A nano-pesticide for preventing and treating anthracnose of citrus and a preparation method thereof

Abstract

The application provides a kind of nanometer pesticide for preventing and treating citrus anthracnose and a preparation method thereof, and belongs to the technical field of pesticide preparation.The nanometer pesticide comprises the following raw materials in parts by weight: active ingredient 1-10 parts, carrier 1-20 parts, organic solvent 20-60 parts, surfactant 2-5 parts, curing agent 0.01-0.2 parts, and dispersant 0.5-6 parts.The active ingredient is chlorothalonil and methyl p-coumarate, and the mass ratio of the two is 9:1-1:1.The carrier is urea-formaldehyde resin.The nanometer pesticide for preventing and treating citrus anthracnose prepared from the above raw materials has good photolysis resistance, a long effective period, and good bactericidal effect.The preparation method has a simple process, small equipment investment, low price, and low production cost.

Description

Technical Field

[0001] This invention relates to the field of pesticide formulation technology, specifically to a nano-pesticide for controlling anthracnose in star fruit and its preparation method. Background Technology

[0002] Nanopesticide formulations have become the mainstream of international green pesticide innovation and development. The active pesticide ingredients in nanopesticide formulations have smaller particle sizes, lower surface tension after dilution with water, better leaf adhesion and coverage, and also have functions such as resistance to photodegradation and control of pesticide release. There are many reports on nanopesticides, such as the patent with publication number CN201911055055.1, entitled "A Pesticide Formulation with Polyurethane as a Carrier and Its Preparation Method." This application discloses a pesticide formulation with polyurethane as a carrier, in which the active pesticide ingredient is encapsulated in the carrier. It can effectively adhere to plant leaves to form a pesticide film, which not only reduces pesticide costs but also has good insecticidal activity, reduces pesticide dosage, and improves the effective utilization rate of pesticides. In addition, in the literature, Qiliang Huang et al. used chitosan-mesoporous silica to adsorb the fungicide azoxystrobin, and the obtained nanoparticle formulation has good sustained-release performance (Qiliang Huang, et al., Nanomaterials 2016, 6, 126; doi:10.3390 / nano6070126). Hiep Minh Nguyen et al. prepared deltamethrin nanoparticle formulations using beeswax and chitin as encapsulation matrices, achieving excellent anti-photodegradation and sustained-release effects (Hiep Minh Nguyen, et.al., Pest management science, 2012, 68(7): 1062-1068).

[0003] However, currently available nanoparticle pesticide formulations often suffer from drawbacks such as low pesticide loading, complex preparation processes, poor stability, short duration of effect, or high cost. Therefore, it is essential to research and develop a nanoparticle pesticide formulation that is simple to prepare, has a high pesticide loading capacity, a long duration of effect, low cost, is environmentally friendly, and possesses excellent sustained-release properties. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a nano-pesticide for controlling anthracnose in star fruit. This nano-pesticide exhibits low surface tension and high bactericidal and preventative efficacy after being diluted with water. The nano-pesticide extends the pesticide's residual effect by encapsulating the active pesticide components chlorfluazuron and methyl coumarate in urea-formaldehyde resin. Furthermore, the use of urea-formaldehyde resin as a carrier allows for controllable pesticide loading, low cost, and a simple and feasible preparation process.

[0005] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted:

[0006] A nanopesticide for controlling anthracnose in star fruit, characterized in that the nanopesticide for controlling anthracnose in star fruit comprises the following raw materials in parts by weight: 1-10 parts of active ingredient, 1-20 parts of carrier, 20-60 parts of organic solvent, 2-5 parts of surfactant, 0.01-0.2 parts of curing agent, and 0.5-6 parts of dispersant; wherein the active ingredient is chlorfluazuril and methyl coumarate, with a mass ratio of 9:1 to 1:1; and the carrier is urea-formaldehyde resin.

[0007] As a preferred technical solution, the solvent is one or a combination of several of the following: butyl acetate, ethyl acetate, sec-butyl acetate, Solvay ADMA810, N,N-dimethylacetamide, isobutyl acetate, n-butyl acetate, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, and solvent oil.

[0008] As a preferred technical solution, the surfactant is a nonionic surfactant, including one or more of the following: sorbitan laurate, octylphenol polyoxyethylene ether, castor oil polyoxyethylene ether, Span 60, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, castor oil polyoxyethylene ether, polyoxyethylene alkylamine, and sorbitan ester.

[0009] As a preferred technical solution, the curing agent is one or a combination of two or more of ammonium chloride, ammonium sulfate, acetic acid, oxalic acid and citric acid.

[0010] As a preferred technical solution, the dispersant is one or more of the following: triphenylethylphenol polyoxyethylene ether, agricultural emulsion 601, isomeric alcohol ether 1605, fatty alcohol polyoxyethylene polyoxypropylene block copolymer, chitin, xanthan gum, methylcellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl starch ether, polyvinyl alcohol, and polyvinylpyrrolidone.

[0011] A method for preparing a nano-pesticide for controlling anthracnose in star fruit, as described above, involves weighing the raw materials according to the specified weight proportions and preparing it according to the following steps:

[0012] (1) Add the active ingredient to an organic solvent, stir to dissolve, and obtain a mixed liquid A;

[0013] (2) Dissolve urea-formaldehyde resin in deionized water by stirring, then add surfactant, and stir to disperse or dissolve thoroughly to obtain a homogeneous urea-formaldehyde resin aqueous solution.

[0014] (3) Under high-speed stirring, the mixed liquid A obtained in step (1) is quickly added to the urea-formaldehyde resin aqueous solution obtained in step (2), and then the curing agent is added. Continue to stir at high speed for 30 minutes to obtain a suspension emulsion.

[0015] (4) Place the suspension emulsion from step (3) at a low temperature of 0-10℃ and ultrasonically disperse for 30-50 minutes to obtain a nano suspension emulsion;

[0016] (5) Add the dispersant to the nano-suspension emulsion obtained in step (4), stir at high speed again for 30-60 minutes, and finally obtain the nano-pesticide with urea-formaldehyde resin as carrier.

[0017] The above-described methods for using nano-pesticides to control anthracnose in star fruit include spraying, spreading, or drenching with water.

[0018] Compared with existing technologies, the nano-pesticides of the present invention have the following beneficial effects:

[0019] 1. By encapsulating pesticide active ingredients with urea-formaldehyde resin polymer, pesticide active ingredients are encapsulated inside nanoparticles to form nanoparticles. Then, the nanoparticles are solidified by a curing agent and a dispersant is added to make the nano-formulation more stable.

[0020] 2. A method for preparing nano-pesticide formulations using urea-formaldehyde resin as a carrier, wherein the pesticide loading of the nano-pesticide is controllable and the preparation process is simple. The main solvent of the nano-formulations of this invention is water, which is inexpensive and environmentally friendly.

[0021] 3. Using urea-formaldehyde resin as the carrier for pesticide active ingredients provides excellent antioxidant and photodegradation resistance, resulting in a longer residual effect, better bactericidal efficacy, reduced photodegradation after spraying, and improved utilization rate of pesticide active ingredients. Compared with other formulations such as emulsifiable concentrates, nano-pesticides offer higher bactericidal and preventative efficacy.

[0022] 4. Pesticide molecules are encapsulated in urea-formaldehyde resin to form nano-pesticide particles, which also have excellent slow-release effects. Urea-formaldehyde resin can degrade in the soil into nitrogen fertilizer that is beneficial to crop growth, thus making it green and environmentally friendly.

[0023] 5. Using urea-formaldehyde resin as a carrier, the nano-pesticide forms a thin film on the leaf and fruit surfaces after being diluted with water and sprayed. The surface tension on the star fruit leaves is significantly reduced, resulting in good adhesion, resistance to rain washout, and protection against photolysis caused by ultraviolet radiation from the sun, thus extending the duration of the pesticide's effectiveness.

[0024] 6. Pesticide molecules are directly encapsulated using urea-formaldehyde resin, thus it has wide applicability and can be used in the preparation of various nano-pesticide formulations.

[0025] 7. Nano-controlled release pesticide formulations using urea-formaldehyde resin as a carrier also have the advantages of simple preparation methods, low equipment investment, and no waste generated during the production process. Attached Figure Description

[0026] Figure 1 This is a dynamic scattering diagram of the particle size determination of the nano-indoxacarb (IN-UF) pesticide formulation obtained in Example 1 of the present invention.

[0027] Figure 2 This is a transmission electron microscope image of the nano-indoxacarb (IN-UF) pesticide formulation obtained in Example 1 of the present invention. Detailed Implementation

[0028] The present invention will be further described in detail below through embodiments. These embodiments are only used to illustrate the present invention and do not limit the scope of protection of the present invention.

[0029] I. Indoor Activity Test: Indoor Activity Determination Test for Controlling Star Fruit Anthracnose

[0030] 1. Test strain: Colletotrichum gloeosporioides, isolated and purified from star fruit exhibiting obvious anthracnose symptoms, and preserved on PDA medium.

[0031] 2. Test reagents

[0032] 98% chlorfluazuron technical grade (BASF Europe), 98% methyl coumarate (Nanjing Qingyun Biotechnology Co., Ltd.)

[0033] Preparation of mother liquor:

[0034] 1) Accurately weigh 0.0020g of chlorfluazuron technical and 0.0102g of methyl coumarate technical, dissolve them separately in acetone, and then...

[0035] Dilute the stock solution to 1000 ml with a 0.1% Tween-80 distilled aqueous solution. Then mix chlorfluazuron and methyl coumarate in ratios of 1:0, 0:1, 7:3, 3:1, 4:1, 17:3, and 9:1, and set up a control with a 0.1% Tween-80 aqueous solution.

[0036] Each formulation was diluted in equal proportions with 0.1% Tween 80 aqueous solution to create five mass concentration gradients. The toxicity of each formulation against Colletotrichum gloeosporioides, the causal agent of star fruit anthracnose, was then determined.

[0037] 3. Test Methods

[0038] The mycelial growth rate method was used. 9 mL of pre-melted PDA medium was added to a sterile Erlenmeyer flask. 1 mL of the drug solution, from low to high concentration, was then quantitatively added to each flask. After thorough mixing, the solution was poured into 9 cm diameter petri dishes to prepare drug-containing plates of the corresponding concentrations. A blank control was prepared using a 0.1% Tween 80 aqueous solution without the drug. Each treatment was repeated three times. Cultured *Starfruit anthracnose* pathogens were taken and punched into 5 mm diameter mycelial discs using a sterile punch. These discs were then transferred to the center of the drug-containing PDA plates (mycelial side down) and incubated at 25 °C for 5 days. Afterward, the colony diameter was measured using the cross-sectional method, and the average colony value and inhibition rate for each treatment were calculated. The inhibition rate was calculated using the following formula:

[0039] Inhibition rate = (Coronary diameter of blank control group - Colony diameter of drug-treated group) / (Coronary diameter of blank control group - Diameter of mycelial cake) × 100%

[0040] 4. Data Analysis: Statistical analysis was performed using DPS software. Linear regression was conducted with the logarithm of the fungicide concentration as x and the corresponding mycelial growth inhibition rate probability value as y to derive the virulence regression equation and the EC50 of the fungicide against the target pathogen. 50 The value was calculated, and the cotoxicity coefficient (CTC) was calculated according to Sun Yunpei's method.

[0041] Toxicity index TI(B) = EC of standard A 50 EC of Agent B 50 ×100

[0042] Actual toxicity index ATI(AB) = EC of A 50 EC ÷AB 50 ×100

[0043] Theoretical toxicity index TTI(AB) = TI(A) × percentage of A in the mixture + TI(B) × percentage of B in the mixture

[0044] Actual Toxicity Index (ATI) = (Standard reagent EC) 50 ÷ Test reagent EC 50 )×100

[0045] Theoretical Toxicity Index (TTI) = Toxicity Index of Agent A × Percentage of A in the Mixture + Toxicity Index of Agent B × Percentage of B in the Mixture

[0046] Co-toxicity coefficient (CTC) = [Actual toxicity index (ATI) of the mixture ÷ Theoretical toxicity index (TTI) of the mixture] × 100

[0047] 5. Evaluation of Measurement Results

[0048] The synergistic effect of the drug was evaluated based on the calculated co-toxicity coefficient (CTC): CTC≤80 indicates antagonistic effect, 80<CTC<120 indicates additive effect, and CTC≥120 indicates synergistic effect. The results are shown in Table 1.

[0049] Table 1. Results of indoor assay for the pathogen controlling anthracnose in star fruit.

[0050]

[0051] The results of the indoor test in Table 1 show that the co-toxicity coefficient of chlorfluazuron to methyl coumarate in the range of 7:3 to 9:1 is greater than 120, showing a significant synergistic effect. When the mass ratio of the two is 2:1, the co-toxicity coefficient is 115.1, which is less than 120 and is an additive effect.

[0052] II. Preparation Examples of the Formulation

[0053] Example 1: 2.5% chlorfluazuron•methyl coumarate nanopesticide (4:1)

[0054] (1) Weigh 2g of pesticide chlorfluazuron and 0.5g of methyl coumarate and stir to dissolve in 43.2g of butyl acetate to obtain mixed solution A;

[0055] (2) Dissolve 1.43g of urea-formaldehyde resin in 48g of deionized water, then add 2.4g of dehydrated sorbitan laurate and stir for 10 minutes to obtain a urea-formaldehyde resin solution.

[0056] (3) Add the mixed solution A obtained in step (1) to the urea-formaldehyde resin solution obtained in step (2) under high-speed stirring, and then add 30 mg of ammonium chloride. Continue to stir at high speed for 30 minutes to obtain a suspension emulsion.

[0057] (4) The suspension emulsion from step (3) is ultrasonically dispersed at a low temperature of 0-10℃ for 30 minutes to obtain a nano suspension emulsion;

[0058] (5) Add 2.4g of dispersant agricultural emulsion 601 to the nano-suspension emulsion in step (4), and stir at high speed for 30 minutes to finally obtain 2.5% chlorfluazuron-methyl p-coumarate nano-pesticide with urea-formaldehyde resin as carrier.

[0059] Example 2: 5% chlorfluazuron•methyl coumarate nanopesticide (17:3)

[0060] (1) Weigh 4.42g of pesticide chlorfluazuron and 0.78g of methyl coumarate and stir to dissolve in 46g of ethyl acetate to obtain mixed solution A;

[0061] (2) Dissolve 2.0g of urea-formaldehyde resin in 40.9g of deionized water, then add 3.0g of Span-60 and stir for 20 minutes to obtain a urea-formaldehyde resin solution;

[0062] (3) Add the mixed solution A obtained in step (1) to the urea-formaldehyde resin solution obtained in step (2) under high-speed stirring, then add 50 mg of ammonium chloride, and continue to stir at high speed for 50 minutes to obtain a suspension emulsion;

[0063] (4) The suspension emulsion described in step (3) is ultrasonically dispersed at a low temperature of 0-10℃ for 50 minutes to obtain a nano suspension emulsion;

[0064] (5) Add 2.9g of dispersant agricultural emulsion 601 to the nano-suspension emulsion in step (4), and stir at high speed for 40 minutes to finally obtain 5% chlorfluazuron-methyl p-coumarate nano pesticide.

[0065] Example 3: 6% chlorfluazuron·methyl coumarate nanopesticide (3:1)

[0066] (1) Weigh 4.5g of chlorfluazuron and 1.5g of methyl coumarate and stir to dissolve them in a mixed solvent of 25.5g of Solvay ADMA810 and 20g of N,N-dimethylacetamide to obtain mixed solution A;

[0067] (2) Dissolve 2.3g of urea-formaldehyde resin in 40g of deionized water, then add 3.0g of octylphenol polyoxyethylene ether and stir for 30 minutes to obtain urea-formaldehyde resin solution;

[0068] (3) Under high-speed stirring, the mixed solution A obtained in step (1) is quickly added to the urea-formaldehyde resin solution obtained in step (2), and then 50 mg of ammonium sulfate is added. Continue high-speed stirring for 60 minutes to obtain a suspension emulsion.

[0069] (4) The suspension emulsion obtained in step (3) is ultrasonically dispersed at a low temperature of 0-10℃ for 60 minutes to obtain a nano suspension emulsion;

[0070] (5) Add 3.0g of dispersant isomeric alcohol ether 1605 to the nano-suspension emulsion in step (4), and stir at high speed for 50 minutes to finally obtain 6% chlorfluazuron-methyl p-coumarate nano-pesticide (3:1) with urea-formaldehyde resin as carrier.

[0071] Example 4: 4% chlorfluazuron·methyl coumarate nanopesticide (7:3)

[0072] (1) Weigh 2.8g of chlorfluazuron and 1.2g of methyl coumarate and stir to dissolve them in a mixed solvent of 30g of sec-butyl acetate and 15g of N,N-dimethylacetamide to obtain mixed solution A;

[0073] (2) Dissolve 2.0g of urea-formaldehyde resin in 48g of deionized water, then add 2.4g of castor oil polyoxyethylene ether and stir for 10 minutes to obtain urea-formaldehyde resin solution;

[0074] (3) Add the mixed solution A obtained in step (1) to the urea-formaldehyde resin solution obtained in step (2) under high-speed stirring, then add 50 mg of ammonium chloride, and continue to stir at high speed for 50 minutes to obtain a suspension emulsion;

[0075] (4) The suspension emulsion obtained in step (3) is ultrasonically dispersed at a low temperature of 0-10℃ for 50 minutes to obtain a nano suspension emulsion;

[0076] (5) Add 2.5g of dispersant triphenylethylphenol polyoxyethylene to the nano-suspension emulsion obtained in step (4), and stir at high speed for 30 minutes to finally obtain 4% chlorfluazuron-methyl p-coumarate nano-pesticide with urea-formaldehyde resin as carrier.

[0077] Example 5: 3% Chlorfluazuron•Methyl coumarate nanopesticide (9:1)

[0078] (1) Weigh 2.7g of chlorfluazuron and 0.3g of methyl coumarate and stir to dissolve in 40g of butyl acetate to obtain mixed solution A;

[0079] (2) Dissolve 1.60g of urea-formaldehyde resin in 50g of deionized water, then add 2.6g of alkylphenol polyoxyethylene ether and stir for 30 minutes to obtain urea-formaldehyde resin solution;

[0080] (3) Add the mixed solution A obtained in step (1) to the urea-formaldehyde resin solution obtained in step (2) under high-speed stirring, and then add 35 mg of ammonium chloride. Continue to stir at high speed for 30 minutes to obtain a suspension emulsion.

[0081] (4) The suspension emulsion obtained in step (3) is ultrasonically dispersed at a low temperature of 0-10℃ for 40 minutes to obtain a nano suspension emulsion;

[0082] (5) Add 2.6g of dispersant fatty alcohol polyoxyethylene polyoxypropylene block copolymer to the nano-suspension emulsion obtained in step (4), and stir at high speed for 30 minutes to finally obtain 3% chlorfluazuron-methyl p-coumarate nano-pesticide with urea-formaldehyde resin as carrier.

[0083] Comparative Example 1: 2.5% chlorfluazuron·methyl coumarate emulsifiable concentrate (4:1)

[0084] (1) Weigh 2g of chlorfluazuron, 0.5g of methyl coumarate, 4g of sorbitan laurate, 1.43g of urea-formaldehyde resin, 30mg of ammonium chloride, and 4g of agricultural emulsion 601 and stir to dissolve in 43.2g of butyl acetate. Then add xylene to make up to 100g and stir for 30 minutes to obtain a uniform liquid, namely 2.5% chlorfluazuron•methyl coumarate emulsifiable concentrate.

[0085] Comparative Example 2: 2.5% Methyl p-coumarate emulsifiable concentrate

[0086] (1) Weigh 2.5g of pesticide methyl coumarate, 4g of sorbitan laurate and 4g of pesticide emulsion 601 and stir to dissolve in 43.2g of butyl acetate, 1.43g of urea-formaldehyde resin and 30mg of ammonium chloride. Then add xylene to make up to 100g and continue stirring for 30 minutes to finally obtain 2.5% methyl coumarate emulsifiable concentrate.

[0087] Blank control: Dissolve 1.43g of urea-formaldehyde resin in 40g of deionized water, add 4.0g of dehydrated sorbitan laurate, 4g of agricultural emulsion 601 and 30mg of ammonium chloride and stir for 30 minutes to obtain urea-formaldehyde resin solution;

[0088] III. Test Example 1.1 Surface Tension and Contact Angle Test

[0089] Take 1 gram of each sample from each embodiment, and then dilute it with water by 500 times, 1000 times, and 1500 times respectively. Detect the surface tension value of each dilution, and drop the dilution onto the leaves of the star fruit plant to detect the contact angle. Repeat 5 times and take the average value. The results are shown in Table 2.

[0090] Table 2. Results of surface tension test

[0091]

[0092] As shown in the table above, compared with Comparative Example 1 and the blank control, the surface tension of the 500-fold, 1000-fold, and 1500-fold dilutions in Example 1 decreased by 22.61%-34.15%, respectively. This improved the spreading properties of the pesticide on the star fruit leaf surface, significantly reduced the amount of pesticide droplets rolling onto the ground, and improved the utilization rate of the fungicide. The surface tension of the nano-pesticides in Examples 2-5 decreased by more than 30% compared with the blank control.

[0093] IV. Light stability test

[0094] Experimental Method: 1 mg of each sample from Examples 1-5, Comparative Examples 1 and 2, and Control Agent A was diluted with deionized water to a concentration of 500 mg / L. 1 ml of the diluted solution was then evenly spread onto a 9 cm diameter glass petri dish. After drying in the dark, the petri dishes were placed 30 cm directly below a 36W UV lamp. The dishes were removed before irradiation, 12 h after irradiation, and 24 h after irradiation. The remaining active ingredients in the petri dishes were extracted with methanol. The contents of chlorfluazuron and methyl coumarate were detected using high-performance liquid chromatography (HPLC). Each treatment was repeated three times, and the average value was taken. The photodegradation rate of the active ingredients was calculated using the following formula. Control Agent A was: 400 g / L chlorfluazuron suspension, registration certificate number PD20220030, purchased from BASF Plant Protection (Jiangsu) Co., Ltd.

[0095] Photodegradation rate (%) = (Active component content before irradiation - Active component content after irradiation) / Active component content before irradiation x 100%

[0096] Table 3. Results of light stability test

[0097]

[0098] The experimental results show that the photodegradation rates of the nano-pesticide diluents prepared in Examples 1-5 of this invention after 12h and 24h of UV irradiation are significantly lower than those of the control examples 1 (emulsifiable concentrate), 2, and A. After 24h of UV irradiation, the photodegradation rates of chlorfluazuron and methyl coumarate in the nano-pesticides prepared in Examples 1-5 were 0.93%-1.16% and 1.27%-1.82% respectively; while in Comparative Example 1, the photodegradation rate of chlorfluazuron was 15.32% and the photodegradation rate of methyl coumarate was 19.89%. The commercially available control agent A showed photodegradation rates of chlorfluazuron of 7.55% and 14.07% after 12h and 24h of UV irradiation, respectively. Therefore, the nano-pesticides prepared in Examples 1-5 of this invention exhibit excellent photostability.

[0099] V. Field efficacy trial of herbal medicine for controlling anthracnose in star fruit

[0100] Test pesticides: Example 1: 2.5% chlorfluazuron-methyl p-coumarate nano-pesticide (4:1); Example 2: 5% chlorfluazuron-methyl p-coumarate nano-pesticide (17:3); Example 3: 6% chlorfluazuron-methyl p-coumarate nano-pesticide (3:1); Example 4: 4% chlorfluazuron-methyl p-coumarate nano-pesticide (7:3); Example 5: 3% chlorfluazuron-methyl p-coumarate nano-pesticide (9:1); All the above nano-pesticides were prepared in-house.

[0101] Comparative Example 1: 2.5% chlorfluazuron-methyl p-coumarate emulsifiable concentrate, prepared in-house;

[0102] Comparative Example 2: 2.5% methyl p-coumarate emulsion, prepared in-house;

[0103] Control agent A: 400 g / L chlorfluazuron suspension, registration certificate number PD20220030, BASF Plant Protection (Jiangsu) Co., Ltd.;

[0104] Blank control: Urea-formaldehyde resin solution, prepared in-house.

[0105] Experimental site conditions: The experimental site was located in a star fruit orchard in Dawan Town, Guiping City, Guangxi Province, where the soil fertility was average. The tested variety was star fruit trees, 3 years old, with poor growth.

[0106] Experimental Design and Methods: The first application of pesticide was conducted during the young fruit stage of star fruit (August 3, 2025). The experiment consisted of 9 treatments, each with 4 replicates, arranged in a randomized block design with protective rows between treatments. Five star fruit trees (tagged) were selected for each treatment and sprayed. The pesticide was diluted with water to the required concentration, and a 3WBD electric sprayer (20L capacity) was used to evenly spray both sides of the leaves and the fruit until completely wet. No other fungicides were used during the experiment, and cultivation management was carried out as usual. A total of 3 sprays were conducted throughout the experiment, once every 10 days. The experiment was mostly sunny or cloudy, and no other fungicides were applied.

[0107] Survey method: In each plot, 2 plants were randomly selected from 5 sprayed (tagged) plants for investigation. Samples were taken from each plant in 5 directions: east, south, west, north and center. 10 fruits were investigated at each point. A total of 100 fruits were investigated in each plot. The number of fruits with diseases at each level and the total number of fruits investigated were recorded.

[0108] The grading of anthracnose in star fruit is based on the "Guidelines for Field Efficacy Trials of Pesticides Part 3: Control of Citrus Anthracnose with Fungicides", and the specific grading standards are as follows:

[0109] Grade 0: No lesions;

[0110] Grade 1: The area of ​​lesions on the non-stem part accounts for less than 2% of the total fruit area;

[0111] Grade 3: Lesions on parts other than the stem cover 3% to 5% of the total fruit area;

[0112] Grade 5: Lesions on parts other than the stem cover 6% to 10% of the total fruit area;

[0113] Grade 7: Lesions on parts other than the stem cover 11% to 20% of the total fruit area;

[0114] Grade 9: Disease spots appear on the stem end or the area of ​​disease spots on non-stem ends accounts for more than 21% of the total fruit area.

[0115] Calculate the disease index and prevention efficacy according to formulas (1) and (2) respectively:

[0116] (1) Disease index (%) = [∑(number of diseased fruits at each level × relative level value) / (total number of fruits surveyed × 9)] × 100

[0117] (2) Prevention and control effect (%) = (disease index after treatment in the blank control area - disease index after treatment in the treatment area) / disease index after treatment in the blank control area × 100.

[0118] Table 4. Results of field efficacy trials for controlling anthracnose in star fruit.

[0119] As shown in the table above, the control efficacy of the nano-pesticides used in Examples 1-5 for controlling anthracnose in star fruit reached over 85% at 20 and 30 days after the last application, which was superior to that of Comparative Example 1, Comparative Example 2, and Control Agent A. Especially at 30 days after the last application, compared with Comparative Example 1 and Control Agent A, the control efficacy of Example 1 (nano-pesticide) was 94.25%, significantly higher than that of Comparative Example 1 (EC) (69.04%) and Control Agent A (60.74%), by 25.21% and 33.51%, respectively. Although the control efficacy of Comparative Example 1 and Control Agent A was over 80% 20 days after the last application, the efficacy decreased significantly after 30 days, with Control Agent A achieving only 60.74%. This further illustrates that nano-pesticides encapsulate pesticide molecules on a urea-formaldehyde resin carrier. After being diluted with water and sprayed, nano-pesticides form a thin film on the leaf surface, which is resistant to rain washout. Furthermore, the urea-formaldehyde resin encapsulation of pesticide molecules can block the photodegradation of pesticide active ingredients caused by ultraviolet radiation from the sun, thus prolonging the duration of the pesticide's effectiveness. The application prospects are promising.

[0120] II. Morphological Characterization of Nano-Controlled-Release Pesticide Formulations Carriered by Urea-Formaldehyde Resin

[0121] Using the 2.5% chlorfluazuron-methyl coumarate nanopesticide obtained in Example 1 as a nano-controlled-release pesticide formulation with urea-formaldehyde resin as a carrier, the microstructure of the prepared nanoparticle pesticide formulation was observed by dynamic light scattering particle size distribution and transmission electron microscopy. The results are as follows: Figure 1 and Figure 2 As shown.

[0122] Figure 1 This is a dynamic light scattering particle size analysis diagram of the sample. Figure 2 This is a transmission electron microscope (TEM) image of the sample. Combined with... Figure 1 and Figure 2As can be seen, the nanoparticle formulation of the present invention has a particle size range of 100-200 nanometers, a spherical shape, and a relatively smooth outer surface, and belongs to a nanoparticle suspension emulsion formulation.

[0123] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Other modifications can be readily implemented by those skilled in the art. Therefore, the present invention is not limited to the specific details without departing from the general concept defined by the claims and their equivalents.

Claims

1. A nano-pesticide for controlling anthracnose in star fruit, characterized in that, The nano-pesticide for controlling anthracnose in star fruit comprises the following raw materials in parts by weight: 1-10 parts of active ingredient, 1-20 parts of carrier, 20-60 parts of organic solvent, 2-5 parts of surfactant, 0.01-0.2 parts of curing agent, and 0.5-6 parts of dispersant; wherein the active ingredient is chlorfluazuron and methyl coumarate, with a mass ratio of 9:1 to 1:1; and the carrier is urea-formaldehyde resin.

2. The nano-pesticide for controlling anthracnose in star fruit according to claim 1, characterized in that, The solvent is one or a combination of several of the following: butyl acetate, ethyl acetate, sec-butyl acetate, Solvay ADMA810, N,N-dimethylacetamide, isobutyl acetate, n-butyl acetate, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, and solvent oil.

3. The nano-pesticide for controlling anthracnose in star fruit according to claim 1, characterized in that, The surfactant is a nonionic surfactant; the nonionic surfactant includes one or more of the following: sorbitan lauryl ester, octylphenol polyoxyethylene ether, castor oil polyoxyethylene ether, Span 60, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, castor oil polyoxyethylene ether, polyoxyethylene alkylamine, and sorbitan ester.

4. The nano-pesticide for controlling anthracnose in star fruit according to claim 1, characterized in that: The curing agent is one or a combination of two or more of ammonium chloride, ammonium sulfate, acetic acid, oxalic acid and citric acid.

5. The nano-pesticide for controlling anthracnose in star fruit according to claim 1, characterized in that, The dispersant is one or more of the following: triphenylethylphenol polyoxyethylene ether, agricultural emulsion 601, isomeric alcohol ether 1605, fatty alcohol polyoxyethylene polyoxypropylene block copolymer, chitin, xanthan gum, methyl cellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl starch ether, polyvinyl alcohol, and polyvinylpyrrolidone.

6. A method for preparing a nano-pesticide for controlling anthracnose in star fruit as described in any one of claims 1-5, characterized in that, Weigh the raw materials according to the specified weight proportions and prepare them according to the following steps: (1) Add the active ingredient to an organic solvent, stir to dissolve, and obtain a mixed liquid A; (2) Dissolve urea-formaldehyde resin in deionized water by stirring, then add surfactant, and stir to disperse or dissolve thoroughly to obtain a homogeneous urea-formaldehyde resin aqueous solution. (3) Add the mixed liquid A obtained in step (1) to the urea-formaldehyde resin aqueous solution obtained in step (2) under high-speed stirring, then add the curing agent, and continue to stir at high speed for 30 minutes to obtain a suspension emulsion; (4) Place the suspension emulsion from step (3) at a low temperature of 0-10℃ and ultrasonically disperse it for 30-50 minutes to obtain a nano suspension emulsion; (5) Add the dispersant to the nano-suspension emulsion obtained in step (4), stir at high speed again for 30 to 60 minutes, and finally obtain the nano-pesticide with urea-formaldehyde resin as carrier.

7. The method of using the nano-pesticide according to any one of claims 1 to 5, or the nano-pesticide for controlling anthracnose in star fruit prepared according to claim 6, characterized in that, Dilute with water and spray, spread, or drench the roots.

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