Nanometer insecticidal bactericide based on biodegradable polymer as well as preparation method and application of nanometer insecticidal bactericide

Abstract

The invention relates to the technical field of pesticides, in particular to a nano insecticidal bactericide based on a biodegradable polymer as well as a preparation method and application of the nano insecticidal bactericide. The nano insecticidal and bactericidal agent based on the biodegradable polymer is prepared from the following preparation raw materials in parts by mass: 0.2 to 0.4 part of difenoconazole, 0.2 to 0.4 part of fludioxonil, 11 to 12 parts of thiamethoxam, 5 to 6 parts of a wetting dispersant, 3.5 to 4.5 parts of an anti-freezing agent, 3 to 4 parts of a thickening agent, 0.2 to 0.3 part of a de-foaming agent, 4 to 5 parts of a composite synergist, 8 to 10 parts of the biodegradable polymer, 0.8 to 1.2 parts of a preservative and 60 to 66 parts of de-ionized water. The nano insecticidal bactericide based on the biodegradable polymer has the advantages of being environmentally friendly, efficient in synergy, long-acting in controlled release, economical, practical, safe, reliable and the like.

Description

Technical Field

[0001] The present application relates to the field of pesticide technology, and in particular to a nano insecticide and fungicide based on a biodegradable polymer, and a preparation method and application thereof. Background Art

[0002] Wheat root rot is a major disease in wheat production, severely impacting yield and quality. Traditional control methods primarily rely on chemical agents, but existing single-agent solutions suffer from strong resistance, short-lasting effects, and a high risk of phytotoxicity. Fungicides such as difenoconazole and fludioxonil, while effective to some extent, struggle to maintain a broad spectrum and safety profile when used alone. Thiamethoxam, as an insecticide, has not been fully exploited for its synergistic effects against seed-borne diseases. Traditional pesticides, such as the 12% difenoconazole, fludioxonil, and thiamethoxam seed treatment suspension concentrate, suffer from high environmental residues, slow degradation, and significant toxicity to non-target organisms. While existing nanopesticides can improve efficacy, they often utilize non-degradable carriers (such as synthetic polymers), which can easily lead to ecological accumulation with long-term use. Furthermore, the large particle size of conventional suspension concentrates results in limited penetration and targeting. Furthermore, existing seed treatment agents lack systematic optimization for wheat germination rate, root development, and environmental compatibility. A highly effective, safe, environmentally friendly, and sustained-release combination formulation is urgently needed. Summary of the Invention

[0003] The purpose of this application is to address the shortcomings of current technology and provide a nano-insecticide based on biodegradable polymers, as well as its preparation method and application. The nano-insecticide based on biodegradable polymers prepared in this application is used for the prevention and control of wheat root rot, aphids, etc., and has the advantages of synergistic enhancement, safety, environmental friendliness and slow release, and has a good prevention and control effect on wheat root rot.

[0004] In the first aspect, the present application provides a nano insecticide and fungicide based on a biodegradable polymer, which adopts the following technical solution: A biodegradable polymer-based nano insecticide and fungicide comprises the following raw materials, measured by weight: 0.2-0.4 parts of difenoconazole, 0.2-0.4 parts of fludioxonil, 11-12 parts of thiamethoxam, 5-6 parts of a wetting and dispersing agent, 3.5-4.5 parts of an antifreeze agent, 3-4 parts of a thickener, 0.2-0.3 parts of a defoaming agent, 4-5 parts of a composite synergist, 8-10 parts of a biodegradable polymer, 0.8-1.2 parts of a preservative, and 60-66 parts of deionized water. The wetting and dispersing agent comprises a dispersant, Morwet D-400, sodium lignin sulfonate, and tristyrylphenol polyoxyethylene ether, and the composite synergist comprises phosphatidylserine and modified silicone.

[0005] By employing the above technical solution, a ternary combination of difenoconazole, fludioxonil, and thiamethoxam synergistically activates sterol synthesis in fungal cell membranes, enhancing the control of root rot. Thiamethoxam, a neonicotinoid insecticide, effectively kills aphids by interfering with the insect nervous system. A specific ratio of these three compounds produces a synergistic effect, enhancing efficacy. Wetting and dispersing agents (such as MORWET D-400, sodium lignin sulfonate, and tristyrylphenol polyoxyethylene ether)—MORWET D-400 (alkylnaphthalene sulfonate polycondensate) stabilizes nanoparticle dispersion through steric hindrance, sodium lignin sulfonate reduces surface tension and enhances particle wettability, and tristyrylphenol polyoxyethylene ether, a nonionic surfactant, enhances emulsion stability—work together to improve the suspension and adhesion properties of the nanopesticide, enhancing field control effectiveness. Composite synergists (such as phosphatidylserine + modified silicone): phosphatidylserine forms a bioadhesive film and prolongs the effective duration; modified silicone: amino groups enhance seed surface adhesion; polyether segments improve permeability, synergistically increasing drug utilization and reducing dosage. Biodegradable polymers (such as polylactic acid or polyhydroxyalkanoates) are used to construct nano-scale sustained-release carriers, achieving sustained release of active ingredients and reducing environmental residues. Thickeners (such as xanthan gum:chitosan:sodium alginate = 5:3:2): xanthan gum provides shear-thinning properties, chitosan enhances the system's antibacterial properties, and sodium alginate improves film-forming properties. This system, through molecular design, achieves a three-level synergistic effect: carrier-active ingredient-adjuvant, enhancing control efficacy while reducing environmental impact, in line with the development of green pesticides.

[0006] Preferably, the mass ratio of difenoconazole, fludioxonil and thiamethoxam is 3:3:114.

[0007] By employing the above technical solution, a specific ratio of difenoconazole, fludioxonil, and thiamethoxam is combined to achieve synergistic and highly effective control of wheat root rot and aphids. This synergistic effect can improve fungicide utilization and reduce drug costs. Difenoconazole (a triazole) and fludioxonil (an pyrrole) inhibit fungi through a dual mechanism of action: difenoconazole blocks ergosterol synthesis (a target of the CYP51 enzyme), while fludioxonil disrupts glucose phosphorylation in the fungus. A 3:3 ratio allows the two to form a complementary fungicidal layer on the seed surface, enhancing the inhibition of root rot pathogens. Thiamethoxam provides a balanced insecticidal and fungicidal effect, with 95% of the effect occurring due to its systemic delivery to all parts of the plant. The LC50 (50% lethal concentration) of neonicotinoid insecticides against aphids (Aphidoidea) is 0.02 mg / L. High doses maintain a long-lasting effect, creating a three-dimensional protective effect with the fungicide, providing both fungicide protection and insecticide control. This ratio achieves the green prevention and control goal of "one-time application - full protection" through precise dosage control, reducing the application frequency by more than 50% compared with conventional pesticides.

[0008] Preferably, the mass ratio of the dispersant Morwet D-400, sodium lignin sulfonate and tristyrylphenol polyoxyethylene ether is 5:2:3-4. Morwet D-400 is an alkylnaphthalene sulfonate polycondensate dispersant produced by Akzo Nobel.

[0009] By employing this technical solution, Morwet D-400, an anionic dispersant, leverages the strong adsorption capacity of alkylnaphthalene sulfonate to form a dense adsorption layer on the nanoparticle surface, providing steric hindrance, improving the suspension stability of the system and preventing nanoparticle sedimentation. It also exhibits excellent compatibility with the biodegradable polymer (polylactic acid) and reduces interfacial tension. Sodium lignin sulfonate, a natural anionic surfactant, reduces the surface tension of the aqueous phase, enhancing wetting and penetration, and provides electrostatic stabilization to prevent particle agglomeration. Its environmentally friendly properties create a synergistic degradation system with the biodegradable polymer. Tristyrylphenol polyoxyethylene ether, a nonionic surfactant, stabilizes the oil / water interface through hydrogen bonding, enhancing the dynamic stability of the emulsion and forming a "charge-complementary" system with the anionic dispersant. Synergistic Mechanism: 1) Dispersion Stability Synergy, Steric Hindrance + Electrostatic Repulsion: The steric hindrance of Morwet D-400 and the electrostatic repulsion of sodium lignin sulfonate work together to stabilize the nanoparticle D50 size at 150±20nm. Wetting-Emulsification Synergy: The rapid wetting of sodium lignin sulfonate combined with the emulsification ability of tristyrylphenol polyoxyethylene ether achieves uniform dispersion of the active ingredient. 2) Improved Environmental Adaptability and Temperature Stability: The cloud point of tristyrylphenol polyoxyethylene ether is ≥75°C. Combined with the thermal stability of Morwet D-400 (decomposition temperature ≥200°C), the nanopesticide remains stable between -5°C and 50°C. Electrolyte Resistance: The chelation effect of sodium lignin sulfonate and the salt tolerance of Morwet D-400 synergize to improve stability in high-hardness water. In short, this ratio achieves the "wetting-dispersion-stabilization" trinity through the scientific combination of anionic / non-ionic surfactants, improves the suspension and adhesion properties of the nanosystem, enhances field control effectiveness, and reduces environmental load, which is in line with the development direction of green pesticide formulations.

[0010] Preferably, the mass ratio of the phosphatidylserine to the modified silicone is 3:4-5.

[0011] By employing this technical solution, phosphatidylserine possesses an amphiphilic structure that forms a thin, sticky protective film on the seed surface. This film adheres to the seed, preventing the active ingredient from penetrating into the soil, enhancing the effectiveness and ensuring long-lasting efficacy. Phosphatidylserine's amphiphilic structure forms a sticky protective film approximately 200-300 nm thick on the seed surface, reducing the loss of active ingredients through soil penetration. The phosphate groups (-PO₄⁻) impart a negative charge to the film, creating an electrostatic attraction with the weakly cationic modified silicone. The natural phospholipid structure enhances affinity with the seed epidermis and promotes germination. The modified silicone's amino groups (-NH₂) form hydrogen bonds with the carboxyl groups (-COOH) on the seed surface, enhancing adhesion. The polyether segments (EO / PO) disrupt the lipid layer of the pathogen's cell membrane, increasing penetration. Phosphatidylserine attracts enzymes secreted by soil microorganisms, activating the fungicide. The amino groups in the modified silicone promote the reaction of the insecticide with the cuticle of the insect's epidermis. In short, this ratio improves the utilization rate of the drug efficacy and the field prevention effect through intermolecular forces and functional complementarity, and has a good preventive and control effect on wheat root rot.

[0012] Preferably, the preparation method of the modified silicone comprises the following steps: S51. Add 60 parts of octamethylcyclotetrasiloxane to 130 parts of deionized water, raise the temperature to 86-90° C., then add 15 parts of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, stir for 20-25 minutes, then add 3 parts of XL-50 and 2 parts of XL-90, react at 86-90° C. for 8-10 hours, cool, adjust the pH to 6.8-7.0 with 25% ammonia water, centrifuge, and remove the solvent to obtain an intermediate product; S52. According to parts by mass: blend polypropylene glycol glycidyl ether with the intermediate product, heat to 75-78° C. and react for 1-2 hours to obtain modified silicone.

[0013] By adopting the above technical solution, octamethylcyclotetrasiloxane is first reacted with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane to obtain an intermediate product into which amino groups are introduced through ring-opening polymerization. The amino groups in the intermediate product are then reacted with polypropylene glycol glycidyl ether containing an epoxy group to achieve the grafting of alkoxy polyether chain segments. A large number of amino groups and long alkoxy chains are introduced into the hydrophobic octamethylcyclotetrasiloxane, achieving hydrophilic modification and making it weakly cationic. This allows the ternary active ingredients (difenoconazole, fludioxonil, and thiamethoxam) to better adhere to the surface of wheat seeds, thereby enhancing the penetration of the ternary active ingredients (difenoconazole, fludioxonil, and thiamethoxam) against root rot and aphids, significantly improving the field control effect, and also increasing wheat yield.

[0014] Preferably, the mass ratio of the polypropylene glycol glycidyl ether to the intermediate product is 11:70-75.

[0015] Preferably, the thickener is prepared by mixing xanthan gum, chitosan and sodium alginate in a mass ratio of 5:3:2; and the biodegradable polymer is one of polylactic acid and polyhydroxyalkanoate.

[0016] Preferably, the preservative is potassium sorbate; the defoaming agent is an organosilicon defoaming agent; and the antifreeze agent is ethylene glycol.

[0017] In a second aspect, the present application provides a method for preparing a nanopesticide based on a biodegradable polymer, using the following technical solution: As a general technical concept, the present application also provides a method for preparing the above-mentioned biodegradable polymer-based nanopesticide, comprising the following steps: S91. Dissolve the biodegradable polymer in acetone according to parts by mass, add difenoconazole, fludioxonil, and thiamethoxam, and ultrasonically disperse for 30-50 minutes; then add deionized water, and emulsify at high shear speed of 8000-12000 rpm for 20-25 minutes to form a nanoemulsion; remove the organic solvent acetone by reduced pressure distillation to obtain a nanoparticle suspension with a particle size of 100-400 nm; S92, adding a wetting dispersant, an antifreeze agent, a thickener, a defoaming agent, a composite synergist, and a preservative to the nanoparticle suspension according to their weight proportions, and pre-dispersing and shearing the mixture at a speed of 3000 rpm for 30 minutes to obtain a mixed solution; S93, subjecting the mixed solution to wet ultrafine grinding, grinding at a rotation speed of 3000 rpm for 4-6 hours, detecting the particle size D90 ≤ 0.2 μm, and filtering to obtain a nano insecticide and fungicide based on a biodegradable polymer.

[0018] In a third aspect, the present application provides an application of a nanopesticide based on a biodegradable polymer, using the following technical solution: As a general technical concept, the present application also provides the above-mentioned biodegradable polymer-based nano insecticide fungicide for use in wheat to prevent and control root rot or aphids.

[0019] In summary, the beneficial technical effects of this application are: 1. Environmental friendliness: Biodegradable polymers (such as PLA or PHA) can degrade within 6-8 months, reducing environmental residues. The use of renewable resources such as sodium lignin sulfonate reduces ecotoxicity.

[0020] 2. Synergistic pest control: Difenoconazole, fludioxonil, and thiamethoxam work synergistically to enhance control effectiveness. Compound synergists (such as phosphatidylserine and modified silicones) enhance long-lasting efficacy and adhesion.

[0021] 3. Nano-controlled sustained release and long-lasting efficacy: Nanoparticles extend the duration of efficacy through a controlled release mechanism. Soil-responsive release matches the disease cycle.

[0022] 4. Optimize the physical properties of the formulation: Improve suspension stability and super-wetting properties. Add antifreeze to ensure low-temperature stability.

[0023] 5. Economic Benefits and Safety: Reduced pesticide costs and dosage per mu. Significant yield increases, with higher thousand-grain weight. Low toxicity and low residue, with minimal impact on non-target organisms.

[0024] 6. Overall field performance: Significantly effective against wheat root rot. Reduces the number of pesticide applications and improves field management efficiency.

[0025] In summary, this application achieves the unity of efficient prevention and control, environmental friendliness and economic benefits through the three-level collaborative design of "nanocarrier-functional adjuvant-active ingredient", breaks through the technical bottleneck of traditional pesticides' "high residue-low efficiency-rapid resistance", and provides innovative solutions for green agriculture. DETAILED DESCRIPTION

[0026] Below in conjunction with embodiment, the embodiment of the present application is described in detail, but those skilled in the art will appreciate that the following examples are merely used to illustrate the application, and should not be considered as limiting the scope of the application. In the embodiment, specific conditions are not indicated, and the conditions according to normal conditions or manufacturer's advice are carried out. Reagents therefor or instrument are not indicated manufacturer, and are all conventional products that can be obtained by commercial purchase. XL-50 and XL-90 are isomeric alcohol ether products of BASF, and Morwet D-400 is a dispersant of an alkyl naphthalene sulfonate polycondensate class produced by Akzo Nobel.

[0027] In the following examples and preparation examples, 1 part means 100 g.

[0028] Preparation Example 1 Preparation of modified silicone The preparation method of modified silicone comprises the following steps: S51. Add 60 parts of octamethylcyclotetrasiloxane to 130 parts of deionized water, raise the temperature to 88° C., then add 15 parts of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, stir for 23 minutes, then add 3 parts of XL-50 and 2 parts of XL-90, react at 88° C. for 9 hours, cool, adjust the pH to 6.9 with 25% ammonia water, centrifuge, and remove the solvent to obtain an intermediate product; S52. According to parts by mass: 11 parts of polypropylene glycol glycidyl ether and 73.5 parts of the intermediate product are mixed, heated to 77° C. and reacted for 1.2 hours to obtain modified silicone. Example 1

[0029] A biodegradable polymer-based nano insecticide and fungicide, comprising the following raw materials, calculated by weight: 0.2 parts of difenoconazole, 0.2 parts of fludioxonil, 11 parts of thiamethoxam, 5 parts of a wetting and dispersing agent, 3.5 parts of ethylene glycol, 3 parts of a thickener, 0.2 parts of an organosilicon defoamer, 4 parts of a composite synergist, 8 parts of a biodegradable polymer, 0.8 parts of potassium sorbate, and 60 parts of deionized water; wherein the wetting and dispersing agent comprises a dispersant Morwet D-400, sodium lignin sulfonate, and tristyrylphenol polyoxyethylene ether in a weight ratio of 5:2:3; the composite synergist comprises phosphatidylserine and modified organosilicon in a weight ratio of 3:4; and the thickener is prepared by mixing xanthan gum, chitosan, and sodium alginate in a weight ratio of 5:3:2; and the biodegradable polymer is polylactic acid. The preparation method of the above-mentioned biodegradable polymer-based nano insecticide and fungicide comprises the following steps: S91. Dissolving the biodegradable polymer in 20 parts by mass of acetone, adding difenoconazole, fludioxonil, and thiamethoxam, and ultrasonically dispersing for 30 minutes; then adding deionized water, and emulsifying at 8000 rpm for 25 minutes to form a nanoemulsion; removing the organic solvent acetone by vacuum distillation to obtain a nanoparticle suspension with a particle size of 100-400 nm; S92, adding a wetting and dispersing agent, ethylene glycol, a thickener, a silicone defoaming agent, a composite synergist, and potassium sorbate to the nanoparticle suspension in parts by mass, and pre-dispersing and shearing at a speed of 3000 rpm for 30 minutes to obtain a mixed solution; S93. The mixed solution is subjected to wet ultrafine grinding, ground at a rotation speed of 3000 rpm for 4 hours, and filtered after the particle size D90 is detected to be ≤ 0.2 μm to obtain a nano insecticide and fungicide based on a biodegradable polymer. Example 2

[0030] A biodegradable polymer-based nano insecticide and fungicide, comprising the following raw materials, calculated by weight: 0.4 parts of difenoconazole, 0.4 parts of fludioxonil, 12 parts of thiamethoxam, 6 parts of a wetting and dispersing agent, 4.5 parts of ethylene glycol, 4 parts of a thickener, 0.3 parts of an organosilicon defoamer, 5 parts of a composite synergist, 10 parts of a biodegradable polymer, 1.2 parts of potassium sorbate, and 66 parts of deionized water; wherein the wetting and dispersing agent comprises a dispersant, Morwet D-400, sodium lignin sulfonate, and tristyrylphenol polyoxyethylene ether, in a weight ratio of 5:2:4; the composite synergist comprises phosphatidylserine and modified organosilicon, in a weight ratio of 3:5; and the thickener is prepared by mixing xanthan gum, chitosan, and sodium alginate, in a weight ratio of 5:3:2; and the biodegradable polymer is a polyhydroxyalkanoate. The preparation method of the above-mentioned biodegradable polymer-based nano insecticide and fungicide comprises the following steps: S91. Dissolve the biodegradable polymer in 20 parts by mass of acetone, add difenoconazole, fludioxonil, and thiamethoxam, and disperse under ultrasonication for 50 minutes; then add deionized water and emulsify at 12,000 rpm for 20 minutes to form a nanoemulsion; remove the organic solvent acetone by vacuum distillation to obtain a nanoparticle suspension with a particle size of 100-400 nm; S92, adding a wetting and dispersing agent, ethylene glycol, a thickener, a silicone defoaming agent, a composite synergist, and potassium sorbate to the nanoparticle suspension in parts by mass, and pre-dispersing and shearing at a speed of 3000 rpm for 30 minutes to obtain a mixed solution; S93, subjecting the mixed solution to wet ultrafine grinding, grinding at a rotation speed of 3000 rpm for 6 hours, detecting the particle size D90 ≤ 0.2 μm, and filtering to obtain a nano insecticide and fungicide based on a biodegradable polymer. Example 3

[0031] A biodegradable polymer-based nano insecticide and fungicide, comprising the following raw materials, calculated by weight: 0.25 parts of difenoconazole, 0.25 parts of fludioxonil, 11.5 parts of thiamethoxam, 5.5 parts of a wetting and dispersing agent, 4 parts of ethylene glycol, 3.5 parts of a thickener, 0.25 parts of an organosilicon defoamer, 4.5 parts of a composite synergist, 9 parts of a biodegradable polymer, 1 part of potassium sorbate, and 64 parts of deionized water; wherein the wetting and dispersing agent comprises a dispersant, Morwet D-400, sodium lignin sulfonate, and tristyrylphenol polyoxyethylene ether, in a weight ratio of 5:2:3.5; the composite synergist comprises phosphatidylserine and modified organosilicon, in a weight ratio of 3:4.5; and the thickener is prepared by mixing xanthan gum, chitosan, and sodium alginate, in a weight ratio of 5:3:2; and the biodegradable polymer is polylactic acid. The preparation method of the above-mentioned biodegradable polymer-based nano insecticide and fungicide comprises the following steps: S91. Dissolving the biodegradable polymer in 20 parts by mass of acetone, adding difenoconazole, fludioxonil, and thiamethoxam, and ultrasonically dispersing for 40 minutes; then adding deionized water, and emulsifying at 10,000 rpm for 22 minutes to form a nanoemulsion; removing the organic solvent acetone by vacuum distillation to obtain a nanoparticle suspension having a particle size of 100-400 nm; S92, adding a wetting and dispersing agent, ethylene glycol, a thickener, a silicone defoaming agent, a composite synergist, and potassium sorbate to the nanoparticle suspension in parts by mass, and pre-dispersing and shearing at a speed of 3000 rpm for 30 minutes to obtain a mixed solution; S93. The mixed solution is subjected to wet ultrafine grinding, ground at a rotation speed of 3000 rpm for 5 hours, and the particle size D90 is detected to be ≤ 0.2 μm, and then filtered to obtain a nano insecticide and fungicide based on a biodegradable polymer. Example 4

[0032] The same as Example 3, except that: difenoconazole 0.3 parts, fludioxonil 0.3 parts, thiamethoxam 11.4 parts.

[0033] Comparative Example 1 The same as Example 4, except that the composite synergist is phosphatidylserine.

[0034] Comparative Example 2 The same as Example 4, except that the composite synergist is modified silicone.

[0035] 1. Performance testing The biodegradable polymer-based nanopesticides prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were sampled and subjected to the following tests. The test results are shown in Table 1.

[0036] Suspension rate test: Test in accordance with GB / T14825-2006 pesticide suspension rate determination method; Pesticide adhesion rate test: A cover glass (2 cm × 2 cm) was vertically immersed in the biodegradable polymer-based nanopesticide prepared in Examples 1 to 4 and Comparative Examples 1 and 2 for 1 minute. The cover glass was then vertically removed and tilted 50° and allowed to stand for 2 minutes. The amount of pesticide on the cover glass was measured and the pesticide adhesion rate was calculated. Temperature stability: refer to GB / T17768-1999 suspension seed coating product standard to test low temperature and heat storage stability.

[0037] Table 1 Performance test

[0038] 2. Indoor safety test of wheat Test method: Indoor culture dish paper bed germination test and potted seedling emergence test.

[0039] Test targets: Zhongmai 122, Liaochun 9 and winter wheat 4199.

[0040] Test basis: NY / T1965.3-2013, Guidelines for Determination of the Safety of Pesticides to Crops, Part 3: Indoor Test Methods for Evaluating the Safety of Seed Treatment Agents to Crops. GB / T3543.4-1995, Procedure for Inspection of Crop Seeds – Germination Test. NY / T1965.1-2010, Guidelines for Determination of the Safety of Pesticides to Crops, Part 1: Indoor Test Methods for Evaluating the Safety of Insecticides and Fungicides to Crops.

[0041] Culture conditions: The culture temperature is 20℃, the relative humidity is 50-60%, and the photoperiod is 12L:12D.

[0042] The biodegradable polymer-based nanopesticide prepared in Example 4 was subjected to an efficacy experiment. The treatment dosage gradient was set as follows: 1650 mL / 100 kg of seeds, 2475 mL / 100 kg of seeds, 3300 mL / 100 kg of seeds, and 4125 mL / 100 kg of seeds. A treatment without the agent was set as a blank control. A total of 5 treatments were performed, with 4 replicates per treatment.

[0043] Test material preparation: For each wheat variety, weigh five 50g portions of seeds (approximately 1000 seeds). Accurately weigh 0.825, 1.238, 1.65, and 2.063ml of the test agent corresponding to four dose gradients and add sterile water to make 3ml of the solution. Coat the seeds, then air-dry and set aside. A blank control was treated with 3ml of sterile water to simulate the coating treatment and set aside.

[0044] For the wheat germination test, a paper bed was used as the germination bed, and for the wheat emergence test, a 1:1 mixture of peat soil and vermiculite was used. The volumetric flasks, graduated cylinders, glassware, filter paper, and the 1:1 mixture of peat soil and vermiculite used in the test were sterilized and dried before use.

[0045] Test treatment: Seed germination test: 400 wheat seeds treated with each agent and blank control were divided into 4 replicates and placed on a moist sterile filter paper bed in a tray. They were cultured in an incubator at 20°C, relative humidity 60-70%, and a photoperiod of 12L:12D.

[0046] Emergence test: Seedling emergence tests were conducted after the seed germination tests were completed. A 1:1 mixture of peat and vermiculite was quantitatively filled into the 4 / 5 of the plastic pots and watered regularly to keep the soil moist. Two hundred wheat seeds, each treated with each agent and a blank control, were sown four times on the flat soil surface of the pots. The seeds were then covered with 1 cm of soil and incubated in an artificial greenhouse (temperature 20°C, relative humidity 60-70%, photoperiod 12L:12D).

[0047] Data investigation and statistical analysis; Survey methods and timing Germination test survey: According to GB / T 3543.4-1995, the first wheat count is on the 4th day, and the final count is on the 8th day. Observe seed germination daily, assessing germination potential on the 4th day and germination rate and root length on the 8th day. Germination potential refers to the percentage of seeds that germinate normally over the total number of seeds tested within the specified number of days at the beginning of the germination test (at the time of the first count).

[0048] Seed germination standard: For cereal crop seeds, the length of the normally developed main root exceeds the length of the seed, and the length of the young sprout exceeds 1 / 2 of the seed length.

[0049] Emergence test survey: Observe the seedlings daily, starting 2 days after emergence, and record the crop growth and description of the phytotoxicity symptoms. The seedling emergence rate of each treatment was recorded and calculated. Fresh weight of each treatment was measured 21 days after emergence, and the inhibition rate was calculated.

[0050] Calculation of the pesticide damage coefficient: The germination potential, germination rate, emergence rate and germination and emergence inhibition rate (%) were calculated according to formulas (1) and (2): Germination rate: G=N1x100 / N2…(1) Where: G-germination rate (germination potential, emergence rate), the unit is percentage (%); N1-normal (emergence) number of germination; N2-test number of seeds.

[0051] Germination inhibition rate (%): G I =(G ck -G T )x100 / G ck …(2).

[0052] Where: G I -Germination inhibition rate, expressed as percentage (%); G CK -Germination rate of blank control; G T - Germination rate after treatment with chemical; The growth rate inhibition rate was calculated according to formula (3) and (4): Growth rate: R=L / D…(3) Where: R is growth rate, in millimeters or grams per day (mm, g / d); L is the new height or length, fresh weight or thousand weight of the plant or branch or root system, in millimeters or grams (mm, g); D is time, in days (d).

[0053] R I =(R CK -R T )x100 / R CK … (4)

[0054] Where: R I-Growth rate inhibition rate, expressed as percentage (%); R CK -Blank control growth rate; R T -Growth rate after drug treatment.

[0055] Statistical analysis: DPS software was used to analyze the experimental data and compare the significance of differences between treatments. The results are shown in Table 2 and Table 3. Table 2 Results of wheat germination and root length after treatment with different dosages

[0056] Note: In Table 2, the same lowercase letters in the same column indicate no significant difference (P<0.05), and the same uppercase letters indicate no extremely significant difference (P<0.01).

[0057] Table 3 Wheat seedling emergence and fresh weight results after 21 days under different dose treatments

[0058] Note: In Table 3, the same lowercase letters in the same column indicate no significant difference (P<0.05), and the same uppercase letters indicate no extremely significant difference (P<0.01).

[0059] The results of the germination test showed that: under the conditions of the present test, after treatment with different dosages of 1650mL / 100kg seeds, 2475mL / 100kg seeds, 3300mL / 100kg seeds, and 4125mL / 100kg seeds of the biodegradable polymer-based nanopesticide prepared in Example 4, no obvious symptoms of seed discoloration, necrosis, and other phytotoxicity were observed during the test: After treatment with different dosages of the biodegradable polymer-based nanopesticide prepared in Example 4, the germination potential was above 90% 4 days after the drug administration, and there was no significant difference between the treatments: There was no significant difference in the germination rate and root length of Zhongmai 122 and Liaochun No. 9 after 8 days of treatment with different dosages of the test agents, and there was no significant difference with the blank control; Winter wheat 4199 was treated with 3300mL / 100kg seeds, 4125mL / 100kg The root length of seeds treated with the drug was significantly different from that of the blank control 8 days after seed treatment, but there was no significant difference between the two treatments; the germination inhibition rate of each nano-insecticide and fungicide treatment was less than 5% 8 days after seed treatment, and the wheat root growth inhibition rate was less than 5%.

[0060] The results of the seedling emergence test showed that after treatment with the biodegradable polymer-based nano insecticide and fungicide prepared in Example 4 at dosages of 1650 mL / 100 kg of seeds, 2475 mL / 100 kg of seeds, 3300 mL / 100 kg of seeds, and 4125 mL / 100 kg of seeds, no obvious symptoms of phytotoxicity such as discoloration, deformity, and wilting were observed visually 21 days after emergence; there was no significant difference in the emergence rate 21 days after thinning among treatments with different dosages, and the emergence inhibition rate 21 days after seedlings was less than 5%; there was no significant difference in the fresh weight 21 days after seedlings, and the fresh weight growth inhibition rate was less than 5% among treatments with different dosages.

[0061] In summary, the biodegradable polymer-based nanopesticide prepared in Example 4 of the present application is safe for wheat within the dosage range of this test.

[0062] 3. Field efficacy test for preventing and controlling wheat root rot Experimental basis: This experiment complies with the "Quality Management Standards for Pesticide Registration Tests" (Announcement No. 2570), the Guidelines for Pesticide Field Efficacy Tests Part 16: Fungicide Control of Wheat Root Rot NY / T 1464.16-2007, and the Standard Operating Procedures for Efficacy Tests of the Institute of Plant Protection, Tianjin Academy of Agricultural Sciences - SOP for Fungicide Control of Wheat Root Rot.

[0063] Test agents: the biodegradable polymer-based nanopesticides prepared in Examples 1 to 4 and Comparative Examples 1 to 2, and a water blank control sample. The concentration of the biodegradable polymer-based nanopesticides prepared in Examples 1 to 4 and Comparative Examples 1 to 2 was 1650 mL / 100 kg of seeds.

[0064] Location of the test site: The test was conducted in the wheat field of the Modern Agriculture Innovation Base (Wuqing) of Tianjin Academy of Agricultural Sciences.

[0065] Test target situation: Wheat root rot (Bipolaris sorokiniana, Fusariumpseudograminearum), the disease is getting worse year by year.

[0066] Trial crops, varieties and growth conditions Wheat, variety "Jinnong No. 6". Mechanical sowing on October 19, 2023, sowing rate 25kg / 666.7m 2 .

[0067] Soil type of the experimental site: The soil of the experimental site is clay loam with a pH value of 7.8 and soil organic matter of 1.8%.

[0068] Water and fertilizer management of the experimental site: diammonium phosphate 20kg / 666.7m3 was applied as base fertilizer. 2Water once before winter, and water in the spring of 2024 for greening, jointing, and filling. In the greening period, apply 20 kg of urea / 666.7 m2 with watering; in the jointing period, apply 15 kg of urea / 666.7 m2 with watering. 2 . Fertilization is uniform.

[0069] Meteorological data: The experimental period was mainly cloudy. The weather conditions on the sowing day were: October 19, 2023, 4.5-13.6℃, ​​average relative humidity 51.5%, no rainfall, and sunshine duration of 9.2 hours.

[0070] Information on pesticides used to control other diseases and pests: No other pesticides were applied in the test site.

[0071] Plot arrangement: A total of 28 plots, 7 treatment plots (corresponding to the biodegradable polymer-based nanopesticides prepared in Examples 1 to 4 and Comparative Examples 1 and 2, and a water blank control sample), were arranged in random blocks, with protective rows set around the plots. The fields were oriented north-south, the plot area was 20 m, and the number of replicates was 4.

[0072] Seed coating will be carried out on October 18, 2023 before wheat sowing.

[0073] The time and number of application of pesticides were October 19, 2023, and the pesticides were applied once in total.

[0074] Survey time and frequency At sowing, a row in each plot under each treatment was manually furrowed between rows and 100 seeds were evenly sown. This served as the treatment for assessing seedling emergence. Fifteen days after wheat sowing (November 3, 2023), all emerged seedlings were counted and the emergence rate was calculated. When wheat root rot was fully established (May 27, 2024), the base of the stem was surveyed for disease, with each plant being graded. Two surveys were conducted in total.

[0075] Survey Methodology Randomly sample 5 points in each plot, and take double rows of 1m at each point to investigate the disease situation at the base of the stem. The investigation is graded based on the plant, and the total number of plants investigated and the number of diseased plants at each level are recorded.

[0076] Grading method: Level 0: no lesions at the base of the stem; Level 1: The lesions surround less than 25% of the stem base; Grade 3: lesions surround 26-50% of the stem base; Grade 5: lesions surround 51-75% of the stem base; Level 7: The lesions surround more than 76% of the stem base, and the plant wilts and is close to death or dead.

[0077] Calculation method of drug efficacy: The disease index and control effect were calculated based on the disease stage. The control results were subjected to arcsine transformation and variance analysis, and the DMRT method was used to compare the significance of the average control effect of each treatment.

[0078]

[0079] The results are shown in Table 5.

[0080] Table 5 Field efficacy test on wheat root rot

[0081] Note: In Table 5, lowercase letter a in the same column indicates no significant difference (P<0.05).

[0082] Analyzing the data in Tables 1 to 5, we can see that: 1) The biodegradable polymer-based nanopesticides prepared in Examples 1 to 4 are used for wheat root rot prevention and treatment. They have the advantages of synergistic effect, safety, environmental friendliness, and slow release, and have a good prevention and treatment effect on wheat root rot.

[0083] 2) A comparative analysis of the performance of the biodegradable polymer-based nanopesticides prepared in combination with Example 4 and Comparative Examples 1-2 showed that the composite synergist consisted of phosphatidylserine and modified silicone in a mass ratio of 3:4.5. By utilizing the coordination between them, through intermolecular forces and functional complementarity, the utilization rate of the efficacy was improved, the field control effect was improved, and a good control effect was achieved on wheat root rot.

[0084] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the above embodiments provide a detailed description of the present application, relevant technical personnel should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the present application.

Claims

1. A nano insecticide based on biodegradable polymer, characterized in that: The preparation method comprises the following raw materials, calculated by weight: 0.2-0.4 parts of difenoconazole, 0.2-0.4 parts of fludioxonil, 11-12 parts of thiamethoxam, 5-6 parts of a wetting and dispersing agent, 3.5-4.5 parts of an antifreeze agent, 3-4 parts of a thickener, 0.2-0.3 parts of a defoaming agent, 4-5 parts of a composite synergist, 8-10 parts of a biodegradable polymer, 0.8-1.2 parts of a preservative, and 60-66 parts of deionized water; wherein the wetting and dispersing agent comprises a dispersant Morwet D-400, sodium lignin sulfonate, and tristyrylphenol polyoxyethylene ether, and the composite synergist comprises phosphatidylserine and modified silicone.

2. The biodegradable polymer-based nanopesticide according to claim 1, characterized in that: The mass ratio of difenoconazole, fludioxonil and thiamethoxam is 3:3:

114.

3. The biodegradable polymer-based nanopesticide according to claim 1, characterized in that: The mass ratio of the dispersant Morwet D-400, sodium lignin sulfonate and tristyrylphenol polyoxyethylene ether is 5:2:3-4.

4. The biodegradable polymer-based nanopesticide according to claim 1, characterized in that: The mass ratio of the phosphatidylserine to the modified silicone is 3:4-5.

5. The biodegradable polymer-based nanopesticide according to claim 1, characterized in that: The preparation method of the modified silicone comprises the following steps: S51. Add 60 parts of octamethylcyclotetrasiloxane to 130 parts of deionized water, raise the temperature to 86-90° C., then add 15 parts of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, stir for 20-25 minutes, then add 3 parts of XL-50 and 2 parts of XL-90, react at 86-90° C. for 8-10 hours, cool, adjust the pH to 6.8-7.0 with 25% ammonia water, centrifuge, and remove the solvent to obtain an intermediate product; S52. According to parts by mass: blend polypropylene glycol glycidyl ether with the intermediate product, heat to 75-78° C. and react for 1-2 hours to obtain modified silicone.

6. The biodegradable polymer-based nanopesticide according to claim 5, characterized in that: The mass ratio of the polypropylene glycol glycidyl ether to the intermediate product is 11:70-75.

7. The biodegradable polymer-based nanopesticide according to claim 1, characterized in that: The thickener is prepared by mixing xanthan gum, chitosan and sodium alginate in a mass ratio of 5:3:2; and the biodegradable polymer is one of polylactic acid and polyhydroxyalkanoate.

8. The biodegradable polymer-based nanopesticide according to claim 1, characterized in that: The preservative is potassium sorbate; the defoaming agent is an organosilicon defoaming agent; and the antifreeze is ethylene glycol.

9. A method for preparing a biodegradable polymer-based nanopesticide according to any one of claims 1 to 8, characterized in that: The following steps are involved: S91. Dissolve the biodegradable polymer in acetone according to parts by mass, add difenoconazole, fludioxonil, and thiamethoxam, and ultrasonically disperse for 30-50 minutes; then add deionized water, and emulsify at high shear speed of 8000-12000 rpm for 20-25 minutes to form a nanoemulsion; remove the organic solvent acetone by reduced pressure distillation to obtain a nanoparticle suspension with a particle size of 100-400 nm; S92, adding a wetting dispersant, an antifreeze agent, a thickener, a defoaming agent, a composite synergist, and a preservative to the nanoparticle suspension according to their weight proportions, and pre-dispersing and shearing the mixture at a speed of 3000 rpm for 30 minutes to obtain a mixed solution; S93, subjecting the mixed solution to wet ultrafine grinding, grinding at a rotation speed of 3000 rpm for 4-6 hours, detecting the particle size D90 ≤ 0.2 μm, and filtering to obtain a nano insecticide and fungicide based on a biodegradable polymer.

10. A use of a biodegradable polymer-based nanopesticide according to any one of claims 1 to 8, characterized in that: The biodegradable polymer-based nano insecticide and fungicide is used for wheat to prevent and control root rot or aphids.

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