Preparation method and application of copper tannate bactericide

Abstract

The invention discloses a preparation method and application of a copper tannate bactericide. The method comprises the following steps: dissolving refined basic cupric carbonate in a hot concentrated sodium bicarbonate solution, slowly dropwise adding a tannic acid solution into the basic cupric carbonate solution to carry out liquid-liquid reaction, and carrying out acid-base neutralization after the tannic acid solution is added because the sodium bicarbonate solution of the basic cupric carbonate is alkaline; a microenvironment with the pH value of 4-5 required by a coordination reaction is formed, and meanwhile, due to excessive copper ions, sufficient coordination combination of the copper ions and tannic acid is promoted, so that the product yield is increased. The whole preparation process is carried out under mild conditions, does not involve highly toxic and high-pollution substances, and is environment-friendly and high in safety. The prepared copper tannate can be applied to prevention and treatment of pathogenic microorganisms in agriculture, has multiple effects of resisting bacteria and viruses, promoting plant growth, enhancing crop stress resistance and the like, can remarkably improve the yield and quality of crops, does not generate drug resistance, and can solve the harm of the pathogenic microorganisms in a short time.

Description

Technical Field

[0001] This invention relates to the field of chemical pesticides, and in particular to a method for preparing a copper tannate bactericide and its application. Background Technology

[0002] Tannic acid is a polyphenolic compound widely found in plants, with the chemical formula C63-C62 ... 76 H 52 O 46 It has a molecular weight of 1700.21. Structurally, it is a typical glucosyl compound, mainly composed of glucose molecules and multiple gallic acid molecules linked by ester or condensation bonds. Its branched structure of polyphenolic hydroxyl groups endows it with a series of unique chemical properties and physiological activities. It can bind to proteins, alkaloids, or polysaccharides, altering their physical and chemical properties; it can complex with various metal ions and undergo electrostatic interactions; it possesses strong biopharmacological activities, such as reducing properties, antioxidant properties, chelating properties, astringent properties, and ultraviolet absorption. Common tannins can be divided into two categories: hydrolyzable tannins and condensed tannins. Hydrolyzable tannins can be hydrolyzed into sugars and gallic acids under acidic or alkaline conditions, while condensed tannins are difficult to hydrolyze and mainly decompose into products such as catechins through oxidation.

[0003] Tannic acid possesses broad antibacterial activity, inhibiting the growth of various bacteria, fungi, and viruses. Its antibacterial mechanism may be related to multiple phenolic hydroxyl groups in the tannic acid molecule. These hydroxyl groups can bind to proteins in the cell walls of bacteria, fungi, and viruses, disrupting cell wall structure and preventing entry into host cells, thereby inhibiting the growth and reproduction of pathogens. Simultaneously, tannic acid's potent antioxidant and free radical scavenging effects, including inhibiting lipid peroxidation (its antioxidant mechanism is mainly related to the phenolic hydroxyl groups in the tannic acid molecule, which can provide hydrogen atoms to bind with free radicals, thus terminating free radical chain reactions), can reduce oxidative stress damage to cells in protected plants, thereby alleviating disease symptoms. Furthermore, studies have shown that tannic acid and its decomposition products can induce disease resistance responses in plants, such as activating defense enzyme systems and strengthening plant cell walls, making plants more resistant to pathogen infection.

[0004] Current research increasingly indicates that tannic acid can be used as a synergist in agricultural plant protection, enhancing the fungicidal effect of pesticides. For example, adding tannic acid to some fungicide formulations can strengthen the inhibitory effect of fungicides against pathogens, reducing pesticide usage and environmental pollution. When used in combination with agricultural antibiotics, tannic acid can enhance the antibacterial effect of antibiotics against drug-resistant bacteria and reduce their resistance. In food preservation, tannic acid is used as a food additive with antibacterial and antioxidant properties, extending the shelf life of food. For example, adding tannic acid to some fruits and vegetables can inhibit microbial growth, maintaining the freshness and quality of the food.

[0005] Copper-containing organometallic fungicides hold a stable position in the global fungicide market due to their broad-spectrum activity, low risk of resistance, and environmental advantages, accounting for approximately 4.0% of the total fungicide market. In agriculture, they are widely used for the control of fungal and bacterial diseases in vegetables (such as tomatoes and cucumbers), fruit trees (such as citrus and apples), cash crops (such as cotton and tobacco), and food crops (such as rice), with a particular strength in controlling bacterial diseases. Existing organocopper fungicides are mainly compounds formed by the complexation of organic ligands with copper ions, exhibiting characteristics such as good compatibility, high safety, and low residue. Traditional registered organic copper fungicides mainly include thiamethoxam, copper rosinate, copper nonazophos, quinoline copper, copper succinate, copper humate, amino acid copper, and copper acetate. Recently developed novel organic copper fungicides, such as L-copper phosphite, have a stable butterfly configuration, inhibit bacterial DNA synthesis, and have a long-lasting effect of 30-45 days, making them suitable for flowering and young fruit stages. Single-atom copper formulations reduce copper usage by 80% using single-atom technology, lowering metal residues and combining fungicidal and crop growth-promoting functions. Registered single-agent and compound organic copper fungicides are used to control bacterial diseases such as citrus canker, cucumber bacterial angular leaf spot, cabbage soft rot, pepper bacterial wilt, and tobacco wildfire; and fungal diseases such as downy mildew, anthracnose, apple ring rot, grape black rot, and mango leaf spot. In green agriculture, they have become the preferred fungicide for organic farming and green food production to reduce chemical pesticide residues. Meanwhile, in non-agricultural sectors, organic copper fungicide formulations (such as 8-hydroxyquinoline copper) have also been extended to areas such as wood, coatings, and textile preservation and mildew prevention.

[0006] There are few reports, both domestically and internationally, on the preparation of copper tannate through complexation reactions of tannic acid and copper ions for the control of pathogenic microorganisms in agriculture. Existing research on the preparation and application of copper tannate mainly focuses on pharmaceuticals and chemicals, with few studies on its synthetic preparation for pathogen control. Furthermore, most existing methods for preparing copper tannate involve directly mixing and stirring tannic acid and inorganic copper ions under specific temperature (50-60℃ water bath constant temperature) and pH (3-5) conditions, followed by cooling and crystallization. This method suffers from problems such as long reaction times (over 3 hours), low yields (approximately 60%-80%), low copper content, irregular and uneven crystals, fine grains, and low efficacy in field bactericidal tests. Summary of the Invention

[0007] The technical problem to be solved by this invention is to overcome the shortcomings of existing preparation reaction technology and provide a method for preparing copper tannate that is low in cost, effective, simple in preparation process, environmentally friendly and pollution-free, can effectively improve the efficacy of pathogen control drugs, and has high safety and low residue. Accordingly, the application of copper tannate as an organic copper bactericide in agriculture for the control of pathogens is proposed.

[0008] This invention provides a method for preparing copper tannate bactericide, which involves first dissolving refined basic copper carbonate in a hot concentrated sodium bicarbonate solution, and then slowly adding tannic acid dropwise to the above solution to carry out the reaction, ultimately obtaining copper tannate.

[0009] Furthermore, the specific steps include:

[0010] (1) Dissolve soluble copper salt in an appropriate amount of deionized water, heat and stir, cool and filter to obtain a refined copper sulfate solution;

[0011] (2) Dissolve the soluble carbonate in an appropriate amount of deionized water and stir until completely dissolved to obtain a soluble carbonate solution;

[0012] (3) The soluble carbonate solution is slowly added dropwise to the soluble copper salt solution, the reaction temperature is controlled and the carbonation reaction is carried out by stirring. After the soluble carbonate solution is added, dilute NaOH solution is added dropwise to gradually increase the pH value of the reaction solution and keep it at 8, so as to produce precipitate.

[0013] (4) After the reaction is complete, filter and centrifuge the precipitate, then disperse the precipitate in an appropriate amount of hot deionized water and wash it. Repeat the washing several times until the pH of the washing water is neutral to obtain the purified precipitate.

[0014] (5) After centrifuging the refined precipitate, place it in an oven to dry, and then pulverize it to obtain the product, namely basic copper carbonate; test the acid content of basic copper carbonate. If the acid content is greater than or equal to 0.05%, repeat steps (4) and (5); if the acid content is less than 0.05%, seal and store for later use.

[0015] (6) Dissolve the basic copper carbonate salt in hot concentrated sodium bicarbonate deionized water and stir to prepare a basic copper carbonate solution of the required concentration.

[0016] (7) Dissolve tannic acid in an appropriate amount of deionized water and heat until completely dissolved to obtain a tannic acid solution;

[0017] (8) The tannic acid is slowly added dropwise to the basic copper carbonate solution according to the concentration ratio, heated in a water bath, stirred for 1-2 hours and then cooled to crystallize; the crystallization method adopts a semi-solid phase, slow cooling combined with low temperature standing to promote crystal growth.

[0018] (9) The crystals obtained in step (8) are centrifuged, dried, and pulverized to obtain copper tannate raw powder. The water of crystallization of the copper tannate product is controlled to be below 1% during drying. During pulverization, a planetary ball mill is used to grind the product to below 200 mesh to obtain copper tannate raw powder, which can be used for the next step of processing into a preparation.

[0019] Furthermore, the soluble copper salt includes one of copper sulfate, copper chloride, or copper nitrate.

[0020] Furthermore, the soluble carbonate is one or both of sodium bicarbonate and sodium carbonate.

[0021] Furthermore, in step (1), the heating and stirring temperature is 50-60℃, and the stirring time is 30 minutes. The cooling process is to cool to room temperature.

[0022] Furthermore, the carbonation reaction temperature in step (3) is 60-70℃, and the stirring reaction time is 0.5-1 hour.

[0023] Furthermore, in step (4), the washing involves dispersing the precipitate in an appropriate amount of deionized water, with a washing and stirring time of 20-30 minutes each time, followed by filtration. This process is repeated 3-5 times. In steps (5) and (9), the drying temperature is 50-70°C to avoid the decomposition of basic copper carbonate and the oxidation of polyphenols.

[0024] Furthermore, in step (6), the temperature of the concentrated sodium bicarbonate deionized water solution is controlled at 60-70℃; in step (7), the concentration of the tannic acid solution is 200.0 g / L-300.0 g / L. Since the tannic acid solution is easily oxidized, it is recommended to prepare it immediately and avoid prolonged exposure to air; in step (8), the total molar ratio of tannic acid to copper ions is 1:5-1:10, and the water bath temperature is controlled at 50-60℃.

[0025] This invention provides a copper tannate bactericide, prepared using the method described above. The molecular structural formula of the copper tannate is:

[0026]

[0027] In the above molecular structural formula, M 2+ This indicates divalent copper ions.

[0028] The present invention also provides an application of copper tannate bactericide, which can be used to prevent and control pathogenic microorganisms of citrus canker or pear rot in agriculture.

[0029] Beneficial effects

[0030] 1. The core process mainly adopts the patented preparation step, in which the refined basic copper carbonate is first dissolved in a hot concentrated sodium bicarbonate solution, and then the tannic acid solution is slowly added dropwise to the basic copper carbonate solution to carry out a liquid-liquid reaction. Since the sodium bicarbonate solution of basic copper carbonate is alkaline (pH about 8.5), when the tannic acid solution is added to the system, it will first undergo acid-base neutralization, which will well form the microenvironment of pH 4-5 required for the coordination reaction. At the same time, due to the excess of copper ions, the copper ions are promoted to fully coordinate and combine with tannic acid, thereby improving the product yield.

[0031] 2. The copper tannate prepared by this invention is a macromolecular organic chelate, precisely chelated from copper ions and tannic acid. The macromolecular polymer structure of the tannic acid allows for strict and safe control of the released copper ion concentration, resulting in a significant slow-release effect. This avoids potential damage to crops caused by copper ions during use, and the effective period reaches 40 days, exhibiting higher safety compared to other inorganic and organic copper fungicides. It can also be mixed and used immediately with most insecticides, acaricides, and fungicides, making it convenient to use. Its fungicidal mechanism mainly involves the copper ions in the organic complex binding to the spores of pathogens, coagulating the proteins in the pathogen's cytoplasm, causing poor cell growth, and blocking its respiration to achieve inactivation. Simultaneously, the phenolic hydroxyl groups in the tannic acid molecule can bind to proteins in the surface cell walls of bacteria, fungi, and viruses, disrupting the cell wall structure and preventing them from entering the host cell, thereby inhibiting the growth and reproduction of pathogenic organisms. The synergistic effect of these two components produces a significant dual fungicidal effect, does not induce drug resistance after use, and can quickly resolve the harm caused by pathogenic microorganisms. Attached Figure Description

[0032] Figure 1 Scanning electron microscope images of copper tannate prepared by different methods Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The preparation method of copper tannate raw powder is as follows:

[0035] (1) Dissolve soluble copper salt in an appropriate amount of deionized water, heat and stir, cool and filter to obtain a refined copper sulfate solution;

[0036] (2) Dissolve the soluble carbonate in an appropriate amount of deionized water and stir until completely dissolved to obtain a soluble carbonate solution;

[0037] (3) The soluble carbonate solution is slowly added dropwise to the soluble copper salt solution, the reaction temperature is controlled and the carbonation reaction is carried out by stirring. After the soluble carbonate solution is added, dilute NaOH solution is added dropwise to gradually increase the pH value of the reaction solution and keep it at 8, so as to produce precipitate.

[0038] (4) After the reaction is complete, filter and centrifuge the precipitate, then disperse the precipitate in an appropriate amount of hot deionized water and wash it. Repeat the washing several times until the pH of the washing water is neutral to obtain the purified precipitate.

[0039] (5) After centrifuging the refined precipitate, place it in an oven to dry, and then pulverize it to obtain the product, namely basic copper carbonate; test the acid content of the basic copper carbonate in (5). If the acid content is greater than or equal to 0.05%, repeat steps (4) and (5); if the acid content is less than 0.05%, seal and store for later use.

[0040] (6) Dissolve the basic copper carbonate salt in hot concentrated sodium bicarbonate deionized water and stir to prepare a basic copper carbonate solution of the required concentration.

[0041] (7) Dissolve tannic acid in an appropriate amount of deionized water, heat until completely dissolved, and then stop heating to obtain a tannic acid solution;

[0042] (8) The tannic acid is slowly added dropwise to the basic copper carbonate solution according to the concentration ratio, heated in a water bath, stirred for 1-2 hours, and then cooled to crystallize.

[0043] (9) The crystals obtained in step (8) are centrifuged, dried, crushed and ground to obtain copper tannate raw powder.

[0044] Example 1

[0045] The preparation steps of copper tannate raw powder are as follows:

[0046] Weigh a certain amount of copper sulfate solid powder, stir and dissolve it in deionized water at 60℃ to prepare a solution with a concentration of 300.0 g / L (calculated as CuSO4), cool and filter to obtain a purified copper sulfate solution. Dissolve sodium bicarbonate powder in deionized water at 50℃ to prepare a solution with a concentration of 100.0 g / L.

[0047] The sodium bicarbonate solution was slowly added dropwise to the refined copper sulfate solution under stirring. The reaction temperature was controlled at 70℃ for the carbonation reaction. After the sodium bicarbonate solution was completely added, dilute NaOH solution was added dropwise to gradually increase the pH of the reaction solution and maintain it at 8. The reaction was continued until the precipitated copper salt turned into a blue-green colloidal precipitate. Heating was then stopped, and the mixture was stirred at a low speed. After the reaction solution cooled to room temperature, crystalline substances were formed. After standing, sedimentation, and filtration, the precipitated crystals were washed with deionized water at 60℃ until the sulfate ion content in the washing solution was less than 0.05%. The product was then centrifuged, dried, and pulverized to obtain the basic copper carbonate product.

[0048] Tannic acid was dissolved in an appropriate amount of deionized water, heated to 60°C and stirred until completely dissolved, to obtain a tannic acid solution with a concentration of 250.0 g / L for later use.

[0049] The refined basic copper carbonate powder, which has been purified to remove sulfate ions, is dissolved in a sodium bicarbonate deionized water solution with a concentration of 150.0 g / L at 60°C, and stirred to prepare a basic copper carbonate solution of the required concentration for later use.

[0050] The tannic acid solution was slowly added dropwise to the basic copper carbonate solution at a molar ratio of tannic acid:copper = 1:8. The reaction temperature was controlled at 60°C in a water bath. After stirring for 2 hours, the mixture was cooled to crystallize. The resulting crystals were then centrifuged, dried, and pulverized to meet the specified specifications to obtain copper tannate powder T0.

[0051] To compare the differences between the preparation method of this invention and the conventional preparation method, three methods for preparing copper tannate reported in the literature were set up for comparison: (I) Using inorganic copper salt to react directly with tannic acid, that is, the refined copper sulfate solution in preparation step (1) reacts with the tannic acid solution in preparation step (7) in a molar ratio of tannic acid:copper = 1:8 to prepare copper tannate, and then the reaction precipitate is centrifuged, dried, pulverized and ground to obtain product T1. (II) Using basic copper carbonate to react directly with tannic acid, that is, the basic copper carbonate prepared in preparation steps (1) to (3) reacts with the tannic acid solution in preparation step (7) in a molar ratio of tannic acid:copper = 1:8 to prepare copper tannate, and then the reaction precipitate is centrifuged, dried, pulverized and ground to obtain product T2. (iii): The basic copper carbonate that has been refined and purified is directly reacted with tannic acid to reduce the influence of acid radical ions on the reaction. That is, the basic copper carbonate prepared in step (1) to (5) reacts with the tannic acid solution in step (7) in a molar ratio of tannic acid: copper = 1:8 to prepare copper tannate. The reaction precipitate is then centrifuged, dried, pulverized and ground to obtain product T3.

[0052] Four copper tannate products obtained by different preparation methods were washed several times with ultrapure water and then vacuum dried. The samples were then characterized by environmental scanning electron microscopy. Figure 1 The copper ion content was then determined by atomic absorption spectrometry after digestion, and the chelation rate and reaction yield were calculated. The coordination ratio was determined and the stability constant log was calculated by observing the changes in the ultraviolet absorption spectra of tannic acid and copper ions at different concentrations (equimolar gradient spectrophotometry). K The results are shown in Table 1.

[0053] Table 1 shows the reaction yield and copper ion content of copper tannate prepared by the same method.

[0054]

[0055] Scanning electron microscopy (SEM) images show that conventional methods, such as directly reacting copper sulfate solution with tannic acid solution or directly reacting basic copper carbonate powder with tannic acid solution, produce fine, irregular crystalline powders with a certain amount of incompletely chelated tannic acid or velvety edges due to the production of copper hydroxide. In contrast, the crystals prepared using this patented invention are more compact, with smooth edges and larger particle sizes. This is mainly due to the liquid-liquid reaction method employed in this invention, where basic copper carbonate is first dissolved in a hot concentrated sodium bicarbonate solution, and then tannic acid is slowly added dropwise to the solution. Since the sodium bicarbonate solution of basic copper carbonate is alkaline (pH approximately 8.5), the addition of tannic acid solution first neutralizes the acid in the system, effectively creating a pH of 4-5 microenvironment required for the coordination reaction. Simultaneously, the excess copper ions in the system also promote the full coordination and binding of copper ions with tannic acid, thereby increasing the product yield. The T3 product, due to the lack of purification of basic copper carbonate, will have a large number of residual acid radical ions, which will have an ionic effect on the overall coordination reaction, resulting in problems such as low reaction chelation rate and fine crystal particles.

[0056] As shown in Table 1, the copper tannate prepared by the step polymerization method of this invention has the highest reaction yield, copper ion content, chelation rate, and complex temperature constant. This is mainly due to:

[0057] 1. Refined preparation process and thorough removal of impurities: By dissolving copper salt, heating and stirring, filtering impurities, and subsequently washing the precipitate multiple times until the pH is neutral, impurity ions can be effectively removed, product purity can be improved, the quality of the agent can be kept stable and reliable, which is conducive to the effectiveness of agricultural use and avoids the adverse effects of impurities on crops.

[0058] 2. Precise control of reaction conditions to ensure product quality: Strictly limiting and precisely controlling parameters such as temperature, stirring time, pH value, and dropping rate of the carbonation reaction and the reaction between tannic acid and copper salt solution can ensure that the reaction proceeds fully and in a favorable direction, reduce production costs, and ensure the stability of the structure and properties of the prepared copper tannate. This can significantly enhance the prevention and control effect, prolong the duration of effectiveness, improve economic benefits, and facilitate the large-scale promotion and application of this agent.

[0059] 3. Environmentally friendly and highly safe: The entire preparation process is carried out under relatively mild conditions (such as conventional heating and stirring), without involving highly toxic or polluting chemicals or complex and dangerous reaction operations. It is environmentally friendly, has a high safety factor in the production process, conforms to the current concept of green agriculture and sustainable development, and is conducive to long-term stable use in the field of agricultural production.

[0060] 4. Good product stability and functionality: The copper tannate raw material obtained by drying, pulverizing and other treatments has a regular and uniform crystal morphology, good dispersibility and stability, and can give full play to its multiple functions in agriculture, such as antibacterial, antiviral, promoting plant growth, and enhancing crop stress resistance, which has a significant effect on improving crop yield and quality.

[0061] 5. The process is highly repeatable and easy to scale up: each step is clearly defined, the parameters are specific and have good repeatability, which makes it easy to scale up production according to production needs. The industrialization process is easy to convert and can meet the needs of different scales of agricultural planting for copper tannate, which strongly promotes the popularization and application of this agricultural agent in agricultural production.

[0062] 6. Semi-solid phase cooling crystallization is adopted to avoid the formation of polynuclear complexes by high-temperature concentration. Furthermore, no organic solvents are used throughout the process, which greatly reduces crystallization costs, effectively improves crystallization yield, results in high-quality products, and simplifies production equipment with low energy consumption.

[0063] Example 2

[0064] Comparison of the in vitro toxicity of copper tannate prepared by different methods:

[0065] The copper tannates prepared by the four representative methods in Example 1 were subjected to indoor toxicity assays to understand their inhibitory or bactericidal ability against target pathogens, clarify their toxicity level, and determine the half-maximal inhibitory concentration (EC50) of copper tannate against pathogens. 50 This provides a reference for field application dosages.

[0066] The growth rate inhibition method was used to determine the virulence of copper tannate prepared by four methods against *Aureobasidium pinnatifida*, the causal agent of apple ring rot. The tested copper tannate raw powder was mixed with kaolin as a filler, finely ground, and diluted to prepare five concentration gradients of mother powder: 2500.00 mg / kg, 500.00 mg / kg, 100.00 mg / kg, 20.00 mg / kg, and 4.00 mg / kg. 49 mL of sterilized, melted, and cooled PDA medium to 50°C was poured into agar plates, and 1 mg of the diluted mother powder was added to the plates. The plates were shaken well to prepare the drug-containing medium. Mycelial cakes were punched using a 6 mm punch and inoculated into the center of the drug-containing PDA medium using an inoculation needle. Copper tannate prepared by different methods constituted one treatment, with each treatment replicated three times. Diluted kaolin as a filler served as a blank control. The culture medium was incubated at 25℃ for 7 days. Colony diameter was measured using the vertical cross-sectional method. The inhibitory effects of four copper tannates on the mycelia of *Rhizoctonia solani* were calculated, and the inhibition rates were determined. The toxicity regression equation was calculated based on the logarithm of the agent dilution concentration and the inhibition probability value, and the effective median concentration (EC50) was then calculated. 50 Value. EC 50The value is the concentration required for a drug to have an effect on 50% of the individuals in a biological population, EC. 50 The lower the value, the stronger the toxicity. The results of the toxicity test of each tested copper tannate against *Aureobasidium aureum* are shown in Table 2.

[0067]

[0068] Table 2. Regression equations and EC values ​​of copper tannate prepared by different methods against apple ring rot. 50 value

[0069]

[0070] Table 2 shows that all four tested copper tannates exhibited varying degrees of inhibitory effects against *Clostridium perfringens*, the causal agent of apple ring rot. However, due to differences in preparation processes, EC... 50 The significant differences in values ​​may be directly related to the precise control of copper ion content in copper tannate. Theoretically, the copper content in copper tannate is approximately 15.5%. In actual experimental samples, the copper content ranged from 11.7% to 15.6%. In laboratory bioassays, it was shown that when the copper content was below 14.5%, the bactericidal effect decreased significantly by about 28%, and a copper content of 15.2% could reduce the diameter of mycelial lesions to 37% of the control group.

[0071] Example 3

[0072] Preparation of copper tannate suspension:

[0073] The copper tannate suspension formulation comprises the following components and weight percentages: copper tannate raw powder (TO) of the present invention: 10%~50%, dispersant: 3~10%, thickener: 0.1~1.5%, antifreeze agent: 2~5%, and the balance being water. The dispersant is a mixture of one or more of the following in any proportion: alkyl naphthalene sulfonate condensate, nonylphenol polyoxyethylene ether, naphthalene sulfonic acid formaldehyde condensate, ethoxylated castor oil, phenethylphenol polyoxyethylene polyoxypropylene ether, castor oil polyoxyethylene ether, or sodium lignosulfonate. The thickener is a mixture of one or more of the following in any proportion: xanthan gum, sodium carboxymethyl (ethyl) cellulose, methyl cellulose, polyvinyl alcohol, or magnesium aluminum silicate. The antifreeze agent is a mixture of one or more of the following in any proportion: ethylene glycol, propylene glycol, glycerol, or polyethylene glycol 400.

[0074] The specific preparation steps are as follows: 300 kg of copper tannate powder is added to 40 kg of commercially available castor oil polyoxyethylene ether and 10 kg of commercially available alkyl naphthalene sulfonate condensate, and the mixture is heated and stirred for 30 minutes to obtain a reaction mixture. The resulting reaction mixture is processed into a fine slurry by a colloid mill, and then the slurry is fed into a sand mill for grinding until the particles reach 2-4 micrometers. Then, 1 kg of commercially available xanthic acid gum and 30 kg of commercially available ethylene glycol are added, and the mixture is ground again. Water is added to a final volume of 1000 kg to obtain a copper tannate suspension with a content of 30%.

[0075] Example 4

[0076] The aforementioned copper tannate suspension was applied to control citrus canker. Four commonly used copper-based fungicides for citrus canker were selected for field efficacy evaluation in a citrus orchard in Hunan Province. The experiment used a randomized block design with six treatments, each replicated four times, covering 24 plots, each containing four citrus trees. The first application was made at the early stage of citrus canker occurrence, i.e., late post-flowering. A second application was made 10 days later (when the citrus was in the young fruit stage), for a total of two applications. The experiment was conducted according to "GB / T 17980.103—2004, Field Efficacy Test Guidelines for Pesticides (II) Part 103: Fungicides for the Control of Citrus Canker". At the time of the first application, citrus canker was still in a sporadic stage, and no baseline survey was conducted. Twenty days after the last application of the pesticide, after the new shoots at all levels of the citrus trees had fully matured, a survey was conducted to investigate and statistically analyze the damage of citrus canker to the citrus leaves. The disease leaf rate, disease index, and control efficacy were calculated using the following formulas. The specific results of the field efficacy trials are shown in Table 3.

[0077]

[0078]

[0079]

[0080] The severity of ulcer disease is classified according to the number of lesions per leaf. The specific grading standards are as follows: Grade 0, no disease; Grade 1, 1-5 lesions per leaf; Grade 3, 6-10 lesions per leaf; Grade 5, 11-15 lesions per leaf; Grade 7, 16-20 lesions per leaf; Grade 9, 21 or more lesions per leaf.

[0081] Table 3. Results of field efficacy trials of different pesticides for controlling citrus (leaf) canker.

[0082]

[0083] Table 3 shows that the disease index of the blank control group on spring shoots was around 15, while the average disease index after copper-based treatment ranged from 0.93 to 3.52. Significant differences were observed between the disease indices of each treatment and the control, indicating that all five copper-based treatments were effective in controlling citrus leaf canker. Since the canker pathogen only infects young tissues at a certain developmental stage, selecting an appropriate period for new shoot growth for chemical control not only improves the control effect but also effectively reduces the number of sprays, achieving the goals of labor saving, energy conservation, and environmental protection. Analysis of the experimental data showed that the average control efficacy of quinoline copper, thiamethoxam copper, and copper tannate against citrus canker was all above 90%, with copper tannate showing the best efficacy. This is mainly because copper ions can bind to proteins on the pathogen's cell membrane, altering cell membrane permeability and causing leakage of intracellular substances, thereby inhibiting the growth and reproduction of the pathogen and even killing it. Meanwhile, once copper ions enter pathogen cells, they interfere with various enzyme systems of the pathogens, such as oxidoreductases and respiratory enzymes, affecting the normal metabolic processes of the pathogens and thus inhibiting their growth, development, and reproduction. The main reason why copper tannate is most effective is that tannic acid and its decomposition products can induce disease resistance responses in plants, such as activating the plant's defense enzyme systems and strengthening the plant's cell walls, making the plant more resistant to pathogen infection.

[0084] Example 5

[0085] The above-mentioned copper tannate suspension was applied to control pear tree rot. The integrated field control trial was conducted strictly in accordance with "GB / T17980.117-2004 Guidelines for Field Efficacy Testing of Pesticides (II) Part 117; Fungicides for the Control of Apple and Pear Tree Rot". The lesion scraping was carried out in early March of that year in a pear orchard in Henan Province. Three agents were applied to the pruning cuts and lesion scraping: 30% copper tannate suspension, 50% metalaxyl-copper wettable powder (composed of 10% metalaxyl and 40% copper dihydroxy acid, belonging to the category of organic copper fungicides), and 40% flusilazole emulsifiable concentrate (recommended). Fifty pear trees with relatively uniform growth were selected, with 10 trees treated with each agent. A water treatment was used as a control. Before applying the medication, scrape away the lesions along with 0.5-1.0 cm of surrounding healthy epidermis. Then, apply the medication to the lesions in a crisscross pattern. Seven days later, repeat the scraping and application process for recurring and newly occurring lesions. A second similar trial was conducted in November of the same year. Half a month after the treatment, a survey was conducted on the incidence of canker before and after the trial, recording the number of new lesions, the number of recurring lesions, and the number of cured lesions. The severity of the disease on each tree was recorded, and the disease index and control effect were calculated. Specific field efficacy trial results are shown in Table 2.

[0086]

[0087]

[0088] Pear tree canker severity is classified into 5 levels: Level 0, no disease on the tree; Level 1, diseased lesions on branches or twigs (regardless of size); Level 2, diseased lesions on the trunk or central trunk with a width less than 1 / 4 of the trunk's circumference at the affected area; Level 3, lesions on the trunk or central trunk with a width greater than 1 / 4 of the trunk's circumference at the affected area; Level 4, lesions on the trunk or central trunk with a width greater than 1 / 2 of the trunk's circumference at the affected area. Cure criteria: A lesion is considered cured when it dries up, shows tissue separation at the diseased-health boundary, and produces callus tissue; conversely, if the lesion expands outwards, it indicates that it is not cured.

[0089] Table 4. Field control effects of different pesticide treatments on pear tree canker.

[0090]

[0091] The results in Table 4 show that the three selected agents all have different degrees of control effects. Among them, the 500-fold dilution of metalaxyl-copper and copper tannate had a cure rate of over 90% and a low recurrence rate after secondary control of pear tree canker, and are worth promoting and using on a large scale in production.

Claims

1. A method for preparing a copper tannate bactericide, characterized in that, First, the refined basic copper carbonate is dissolved in a hot concentrated sodium bicarbonate solution. Then, tannic acid is slowly added dropwise to the solution to carry out the reaction, and finally copper tannate is obtained.

2. The preparation method of the copper tannate bactericide as described in claim 1, characterized in that, Specifically, the following steps are included: (1) Dissolve soluble copper salt in an appropriate amount of deionized water, heat and stir, cool and filter to obtain a refined copper sulfate solution; (2) Dissolve the soluble carbonate in an appropriate amount of deionized water and stir until completely dissolved to obtain a soluble carbonate solution; (3) The soluble carbonate solution is slowly added dropwise to the soluble copper salt solution, the reaction temperature is controlled and the carbonation reaction is carried out by stirring. After the soluble carbonate solution is added, dilute NaOH solution is added dropwise to gradually increase the pH value of the reaction solution and keep it at 8, so as to produce precipitate. (4) After the reaction is complete, filter and centrifuge the precipitate, then disperse the precipitate in an appropriate amount of hot deionized water and wash it. Repeat the washing several times until the pH of the washing water is neutral to obtain the purified precipitate. (5) After centrifuging the refined precipitate, place it in an oven to dry, and then pulverize it to obtain the product, namely basic copper carbonate. (6) Dissolve the basic copper carbonate in hot concentrated sodium bicarbonate deionized water and stir to prepare a basic copper carbonate solution of the required concentration. (7) Dissolve tannic acid in an appropriate amount of deionized water and heat until completely dissolved to obtain a tannic acid solution; (8) The tannic acid solution is slowly added dropwise to the basic copper carbonate solution according to the concentration ratio, heated in a water bath, stirred for 1-2 hours, and then cooled to crystallize. (9) The crystals obtained in step (8) are centrifuged, dried, crushed and ground to obtain copper tannate raw powder.

3. The method for preparing a copper tannate bactericide according to claim 2, characterized in that, The soluble copper salt includes one of copper sulfate, copper chloride, or copper nitrate.

4. The method for preparing a copper tannate bactericide according to claim 2, characterized in that, The soluble carbonate is one or both of sodium bicarbonate and sodium carbonate.

5. The method for preparing a copper tannate bactericide according to claim 2, characterized in that, In step (1), the heating and stirring temperature is 50-60℃, and the cooling is to cool to room temperature.

6. The method for preparing a copper tannate bactericide according to claim 2, characterized in that, The carbonation reaction temperature in step (3) is 60-70℃, and the stirring reaction time is 0.5-1 hour.

7. The method for preparing a copper tannate bactericide according to claim 2, characterized in that, In step (4), the washing involves dispersing the precipitate in an appropriate amount of deionized water, with a washing and stirring time of 20-30 minutes each time, followed by filtration. This process is repeated 3-5 times. In steps (5) and (9), the drying temperature is 50-70°C.

8. The method for preparing a copper tannate bactericide according to claim 2, characterized in that, In step (6), the temperature of the concentrated sodium bicarbonate deionized water solution is controlled at 60-70℃; in step (7), the concentration of the tannic acid solution is 200.0 g / L-300.0 g / L; in step (8), the total molar ratio of tannic acid to copper ions is 1:5-1:10, and the water bath temperature is controlled at 50-60℃.

9. A copper tannate bactericide, characterized in that, The copper tannate is prepared by the method according to any one of claims 1-8, and the molecular structural formula of the copper tannate is as follows: ； In the above molecular structural formula, M 2+ This indicates divalent copper ions.

10. The application of the copper tannate bactericide as described in claim 9, characterized in that, The copper tannate bactericide can be used to prevent and control pathogenic microorganisms of citrus canker or pear rot in agriculture.

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