water to create five concentration gradients (common ratio r=2). Potato dextrose agar was added to prepare plates, and a 5 mm diameter *Pythium oxysporum* mycelium cake was inoculated in the center of each plate. The plates were incubated at 28°C for 72 h. Colony diameter was measured using the cross-hatching method, and the mycelial growth inhibition rate was calculated. Each treatment was replicated four times, with a water treatment containing an equal amount of DMSO serving as a blank control. Virulence regression analysis was performed using the DPS data processing system to obtain the EC50 values ​​for each treatment. 50 .

[0063] The co-toxicity coefficient is calculated as follows: using metalaxyl as the standard agent, its toxicity index (ATI) is set to 100; the actual toxicity index (ATI) of each of the other tested samples is equal to the metalaxyl EC. 50 Divide by the EC of the sample 50 Then multiply by 100; the Theoretical Toxicity Index (TTI) of the mixture is equal to the sum of the products of the ATI of each component and its mass fraction in the active ingredient of the mixture; CTC is equal to ATI divided by TTI and then multiplied by 100. A CTC of not less than 120 indicates synergistic effect, between 80 and 120 indicates additive effect, and less than 80 indicates antagonism.

[0064] The measurement results are shown in Table 2. The CTC values ​​of Examples 1 to 4 are compared with those of Comparative Example 1. Figure 1 As shown. By Figure 1The bar chart clearly shows that the CTC of Comparative Example 1 (a binary system without sodium selenite) was 120.5, which was just enough to reach the synergistic effect threshold. However, the CTC of all examples was significantly increased after the addition of sodium selenite. The CTC of the preferred formulation in Example 1 reached 148.3, which was 23.1% higher than that of Comparative Example 1. Figure 1 The differences in column heights indicate that there is a positive correlation between the amount of sodium selenite added and the increase in CTC. However, when the amount of sodium selenite exceeds the preferred value (Example 3), the CTC drops slightly to 143.6, indicating that there is an optimal range of 0.2 to 2.0 parts for the amount of sodium selenite.

[0065] from Figure 1 The data reflects a synergistic effect between sodium selenite, metalaxyl, and tebuconazole, with the combined bactericidal activity significantly higher than the theoretical values ​​calculated based on the toxicity of each individual agent. The mechanism of this synergistic effect is as follows: when metalaxyl acts alone, the pathogen *Pythium* can enhance its oxidative stress defense by upregulating glutathione synthase activity, leading to adaptive resistance; when tebuconazole acts alone, it inhibits CYP51, resulting in ergosterol deficiency in the cell membrane and increased cell membrane permeability, but the bacteria can still rely on the glutathione system to resist oxidative stress caused by membrane damage; after sodium selenite enters the bacterial cells, SeO3... 2- By competitively inhibiting fungal glutathione synthase and thioredoxin reductase, the oxidative stress defense system of the fungi is rendered ineffective, thereby simultaneously eliminating the molecular basis for the development of resistance to metalaxyl and tebuconazole. At the same time, the increased cell membrane permeability induced by tebuconazole promotes the release of SeO3. 2- More effectively entering bacterial cells, leading to increased membrane permeability and SeO3. 2- A self-reinforcing closed-loop effect characterized by enhanced influx, suppressed glutathione defense, and increased bacterial sensitivity to metalaxyl and cymoxanil.

[0066] Table 2. Results of toxicity tests on *Pythium cerevisiae* for each tested sample.

[0067]

[0068] Example 2: Physicochemical Properties and Thermal Storage Stability Testing of the Formulation; This example uses products prepared in Examples 1 to 4, and their physicochemical properties are tested according to the following standards: suspension rate is determined according to GB / T14825-2006 Method for Determination of Suspension Rate of Pesticides; pH is determined according to GB / T1601-1993 Method for Determination of pH Value of Pesticides; particle size is determined using a laser particle size analyzer. 90Value; thermal storage stability is determined according to GB / T19136-2021, the method for determining the thermal storage stability of pesticides. The pesticides are stored at a constant temperature of 54℃ for 14 days, and samples are taken at 0, 3, 7 and 14 days. The mass fractions of metalaxyl and cymoxanil are determined by HPLC, and the sodium selenite content is determined by HG-AFS. The retention rate of active ingredients (%) is calculated according to the formula. The retention rate is not less than 95% (i.e., the decomposition rate is not more than 5%) and is considered qualified.

[0069] The curves showing the changes in the retention rate of each effective component over time during thermal storage are as follows: Figure 4 As shown in Table 3, the comprehensive physicochemical properties of each formulation are presented. Figure 4 It can be observed that the retention rate curves of the three active ingredients are always above the 95% lower limit of compliance (red dotted line). Among them, the retention rate of styraxazole is the highest (99.1% at 14 days), followed by metalaxyl-M (98.1% at 14 days), and the retention rate of sodium selenite is relatively the lowest (95.9% at 14 days), but it still meets the compliance requirements. Figure 4 The difference in the slope of the three broken lines reveals the essential differences in the thermal stability of the three components: metalaxyl and cymoxanil are both organic molecules, which mainly undergo slow hydrolysis at 54℃, while the slight decrease in sodium selenite content is related to SeO3. 2- It is related to partial reduction in a weakly acidic microenvironment, but this variation is within the safe range of the process design.

[0070] Figure 4 The stability data reflects that the operational strategy of introducing the sodium selenite aqueous solution separately after sand milling in step S41 of this invention effectively protects the chemical stability of sodium selenite and avoids the formation of SeO3. 2- Under the heat generated by high-speed sand milling, the organic active ingredient undergoes an oxidative degradation reaction through direct contact, thereby ensuring the long-term coexistence stability of the three active ingredients in the formulation.

[0071] Table 3. Physicochemical property test results of each embodiment

[0072]

[0073] Example 3: Field Efficacy Test. This example evaluated the field efficacy of fungicides for controlling corn smut according to GB / T17980.15-2000 Field Efficacy Test Guidelines for Pesticides, Part II: Control of Corn Smut, and NY / T1464.8-2007 Field Efficacy Test Guidelines for Pesticides, Part 8: Control of Corn Stalk Rot. The test site was located in the main corn-producing area of ​​Suihua City, Heilongjiang Province, where stalk rot and corn smut have historically occurred together. The soil type was black soil with an organic matter content of 3.2% and a soil available selenium background value of 0.062 mg / kg. The tested corn variety was Zhengdan 958, and the seeding rate was 4 kg / mu.

[0074] The experiment was designed as a randomized block design with a plot size of 67m². 2 The treatment was repeated four times, with seed coating applied before sowing. Examples 1 to 4 and Comparative Example 1 were applied at 200 mL of commercial dosage per 100 kg of seeds. Comparative Examples 2 and 3 were also applied at 200 mL / 100 kg, and Comparative Example 4 was applied at the registered dosage of 100 mL / 100 kg. The incidence of stem rot was assessed at the jointing stage (approximately 55 days after sowing), and the incidence of head smut was assessed at the heading stage (approximately 80 days after sowing). Control efficacy was calculated using the formula: Control efficacy (%) = (Difference between the disease rate in the control group and the disease rate in the treatment group) / (Difference between the disease rate in the control group and the disease rate in the treatment group) / (Difference between the disease rate in the control group and the disease rate in the treatment group) multiplied by 100. The control efficacy results for each treatment are shown in Table 4. Figure 2 (a) and Figure 2 (b) The field control efficacy of each treatment against maize stem rot and maize smut is compared.

[0075] from Figure 2 (a) The following information can be obtained intuitively: the control efficacy of metalaxyl-M single agent (Comparative Example 2) against corn stalk rot was 52.8%, while the control efficacy of tebuconazole single agent (Comparative Example 3) against corn stalk rot was only 39.1%, which is completely consistent with the understanding in the background art that tebuconazole has weak activity against stalk rot caused by oomycetes; the control efficacy of Comparative Example 1 (a binary system without sodium selenite) was 78.5%, and the control efficacy of Comparative Example 4 (a ternary copper-containing commercially available product) was 85.2%; while the control efficacy of Example 1 (preferred ternary system) reached 89.8%, which was 11.3 percentage points higher than Comparative Example 1 and 4 percentage points higher than Comparative Example 4, and the control efficiencies of Examples 2 to 4 were all between 80.3% and 89.4%, which comprehensively surpassed Comparative Example 1.

[0076] from Figure 2 (b) Data on the control efficacy against common smut showed that: the control efficacy of metalaxyl alone (Comparative Example 2) was only 28.8%, further confirming that metalaxyl is basically ineffective against *Ustilago maydis*, a basidiomycete; the control efficacy of tebuconazole alone (Comparative Example 3) was 75.2%, reflecting the specificity of tebuconazole against common smut; the control efficacy of common smut in Example 1 reached 93.5%, which was significantly higher than 88.2% in Comparative Example 4 and also higher than 82.4% in Comparative Example 1, which highly corresponds to the synergistic effect mechanism of sodium selenite demonstrated in Experiment 1.

[0077] Will Figure 2 (a) and Figure 2(b) The combined analysis shows that the natural complementarity of the two active ingredients, metalaxyl and cymoxanil, in the fungicidal spectrum of this invention (metalaxyl targets Oomycetes, and cymoxanil targets Basidiomycetes) makes the compound preparation effective against both diseases. On this basis, the introduction of sodium selenite further improves the efficacy against both diseases to 90% without the addition of heavy metal copper, which is superior to commercially available ternary products containing quinoline copper, while avoiding the risk of soil microbial community damage caused by the accumulation of copper ions in the soil.

[0078] Table 4. Field control efficacy of each treatment against maize stalk rot and head smut.

[0079]

[0080] Note: Different lowercase letters after the data in the same column indicate that the differences are significant at the P<0.05 level according to Duncan's new multiple range test; data are expressed as mean ± standard deviation (n=4).

[0081] Experiment Example 4: Verification of Soil Effective Selenium Remediation Effect and Selective Antibacterial Effect of Sodium Selenite; This experiment uses the product from Example 1. The pot experiment verifies the remediation effect of the sodium selenite component in the formulation on selenium-deficient soil, and simultaneously verifies the selective inhibitory effect of sodium selenite on rhizosphere pathogens, as well as the antimicrobial compound function and soil selenium remediation function.

[0082] The pot experiment was designed as follows: Soil was taken from low-selenium farmland in Suihua City, Heilongjiang Province (background effective selenium value 0.062 mg / kg). Pots were filled at 5 kg / pot rate. Four pots were set up for the Example 1 treatment group (200 mL commercial seed dressing per 100 kg of seeds, equivalent to approximately 0.05 mL per pot) and four pots for the blank control group (seed dressing with water). Rhizosphere soil samples were collected at 0, 7, 15, 30, and 60 days after sowing, within a 0-5 mm radius from the root surface. The effective selenium content was determined using hydride generation atomic fluorescence spectrometry (HG-AFS) according to HJ680-2013, "Determination of Mercury, Arsenic, Selenium, Bismuth, and Antimony in Soils and Sediments" (detection limit 0.003 mg / kg). The curve showing the change in effective selenium content with sowing time is shown below. Figure 3 As shown in Table 5, the measurement data at each time point are as follows.

[0083] Table 5. Changes in available selenium content in rhizosphere soil over time during pot experiments (mg / kg, mean ± standard deviation, n=4)

[0084]

[0085] from Figure 3As can be seen, the trends of the two curves are significantly different. In the blank control group (blue circle curve), the available selenium content in the rhizosphere soil remained stable between 0.062 and 0.064 mg / kg throughout the 60-day observation period, falling below the selenium deficiency level of 0.1 mg / kg, indicating that the available selenium content in the soil does not spontaneously increase under natural conditions. The treatment group of Example 1 (red square curve) exhibits a clear dynamic release pattern of first increasing and then stabilizing: from 7 to 30 days after sowing, the available selenium content continuously increased as sodium selenite migrated and accumulated in the rhizosphere, reaching a peak of 0.138 mg / kg at 30 days after sowing, entering the selenium-adequate range (green shaded area, 0.10 to 0.30 mg / kg); at 60 days after sowing, the available selenium content slightly decreased to 0.121 mg / kg, but still remained within the selenium-adequate range, indicating that the available selenium supply from sodium selenite in the rhizosphere is persistent.

[0086] Figure 3 The revealed kinetics of available selenium release from soil indicate that sodium selenite in the formulation is uniformly dispersed in the suspension system in an ionic state. After the coated seeds are sown, sodium selenite migrates into the rhizosphere from the soil with rainwater or irrigation water, releasing SeO3. 2- The process by which selenium is partially reduced to organic form by rhizosphere microorganisms further enhances the bioavailability of available selenium; under low concentration conditions (0.062 to 0.138 mg / kg), SeO3... 2- It has a selective inhibitory effect on pathogenic bacteria such as Pythium spp. in soil, while having no significant adverse effects on beneficial bacteria in the soil, demonstrating the functional value of sodium selenite as an antimicrobial compound in rhizosphere microecological restoration.

[0087] To further confirm the selective antimicrobial effect of sodium selenite on the rhizosphere, rhizosphere soil was collected 30 days after sowing. The number of viable rhizosphere bacteria (CFU / g dry soil) in *Pythium* (selective medium) and total soil bacteria (LB medium) was counted using the dilution plate count method. The results showed that the number of viable *Pythium* bacteria in the rhizosphere of the treatment group (Example 1) was reduced by 62.4% compared to the control (P<0.05), while the number of total soil bacteria was not significantly different from the control (P>0.05). This result confirms, at the microbial community level, that sodium selenite has selective inhibitory antimicrobial activity against oomycete pathogens at the applied concentration.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compound seed treatment agent of metalaxyl-methyl and cymoxanil, characterized in that, It consists of the following components in parts by weight: The mixture comprises 10-20 parts of metalaxyl-M, 30-60 parts of tebuconazole, 0.2-2.0 parts of sodium selenite, 10-30 parts of phenethylphenol polyoxyethylene ether, 10-20 parts of calcium lignosulfonate, 30-60 parts of ethylene glycol, 1-3 parts of polydimethylsiloxane, 1-2 parts of sodium benzoate, 0.5-1.5 parts of xanthan gum, 5-20 parts of polyvinyl alcohol, 0.3-0.5 parts of rhodamine B, and deionized water to a balance of 1000 parts; the mass ratio of metalaxyl-M to tebuconazole is 1:2 to 1:

4.

2. The compound seed treatment agent according to claim 1, characterized in that, The dosage of metalaxyl is 15 parts, the dosage of cymoxanil is 45 parts, and the mass ratio of metalaxyl to cymoxanil is 1:3; the dosage of sodium selenite is 0.8 to 1.2 parts.

3. A method for preparing the metalaxyl-mancozeb-carbendazim compound seed treatment agent as described in claim 1 or 2, characterized in that, Includes the following steps: S1: Raw material preparation; Sodium selenite is dissolved alone in deionized water to prepare an aqueous solution of sodium selenite; Xanthan gum is mixed with deionized water and swollen to prepare a xanthan gum dispersion; Polyvinyl alcohol is dissolved in hot deionized water and cooled for later use; S2: Mixed pre-dispersion; Metalaxyl, cymoxanil and various adjuvants are mixed with deionized water and pre-dispersed by high-speed shearing to obtain pre-dispersed material; S3: Grinding and refining; Grind the pre-dispersed material obtained in S2 to a particle size D. 90 ≤5μm, remove the grinding media to obtain the finished sand-milled material; S4: Post-processing molding; Add sodium selenite aqueous solution, polyvinyl alcohol aqueous solution and rhodamine B solution obtained in S1 to the sand-milled material obtained in S3 in sequence, add deionized water to 1000 parts, stir evenly, and the product is obtained.

4. The method according to claim 3, characterized in that, Step S1 includes the following specific steps: S11: Add sodium selenite solid to deionized water and stir until completely dissolved to obtain a clear, colorless solution. The mass ratio of sodium selenite to deionized water is 1:99 to 1:

199. Add dilute hydrochloric acid dropwise to the obtained solution, monitoring the pH in real time with a pH meter. Stop adding dilute hydrochloric acid when the pH of the solution stabilizes in the range of 6.5 to 7.

5. Seal and store for later use. The obtained solution is an aqueous solution of sodium selenite. S12: Take solid xanthan gum, add it to deionized water, stir evenly, and let it stand to swell until the system is a uniform semi-transparent colloidal dispersion with no dry powder particles or lumps. This is the xanthan gum dispersion for later use. S13: Add solid polyvinyl alcohol with a degree of hydrolysis of 88% to hot deionized water and stir continuously until the system is clear and transparent with no insoluble particles. After cooling to room temperature, seal and store for later use. The resulting solution is the polyvinyl alcohol aqueous solution for later use.

5. The method according to claim 3, characterized in that, Step S2 includes the following specific steps: S21: Add the remaining deionized water to the mixing container, and add sodium benzoate, xanthan gum dispersion obtained in S12, ethylene glycol, calcium lignosulfonate, and phenylethylphenol polyoxyethylene ether in sequence while continuously stirring. Stir until visually uniform after each addition before adding the next component. Subsequently, metalaxyl-M technical solid and cymoxanil technical solid were added simultaneously and stirred until the solid technical solids were initially wetted and dispersed in the liquid phase. Then, polydimethylsiloxane was added and stirred evenly. The resulting material was a coarsely dispersed suspension containing large particle agglomerates, which is the premix. S22: Place the premix obtained in S21 into a high-shear disperser and shear it until there are no visible agglomerates of the original drug in the material and the whole material has a uniform suspended appearance. Stop shearing. The resulting material is the pre-dispersed material.

6. The method according to claim 3, characterized in that, Step S3 includes the following specific steps: S31: Transfer the pre-dispersed material obtained in S2 into a sand mill, and add zirconium beads with a diameter of 0.8 to 1.0 mm into the sand mill. The ratio of the volume of zirconium beads to the volume of the material is 6:4 to 7:

3. Start the sand mill and take samples every 30 minutes to measure the particle size D using a laser particle size analyzer. 90 ; When D 90 Stop milling when the zirconium beads are ≤5μm. Open the mill outlet to allow the material to flow out and be separated by a screen. The collected uniform and fine suspension is the material after sand milling.

7. The method according to claim 3, characterized in that, Step S4 includes the following specific steps: S41: Slowly add the sodium selenite aqueous solution obtained in S11 to the sand-milled material obtained in S3 under continuous stirring, and stir until the material is visually uniform in color and without layering or streaks. Add the polyvinyl alcohol aqueous solution obtained from S13, stir evenly, and obtain a uniform suspension containing each active ingredient; S42: Dissolve Rhodamine B solid in a small amount of deionized water to prepare a 0.1% (w / w) Rhodamine B solution; add the Rhodamine B solution to the homogeneous suspension obtained in S41 and stir until the color distribution is uniform; add deionized water until the total mass of all components reaches 1000 parts, stir again until homogeneous, and obtain the product to be tested; test the product to be tested item by item, including the mass fraction of metalaxyl and tebuconazole, and the sodium selenite content; simultaneously meet the following requirements: pH 6.0–8.0; suspension rate ≥90%; particle size D 90 ≤5μm; after all the above tests are passed, the compound seed treatment agent is obtained.

8. The use of the metalaxyl-methyl-fungicide-ammonium compound seed treatment agent as described in claim 1 or 2 in the prevention and control of corn stalk rot and / or corn smut.

9. The use according to claim 8, characterized in that, The compound seed treatment agent is applied by seed coating. The application rate is 100-300 ml of the compound seed treatment agent per 100 kg of corn seeds. The application procedure is as follows: mix the compound seed treatment agent with corn seeds in a seed coating machine and rotate until a uniform and continuous film is formed on the seed surface. Then, let the seeds air dry naturally before sowing.

10. The use of the metalaxyl-methyl-zoxystrobin compound seed treatment agent as described in claim 1 or 2 in the remediation of selenium-deficient soil.

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