A pentafluoro sulfonyl amine chloro pyrimidine dry suspending agent for preventing and removing licorice field weeds and a preparation method thereof

Abstract

This invention discloses a penoxsulam·clopyralid dry suspension concentrate for controlling weeds in licorice fields and its preparation method, belonging to the field of herbicide technology. The dry suspension concentrate has a core-shell structure. The core contains penoxsulam and clopyralid, with clopyralid having a particle size D90 of 1–3 μm and penoxsulam having a particle size D90 of 15–20 μm. The outer shell contains methyl hesperidin, polyether-modified trisiloxane, and PVP-K30. The core is granulated using a stepwise granulation process, and the outer shell is coated onto the core surface via fluidized bed bottom spraying. The outer shell rapidly dissolves in water, releasing methyl hesperidin, which inhibits the activity of weed P450 and GST detoxification enzymes, while simultaneously opening the cuticle absorption channels. Subsequently, the core disintegrates and releases the herbicide, achieving a time-controlled release of enzyme inhibition followed by weed control. This product exhibits excellent control efficacy against sedges and broadleaf weeds, combining rapid and sustained effects. It is safe for sweet potatoes, environmentally friendly, and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of herbicide technology, and in particular to a penoxsulam·chlorpyrifos dry suspension for controlling weeds in licorice fields and its preparation method. Background Technology

[0002] Sweet potato (Ipomoea batatas L.) is an important food, feed, industrial raw material, and new energy crop in my country, with an annual planting area of ​​approximately 60 million mu (about 4 million hectares) and production ranking first in the world. Sweet potato fields are plagued by a wide variety of weeds; 74 species from 20 families are common in Chinese sweet potato fields. Among them, purslane, amaranth retroflexus, and nutgrass are prevalent and cause significant damage. Weeds compete with sweet potatoes for light, water, fertilizer, and space, generally leading to a 5%–15% reduction in yield, and in severe cases, exceeding 50%, seriously hindering the improvement of sweet potato yield and quality.

[0003] Chemical weeding is currently the main method for weed control in sweet potato fields. However, compared with major grain crops such as rice and wheat, the number and variety of herbicides registered for sweet potato fields are severely insufficient. As of March 2023, only nine herbicide products were validly registered for sweet potato fields in my country, involving four active ingredients: bentazon, isolazid, quizalofop-P-ethyl, and pyrimethanil. As of 2021, only six herbicide products were registered. The existing registered products are mostly in emulsifiable concentrate and aqueous solution formulations, with a large amount of organic solvents used, and their efficacy against perennial sedges such as nutgrass is not ideal. Furthermore, while penoxsulam, as a broad-spectrum ALS inhibitor, is highly effective against weeds in rice fields, sweet potatoes are quite sensitive to it, and conventional formulations often result in phytotoxicity symptoms such as leaf yellowing and stunted growth.

[0004] In summary, the problems of insufficient variety of herbicides for sweet potato fields, outdated formulations, inadequate control of noxious weeds, and easy phytotoxicity are very prominent. There is an urgent need to develop a new type of herbicide formulation for sweet potato fields that is highly efficient, safe, and environmentally friendly. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a penoxsulam·chlorpyrifos dry suspension for controlling weeds in licorice fields and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention first proposes a penoxsulam·chlorpyrifos dry suspension for controlling weeds in sweet potato fields. The dry suspension has a core-shell structure, including a core and a shell functional layer covering the surface of the core. Employing a core-shell hierarchical structure with a core carrying the drug and an outer shell functional layer, precise stratification is achieved through a fluidized bed bottom spray coating process. Its release behavior follows a dissolution cascade time-sequential controlled-release mechanism, enabling the orderly release of functional and herbicidal components in both space and time.

[0007] The core contains penoxsulam and chlorpyrifos in a mass ratio of 1:2 to 2:1 as herbicidal active ingredients, as well as wetting agents, dispersants, disintegrants, binders and fillers; Among them, the particle size D90 of chlorpyrifos is 1-3 μm, and the particle size D90 of penoxsulam is 15-20 μm; The mass ratio of the herbicidal active ingredient, wetting agent, dispersant, disintegrant, binder and filler is 30:2~4:7~9:3~5:1~3:50~55; The outer shell functional layer includes a penetration enhancer, a surfactant, and a film-forming agent; The mass of the outer shell functional layer is 2% to 3% of the total mass of the dry suspension agent.

[0008] Preferably, the wetting agent is at least one of succinate and succinate sulfonate; the dispersant is at least one of tristyrylphenol phosphate, tristyrylphenol sulfonate, tristyrylphenol carboxylate, and sodium lignin; the disintegrant is sodium carboxymethyl starch; the binder is polyvinylpyrrolidone K30 (PVP-K30); and the filler is at least one of silica, kaolin, and light calcium carbonate.

[0009] PVP-K30 is a water-soluble polymer with extremely strong hydration and swelling capacity. It can completely dissolve and disintegrate within 1 minute after application into water, simultaneously releasing penetration enhancers and detoxification enzyme inhibitors. It acts on the surface of weed leaves and physiological systems before the herbicide is released, completing the preparatory work of opening absorption channels and suppressing detoxification capacity, thus solving the problem of weeds responding too quickly to the detoxification defense of traditional formulations.

[0010] The core is a dry suspension masterbatch of penoxsulam and chlorpyrifos, containing wetting agents, dispersants, and sodium carboxymethyl starch disintegrant. After the outer shell dissolves, it gradually absorbs water and disintegrates, releasing the active herbicide ingredient. This allows the herbicide to enter the plant during the window period when the cuticle channels of the weeds are open and the activity of detoxification enzymes is inhibited, greatly improving the bioavailability of the active ingredient. At the same time, the slow disintegration of the core can prolong the action time of the herbicide in the meristematic tissue of the weeds, taking into account both rapid action and long-lasting effect.

[0011] Preferably, in the outer shell functional layer, the penetration enhancer is methyl hesperidin, the surfactant is polyether-modified trisiloxane, and the film-forming agent is polyvinylpyrrolidone K30 (PVP-K30). More than 60% of weed resistance to ALS inhibitor herbicides originates from non-target resistance (NTSR), which is achieved through the overexpression of detoxification enzymes such as cytochrome P450 monooxygenase (CYP450) and glutathione S-transferase (GST), rapidly metabolizing herbicides into non-toxic products. Methylhesperidin, as a flavonoid derivative, suppresses detoxification capacity from both enzyme activity and expression levels. Inhibition of P450-mediated hydroxylation detoxification: The P450 enzyme system is the core pathway for the metabolism of sulfonylurea herbicides in weeds, inactivating herbicides through hydroxylation and demethylation reactions. Methyl hesperidin can competitively bind to the heme active site of P450 enzymes, blocking their catalytic oxidation function, reducing the hydroxylation metabolic rate of penoxsulam and chlorpyrifos, and prolonging the half-life of the active ingredients in weeds. This is similar to the stress-resistance synergistic mechanism of synergist ethers (PBO), but with greater plant-derived safety.

[0012] Downregulating the binding and detoxification activity of GST enzymes: GST enzymes catalyze the binding of herbicides to glutathione, forming a water-soluble complex that is released from vacuoles, representing the second largest detoxification pathway in weeds. Studies have shown that GST activity is significantly higher in resistant weed populations than in susceptible populations, which is a key reason for their herbicide tolerance. Methylhesperidin can regulate oxidative stress pathways, downregulate GST gene expression levels, reduce glutathione binding reactions, and prevent the rapid detoxification and isolation of herbicides.

[0013] Synergistic effect of timing: The outer shell functional layer is released in advance, and methyl hesperidin can inhibit the activity of detoxification enzymes before the herbicide enters the weed, so that the weed is in a state of detoxification incompetence; after the subsequent herbicide is released, it cannot be effectively metabolized and directly reaches the target of the meristematic tissue, greatly increasing toxicity, while slowing down the evolution of herbicide-resistant weed populations.

[0014] The mass ratio of methyl hesperidin, polyether-modified trisiloxane, and polyvinylpyrrolidone K30 is 10–20:5–15:5–10.

[0015] The present invention also proposes a method for preparing the aforementioned penoxsulam·chlorpyrifos dry suspension, comprising the following steps: (1) Preparation of graded core particles: The technical grade penoxsulam is mixed with wetting agent, dispersant, disintegrant, binder and filler and coarsely pulverized to control the particle size D90 of penoxsulam to be 15-20 μm. The mixture is then granulated by top spraying in a fluidized bed and dried to obtain penoxsulam sustained-release skeleton particles. The technical grade of chlorpyrifos was ultra-finely pulverized to a particle size D90 of 1-3 μm and prepared into a suspension. It was then loaded onto the surface of penoxsulam sustained-release skeleton particles by top spraying through a fluidized bed and dried to obtain graded core particles. (2) Preparation of the outer shell functional layer spray liquid: Add the penetration promoter, surfactant and film-forming agent to the organic solvent and stir until completely dissolved to obtain the functional layer spray liquid; (3) Spray coating of outer shell functional layer: The core particles are placed in a fluidized bed and sprayed onto the surface of the core particles by bottom spraying. After drying, penoxsulam·chlorpyrifos dry suspension is obtained.

[0016] Preferably, in step (1), the fluidized bed top spray granulation process conditions for preparing penoxsulam sustained-release skeleton particles are: inlet air temperature 50-65℃, material temperature 40-50℃, fluidization velocity 1.5-3.0m / s, and atomization pressure 0.10-0.20MPa; the solid content of the chlorpyrifos suspension is 15%-20%; the top spray process conditions for preparing graded core particles are: inlet air temperature 50-55℃, material temperature 40-45℃, fluidization velocity 1.5-2.0m / s, and atomization pressure 0.15-0.25MPa.

[0017] Preferably, in step (2), the functional layer spray liquid contains 5% to 25% methyl hesperidin, 3% to 20% polyether-modified trisiloxane, and 2% to 15% polyvinylpyrrolidone K30; the organic solvent is anhydrous ethanol.

[0018] Preferably, in step (3), the conditions for fluidized bed bottom spray coating are: inlet air temperature 40-50℃, material temperature 35-40℃, fluidization air velocity 0.6-1.2m / s, and atomization pressure 0.2-0.5MPa; When coating a fluidized bed with bottom spray, the ratio of the distance from the nozzle to the bottom screen to the diameter of the bottom screen is 2 to 4:1.

[0019] Both penoxsulam and chlorpyrifos are acetolactate synthase (ALS / AHAS) inhibitors, but they belong to different chemical classes and complement each other in terms of target binding, absorption and translocation, and herbicidal spectrum. 1. Common target: Blocking branched-chain amino acid synthesis and inhibiting meristematic tissue growth. ALS is a key rate-limiting enzyme in the biosynthesis of branched-chain amino acids (valine, leucine, and isoleucine) in plants. This enzyme is absent in mammals, thus herbicides exhibit selective toxicity. Both herbicides block amino acid synthesis by binding to the catalytic subunit of the ALS enzyme, leading to cell division arrest, meristematic tissue necrosis, and ultimately, weed growth stagnation and death.

[0020] 2. Differences in binding sites reduce the risk of resistance. Penflusulfonamide belongs to the triazolopyrimidine sulfonamide class and binds to the B domain of ALS enzymes. Clopyrimethanil belongs to the sulfonylurea class and binds to the A domain of ALS enzymes.

[0021] When the two are combined in a mass ratio of 1:2 to 2:1, they can simultaneously bind to different subunits of the ALS enzyme to form multi-site synergistic inhibition, significantly improving the enzyme inhibition intensity; at the same time, they reduce the risk of target resistance in weeds caused by single-site mutations (such as Pro197 and Trp574 mutations), and still maintain high control efficacy against resistant weed populations.

[0022] 3. Complementary absorption and conduction, covering the entire spectrum of weeds in sweet potato fields. Penflusulfonamide: It can be absorbed through multiple pathways such as stems, leaves, young buds and roots. It is translocated to the apical meristem through the xylem and phloem. It has excellent control effect on annual broadleaf weeds and young sedges, and the effective period can reach 30 to 60 days.

[0023] Clopyrimisulfuron: It has strong systemic conductivity and is particularly good at being absorbed through the roots and transported to underground tubers. It is especially effective against perennial sedges with underground reproductive organs, such as Cyperus rotundus. It can block the accumulation of nutrients in tubers and germination, thus achieving the effect of root removal.

[0024] Penflusulfonamide belongs to the triazolidine sulfonamide class of ALS inhibitors. Sweet potatoes have a slow metabolic and detoxification rate, and high-concentration exposure during the seedling stage can easily cause phytotoxicity symptoms such as leaf yellowing, twisted central leaves, and stunted growth. The drug dissolution rate is inversely proportional to the particle size; as the particle size increases, the specific surface area decreases, and the dissolution rate decreases significantly.

[0025] Increasing the particle size of penoxsulam from the conventional D90 of 3–5 μm to 15–20 μm extends its saturation dissolution time by 3–5 times, avoiding high concentration peaks in the soil solution or pesticide solution shortly after application. This ensures that the pesticide concentration in contact with sweet potato roots / stems and leaves remains below the phytotoxicity threshold. Larger particles have weaker leaching and lateral diffusion capabilities in the soil, remaining more in the topsoil where weed seeds germinate, reducing migration to deeper tuberous roots and decreasing root absorption. The slowly released, low-concentration pesticide, once inside the sweet potato plant, is gradually metabolized and detoxified by its own P450 enzyme system, preventing cumulative pesticide damage. Weeds are more sensitive to penoxsulam; continuous low-concentration exposure can inhibit meristematic growth, achieving long-lasting weed control at low concentrations.

[0026] Clopyralid is a sulfonylurea ALS inhibitor. Sweet potatoes naturally exhibit high tolerance to clopyralid because they rapidly metabolize it into an inactive product, and even high-concentration, rapid release poses no significant phytotoxicity risk. Refining clopyralid to a particle size of 1–3 μm (D90) increases its specific surface area by 5–8 times, allowing it to dissolve completely in water within minutes and quickly reach lethal concentrations for weeds. Simultaneously, the smaller particle size facilitates penetration through leaf stomata and cuticle gaps, increasing foliar absorption efficiency by over 40%. This small-particle-size clopyralid acts rapidly, suppressing broadleaf weeds such as purslane and amaranth, as well as young sedges, within 3–5 days, compensating for the insufficient rapid-acting effect of penoxsulam's slow-release formulation.

[0027] When combined, the two herbs precisely cover the core weeds in sweet potato fields: broadleaf weeds such as purslane and amaranth, as well as sedges such as nutgrass, with complementary weed control spectrum to reduce missed weeds.

[0028] This invention also proposes the application of the aforementioned dry suspension agent in the control of weeds in sweet potato fields.

[0029] Preferably, the weeds are sedges and / or broadleaf weeds, including purslane, amaranth, and nutgrass.

[0030] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention overcomes the inherent contradiction between the phytotoxicity risk of penflusulfuron and the efficacy of chlorpyrifos by using differentiated particle size design and a core-shell time-release structure, unlike the simple compounding mode of two components with uniform particle size in existing technologies. Based on the Noyes-Whitney dissolution law, penflusulfuron is controlled in a large-particle-size slow-release state, reducing the specific surface area to lower the dissolution rate and prevent the pesticide concentration from rapidly reaching the sweet potato phytotoxicity threshold after application. At the same time, it reduces soil leaching and migration, and reduces the amount of sweet potato root absorption and exposure. Chlorpyrifos uses ultra-fine particles to achieve rapid dissolution, improving absorption efficiency and translocation to underground bulbs. Combined with the core-shell layered release sequence, it maximizes herbicidal activity while ensuring the safety of sweet potatoes, achieving a balance between harm reduction and efficacy enhancement.

[0031] 2. This invention utilizes a dual-pathway synergistic mechanism of the outer shell functional layer to simultaneously overcome the physical barriers and metabolic defense systems of weeds, significantly outperforming existing technologies that only add a single wetting and penetrating adjuvant. The polyether-modified trisiloxane achieves ultra-spreading wetting through ultra-low surface tension, bypassing the hydrophobic barrier of the cuticle via stomatal wetting pathways and disrupting the lipid structure of the cuticle to enhance translayer penetration efficiency. Methyl hesperidin inhibits weed detoxification enzymes such as P450 and GST at both enzyme activity and expression levels, blocking the herbicide hydroxylation and glutathione binding detoxification pathways. The time-sequenced design of preferential release from the functional layer allows for pretreatment before the herbicide arrives, significantly improving the bioavailability of the active ingredient while slowing down the evolution of weed metabolic resistance.

[0032] 3. This invention achieves precise coverage and enhanced efficacy against weeds in sweet potato fields through synergistic targeting of dual active ingredients and structural adaptation design, overcoming the shortcomings of existing single-agent or ordinary compound formulations that have narrow weed control spectrum and are prone to inducing target resistance. Although penoxsulam and chlorpyrifos are both ALS inhibitors, they bind to different structural domains of the enzyme, and their dual-site synergistic effect can enhance the blocking effect of branched-chain amino acid synthesis, significantly reducing the probability of weeds developing target resistance due to single point mutations. The two have complementary conduction characteristics: chlorpyrifos focuses on root systemic absorption and killing underground bulbs, while penoxsulam has both foliar and soil activity to achieve long-term weed control. Combined with the stratified release structure, they precisely target the core weeds in sweet potato fields, improving efficacy while reducing the amount of pesticide used per unit area. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0034] Example 1 (Pentoxanil: Clopyralid = 1:1): Table 1. Dry suspension formulation

[0035] Preparation of hierarchical core particles: (1a) The penoxsulam technical material, wetting agent, dispersant, disintegrant, binder, and filler were premixed in a conical mixer for 20 minutes, followed by coarse grinding with airflow to control the penoxsulam particle size D90 = 18 ± 0.5 μm. The mixed powder was fed into a GPCG-1 fluidized bed granulator (top spray system), with the inlet air temperature set at 60℃, material temperature at 45℃, fluidization velocity at 2.0 m / s, and atomization pressure at 0.15 MPa. Pure water was used as the binder (at a rate of 22% of the powder mass) and sprayed at a rate of 6 g / min for spray granulation. After drying, the powder was sieved (pore size 200–400 μm) to obtain penoxsulam sustained-release skeleton particles.

[0036] (1b) The technical grade chlorpyrifos was pulverized with an ultrafine airflow to a particle size of D90 = 2 ± 0.5 μm, and then mixed with deionized water to prepare a suspension with a solid content of 18%. The penoxsulam sustained-release skeleton particles obtained in step (1a) were placed in a fluidized bed (top spray system), with the inlet air temperature set at 52°C, the material temperature at 42°C, the fluidization velocity at 1.8 m / s, and the atomization pressure at 0.20 MPa. The chlorpyrifos suspension was sprayed in at a uniform speed, and after drying, graded core particles were obtained.

[0037] Preparation of the spray liquid for the outer shell functional layer: Methyl hesperidin, polyether-modified trisiloxane, and PVP-K30 were added sequentially to anhydrous ethanol and stirred until completely dissolved. Then, pure water was slowly added and stirring was continued for 10 minutes to obtain the functional layer spray.

[0038] Spray coating of the outer shell functional layer: 1000g of graded core particles were added to a fluidized bed, and the bottom spray (Wurster) assembly was replaced. The bottom spray mode was activated, with the inlet air temperature set to 46℃, material temperature to 38℃, fluidization velocity to 0.9m / s, and the ratio of nozzle-to-bottom screen distance to bottom screen diameter to 3:1. Pre-fluidization was performed for 5 minutes. The atomization pressure was set to 0.3MPa, and the spray rate to 8g / min. 100g of functional layer spray solution was uniformly sprayed into the fluidized bed. After spraying, fluidization and drying continued for 10 minutes. The solution was then cooled to room temperature and discharged, sieved (pore size 300–450μm) to obtain a core-shell structured dry suspension with an outer shell functional layer mass of 2.5% of the total dry suspension mass.

[0039] Example 2 (Pentoxanil: Clopyralid = 2:1): Table 2. Core Particle Formulation

[0040] Preparation method: Same as in Example 1, except that the particle size of penoxsulam is controlled to D90=20±0.5μm, and the particle size of chlorpyrifos is controlled to D90=1.5±0.5μm. In the shell functional layer spray formulation, the ratio of methyl hesperidin:polyether-modified trisiloxane:PVP-K30 is 20:10:8 (mass ratio), and the mass of the shell functional layer is 2.8% of the total mass of the dry suspension.

[0041] Example 3 (Pentoxanil: Clopyralid = 1:2): Table 3. Core Particle Formulation

[0042] 2. Preparation method: Same as in Example 1, except that the particle size of penoxsulam is controlled to D90=15±0.5μm, and the particle size of chlorpyrifos is controlled to D90=3±0.5μm. In the shell functional layer spray formulation, the ratio of methyl hesperidin:polyether-modified trisiloxane:PVP-K30 is 10:8:5 (mass ratio), and the mass of the shell functional layer is 2.0% of the total mass of the dry suspension.

[0043] The following comparison model was also set: Comparative Example 1 (Conventional dry suspension, non-core-shell structure): Following the same core formulation as in Example 1, all active ingredients and adjuvants (pentoxuron and chlorpyrifos were pulverized together to D90=5±0.5μm) were mixed and then directly subjected to air jet milling and fluidized bed granulation without outer shell functional layer coating to obtain a common dry suspension.

[0044] Comparative Example 2 (the outer shell functional layer does not contain methylhesperidin): The preparation method is the same as in Example 1, except that methyl hesperidin is not added to the outer shell functional layer spray liquid (only polyether modified trisiloxane and PVP-K30 are added), and the rest remains the same.

[0045] Comparative Example 3 (Pentoxane particle size is conventional fine particle size): The same formulation and preparation method as in Example 1 were used, except that penoxsulam was pulverized to D90=3±0.5μm (conventional fine particle size) in step (1a), while the rest remained unchanged.

[0046] Comparative Example 4 (clopyrazolone acetonide has a conventional large particle size): The same formulation and preparation method as in Example 1 were used, except that in step (1b), clopyralid was pulverized to D90=15±0.5μm (without ultrafine pulverization), and the rest remained the same.

[0047] Table 4. Product Quality Indicators

[0048] Performance testing: 1. Experimental Design Field efficacy trials were conducted in sweet potato fields in Shucheng County, Anhui Province. The tested weeds were purslane (broadleaf weed), amaranth (broadleaf weed), and cyperus (sedge weed) at the 3-5 leaf stage. The trials used a core-shell structured penoxsulam·chlorpyrifos dry suspension concentrate (50 g / mu) prepared in Examples 1-3, with formulations prepared in Comparative Examples 1-4 as controls and water as a blank control. Conventional foliar spraying was employed, with four replicates per treatment, arranged in a randomized block design.

[0049] 2. Standards for evaluating phytotoxicity Seven days after application, observe the symptoms of herbicide damage in sweet potatoes and evaluate them according to the following standards: Grade 0 (no herbicide damage); Grade 1 (slight yellowing, <10%); Grade 2 (moderate yellowing, 10%–30%); Grade 3 (severe yellowing / twisted heart leaves, 30%–50%); Grade 4 (plants are significantly inhibited, >50%).

[0050] Table 5. Herbicidal performance test results of various herbicides

[0051] Data Analysis: The core-shell structure penoxsulam·chlorpyrifos dry suspension concentrates of Examples 1-3 showed excellent control efficacy against purslane (broadleaf weed) and nutgrass (sedge weed) in sweet potato fields. The control efficacy per plant was 97.2%-97.8% and 95.4%-97.5% 30 days after application, respectively, with no significant difference among the three (P>0.05), indicating that broad-spectrum and efficient weed control can be achieved within the range of 1:2 to 2:1 of active ingredients.

[0052] Comparative Example 1 (without the outer shell functional layer) showed control efficacy of only 82.1% (purslane) and 80.6% (cyperus rhizome) 30 days after application, which was 15.1 and 16.2 percentage points lower than Example 1, respectively. This confirms that the preparatory work of the outer shell functional layer in opening absorption channels and suppressing detoxification enzyme activity is crucial for improving efficacy. Comparative Example 2 (without methyl hesperidin in the outer shell) showed a control efficacy of 88.3%, which was 8.9 percentage points lower than Example 1, indicating that methyl hesperidin significantly enhanced the herbicidal effect by inhibiting the CYP450 / GST detoxification enzyme system of weeds.

[0053] Comparative Example 3 (fine particle size of penoxsulam, D90=3μm) showed better rapid efficacy than the Example 1 (7 days after application, control efficacy was 85.3%–88.6% and 78.3%–82.5%, respectively). However, the sweet potato phytotoxicity reached level 3 (severe yellowing / twisted heart leaves), while the Example 1 was level 0. This demonstrates that increasing the particle size of penoxsulam to 15–20μm can effectively avoid peak phytotoxicity. Comparative Example 4 (large particle size of chlorpyrifos, D90=15μm) showed a significant decrease in rapid efficacy 7 days after application (58.7%), which was 19.6 percentage points lower than Example 1. This indicates that refining the particle size of chlorpyrifos to 1–3μm is crucial for rapid weed control.

[0054] All examples showed grade 0 herbicide damage to sweet potatoes, with normal crop growth. Combining the data from the examples and Comparative Example 4, even large-sized chlorpyrifos particles did not cause herbicide damage, confirming the natural high tolerance of sweet potatoes to it. In conclusion, the differentiated particle size design with a core-shell structure achieves a balance between safe and efficient herbicide control in sweet potatoes.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A dry suspension concentrate of penoxsulam·chlorpyrifos for controlling weeds in sweet potato fields, characterized in that, The dry suspension has a core-shell structure, including a core and a shell functional layer covering the surface of the core; The core contains penoxsulam and chlorpyrifos in a mass ratio of 1:2 to 2:1 as herbicidal active ingredients, as well as wetting agents, dispersants, disintegrants, binders and fillers; Among them, the particle size D90 of chlorpyrifos is 1-3 μm, and the particle size D90 of penoxsulam is 15-20 μm; The mass ratio of the herbicidal active ingredient, wetting agent, dispersant, disintegrant, binder and filler is 30:2~4:7~9:3~5:1~3:50~55; The outer shell functional layer includes a penetration enhancer, a surfactant, and a film-forming agent; The mass of the outer shell functional layer is 2% to 3% of the total mass of the dry suspension agent.

2. The dry suspension agent according to claim 1, characterized in that, The wetting agent is at least one of succinate and succinate sulfonate; the dispersant is at least one of tristyrylphenol phosphate, tristyrylphenol sulfonate, tristyrylphenol carboxylate, and sodium lignin; the disintegrant is sodium carboxymethyl starch; the binder is polyvinylpyrrolidone K30; and the filler is at least one of silica, kaolin, and light calcium carbonate.

3. The dry suspension agent according to claim 1, characterized in that, In the outer shell functional layer, the penetration promoter is methyl hesperidin, the surfactant is polyether-modified trisiloxane, and the film-forming agent is polyvinylpyrrolidone K30. The mass ratio of methyl hesperidin, polyether-modified trisiloxane, and polyvinylpyrrolidone K30 is 10–20:5–15:5–10.

4. A method for preparing a penoxsulam·chlorpyrifos dry suspension as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Preparation of graded core particles: The technical grade penoxsulam is mixed with wetting agent, dispersant, disintegrant, binder and filler and coarsely pulverized to control the particle size D90 of penoxsulam to be 15-20 μm. The mixture is then granulated by top spraying in a fluidized bed and dried to obtain penoxsulam sustained-release skeleton particles. The technical grade of chlorpyrifos was ultra-finely pulverized to a particle size D90 of 1-3 μm and prepared into a suspension. It was then loaded onto the surface of penoxsulam sustained-release skeleton particles by top spraying through a fluidized bed and dried to obtain graded core particles. (2) Preparation of the outer shell functional layer spray liquid: Add the penetration promoter, surfactant and film-forming agent to the organic solvent and stir until completely dissolved to obtain the functional layer spray liquid; (3) Spray coating of outer shell functional layer: The graded core particles are placed in a fluidized bed and the outer shell functional layer spray liquid is atomized and sprayed onto the surface of the core particles by bottom spraying. After drying, penoxsulam·chlorpyrifos dry suspension is obtained.

5. The preparation method according to claim 4, characterized in that, In step (1), the fluidized bed top spray granulation process for preparing penoxsulam sustained-release skeleton particles is as follows: inlet air temperature 50-65℃, material temperature 40-50℃, fluidization velocity 1.5-3.0m / s, and atomization pressure 0.10-0.20MPa; the solid content of the chlorpyrifos suspension is 15%-20%; the top spray process for preparing graded core particles is as follows: inlet air temperature 50-55℃, material temperature 40-45℃, fluidization velocity 1.5-2.0m / s, and atomization pressure 0.15-0.25MPa.

6. The preparation method according to claim 4, characterized in that, In step (2), the mass percentage of methyl hesperidin in the functional layer spray is 5% to 25%, the mass percentage of polyether-modified trisiloxane is 3% to 20%, and the mass percentage of polyvinylpyrrolidone K30 is 2% to 15%; the organic solvent is anhydrous ethanol.

7. The preparation method according to claim 4, characterized in that, In step (3), the conditions for fluidized bed bottom spray coating are: inlet air temperature 40-50℃, material temperature 35-40℃, fluidization air velocity 0.6-1.2m / s, and atomization pressure 0.2-0.5MPa; When coating a fluidized bed with bottom spray, the ratio of the distance from the nozzle to the bottom screen to the diameter of the bottom screen is 2 to 4:

1.

8. The application of the dry suspension agent according to any one of claims 1 to 3 in the control of weeds in sweet potato fields.

9. The application according to claim 8, characterized in that, The weeds are sedges and / or broadleaf weeds, including purslane, amaranth, and nutgrass.

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