An antibacterial agent for preventing and treating tobacco bacterial wilt and preparation method thereof

Abstract

The present invention discloses an antimicrobial agent for preventing and treating tobacco bacterial wilt and a preparation method thereof, belonging to the technical field of pesticides. The antimicrobial agent comprises the following raw materials: CuO@g-C3N4, resistant starch, p-toluenesulfonate, monodecanoate, polyethylene oxide, stearic acid, triethanolamine, and glycerol. The preparation method comprises the following steps: first preparing a CuO@g-C3N4 composite material, and then using the composite material as the main active ingredient to prepare an antimicrobial agent for preventing and treating tobacco bacterial wilt. The above scheme solves the problems of chemical agent residue, strong toxicity, and low efficiency. At the same time, it has good dispersibility, is not easy to agglomerate, plants will not develop drug resistance, the dosage is small, and the harm to the environment is small, and it has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticides, and in particular to an antibacterial agent for preventing and treating tobacco bacterial wilt and a preparation method thereof. Background Art

[0002] Tobacco is one of the world's most widely cultivated and most popular cash crops. Due to long-term continuous cropping and soil acidification, it has become subject to widespread soil-borne diseases. Tobacco bacterial wilt, a soil-borne bacterial disease caused by Ralstonia solanacearum, is a typical vascular disease characterized by a wide host range, widespread geographic distribution, and strong pathogenicity. When the epidermis of tobacco root hairs is damaged, Ralstonia solanacearum invades the tobacco plant through the damaged area, infecting it. Within the tobacco plant, Ralstonia solanacearum is transported through the stem to the leaves, infecting the entire plant and ultimately causing plant wilt and death. High temperatures and high humidity are prerequisites for the spread of tobacco bacterial wilt. Low-lying areas and heavily clayey soils are particularly susceptible to the disease, and neutral to slightly acidic soils also favor its occurrence. Today, tobacco bacterial wilt has become a major threat to tobacco growth and a key epidemic disease for tobacco pest and disease control.

[0003] Currently, the main control methods for tobacco bacterial wilt include chemical control, biological control, and integrated control. Biological control involves isolating microorganisms that inhibit bacterial wilt from the in situ soil of the disease source and producing them into microbial organic fertilizers or microbial agents. However, biological control is significantly affected by soil and environmental factors, resulting in variable and unstable control effectiveness. Integrated control involves selecting disease-resistant varieties, seedbed disinfection, proper crop rotation, early sowing and planting, attention to field hygiene, and enhanced field management. However, breeding disease-resistant varieties requires a long time, and bacterial wilt is controlled by multiple genes, making it difficult to select resistant varieties. Given my country's large population and limited land, the availability of flue-cured tobacco fields makes measures like proper crop rotation difficult to implement and can only provide limited control of bacterial wilt. Chemical control remains an important means of controlling tobacco bacterial wilt. Numerous studies have shown that the use of single chemical agents is often ineffective. While the use of combined chemical agents can significantly improve tobacco disease control, residual chemical residues during use can cause a certain degree of environmental pollution. Therefore, from the perspective of sustainable development, finding an efficient and green antibacterial agent for preventing and controlling tobacco bacterial wilt and its preparation method has become a difficult problem that researchers urgently need to solve. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an antibacterial agent for preventing and treating tobacco bacterial wilt and a preparation method thereof, so as to solve the problems of residual, strong toxicity and low efficiency of chemical agents used in the past to prevent and treat tobacco bacterial wilt.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] An antibacterial agent for preventing and treating tobacco bacterial wilt, comprising the following raw materials: 4×10 -2 -15.9×10 -2 parts by mass of CuO@g-C3N4, 10-28 parts by mass of resistant starch, 6-22 parts by mass of p-toluenesulfonate, 2-7 parts by mass of monodecanoate, 0.6-3.9 parts by mass of polyethylene oxide, 30-90 parts by mass of stearic acid, 0.1-2.5 parts by mass of triethanolamine, and 1-5 parts by mass of glycerol.

[0007] Optimally, the antibacterial agent comprises the following raw materials: 8.25×10 -2 parts by mass of CuO@g-C3N4, 19 parts by mass of resistant starch, 11 parts by mass of p-toluenesulfonate, 5 parts by mass of monodecanoate, 2.2 parts by mass of polyethylene oxide, 60 parts by mass of stearic acid, 2.3 parts by mass of triethanolamine, and 3 parts by mass of glycerol.

[0008] A method for preparing an antibacterial agent for preventing and treating tobacco bacterial wilt, the preparation method comprises the following steps:

[0009] (1) CuO@g-C3N4 and p-toluenesulfonate were ultrasonically dispersed in water to form a suspension. Polyoxyethylene, stearic acid, and triethanolamine were weighed. Polyoxyethylene and triethanolamine were first mixed, and then stearic acid was added and mixed evenly. The mixture was placed in a water bath and the suspension was added dropwise while ultrasonicating to form a transparent and uniform emulsion.

[0010] (2) Resistant starch, monocaprate, and propylene glycol were mixed and dissolved in water to form a mixed solution. After the mixture was completely dissolved, the emulsion was added and homogenized at 4000-5000 r / min for 2-4 minutes to prepare an antibacterial agent for preventing and treating tobacco bacterial wilt.

[0011] When the prepared CuO@g-C3N4 is irradiated with visible light, the holes and electrons in the material react with the surrounding water and oxygen to produce reactive oxygen species to inhibit bacterial growth. The trace amount of copper not only effectively supplements the copper demand in tobacco, but also induces the accumulation of proline and soluble sugars, enhancing the plant's disease resistance. It can also stimulate the plant to produce ethylene and transmit disease resistance signals. CuO@g-C3N4 can effectively inhibit the growth of Ralstonia solanacearum, with a high mortality rate and strong accuracy. However, CuO@g-C3N4 is difficult to dissolve, has poor dispersibility, and is prone to agglomeration, affecting the ultimate prevention and control effect. The use of ordinary dispersants cannot effectively achieve the purpose of improving its dispersibility, so an antibacterial agent is prepared to improve the overall dispersibility.

[0012] First, a first-layer emulsion was prepared, using stearic acid as the oil phase and triethanolamine and polyethylene oxide as emulsifiers. A suspension of CuO@g-C3N4 and p-toluenesulfonate was encapsulated within this layer, forming a well-dispersed liquid particle structure. This improved dispersibility and addressed the difficulties of CuO@g-C3N4 in dissolving, dispersing, and agglomerating. A mixture of resistant starch, monocaprate, and glycerol was then encapsulated around the oil phase to create an antimicrobial agent with multiple emulsion properties. In actual tobacco bacterial wilt treatment, the external aqueous phase of the antimicrobial agent was first absorbed by tobacco roots. The resistant starch, with its dense and partially crystalline structure, decomposes to produce butyric acid, which has antibacterial and antimicrobial properties, cleansing the root environment and reducing the accumulation of Ralstonia solanacearum in wounds. The stearic acid is subsequently released, which can remove foamy substances produced by bacterial proliferation in the plant body, unclog the conduits, and prevent bacteria and substances produced by the proliferation from clogging the conduits and losing their transport function. At the same time, the CuO@g-C3N4 contained in the internal aqueous phase reacts with the surrounding water and oxygen to produce reactive oxygen species, which rapidly oxidize the cell walls and core materials of bacteria and viruses, thereby inhibiting bacterial growth. At the same time, due to the consumption of oxygen, the production of bacterial exopolysaccharides is affected, further affecting the subsequent reproduction of bacteria. The antibacterial agent prepared by the present invention can effectively contact pathogens, improve antibacterial activity, and at the same time, under the synergistic effect of chemical osmotic pressure and physical damage to cell structure, make pathogens less likely to develop drug resistance.

[0013] Furthermore, the CuO@g-C3N4 comprises the following raw materials in a mass volume ratio: double distilled water: anhydrous ethanol: g-C3N4 powder: copper nitrate trihydrate = (13-17) mL: (13-17) mL: (80-120) × 10 -3 g: (160-240) × 10 -3 g.

[0014] Furthermore, the preparation steps of the CuO@g-C3N4 are as follows:

[0015] (1) First, double-distilled water and anhydrous ethanol were mixed to form a mixed solution, and then g-C3N4 powder was weighed and added to the mixed solution. The mixture was ultrasonicated for 30 minutes to prepare a suspension. Copper nitrate trihydrate was added to the suspension, and then the pH was adjusted to 8.5-9.5 under magnetic stirring. After stirring for 2-3 hours, the mixture was filtered and washed, and refrigerated at -20°C to obtain a light blue solid;

[0016] (2) Copper nitrate trihydrate and g-C3N4 powder were thoroughly stirred and evenly mixed to precipitate copper oxide particles on the surface of g-C3N4 nanosheets to obtain a powdered composite material. The powdered composite material and the light blue solid were freeze-dried and calcined for 2-3 hours to obtain CuO@g-C3N4.

[0017] In addition, when preparing powdered composite materials, they can also be prepared by co-precipitation method.

[0018] Furthermore, the temperature of the water bath in step (2) of preparing the antibacterial agent is 23-27°C.

[0019] Furthermore, the volume ratio of the emulsion to the mixed liquid is 1:(3-5).

[0020] Furthermore, in the preparation step (2) of CuO@g-C3N4, the calcination temperature is 200°C and the heating rate is 5°C / min.

[0021] Furthermore, the freeze-drying temperature in the preparation step (2) of CuO@g-C3N4 is minus 55°C.

[0022] Beneficial effects:

[0023] 1. The present invention provides a method for preparing a CuO@g-C3N4 composite material. The prepared medicine has a simple ratio, is easy to operate, and has high safety.

[0024] 2. The present invention provides a CuO@g-C3N4 composite material. The prepared composite material is used as the main active ingredient of the medicine and has the advantages of high sterilization efficiency and low toxicity.

[0025] 3. The antibacterial agent of the present invention not only has a significant preventive effect on tobacco bacterial wilt, but also has good suspension performance, good dispersibility, is not easy to agglomerate, has good efficacy, requires a small amount of medicine, does not cause residue, has little harm to the environment, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 :Characterization diagram of CuO@g-C3N4 composite material;

[0027] Figure 2 : Growth curve of Ralstonia solanacearum in the CuO@g-C3N4 composite material;

[0028] Figure 3 : Scanning electron micrograph of Ralstonia solanacearum grown in deionized water containing CuO@g-C3N4 composites. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to specific embodiments and accompanying drawings:

[0030] The present invention provides an antibacterial agent for preventing and treating tobacco bacterial wilt and a preparation method thereof. However, first, CuO@g-C3N4 needs to be prepared. The preparation process is shown in Examples 1-3:

[0031] Example 1: Preparation of CuO@g-C3N4

[0032] (1) First, 15 mL of double-distilled water and 15 mL of anhydrous ethanol were mixed to form a mixed solution. 50 mg of g-C3N4 powder was weighed and added to the mixed solution. The suspension was ultrasonicated at 550 W for 30 min to prepare a suspension. 100 mg of copper nitrate trihydrate was added to the suspension. The pH was then adjusted to 9 under magnetic stirring at 200 rpm. After stirring for 2.5 h, the suspension was filtered, washed, and refrigerated at -20°C to obtain a light blue solid.

[0033] (2) 100 mg of copper nitrate trihydrate and 50 mg of g-C3N4 powder were thoroughly stirred at 200 r / min, thereby precipitating copper oxide particles on the surface of g-C3N4 nanosheets to obtain a powdered composite material. The powdered composite material and the light blue solid were freeze-dried at -55°C and then calcined at a heating rate of 5°C / min and calcined at 200°C for 2.5 h to obtain CuO@g-C3N4.

[0034] Example 2: Preparation of CuO@g-C3N4

[0035] (1) First, 13 mL of double-distilled water and 13 mL of anhydrous ethanol were mixed to form a mixed solution. Then, 40 mg of g-C3N4 powder was weighed and added to the mixed solution. The mixture was ultrasonicated at 500 W for 30 min to prepare a suspension. 80 mg of copper nitrate trihydrate was added to the suspension. The pH was then adjusted to 8.5 under magnetic stirring at 190 rpm. After stirring for 3 h, the mixture was filtered, washed, and refrigerated at -20°C to obtain a light blue solid.

[0036] (2) 80 mg of copper nitrate trihydrate and 40 mg of g-C3N4 powder were thoroughly stirred at 190 r / min, thereby precipitating copper oxide particles on the surface of g-C3N4 nanosheets to obtain a powdered composite material. The powdered composite material and the light blue solid were freeze-dried at -55°C and then calcined at a heating rate of 5°C / min and calcined at 200°C for 2 h to obtain CuO@g-C3N4.

[0037] Example 3: Preparation of CuO@g-C3N4

[0038] (1) First, 17 mL of double-distilled water and 17 mL of anhydrous ethanol were mixed to form a mixed solution. Then, 60 mg of g-C3N4 powder was weighed and added to the mixed solution. The mixture was ultrasonicated at 600 W for 30 min to prepare a suspension. 120 mg of copper nitrate trihydrate was added to the suspension. Then, the pH was adjusted to 9.5 under magnetic stirring at 220 r / min. After stirring for 2 h, the mixture was filtered and washed, and refrigerated at -20°C to obtain a light blue solid.

[0039] (2) 120 mg of copper nitrate trihydrate and 60 mg of g-C3N4 powder were thoroughly stirred at 220 r / min, thereby precipitating copper oxide particles on the surface of g-C3N4 nanosheets to obtain a powdered composite material. The powdered composite material and the light blue solid were freeze-dried at -55°C and then calcined at a heating rate of 5°C / min and calcined at 200°C for 3 h to obtain CuO@g-C3N4.

[0040] Take 10 mg of the CuO@g-C3N4 composite material prepared in Example 1 and send it to the company for testing according to the conventional testing method. The measured data are as follows Figure 1 As shown, it can be seen that the composite material is CuO@g-C3N4.

[0041] Example 4: Preparation of antibacterial agent

[0042] (1) 82.5 g of CuO@g-C3N4 prepared in Example 1 and 11 kg of p-toluenesulfonate were ultrasonically dispersed in 50 kg of water at a power of 500 W to form a suspension. 2.2 kg of polyoxyethylene, 60 kg of stearic acid, and 2.3 kg of triethanolamine were weighed. The polyoxyethylene and triethanolamine were first thoroughly mixed, and then stearic acid was added and mixed evenly. The mixture was placed in a 25°C water bath and the suspension was slowly added dropwise while ultrasonicating at 200 W to form a transparent, uniform emulsion.

[0043] (2) 19 kg of resistant starch, 5 kg of monocaprate, and 3 kg of propylene glycol were selected and mixed, dissolved in 500 kg of water to form a mixed solution. After complete dissolution, the emulsion was added and homogenized at 4500 r / min for 3 minutes to prepare an antibacterial agent for preventing and treating tobacco bacterial wilt.

[0044] Example 5: Preparation of antibacterial agent II

[0045] (1) 44.5 g of CuO@g-C3N4 prepared in Example 1 and 6 kg of p-toluenesulfonate were ultrasonically dispersed in 30 kg of water at a power of 400 W to form a suspension. 0.6 kg of polyoxyethylene, 30 kg of stearic acid, and 0.1 kg of triethanolamine were weighed. The polyoxyethylene and triethanolamine were first thoroughly mixed, and then stearic acid was added and mixed evenly. The mixture was placed in a 23°C water bath and the suspension was slowly added dropwise while ultrasonicating at 180 W to form a transparent, uniform emulsion.

[0046] (2) 10 kg of resistant starch, 2 kg of monocaprate, and 1 kg of propylene glycol were selected and mixed, dissolved in 321 kg of water to form a mixed solution. After complete dissolution, the emulsion was added and homogenized at 4000 r / min for 4 minutes to prepare an antibacterial agent for preventing and treating tobacco bacterial wilt.

[0047] Example 6: Preparation of antibacterial agent 3

[0048] (1) 159 g of CuO@g-C3N4 prepared in Example 1 and 22 kg of p-toluenesulfonate were ultrasonically dispersed in 77 kg of water at a power of 600 W to form a suspension. 3.9 kg of polyoxyethylene, 90 kg of stearic acid, and 2.5 kg of triethanolamine were weighed. The polyoxyethylene and triethanolamine were first thoroughly mixed, and then stearic acid was added and mixed evenly. The mixture was placed in a 27°C water bath and the suspension was slowly added dropwise while ultrasonicating at 220 W to form a transparent, uniform emulsion.

[0049] (2) 28 kg of resistant starch, 7 kg of monocaprate, and 5 kg of propylene glycol were selected and mixed, dissolved in 560 kg of water to form a mixed solution. After complete dissolution, the emulsion was added and homogenized at 5000 r / min for 2 minutes to prepare an antibacterial agent for preventing and treating tobacco bacterial wilt.

[0050] Comparative Example 1: Preparation of antibacterial agent

[0051] The same as Example 4, the only difference is that the raw material CuO@g-C3N4 is missing in this comparative example. The remaining steps and raw materials used are the same as those in Example 4. The specific step (1) is as follows:

[0052] (1) 11 kg of p-toluenesulfonate was ultrasonically dispersed in 50 kg of water at a power of 500 W to form a suspension. 2.2 kg of polyoxyethylene, 60 kg of stearic acid, and 2.3 kg of triethanolamine were weighed. The polyoxyethylene and triethanolamine were first thoroughly mixed, and then stearic acid was added and mixed evenly. The mixture was placed in a 25°C water bath and the suspension was slowly added dropwise at 200 W while ultrasonicating to form a transparent, uniform emulsion.

[0053] Comparative Example 2: Preparation of antibacterial agent

[0054] The same as Example 4, the only difference is that step (2) is missing in this comparative example, and the remaining steps and raw materials used are the same as those in Example 4. The specific steps are as follows:

[0055] (1) 7.5 g of CuO@g-C3N4 prepared in Example 1 and 11 kg of p-toluenesulfonate were ultrasonically dispersed in 50 kg of water at a power of 500 W to form a suspension. 2.2 kg of polyoxyethylene, 60 kg of stearic acid, and 2.3 kg of triethanolamine were weighed. The polyoxyethylene and triethanolamine were first thoroughly mixed, and then stearic acid was added and mixed evenly. The mixture was placed in a 25°C water bath and the suspension was slowly added dropwise while ultrasonicating at 220 W to form a transparent, uniform emulsion, which was the antibacterial agent.

[0056] Comparative Example 3: Preparation of antibacterial agent

[0057] The same as Example 4, the only difference is that the raw materials resistant starch and p-toluenesulfonate are missing in this comparative example. The remaining steps and raw materials used are the same as those in Example 4. The specific steps are as follows:

[0058] (1) 7.5 g of CuO@g-C3N4 prepared in Example 1 was ultrasonically dispersed in 50 kg of water at a power of 500 W to form a suspension. 2.2 kg of polyoxyethylene, 60 kg of stearic acid, and 2.3 kg of triethanolamine were weighed. The polyoxyethylene and triethanolamine were first thoroughly mixed, and then stearic acid was added and mixed evenly. The mixture was placed in a 25°C water bath and the suspension was slowly added dropwise while ultrasonicating at 200 W to form a transparent, uniform emulsion.

[0059] (2) 5 kg of monocaprate and 3 kg of propylene glycol were mixed and dissolved in 500 kg of water to form a mixed solution. After the mixture was completely dissolved, the emulsion was added and homogenized at 4500 r / min for 3 minutes to prepare an antibacterial agent for preventing and treating tobacco bacterial wilt.

[0060] Comparative Example 4: Preparation of antibacterial agent

[0061] The same as Example 4, the only difference is that the raw material CuO@g-C3N4 is replaced by g-C3N4 in this comparative example, and the remaining steps and raw materials used are the same as those in Example 4. The specific step (1) is as follows:

[0062] (1) 7.5 g of g-C3N4 and 11 kg of p-toluenesulfonate were ultrasonically dispersed in 50 kg of water at a power of 500 W to form a suspension. 2.2 kg of polyoxyethylene, 60 kg of stearic acid, and 2.3 kg of triethanolamine were weighed. The polyoxyethylene and triethanolamine were first thoroughly mixed, and then the stearic acid was added and mixed evenly. The mixture was placed in a 25°C water bath and the suspension was slowly added dropwise while ultrasonicating at 200 W to form a transparent, uniform emulsion.

[0063] (2) 19 kg of resistant starch, 5 kg of monocaprate, and 3 kg of propylene glycol were selected and mixed, dissolved in 500 kg of water to form a mixed solution. After complete dissolution, the emulsion was added and homogenized at 4500 r / min for 3 minutes to prepare an antibacterial agent for preventing and treating tobacco bacterial wilt.

[0064] Comparative Example 5: Preparation of antibacterial agent

[0065] The same as Example 4, except that in this comparative example, 7.5 g of CuO@g-C3N4 prepared in Example 1 is directly ultrasonically dispersed in 50 kg of water at a power of 500 W to form a suspension, thereby preparing an antibacterial agent.

[0066] Experiment 1: Antibacterial activity of CuO@g-C3N4 and bacterial viability

[0067] 1. Preparation of bacterial suspension: Ralstonia solanacearum was obtained from the College of Plant Protection, Southwest University, and named CQPS. The strain accession number is ACCC01474. A highly active bacterial suspension was obtained by overnight culture of Ralstonia solanacearum. The concentration of the activated bacterial suspension was 1.0 × 10 8 -1.0×10 10 cfu / mL.

[0068] 2. Experimental grouping: CuO@g-C3N4 composite material was added to the bacterial solution to make the final concentration of CuO@g-C3N4 composite material 50, 100, 150, 200 and 250 mg / L; deionized water without CuO@g-C3N4 composite material was set as the control group (CK);

[0069] 3. Test method: Place the treated bacterial solution in a shaker at 28°C and measure the absorbance of the bacterial solution every 2 hours; use a UV spectrophotometer to measure the growth of Ralstonia solanacearum within 26 hours at an optical density of OD600; the results are as follows: Figure 2 shown.

[0070] Experiment 2: Interaction between CuO@g-C3N4 composite and Ralstonia solanacearum

[0071] The fresh suspension of Ralstonia solanacearum cultured overnight in Experiment 1 was added to the CuO@g-C3N4 composite material to make the final concentration of the CuO@g-C3N4 composite material 0mg / L, 150mg / L, and 250mg / L. It was then placed on a 28°C horizontal shaker for 12 hours of shaking culture, centrifuged and the precipitate collected, fixed with 2.5% glutaraldehyde for more than 12 hours, and dehydrated with a mixture of 50%, 70%, and 90% tert-butanol / ethanol for 5 minutes each; dehydrated twice with 100% tert-butanol, each for 5 minutes. The tert-butanol in the test tube was drained and placed in a 4°C refrigerator for 5-10 minutes. When the tert-butanol was solid, it was freeze-dried for 30-60 minutes. The sample was photographed and analyzed using a scanning electron microscope. The results are as follows. Figure 3 shown.

[0072] from Figure 2 、 Figure 3 It can be seen that different concentrations of CuO@g-C3N4 composite materials can effectively inhibit the growth of Ralstonia solanacearum, and the 150 mg / L CuO@g-C3N4 composite material has the best antibacterial effect.

[0073] Experiment 3: Field experiment

[0074] 1. Preparation

[0075] The experiment was conducted in a field plot (1210m above sea level) in Hongxing Village, Nanmudu Town, Kaiyang County, Guizhou Province, where the disease has occurred year after year. "Dexue No. 1" was selected as the tobacco variety for this experiment. Tobacco was sown in January 2021. At the end of April of the same year, 1,400 tobacco plants in good health, free of pests and diseases, and entering the vigorous growth period were selected and transplanted to the diseased field. Seven treatments were set up, namely experimental group 1 and control groups 1-6. The randomized block arrangement was carried out, and each plot was 100m 2 The row spacing is 50cm×100cm, and 200 tobacco plants are planted in each plot.

[0076] 2. Drug selection

[0077] Experimental group 1: the antibacterial agent prepared in Example 4 was used;

[0078] Control group 1-5: the antibacterial agent prepared in comparative example 1-5 was selected;

[0079] Blank control: Use clean water instead of antibacterial agents.

[0080] 3. Experimental Methods: The pesticide was applied once to the roots of each tobacco plant at the time of transplanting, at a rate of 50 mL per plant. The initial onset of tobacco bacterial wilt was recorded for each group, and a disease survey was conducted. Thereafter, all tobacco plants were surveyed for bacterial wilt every 10 days. Tobacco disease incidence was surveyed according to the national standard GB / 23222-2008, "Grading and Survey Methods for Tobacco Pests and Diseases." Based on local disease characteristics, a systematic survey was conducted focusing on tobacco bacterial wilt. The number of affected plants and the severity level in each plot were investigated to calculate the incidence rate. The results are shown in Table 1.

[0081] Table 1

[0082]

[0083] From Table 1 we can see that:

[0084] 1. Compared with experimental group 1, control groups 1, 3, and 4 only showed changes in the antibacterial agent components. Control group 1 did not add CuO@g-C3N4 to the antibacterial agent. 10 days after transplanting, the diseased plant rate was 18%, compared to the blank control group treated with clean water, which had a control effect of 90.27%. 30 days after transplanting, the diseased plant rate reached 60%, and the control effect was 46.11%. This is because compared with experimental group 1, the antibacterial agent prepared in control group 1 did not contain the main bactericidal ingredients, resulting in poor control effect. However, the remaining components in the antibacterial agent in control group 1 still had certain antibacterial capabilities. Control group 3 lacks the raw materials resistant starch and p-toluenesulfonate. The diseased plant rate is 0% 10 days after transplanting and 24% 30 days after transplanting. The prevention and control effect is 73.42% compared with the blank control group treated with clear water. Control group 4 replaces the raw material CuO@g-C3N4 with g-C3N4. The diseased plant rate is 0% 10 days after transplanting and 33% 30 days after transplanting. The prevention and control effect is 68.56% compared with the blank control group treated with clear water. Although g-C3N4 can also produce a certain amount of active oxygen with water and oxygen, the dispersibility of g-C3N4 is worse. The CuO@g-C3N4 prepared by the present invention can improve the dispersibility of the material due to the addition of copper ions. Combined with the preparation steps, it can play a protective role against bacterial wilt for a long time.

[0085] 2. Compared with experimental group 1, control group 2 had a changed structure of antibacterial agent. The disease rate of plants was 18% 10 days after transplanting and 60% 30 days after transplanting, which was 46.11% higher than that of the blank control group. Control group 5 directly dispersed CuO@g-C3N4 ultrasonically in water without preparing multiple emulsions. The disease rate of plants was 7% 10 days after transplanting and 53% 30 days after transplanting, which was 52.84% higher than that of the blank control group. The control effect of experimental group 1 was better both in the long and short term.

[0086] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that the technical solutions of the present invention may be modified or replaced with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and such modifications or equivalents shall be encompassed by the claims of the present invention. Any techniques, shapes, and structures not described in detail herein are well known.

Claims

1. An antibacterial agent for preventing and treating tobacco bacterial wilt, characterized in that: The antibacterial agent includes the following raw materials: 4×10 -2 -15.9×10 -2 parts by mass of CuO@g-C3N4, 10-28 parts by mass of resistant starch, 6-22 parts by mass of p-toluenesulfonate, 2-7 parts by mass of monodecanoate, 0.6-3.9 parts by mass of polyethylene oxide, 30-90 parts by mass of stearic acid, 0.1-2.5 parts by mass of triethanolamine, and 1-5 parts by mass of glycerol; Preparation method of the antibacterial agent: (1) Ultrasonic dispersion of CuO@g-C3N4 and p-toluenesulfonate in water to form a suspension. Polyoxyethylene, stearic acid, and triethanolamine were weighed. Polyoxyethylene and triethanolamine were first mixed, and then stearic acid was added and mixed evenly. The mixture was placed in a water bath and the suspension was added dropwise while ultrasonication to form a transparent and uniform emulsion. (2) Resistant starch, monocaprate, and propylene glycol were weighed, mixed, and dissolved in water to form a mixed solution. After dissolution, the emulsion was added and homogenized at 4000-5000 r / min for 2-4 minutes to prepare an antibacterial agent for preventing and treating tobacco bacterial wilt.

2. The antibacterial agent for preventing and treating tobacco bacterial wilt according to claim 1, characterized in that: The antibacterial agent includes the following raw materials: 8.25×10 -2 parts by mass of CuO@g-C3N4, 19 parts by mass of resistant starch, 11 parts by mass of p-toluenesulfonate, 5 parts by mass of monodecanoate, 2.2 parts by mass of polyethylene oxide, 60 parts by mass of stearic acid, 2.3 parts by mass of triethanolamine, and 3 parts by mass of glycerol.

3. The antibacterial agent for preventing and treating tobacco bacterial wilt according to claim 2, characterized in that: The CuO@g-C3N4 comprises the following raw materials in a mass-volume ratio: double distilled water: anhydrous ethanol: g-C3N4 powder: copper nitrate trihydrate = (13-17) mL: (13-17) mL: (80-120) × 10 -3 g: (160-240) × 10 -3 g.

4. The method for preparing an antibacterial agent for preventing and treating tobacco bacterial wilt according to claim 3, characterized in that: The preparation steps of the CuO@g-C3N4 are as follows: (1) First, double-distilled water and anhydrous ethanol were mixed to form a mixed solution, and then g-C3N4 powder was weighed and added to the mixed solution. The mixture was ultrasonicated for 30 minutes to prepare a suspension. Copper nitrate trihydrate was added to the suspension, and then the pH was adjusted to 8.5-9.5 under magnetic stirring. After stirring for 2-3 hours, the suspension was filtered and washed, and then refrigerated at -20°C to obtain a light blue solid. (2) Copper nitrate trihydrate and g-C3N4 powder were fully stirred to obtain a powdered composite material. The powdered composite material and the light blue solid were freeze-dried and calcined for 2-3 h to obtain CuO@g-C3N4.

5. The method for preparing an antibacterial agent for preventing and treating tobacco bacterial wilt according to claim 4, characterized in that: The temperature of the water bath in the preparation step (2) of the antibacterial agent is 23-27°C.

6. The method for preparing an antibacterial agent for preventing and treating tobacco bacterial wilt according to claim 5, characterized in that: The volume ratio of the emulsion to the mixed liquid is 1:(3-5).

7. The method for preparing an antibacterial agent for preventing and treating tobacco bacterial wilt according to claim 6, characterized in that: In the preparation step (2) of CuO@g-C3N4, the calcination temperature is 200°C and the heating rate is 5°C / min.

8. The method for preparing an antibacterial agent for preventing and treating tobacco bacterial wilt according to claim 7, characterized in that: The freeze-drying temperature in the preparation step (2) of CuO@g-C3N4 is minus 55°C.

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