A slow-release preparation for preventing and treating melon nematode disease in saline-alkali soil and a preparation method thereof

Abstract

The application relates to the technical field of environment-responsive pesticide preparation, and particularly discloses a slow-release preparation for preventing and treating melon nematode disease in saline-alkali soil and a preparation method thereof. The slow-release preparation for preventing and treating melon nematode disease in saline-alkali soil comprises the following raw materials in mass fraction: 55-57% of 30% fosetyl-Al microcapsule suspension, 19-21% of 15% fluopyram microcapsule suspension, 4-6% of a response component, 5-7% of a surfactant, 0.5-0.6% of a thickening agent, 0.03-0.04% of a preservative and 0.01-0.02% of a defoaming agent, and the rest is water. In addition, the preparation method has the advantages that the slow-release and synergistic effect of the compound preparation of fosetyl-Al and fluopyram can be realized, and the high-pH environment of the saline-alkali soil can be adapted.

Description

Technical Field

[0001] This application relates to the field of environmentally responsive pesticide formulation technology, and more specifically, it relates to a slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes and its preparation method. Background Technology

[0002] In the field of environmentally responsive pesticide formulation technology, with the continuous development of agriculture, the requirements for pesticide formulations are also increasing. Especially in special environments such as saline-alkali land, crops face threats from various pests and diseases, such as root-knot nematode disease in cucurbits. Effective control measures are crucial to ensuring crop yield and quality. At the same time, people are paying increasing attention to the safety, stability, and environmental friendliness of pesticide formulations, which is driving continuous innovation and development in related technologies to meet the actual needs of agricultural production.

[0003] In the past, various methods were used to control root-knot nematodes in cucurbits in alkaline soils. For example, thiazophos and fluopyram compound formulations commonly used a single encapsulation material to allow both active ingredients to be released simultaneously in alkaline soil; or fluopyram was combined with hymexazol to broaden the control spectrum; or a combination of abamectin, thiazophos, and garlic oil was used, relying on fumigation to improve soil permeability; or thiazophos was used as a single agent; or a combination of abamectin and thiophanate-methyl was employed; or a compound product of Paecilomyces lilacinus was used. Other formulations included emulsifiable concentrates, soluble concentrates, and granules.

[0004] However, existing technologies have significant drawbacks. Conventional thiazophos and fluopyram compound formulations use a single encapsulation material, leading to premature release of highly volatile thiazophos and the risk of phytotoxicity, while failing to meet the slow-release requirements of fluopyram. Furthermore, existing formulations are not optimized for the high pH environment of saline-alkali land, resulting in reduced efficacy and a lack of soil-improving functions. Other compound formulations also suffer from problems such as undisclosed co-toxicity coefficients, unclear synergistic mechanisms, unresolved stability issues of highly volatile components, easy degradation of some components, significant resistance to specific nematodes, short duration of action, soil pollution and excessive residues in agricultural products, inhibited microbial activity, susceptibility to phytotoxicity, unsuitability for drip irrigation systems, unstable release rates, and low inhibition rate of egg hatching. Summary of the Invention

[0005] In order to achieve targeted release and synergistic effect of the compound agent of thiazophos and fluopyram, and to adapt to the high pH environment of saline-alkali land, this application provides a slow-release formulation for the control of root-knot nematode disease in sweet potatoes in saline-alkali land and its preparation method.

[0006] In a first aspect, this application provides a slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes, employing the following technical solution:

[0007] A slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes comprises the following raw materials in the following mass fractions: 55-57% 30% thiazophos microcapsule suspension, 19-21% 15% fluopyram microcapsule suspension, 4-6% responsive component, 5-7% surfactant, 0.5-0.6% thickener, 0.03-0.04% preservative, 0.01-0.02% defoamer, and the balance being water. The responsive component comprises the following raw materials in the following mass fractions: 85-90% wood vinegar fraction, 2-3% fatty alcohol ether phosphate, 2-3% EO-PO block polyether, 0.5-0.6% polyvinyl alcohol, 3-4% ethylene glycol, and the balance being water.

[0008] By employing the above-mentioned technical solution, the thicker walls of thiazophosphazene microcapsules and the thinner walls of fluopyram microcapsules, when combined, enable the gradient release of thiazophosphazene and fluopyram. Fluopyram is released first, quickly establishing an effective control concentration, while the thiazophosphazene microcapsules exhibit slow-release characteristics, achieving long-term slow-release control. The responsive components allow the slow-release formulation to maintain an acidic environment, which is beneficial for ensuring storage stability. After application, it can preferentially neutralize soil alkalinity, triggering the rupture and release of fluopyram and thiazophosphazene microcapsules, achieving targeted release in saline-alkali land.

[0009] Preferably, the 30% thiazophosphine microcapsule suspension comprises the following raw materials in the following mass fractions: 4-6% diphenylmethane diisocyanate, 1.5-2.5% ethylenediamine, 30% thiazophosphine, 1-2% lignin sulfonate, 4-6% sodium methylene bisnaphthalene sulfonate, and the balance being water.

[0010] Preferably, the preparation method of the 30% thiazophosphine microcapsule suspension includes the following steps: thiazophosphine, diphenylmethane diisocyanate, lignin sulfonate and water are measured separately and added sequentially to a mixing vessel, stirred, heated to 60-65℃ to fully dissolve, stirred, cooled, and then ethylenediamine is added dropwise while stirring. After the addition is complete, sodium methylene bis(naphthalene) sulfonate is added to adjust the pH to 6-7, thereby obtaining the 30% thiazophosphine microcapsule suspension.

[0011] By adopting the above technical solution, the encapsulation efficiency of the prepared thiazophosphorus microcapsules is high and the wall thickness is ≥5μm, which can achieve stable storage and long-term sustained release of thiazophosphorus microcapsules, which helps to achieve long-term stable prevention and control effects. Moreover, the response speed in saline-alkali land is faster and higher, and the sustained release rate is further improved.

[0012] Preferably, the 15% fluopyram microcapsule suspension comprises the following raw materials in the indicated mass fractions: 4-5% gelatin, 4-5% gum arabic, 15% fluopyram, 44-46% toluene, 19-21% dimethyl sulfoxide, and the balance being water.

[0013] Preferably, the preparation method of the 15% fluopyram microcapsule suspension includes the following steps: mixing gum arabic with water to obtain a 10-50% gum arabic pre-dissolved solution for later use; mixing gelatin with water to obtain a 20-70% gelatin pre-dissolved solution for later use; mixing fluopyram, toluene, dimethyl sulfoxide and the remaining water; homogenizing under high pressure to form a homogeneous emulsion; adding the gum arabic pre-dissolved solution dropwise; mixing evenly; adding the gelatin pre-dissolved solution dropwise under high pressure homogenization; mixing evenly; cooling; adjusting the pH to 6-7; and obtaining the 15% fluopyram microcapsule suspension.

[0014] By adopting the above technical solution, the prepared fluopyram microcapsule suspension has a good encapsulation effect, and the microcapsule wall thickness is ≤0.5μm. After release, it can quickly rupture and release fluopyram, meeting the rapid control requirements of the releasing plants.

[0015] Preferably, the method for preparing the responsive component includes the following steps: mixing wood vinegar fraction with EO-PO block polyether, stirring thoroughly to form a homogeneous solution, adding it to water containing fatty alcohol ether phosphate, shearing and emulsifying to form an emulsion, and then adding polyvinyl alcohol and ethylene glycol to obtain the responsive component.

[0016] By adopting the above technical solution, the prepared response component can maintain the environment in an acidic state, which is conducive to the stable storage of fluopyram microcapsules and thiazophosphorus microcapsules. In saline-alkali land, it can effectively neutralize soil alkalinity and trigger the rapid release of fluopyram and the slow-release application of thiazophosphorus. At the same time, the wood vinegar has the effects of soil remediation and pathogen inhibition, which can realize the triple synergistic mechanism of targeted application, pH adjustment and pathogen inhibition. Furthermore, fluopyram and thiazophosphorus can still exert their effects in high pH environments, achieving short-term and long-term dual control of root-knot nematode disease.

[0017] Secondly, this application provides a method for preparing a slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes, using the following technical solution:

[0018] A method for preparing a slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes includes the following steps: mixing 30% thiazophosphorus microcapsule suspension, 15% fluopyram microcapsule suspension, and a response component; adding a surfactant and stirring evenly; and then sequentially adding a thickener, an antifoaming agent, water, and a preservative to obtain the slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes.

[0019] By adopting the above technical solution, the combination of thiazophos and fluopyram asymmetric microcapsule system is realized, and a slow-release formulation suitable for the control of root-knot nematode disease in saline-alkali sweet potatoes is prepared. This achieves targeted release and synergistic effect of the agent in saline-alkali soil, solves the problems of poor stability of highly volatile pesticides and low soil compatibility of conventional formulations, realizes biphasic release of the agent, improves the slow release rate and efficacy in alkaline soil, activates plant SAR resistance and reduces the amount of pesticide used.

[0020] In summary, this application has the following beneficial effects:

[0021] 1. Because the walls of the thiazophosphatidylcholine microcapsules in this application are thicker and the walls of the fluopyram microcapsules are thinner, the combination of the two microcapsules can achieve a gradient release of thiazophosphatidylcholine and fluopyram. Fluopyram can be released first to quickly establish an effective control concentration, and then the thiazophosphatidylcholine microcapsules exhibit slow-release characteristics to achieve long-term slow-release control. The responsive components can enable the slow-release formulation to maintain an acidic environment, which is conducive to ensuring the stability of storage. After application, it can preferentially neutralize the alkalinity of the soil, triggering the rupture and release of fluopyram and thiazophosphatidylcholine microcapsules, thus achieving targeted release in saline-alkali land.

[0022] 2. The thiazophosphine microcapsules prepared in this application have a high encapsulation efficiency and a wall thickness of ≥5μm, which enables stable storage and long-term sustained release of thiazophosphine microcapsules, which helps to achieve long-term stable prevention and control effects. Moreover, the response speed is faster and higher in saline-alkali land, and the sustained release rate is further improved.

[0023] 3. The response components prepared in this application can maintain an acidic environment, which is conducive to the stable storage of fluopyram microcapsules and thiazophosphorus microcapsules. In saline-alkali land, they can effectively neutralize soil alkalinity and trigger the rapid release of fluopyram and the slow-release application of thiazophosphorus. At the same time, the wood vinegar has the effects of soil remediation and pathogen inhibition, which can realize the triple synergistic mechanism of targeted application, pH adjustment and pathogen inhibition. Furthermore, fluopyram and thiazophosphorus can still exert their effects in high pH environments, achieving short-term and long-term dual control of root-knot nematode disease. Attached Figure Description

[0024] Figure 1(a) shows the soil release kinetics curves of thiazophosphonate microcapsules and fluopyram microcapsules;

[0025] Figure 1(b) shows the release kinetics curves of thiazophosphonate microcapsules and fluopyram microcapsules in soils with different pH values;

[0026] Figure 2(a) is an electron micrograph of thiazophosphine microcapsules;

[0027] Figure 2(b) is an electron micrograph of fluopyram microcapsules;

[0028] Figure 2(c) is an electron micrograph of the mixture of thiazophosphonate microcapsules and fluopyram microcapsules. The gray microcapsules are thiazophosphonate microcapsules, and the purple microcapsules are fluopyram microcapsules. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Preparation of 30% thiazophosphine microcapsule suspension: Examples 1-2

[0031] Preparation Example 1

[0032] The 30% thiazophosphonate microcapsule suspension comprises the following raw materials by mass fraction: 4% diphenylmethane diisocyanate, 1.5% ethylenediamine, 30% thiazophosphonate, 1% lignin sulfonate, 4% sodium methylene bisnaphthalene sulfonate, and the balance being water.

[0033] Thiazolphosphine, diphenylmethane diisocyanate, lignin sulfonate, and water were measured, pulverized, and added sequentially to a mixing vessel. The mixture was stirred, heated to 60°C to fully dissolve, stirred, and cooled. Ethylenediamine was added dropwise while stirring. After the addition was complete, sodium methylene bisnaphthalene sulfonate was added to adjust the pH to 7, thus obtaining a 30% thiazophosphine microcapsule suspension.

[0034] Preparation Example 2

[0035] The 30% thiazophosphonate microcapsule suspension comprises the following raw materials by mass fraction: 6% diphenylmethane diisocyanate, 2.5% ethylenediamine, 30% thiazophosphonate, 2% lignin sulfonate, 5% sodium methylene bisnaphthalene sulfonate, and the balance being water.

[0036] Thiazolphosphine, diphenylmethane diisocyanate, lignin sulfonate, and water were measured, pulverized, and added sequentially to a mixing vessel. The mixture was stirred, heated to 65°C to fully dissolve, stirred, and cooled. Ethylenediamine was added dropwise while stirring. After the addition was complete, sodium methylene bisnaphthalene sulfonate was added to adjust the pH to 6, thus obtaining a 30% thiazophosphine microcapsule suspension.

[0037] Preparation of 15% Fluopyram microcapsule suspension (Examples 3-4)

[0038] Preparation Example 3

[0039] The 15% fluopyram microcapsule suspension comprises the following raw materials by mass fraction: 4% gelatin, 4% gum arabic, 15% fluopyram, 44% toluene, 21% dimethyl sulfoxide, and the balance being water.

[0040] A 10% pre-dissolved gum arabic solution was prepared by mixing gum arabic with water. A 60% pre-dissolved gelatin solution was prepared by mixing gelatin with water. Fluopyram, toluene, dimethyl sulfoxide, and the remaining water were mixed and homogenized under high pressure to form a homogeneous emulsion. The pre-dissolved gum arabic solution was added dropwise and mixed evenly. The pre-dissolved gelatin solution was then added dropwise under high pressure homogenization and mixed evenly. After cooling, the pH was adjusted to 7 to obtain a 15% fluopyram microcapsule suspension.

[0041] Preparation Example 4

[0042] The 15% fluopyram microcapsule suspension comprises the following raw materials by mass fraction: 5% gelatin, 4% gum arabic, 15% fluopyram, 45% toluene, 20% dimethyl sulfoxide, and the balance being water.

[0043] A 30% pre-dissolved gum arabic solution was prepared by mixing gum arabic with water. A 50% pre-dissolved gelatin solution was prepared by mixing gelatin with water. Fluopyram, toluene, dimethyl sulfoxide, and the remaining water were mixed and homogenized under high pressure to form a homogeneous emulsion. The pre-dissolved gum arabic solution was added dropwise, and after mixing evenly, the pre-dissolved gelatin solution was added dropwise under high pressure homogenization. After mixing evenly, the mixture was cooled and the pH was adjusted to 6 to obtain a 15% fluopyram microcapsule suspension.

[0044] Preparation examples of responsive components 5-6

[0045] Preparation Example 5

[0046] The response components consist of the following raw materials by mass fraction: 85% wood vinegar fraction, 2% fatty alcohol ether phosphate, 3% EO-PO block polyether, 0.5% polyvinyl alcohol, 4% ethylene glycol, and the balance being water.

[0047] The wood vinegar fraction was mixed with EO-PO block polyether and stirred thoroughly to form a homogeneous solution. This solution was then added to water containing dissolved fatty alcohol ether phosphate. After shearing and emulsification to form an emulsion, polyvinyl alcohol and ethylene glycol were added to obtain the responsive component.

[0048] Preparation Example 6

[0049] The response components consist of the following raw materials by mass fraction: 90% wood vinegar fraction, 3% fatty alcohol ether phosphate, 2% EO-PO block polyether, 0.6% polyvinyl alcohol, 3% ethylene glycol, and the balance being water.

[0050] The wood vinegar fraction was mixed with EO-PO block polyether and stirred thoroughly to form a homogeneous solution. This solution was then added to water containing dissolved fatty alcohol ether phosphate. After shearing and emulsification to form an emulsion, polyvinyl alcohol and ethylene glycol were added to obtain the responsive component.

[0051] Example

[0052] Example 1

[0053] A slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes comprises the following raw materials in the following mass fractions: 56.67% 30% thiazophosphatidylcholine microcapsule suspension, 20% 15% fluopyram microcapsule suspension, 5% response component, 6% surfactant, 0.5% thickener, 0.04% preservative, 0.02% defoamer, and the balance being water. The 30% thiazophosphatidylcholine microcapsule suspension is selected from the 30% thiazophosphatidylcholine microcapsule suspension prepared in Preparation Example 1, the 15% fluopyram microcapsule suspension is selected from the 15% fluopyram microcapsule suspension prepared in Preparation Example 3, the response component is selected from the response component prepared in Preparation Example 5, the surfactant includes 1.5% sodium methylene bis(naphthalene) sulfonate and 4.5% lignin sulfonate, the thickener includes 0.05% xanthan gum and 0.45% magnesium aluminum silicate, and the preservative is Kathon.

[0054] The preparation method of the above-mentioned slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes includes the following steps: mixing 30% thiazophosphorus microcapsule suspension, 15% fluopyram microcapsule suspension and response components, adding surfactant and stirring evenly, and then adding thickener, defoamer, water and preservative in sequence to obtain the slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes.

[0055] Example 2

[0056] A slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes comprises the following raw materials in the indicated mass fractions: 57% 30% thiazophosphatidylcholine microcapsule suspension, 19% 15% fluopyram microcapsule suspension, 6% response component, 7% surfactant, 0.6% thickener, 0.03% preservative, 0.01% defoamer, and the balance being water. The 30% thiazophosphatidylcholine microcapsule suspension is selected from the 30% thiazophosphatidylcholine microcapsule suspension prepared in Preparation Example 2, the 15% fluopyram microcapsule suspension is selected from the 15% fluopyram microcapsule suspension prepared in Preparation Example 4, the response component is selected from the response component prepared in Preparation Example 6, the surfactant includes 2% sodium methylene bis(naphthalene) sulfonate and 5% lignin sulfonate, the thickener includes 0.1% xanthan gum and 0.5% magnesium aluminum silicate, and the preservative is Kathon.

[0057] The preparation method of the above-mentioned slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes includes the following steps: mixing 30% thiazophosphorus microcapsule suspension, 15% fluopyram microcapsule suspension and response components, adding surfactant and stirring evenly, and then adding thickener, defoamer, water and preservative in sequence to obtain the slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes. Comparative Example

[0058] Comparative Example 1

[0059] The difference between Comparative Example 1 and Example 1 is that, in Comparative Example 1, a slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes includes the following raw materials in the following mass fractions: 40% 30% thiazophosphorus microcapsule suspension, 25% 15% fluopyram microcapsule suspension, 4% responsive component, 5% surfactant, 0.5% thickener, 0.04% preservative, 0.02% defoamer, and the balance being water.

[0060] Comparative Example 2

[0061] The difference between Comparative Example 2 and Example 1 is that, in Comparative Example 2, a slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes includes the following raw materials in the following mass fractions: 65% 30% thiazophosphorus microcapsule suspension, 12% 15% fluopyram microcapsule suspension, 5% responsive component, 5% surfactant, 0.5% thickener, 0.04% preservative, 0.02% defoamer, and the balance being water.

[0062] Performance testing

[0063] 1. Plotting Soil Release Kinetics Curves

[0064] Brown soil (topsoil layer 0-20cm) collected from farmland in North China was sieved through a 2mm sieve to remove stones and plant roots. Its moisture content, organic matter content, and pH were measured. The organic matter content was 2.1%, and the pH was 7.5. To avoid interference from microbial degradation, the experimental soil was sterilized in a 121℃ autoclave for 20 minutes. The moisture content of the sterilized soil was determined using the drying loss method, and water was added to bring the soil moisture content to 60% of its maximum water holding capacity. The soil was then pre-equilibrated at 25℃ for 24 hours. Multiple 100g portions of soil (dry weight) were weighed into 250mL wide-mouth bottles.

[0065] Experimental group: Thiazophosphine·fluopyram microcapsule suspension was taken, diluted with a small amount of water, and then sprayed onto the soil very slowly and evenly with stirring using a micro sprayer, so that the final concentration was 10 mga.i. / kg soil (ai represents active ingredient).

[0066] Control group: Sprayed with an equal amount of deionized water.

[0067] All wide-mouth bottles were covered with plastic wrap and perforated with a needle to ensure air permeability, then placed in a 25°C incubator in the dark. Sampling time points were set at: 6h (initial), 12h, 24h, 48h, 72h, 5d, 10d, 20d, 30d, 45d, 60d, and 80d. Three replicates were set for each treatment at each time point. At the predetermined time points, the entire bottle of soil was removed, and extraction analysis was performed immediately.

[0068] Add 50g of anhydrous sodium sulfate to 100g of soil sample and grind to remove moisture. Transfer the dried soil to a stoppered conical flask and add 100mL of a 1:1 (v / v) mixture of acetonitrile and acetone. Extract by horizontal shaking for 1 hour. Filter a portion of the extract through a 0.22μm organic filter membrane and transfer it to a brown sample vial for HPLC analysis.

[0069] The HPLC analysis conditions were as follows: column: C18, 4.6×250mm, 5μm; mobile phase: acetonitrile:water = 75:25 (v / v); flow rate: 1.0mL / min; column temperature: 30℃; detection wavelength: 245nm; injection volume: 10μL.

[0070] A series of standard solutions of thiazophosphonate and fluopyram (e.g., 0.5, 1, 5, 10, 20, 50 mg / L) were prepared using acetonitrile. These solutions were injected sequentially, and a linear regression was performed on the peak area (Y) against the concentration (X, mg / L) to obtain the standard curve equation Y = aX + b. The correlation coefficient R² was required to be greater than 0.999. Release curves for both active ingredients were plotted, and the results are shown in Figure 1(a).

[0071] pH test group: 100g of experimental soil was taken and sulfur powder was added. The pH of the experimental soil was adjusted to 3, 6 and 9 respectively. Thiazolephosphine·fluopyram microcapsule suspension was taken, diluted with a small amount of water, and sprayed into the soil very slowly and evenly with stirring using a micro sprayer, so that the final concentration was 10mga.i. / kg soil (ai represents active ingredient), which was used as the pH test group.

[0072] pH control group: 100g of experimental soil was taken and sulfur powder was added to adjust the pH of the experimental soil to 7. Thiazophosphine·fluopyram microcapsule suspension was then transferred, diluted with a small amount of water, and sprayed very slowly and evenly into the soil using a micro-sprayer with stirring, resulting in a final concentration of 10 mga.i. / kg soil (ai represents the active ingredient), serving as the pH control group. Release curves for the two active ingredients were plotted, and the results are shown in Figure 1(b). A series of thiazophosphine and fluopyram standard solutions (e.g., 0.5, 1, 5, 10, 20, 50 mg / L) were prepared using acetonitrile. These were injected sequentially, and a linear regression was performed on the peak area (Y) against the concentration (X, mg / L) to obtain the standard curve equation Y = aX + b. The correlation coefficient R² was required to be > 0.999. Release curves for the two active ingredients were plotted, and the results are shown in Figure 1(a).

[0073] pH test group: 100g of experimental soil was taken and sulfur powder was added. The pH of the experimental soil was adjusted to 3, 6 and 9 respectively. Thiazolephosphine·fluopyram microcapsule suspension was taken, diluted with a small amount of water, and sprayed into the soil very slowly and evenly with stirring using a micro sprayer, so that the final concentration was 10mga.i. / kg soil (ai represents active ingredient), which was used as the pH test group.

[0074] pH control group: 100g of experimental soil was taken and sulfur powder was added to adjust the pH of the experimental soil to 7. Thiazophosphine·fluopyram microcapsule suspension was then transferred, diluted with a small amount of water, and sprayed very slowly and evenly into the soil using a micro-sprayer with stirring, so that the final concentration was 10 mga.i. / kg soil (ai represents the active ingredient), which served as the pH control group. Release curves of the two active ingredients were plotted separately, and the results are shown in Figure (b).

[0075] Cumulative release (mg) = C t ×V total C t V represents the drug concentration in the release medium at time t. total To release the total volume of the medium;

[0076] Cumulative release percentage (%) = Q t / M total ×100%, Q t M represents the cumulative release amount. total This refers to the total mass of the drug within the microcapsules;

[0077] Release rate (mg / d) = dQ / dt ≈ ∆Q / ∆t, where dQ / dt is the cumulative release amount as a constant with respect to time (instantaneous release rate), ∆Q is the change in release amount over time interval ∆t, and ∆t is the time interval.

[0078] Relative change rate (%) = (release rate of pH test group - release rate of pH control group) / release rate of pH control group × 100%;

[0079] The release rates and relative change rates were calculated by measuring the cumulative release amounts in the pH control group and the pH test group. Based on the relationship between the cumulative release amount and time, the release characteristics of fluopyram microcapsules and thiazophos were analyzed.

[0080] 2. Life test

[0081] Commercially available products were selected, namely "Lufida®" 41.7% fluopyram SC produced by Bayer Crop Science and "Baodian®" 20% thiazophos EW produced by Hebei Sannong. The two single-agent products were compared in tank mix combination, and a biotest was conducted.

[0082] An indoor potted seedling cultivation method was used to conduct a comparative experiment on the efficacy of the test product and a commercially available product of the same type, using equal amounts of the active ingredients. The dwarf tomato variety "Little Tom," with consistent agronomic traits, was used as the model variety for the experiment. Transplanted seedlings with uniform growth in each treatment were selected and transplanted into field soil containing nematodes. After 5 days of recovery, the test agent and the commercially available product were applied. The nematode population inhibition rate in the rhizosphere soil was measured at 7 and 14 days after application, and the fresh weight of tomato roots and the number of root knots were measured at 45 days after application. The root necrosis rate and control efficacy were calculated, and the results are recorded in Table 1.

[0083] Table 1. Control efficacy of root-knot nematode disease

[0084] Test sample 7-day insect population reduction rate (%) 14-day insect population reduction rate (%) 45-day insect population reduction rate (%) Root weight (g) Number of root knots (units / g) Root necrosis rate (%) Prevention and control efficacy (%) Example 1 79.23 97.28 98.53 1.79±0.29 57.69±15.82 1.50 96.27 Example 2 80.02 96.92 98.26 1.76±0.28 56.95±15.12 1.53 96.12 Comparative Example 1 82.69 95.62 72.62 1.53±0.24 61.95±18.52 3.12 92.62 Comparative Example 2 73.25 95.12 83.62 1.55±0.23 62.35±17.32 3.05 91.15 Commercially available products 82.79 95.69 71.35 1.56±0.22 87.12±21.45 5.25 81.49 control group —— —— —— 1.13±0.04 270.52±12.17 21.25 ——

[0085] Combining Figures 1(a), 1(b), 2(a), 2(b), 2(c) and Example 1, it can be seen that the fluopyram microcapsule component exhibits typical rapid-release characteristics, with a release rate of approximately 60% in 6 hours, consistent with the Higuchi model. It rapidly reaches its peak release rate within 24 hours, indicating excellent initial release efficiency and the ability to quickly establish an effective control concentration. The release rate gradually decreases after 72 hours, meeting the design expectation of high-efficiency initial control. The thiazophos microcapsule component, on the other hand, exhibits slow-release characteristics. Initially, the release is slow, with a release rate of approximately 6% in 6 hours. The release rate then steadily increases, reaching its peak around day 7 and maintaining a high release level until 30 days before gradually declining. The release cycle can last up to 80 days, consistent with the Korsmeyer-Peppas model. This release pattern effectively extends the duration of effectiveness and helps achieve long-term stable control effects. The two microcapsule suspensions differ in size and wall thickness, and the combination of differentiated release kinetics allows fluopyram and thiazophos to achieve staggered release peaks with non-overlapping action cycles. This synergistically meets the dual needs of crops for both rapid and sustained efficacy during their growth period, reducing the frequency of application and improving pesticide utilization. It has significant agricultural application value. Furthermore, the corrosion inhibitor prepared in this application exhibits an increased release rate with increasing pH, and can still exert its slow-release effect in saline-alkali soils with higher pH. It can also achieve targeted release in saline-alkali soils, effectively controlling root-knot nematode disease in cucurbits under saline-alkali conditions.

[0086] As can be seen from Table 1, Example 1, and commercially available products, the microcapsule suspension composition provided in Example 1 exhibits significantly superior overall performance compared to commercially available products in controlling tomato root-knot nematodes. This formulation demonstrates high and rapid efficacy within 7 days of application, with a 79.23% reduction rate in nematode population, further increasing to 97.28% by day 14, indicating rapid and sustained insecticidal activity. Even at day 45, the nematode population reduction rate remains at a high level of 98.53%, significantly better than the 71.35% reduction rate of commercially available products, proving its excellent sustained efficacy.

[0087] Regarding the promotion of crop growth, the root weight of the treatment group in Example 1 reached 1.79g, significantly higher than that of the commercially available product group and the blank control group, indicating that the formulation has a positive promoting effect on crop root development. Simultaneously, the number of root knots was significantly reduced to 57.69 / g, the root necrosis rate was only 1.50%, and the final control effect reached 96.27%, with comprehensive performance significantly superior to the commercially available control product. These data fully demonstrate that the microcapsule suspension composition provided by this invention can effectively coordinate the balance between rapid and sustained effects, significantly improving crop health while enhancing control efficacy, and possessing outstanding agricultural application value.

[0088] Combining Examples 1-2 and Comparative Examples 1-2, it can be seen that when the mass fraction of 30% thiazophos microcapsule suspension and 15% fluopyram microcapsule suspension changes, the decrease in the content of fluopyram microcapsules leads to a significant decrease in the control effect at 7 days. It is speculated that the decrease in the content of fluopyram microcapsules prevents them from reaching the control concentration in a short period of time, thus reducing the short-term control effect. Increasing the content of fluopyram microcapsules does not significantly improve the short-term control effect. The decrease in the content of thiazophos microcapsules directly affects the control effect at 45 days because the decrease in the content of thiazophos microcapsules affects the long-term sustained-release effect of the sustained-release formulation, thereby reducing the long-term control effect.

[0089] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes, characterized in that: The raw materials include the following mass fractions: 55-57% 30% thiazophosphorus microcapsule suspension, 19-21% 15% fluopyram microcapsule suspension, 4-6% responsive component, 5-7% surfactant, 0.5-0.6% thickener, 0.03-0.04% preservative, 0.01-0.02% defoamer, and the balance being water. The wall thickness of the thiazophosphorus microcapsules is ≥5μm, and the wall thickness of the fluopyram microcapsules is ≤0.5μm. The response component comprises the following raw materials in the following mass fractions: 85-90% wood vinegar fraction, 2-3% fatty alcohol ether phosphate, 2-3% EO-PO block polyether, 0.5-0.6% polyvinyl alcohol, 3-4% ethylene glycol, and the balance being water; The method for preparing the response component includes the following steps: mixing wood vinegar fraction with EO-PO block polyether, stirring thoroughly to form a homogeneous solution, adding it to water containing fatty alcohol ether phosphate, shearing and emulsifying to form an emulsion, and then adding polyvinyl alcohol and ethylene glycol to obtain the response component.

2. The slow-release formulation for controlling root-knot nematode disease in saline-alkali sweet potatoes according to claim 1, characterized in that: The 30% thiazophosphonate microcapsule suspension comprises the following raw materials in the following mass fractions: 4-6% diphenylmethane diisocyanate, 1.5-2.5% ethylenediamine, 30% thiazophosphonate, 1-2% lignin sulfonate, 4-6% sodium methylene bisnaphthalene sulfonate, and the balance being water.

3. The slow-release formulation for controlling root-knot nematode disease in saline-alkali sweet potatoes according to claim 2, characterized in that: The preparation method of the 30% thiazophosphonate microcapsule suspension includes the following steps: thiazophosphonate, diphenylmethane diisocyanate, lignin sulfonate and water are measured, pulverized and added sequentially to a mixing vessel, stirred, heated to 60-65℃ to fully dissolve, stirred and cooled, and ethylenediamine is added dropwise while stirring. After the addition is complete, sodium methylene bisnaphthalene sulfonate is added and the pH is adjusted to 6-7 to obtain the 30% thiazophosphonate microcapsule suspension.

4. The slow-release formulation for controlling root-knot nematode disease in saline-alkali sweet potatoes according to claim 1, characterized in that: The 15% fluopyram microcapsule suspension comprises the following raw materials by mass fraction: 4-5% gelatin, 4-5% gum arabic, 15% fluopyram, 44-46% toluene, 19-21% dimethyl sulfoxide, and the balance being water.

5. The slow-release formulation for controlling root-knot nematode disease in saline-alkali sweet potatoes according to claim 4, characterized in that: The preparation method of the 15% fluopyram microcapsule suspension includes the following steps: mixing gum arabic with water to obtain a 10-50% gum arabic pre-dissolved solution for later use; mixing gelatin with water to obtain a 20-70% gelatin pre-dissolved solution for later use; mixing fluopyram, toluene, dimethyl sulfoxide and the remaining water; homogenizing under high pressure to form a homogeneous emulsion; adding the gum arabic pre-dissolved solution dropwise; mixing evenly; adding the gelatin pre-dissolved solution dropwise under high pressure homogenization; mixing evenly; cooling; adjusting the pH to 6-7; and obtaining the 15% fluopyram microcapsule suspension.

6. A method for preparing a slow-release formulation for controlling root-knot nematode disease in saline-alkali sweet potatoes according to any one of claims 1-5, characterized in that: Includes the following steps: A slow-release formulation for the control of root-knot nematode disease in saline-alkali sweet potatoes was prepared by mixing 30% thiazophos microcapsule suspension, 15% fluopyram microcapsule suspension, and the response component, adding surfactant and stirring evenly, and then adding thickener, defoamer, water and preservative in sequence.

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