Insecticidal composition and preparation method thereof

Abstract

The invention relates to the field of pesticide materials, and provides an insecticidal composition and a preparation method thereof, and the insecticidal composition comprises pyrethrin-loaded hydrogel powder, copolymer coated neem oil microspheres, lecithin, tea saponin, fructus cnidii, sophocarpidine, gallic acid, chitosan, piperine, deionized water and a citric acid buffer agent. The pyrethrin-loaded hydrogel powder is prepared by taking sodium alginate, gelatin and silanized cellulose as matrixes, forming hydrogel through Cacrosslinking, and performing freeze drying and grinding; the copolymer coated neem oil microspheres are prepared by adopting a polylactic acid-glycolic acid copolymer as a carrier through water-in-oil emulsification, high-speed homogenization, solvent volatilization, centrifugal purification and freeze drying. The preparation method comprises the steps of dissolving, stirring, homogenizing, emulsifying, microsphere curing, drying and grinding. Through a hydrogel and microsphere sustained-release system, the stability and persistence of insecticidal active ingredients are improved, the environmental protection problem and long-acting release are solved, and the hydrogel microsphere has wide agricultural application value.

Description

Technical Field

[0001] The present invention relates to the field of pesticide materials, and in particular to an insecticide composition and a preparation method thereof. Background Art

[0002] In the fields of agricultural production and public health, pest control is essential for increasing crop yields, ecological balance and human health. Although traditional chemical pesticides can effectively control pest populations, their irrational use may lead to environmental pollution, accumulation of biological toxicity and enhanced pest resistance. Therefore, the development of efficient, environmentally friendly and long-acting release insecticide compositions has become a core demand in this field. The ideal insecticide composition should have excellent biodegradability to reduce long-term pollution to soil and water bodies, and its active ingredients should be able to be continuously released during the life cycle of the target pests through a reasonable slow-release mechanism to reduce the frequency of application, reduce pesticide loss and improve insecticide efficiency. In addition, the composition must have good stability during the actual application process to adapt to the use requirements under different environmental conditions, such as maintaining the slow-release characteristics of the active ingredients under high temperature, high humidity or strong light exposure environments, while avoiding the loss of efficacy caused by rapid degradation or evaporation. Furthermore, the insecticide composition should have high selectivity for target pests to ensure that the impact on non-target organisms is minimized to meet the needs of ecological agriculture and sustainable development. Therefore, constructing an insecticidal composition that is both environmentally friendly and has long-lasting release performance can not only effectively reduce the impact of traditional pesticides on the environment, but also improve the economy and sustainability of pest control and promote the green upgrade of agricultural plant protection technology.

[0003] At present, research on environmentally friendly long-acting insecticidal compositions has made certain progress, but there are still many technical bottlenecks. For example, the Chinese patent with publication number CN107494610A discloses an insecticidal composition based on natural plant extracts. Although it uses biological active ingredients to improve environmental friendliness, due to the lack of a reasonable sustained-release mechanism, its effective ingredients are susceptible to degradation or loss, resulting in a high frequency of application, thereby reducing the economy and feasibility of field application. In addition, another Chinese patent with publication number CN102308837A proposes an insecticidal composition that achieves sustained release through microcapsule coating technology. Although it prolongs the duration of drug efficacy to a certain extent, its carrier material may produce potential environmental pollutants during the degradation process, and fails to completely solve the environmental protection problem. At the same time, some existing technologies have the problem that the release rate is difficult to accurately control during the sustained-release process, resulting in the release of the effective ingredients too fast or too slow, affecting the insecticidal effect. Therefore, how to ensure the environmental friendliness of the carrier material while improving the insecticidal persistence and optimize the release kinetics of the effective ingredients is a key scientific problem that needs to be solved in this field. Summary of the invention

[0004] The purpose of the present invention is to provide an insecticidal composition and a preparation method thereof, so as to solve the problems of the current insecticidal composition being insufficient in environmental protection and long-term release.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: An insecticide composition comprises the following components, measured in parts by weight: 20-30 parts of pyrethrin-loaded hydrogel powder, 4.0-8.0 parts of copolymer-coated neem oil microspheres, 10-25 parts of lecithin, 5.0-8.0 parts of tea saponin, 8.0-15.0 parts of cnidium monnieri, 10.0-15.0 parts of matrine, 0.5-2.0 parts of gallic acid, 2.0-5.0 parts of chitosan, 0.5-1.5 parts of piperine, 50-80 parts of deionized water and a certain amount of citric acid buffer, wherein the amount of the citric acid buffer added is based on adjusting the pH value of the insecticide composition to 5.5-6.5.

[0006] Furthermore, the pyrethrin-loaded hydrogel powder is made of sodium alginate, gelatin, and silanized cellulose as a matrix, and is cross-linked by Ca²⁺ to form a hydrogel loaded with pyrethrin, which is then freeze-dried and ground.

[0007] Furthermore, the copolymer-coated neem oil microspheres are prepared from polylactic acid-glycolic acid copolymer as a carrier and neem oil as an active ingredient through oil-in-water emulsification, high-speed homogenization, solvent volatilization, centrifugal purification and freeze drying.

[0008] Further, the preparation method of the pyrethrin-loaded hydrogel powder is as follows: by weight, 20 to 35 parts of sodium alginate and 20 to 35 parts of gelatin are dissolved in 100 to 140 parts of deionized water, and then stirred at 50 to 60°C at a stirring rate of 200 to 300 rpm for 120 to 200 min to obtain a uniform solution, and then 2.5 to 12 parts of pyrethrin are added to the solution, and homogenized at a stirring rate of 10,000 to 12,000 rpm for 5.0 to 10 min to obtain a pyrethrin emulsion, and then the pyrethrin emulsion and silanized cellulose are mixed uniformly at a mass ratio of 1: (1.0 to 4.0), and then placed in a 5% mass fraction of CaCl 2 The solution was stirred to obtain a pyrethrin-loaded hydrogel, and then the pyrethrin-loaded hydrogel was placed in a freeze dryer for 8 to 12 hours, and finally ground to obtain a pyrethrin-loaded hydrogel powder.

[0009] Furthermore, the preparation method of the silanized cellulose is as follows: by weight, 3.0-5.0 parts of cellulose and 90-120 parts of 0.1 mol / L sodium hydroxide solution are mixed, the mixed raw materials are placed in 400-600 parts of anhydrous ethanol, 3.0-6.0 parts of vinyl triethoxy silane are added, the stirring rate is 200-500 rpm, and the stirring is performed for 60-120 min until a uniform mixed suspension is formed, then the obtained suspension is transferred to a closed reaction container, the mixed solution is heated to 90-110°C, the temperature is increased at a heating rate of 3-7°C / min, the heat preservation time is 50-70 min, and the mixture is heated at 90-110°C. The mixture was stirred at a constant temperature of 8000-10000 rpm for 5.0-10.0 min and solid powder was collected. The solid powder was then washed with anhydrous ethanol for 3 times. Finally, the solid powder was dried in a vacuum drying oven at 40-50 ℃ for 8-12 h to obtain silanized cellulose.

[0010] The present invention adopts the synergistic design of pyrethrin-loaded hydrogel powder and silanized cellulose, which is mainly used to enhance the environmental protection and long-term release performance of the composition. The special structure of the hydrogel gives pyrethrin excellent sustained-release properties to reduce the rapid loss of active ingredients, and at the same time, combined with the modification effect of silanized cellulose, the stability and environmental adaptability of the system are improved. During the preparation process, sodium alginate and gelatin, as hydrogel matrices, can form a three-dimensional network structure through Ca²⁺ cross-linking, effectively embed pyrethrin, and gradually release its active ingredients under the action of environmental factors. In addition, the use of freeze-drying technology can further increase the specific surface area of ​​the hydrogel powder, so that it can quickly absorb water and swell when used, forming a hydrogel system with controllable release ability, thereby extending the insecticidal action time and reducing the amount of pesticide used. On the other hand, the introduction of silanized cellulose not only enhances the mechanical strength of the hydrogel powder, but also improves the loading capacity and sustained-release regulation ability of pyrethrin through its surface modification characteristics. After cellulose is pretreated with sodium hydroxide, a silanized product is formed under the action of vinyltriethoxysilane, and its hydrophobicity and stability are significantly improved, so that it can further regulate the water migration rate in the hydrogel system, which helps to optimize the release curve of pyrethrin. In addition, the design also gives the composition stronger environmental tolerance, so that it can maintain a better insecticidal effect under different humidity and temperature conditions. Finally, through the synergistic effect of the pyrethrin-loaded hydrogel powder and silanized cellulose, the present invention not only effectively improves the sustained-release performance of pyrethrin, but also realizes the sustainability and environmental friendliness of the insecticide preparation, providing a high-efficiency and low-pollution solution for green agriculture and ecological plant protection.

[0011] Further, the preparation method of the copolymer-coated neem oil microspheres is as follows: by weight, 2.0-4.0 parts of a mixture of high molecular weight polyvinyl alcohol and low molecular weight polyvinyl alcohol in a mass ratio of 10:1 are dissolved in 100-150 parts of deionized water, and stirred at 50-55° C. for 60-120 minutes to obtain an aqueous phase; then 50-60 parts of polylactic acid-glycolic acid copolymer are dissolved in 10-18 parts of dichloromethane, ultrasonically treated for 5-10 minutes, and then 5.0-10.0 parts of neem oil and 1.5-2.5 parts of Tween 80 are added, and then ultrasonicated for 10-15 minutes to obtain an oil phase; the oil phase is dripped into the aqueous phase drop by drop, and after the dripping is completed, an ultra-high-speed homogenizer is used to stir for 10-15 minutes at a stirring rate of 10000-13000 rpm under ice bath conditions. min to form an oil-in-water emulsion, and the obtained oil-in-water emulsion was further stirred at room temperature for 10-20 h to allow the dichloromethane to evaporate slowly to promote the solidification of the microspheres. After the solidification was completed, the obtained microsphere suspension was washed with deionized water for 3 times, and then the microsphere suspension was collected, and then the suspension was centrifuged at 12000-15000 rpm for 10-15 min, and then the microspheres were collected and freeze-dried in a freeze dryer for 24-36 h to finally obtain copolymer-coated neem oil microspheres.

[0012] Furthermore, the molecular weight of the polylactic acid-glycolic acid copolymer is 65-95 kDa.

[0013] Furthermore, the molecular weight of the high molecular weight polyvinyl alcohol is 146-186 kDa, and the degree of hydrolysis is 87-89%; the molecular weight of the low molecular weight polyvinyl alcohol is 30-70 kDa, and the degree of hydrolysis is 87-90%.

[0014] Furthermore, the average diameter of the copolymer-coated neem oil microspheres is 5.0-12.0 μm.

[0015] The present invention adopts the design of copolymer-coated neem oil microspheres mainly for enhancing the environmental protection and long-acting release performance of the composition. Through the reasonable selection of polymer materials and the optimization of preparation process, the microspheres are given excellent sustained-release properties to reduce the rapid degradation and loss of active ingredients, and the environmental stability and biocompatibility of the preparation are improved. In the preparation process, high molecular weight polyvinyl alcohol and low molecular weight polyvinyl alcohol are proportioned according to a specific ratio to form a stable aqueous phase system, ensuring that the microspheres have suitable surface tension and uniform particle size distribution during the emulsification process. At the same time, polylactic acid-glycolic acid copolymer is used as the main material of the microspheres, and the microspheres are solidified by a solvent volatilization method. Its suitable molecular weight gives the microspheres good mechanical strength and biodegradability, and can be gradually hydrolyzed in an in vitro environment to ensure the controlled release of neem oil. Neem oil, as the core insecticidal component, is uniformly dispersed through an oil-in-water emulsification system, and the dispersion stability is improved under the auxiliary effect of Tween 80, ensuring the formation of a microsphere system with uniform particle size and stable structure. In addition, the average diameter of the microspheres is controlled within a suitable range, so that it can not only ensure good fluidity and dispersibility, but also slowly release the active ingredients during the application process, prolong the insecticidal action time, and reduce the frequency of application. The synergistic effect of ultrasonic treatment and high-speed homogenization effectively reduces the aggregation of microspheres, improves the coating efficiency, and further stabilizes the microsphere structure through freeze-drying technology to prevent particle collapse or degradation during storage. Finally, through the collaborative design of copolymer-coated neem oil microspheres, the present invention achieves the long-term release of insecticides, while reducing the loss of active ingredients, improving environmental friendliness, and providing an efficient and sustainable solution for agricultural pest control.

[0016] The present invention realizes long-term release and environmental protection optimization through the coordinated design of copolymer-coated neem oil microspheres and pyrethrin-loaded hydrogel powder. The microspheres utilize the sustained-release characteristics of PLGA to gradually release neem oil through controlled degradation, while the hydrogel relies on the swelling-diffusion mechanism to regulate the release of pyrethrins and enhance environmental adaptability. The two interact with each other in terms of structural synergy (hydrogel provides adhesion and delays the diffusion of microspheres), interface synergy (hydrophilic-hydrophobic dual release) and functional complementarity (hydrogel provides initial insecticide effect, and microspheres maintain long-term efficacy), thereby optimizing the utilization rate of pesticides, reducing environmental pollution, and improving the insecticide persistence.

[0017] The present invention also discloses a method for preparing an insecticide composition, comprising the following steps: The pyrethrin-loaded hydrogel powder and copolymer-coated neem oil microspheres were placed in a stirring tank, and deionized water was added. The stirring rate was 500-800 rpm and the stirring time was 20-30 min until a uniform dispersion was formed. Subsequently, lecithin and tea saponin were slowly added to the dispersion and the stirring was continued for 15-25 min until the solution was a milky and uniformly dispersed system. Heat the solution obtained in the previous step to 40-60 °C, increase the temperature at a rate of 2-5 °C / min, and maintain constant temperature stirring for 30-60 min. Subsequently, add Cnidium monnieri, matrine and gallic acid, and maintain constant temperature stirring for 20-40 min to allow the active ingredients to be fully dissolved and dispersed.

[0018] At 40-60 °C, chitosan was slowly added and stirred for 30-60 min until a uniform stable colloidal system was formed. Subsequently, piperine and citric acid buffer were slowly added to the system and stirred for 10-20 min. After cooling to room temperature, an insecticide composition was obtained.

[0019] The present invention adopts the synergistic design of pyrethrin-loaded hydrogel powder and copolymer-coated neem oil microspheres, which is mainly used to enhance the long-term release and environmental stability of the insecticidal composition. Through the reasonable combination of different carriers, the sustained release regulation of the active ingredients of the aqueous phase and the oil phase is realized, and the dispersibility, stability and biological activity of the system are optimized in combination with a variety of adjuvants. The pyrethrin-loaded hydrogel powder relies on the sodium alginate-gelatin cross-linking network to achieve the controlled release of water-soluble pyrethrins, while the copolymer-coated neem oil microspheres maintain the sustained release of oil-soluble neem oil through the gradual degradation of PLGA, and the two form a complementary effect under different environmental conditions. The introduction of lecithin and tea saponin enhances the emulsification stability of the system, fully mixes the aqueous phase with the oil phase, and improves the uniformity of the active ingredients. Further, the addition of cnidium monnieri, matrine and gallic acid not only enhances the insecticidal activity, but also optimizes the dissolution and dispersion behavior of the active ingredients through interfacial action. As a natural polysaccharide, chitosan forms a stable colloidal network during constant temperature stirring, improves the mechanical strength of the system, and gives it certain antibacterial properties and sustained release functions. The addition of piperine enhances the permeability of the insecticide composition and improves the bioavailability of the active ingredients, while the citric acid buffer maintains the pH stability of the system and optimizes the chemical stability of the active ingredients. Through this systematic design, the present invention optimizes the performance of the insecticide composition from multiple perspectives of structural synergy, interface stability and functional complementarity, achieves a long-lasting, stable and efficient pest control effect, and at the same time reduces the amount of pesticides used, reduces environmental pollution, and promotes the development of green pesticides.

[0020] The present invention realizes the long-term release and environmental stability of the insecticide through the coordinated design of pyrethrin-loaded hydrogel powder and copolymer-coated neem oil microspheres. The hydrogel network controls the release of water-soluble pyrethrins, and the PLGA microspheres slowly release oil-soluble neem oil, and the two complement each other to optimize the release curve. Lecithin and tea saponin enhance the emulsification stability, chitosan constructs a stable colloid, improves adhesion and slow-release effect, piperine promotes penetration, and the citric acid buffer system optimizes pH stability. The overall formula reduces pesticide loss, improves bioavailability, reduces environmental pollution, and provides an efficient and sustainable pest control solution for green agriculture.

[0021] Beneficial technical effects 1. The present invention achieves the long-term release and environmental friendliness of the insecticide through the coordinated design of pyrethrin-loaded hydrogel powder and silanized cellulose. The hydrogel matrix relies on Ca²⁺ cross-linking to form a three-dimensional network, which effectively encapsulates and slowly releases pyrethrin, reduces the loss of effective ingredients, and freeze-drying increases the specific surface area, allowing it to quickly absorb water and swell after application, prolonging the insecticidal effect. Silanized cellulose enhances the mechanical strength of the hydrogel, and regulates the water migration rate through surface hydrophobic modification to optimize the release curve. The synergistic effect of the two improves stability and environmental adaptability, maintains excellent insecticidal effects under different humidity and temperature conditions, reduces the use of pesticides and environmental pollution, and provides an efficient and sustainable solution for green agriculture.

[0022] 2. The present invention realizes the long-term release and environmental friendliness of insecticides through the collaborative design of copolymer-coated neem oil microspheres. The polylactic acid-glycolic acid copolymer gives the microspheres excellent sustained-release ability, so that neem oil is gradually released in an in vitro environment, reducing the loss of active ingredients. At the same time, the optimized ratio of polyvinyl alcohol improves the emulsification stability and ensures that the microsphere particle size is uniform. Ultrasonic treatment and high-speed homogenization technology work together to reduce aggregation, and freeze-drying technology enhances the storage stability of microspheres, ultimately achieving controlled release of insecticides, reducing the frequency of application, improving the efficiency of agricultural pest control, and reducing environmental pollution, promoting the development of green pesticide technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope morphology image of the copolymer-coated neem oil microspheres prepared in Example 1 of the present invention.

[0024] Figure 2 This is a scanning electron microscope morphology image of the pyrethrin-loaded hydrogel powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0026] Example 1 The present embodiment provides an insecticidal composition, which comprises the following components in parts by weight: 20 parts of pyrethrin-loaded hydrogel powder, 4.0 parts of copolymer-coated neem oil microspheres, 10 parts of lecithin, 5.0 parts of tea saponin, 8.0 parts of cnidium monnieri, 10.0 parts of matrine, 0.5 parts of gallic acid, 2.0 parts of chitosan, 0.5 parts of piperine, 50 parts of deionized water and some citric acid buffer, wherein the amount of citric acid buffer added is based on adjusting the pH of the insecticidal composition to 5.5; The preparation method of the pyrethrin-loaded hydrogel powder is as follows: by weight, 20 parts of sodium alginate and 20 parts of gelatin are dissolved in 100 parts of deionized water, and then stirred at 50°C at a stirring rate of 200 rpm for 120 min to obtain a uniform solution, and then 2.5 parts of pyrethrin are added to the solution, and homogenized at a stirring rate of 10000 rpm for 5.0 min to obtain a pyrethrin emulsion, and then the pyrethrin emulsion and silanized cellulose are mixed uniformly at a mass ratio of 1:1.0, and then placed in a CaCl 2 The solution was stirred to obtain a pyrethrin-loaded hydrogel, and then the pyrethrin-loaded hydrogel was placed in a freeze dryer for 8 hours, and finally ground to obtain a pyrethrin-loaded hydrogel powder.

[0027] The preparation method of silanized cellulose is as follows: 3.0 parts of cellulose and 90 parts of 0.1 mol / L sodium hydroxide solution are mixed by weight, the mixed raw materials are placed in 400 parts of anhydrous ethanol, 3.0 parts of vinyltriethoxysilane are added, and the mixture is stirred for 60 minutes at a stirring rate of 200 rpm until a uniform mixed suspension is formed, then the obtained suspension is transferred to a closed reaction container, the mixed solution is heated to 90°C, the temperature is increased at a heating rate of 3°C / min, the heat preservation time is 50 minutes, and constant temperature stirring is maintained at 90°C. After stirring, the mixture is centrifuged at a centrifugal rate of 8000 rpm for 5.0 minutes and solid powder is collected, then the solid powder is washed 3 times with anhydrous ethanol, and finally the solid powder is dried in a vacuum drying oven at 40°C for 8 hours to obtain silanized cellulose.

[0028] The preparation method of copolymer-coated neem oil microspheres is as follows: by weight, 2.0 parts of a mixture of high molecular weight polyvinyl alcohol and low molecular weight polyvinyl alcohol in a mass ratio of 10:1 are dissolved in 100 parts of deionized water, and stirred at 50°C for 60 minutes to obtain an aqueous phase; then 50 parts of polylactic acid-glycolic acid copolymer are dissolved in 10 parts of dichloromethane, ultrasonically treated for 5 minutes, and then 5.0 parts of neem oil and 1.5 parts of Tween are added. 80, and then continue ultrasonication for 10 minutes to obtain the oil phase; the oil phase is dripped into the water phase drop by drop, and after the dropwise addition is completed, an ultra-high speed homogenizer is used to stir at a stirring rate of 10000 rpm for 10 minutes under ice bath conditions to form an oil-in-water emulsion, and the obtained oil-in-water emulsion is continued to be stirred at room temperature for 10 hours to allow the dichloromethane to evaporate slowly to promote the solidification of the microspheres. After the solidification is completed, the obtained microsphere suspension is washed 3 times with deionized water, and then the microsphere suspension is collected, and then the suspension is centrifuged at 12000 rpm for 10 minutes, and then the microspheres are collected and freeze-dried in a freeze dryer for 24 hours to finally obtain copolymer-coated neem oil microspheres.

[0029] The molecular weight of the polylactic acid-glycolic acid copolymer is 65 kDa. The molecular weight of the high molecular weight polyvinyl alcohol is 146 kDa, and the degree of hydrolysis is 87%; the molecular weight of the low molecular weight polyvinyl alcohol is 30 kDa, and the degree of hydrolysis is 87%. The average diameter of the copolymer-coated neem oil microspheres is 5.0 μm.

[0030] The method for preparing the insecticidal composition of the present invention comprises the following steps: S1. The pyrethrin-loaded hydrogel powder and the copolymer-coated neem oil microspheres were placed in a stirring tank, deionized water was added, the stirring rate was 500 rpm, the stirring time was 20 min, until a uniform dispersion was formed, then lecithin and tea saponin were slowly added to the dispersion, and stirring was continued for 15 min until the solution was a milky uniform dispersion system; S2. Heat the solution obtained in S1 to 40°C at a heating rate of 2°C / min, maintain constant temperature and stirring for 30 minutes, then add Cnidium monnieri, matrine and gallic acid, maintain constant temperature and stirring for 20 minutes to allow the active ingredients to be fully dissolved and dispersed.

[0031] S3. At 40°C, chitosan was slowly added and stirring was continued for 30 minutes until a uniform stable colloidal system was formed. Subsequently, piperine and citric acid buffer were slowly added to the system and stirring was continued for 10 minutes. After cooling to room temperature, an insecticide composition was obtained.

[0032] Depend on Figure 1 It can be seen that the copolymer-coated neem oil microspheres prepared in Example 1 of the present invention present a uniform spherical structure, a smooth surface and a uniform particle size distribution, indicating that this method can effectively coat neem oil and improve its stability and sustained-release performance. Figure 2 The scanning electron microscope morphology of the pyrethrin-loaded hydrogel powder prepared in Example 1 of the present invention is shown. It can be observed that the hydrogel powder has a porous structure, which helps to increase the loading amount and sustained-release performance of the active ingredient. The combination of these two images can prove that the method of the present invention can successfully prepare a pesticide particle system with a stable structure, uniform distribution and good sustained-release effect, thereby improving its application performance.

[0033] Example 2 The present embodiment provides an insecticidal composition, which comprises the following components in parts by weight: 23 parts of pyrethrin-loaded hydrogel powder, 5.2 parts of copolymer-coated neem oil microspheres, 15 parts of lecithin, 5.9 parts of tea saponin, 10.1 parts of cnidium monnieri, 11.5 parts of matrine, 0.9 parts of gallic acid, 2.9 parts of chitosan, 0.8 parts of piperine, 59 parts of deionized water and some citric acid buffer, wherein the amount of citric acid buffer added is based on adjusting the pH of the insecticidal composition to 5.8; The preparation method of the pyrethrin-loaded hydrogel powder is as follows: by weight, 24 parts of sodium alginate and 24 parts of gelatin are dissolved in 112 parts of deionized water, and then stirred at 53°C at a stirring rate of 230 rpm for 144 min to obtain a uniform solution, and then 5.3 parts of pyrethrin are added to the solution, and homogenized at a stirring rate of 10600 rpm for 6.5 min to obtain a pyrethrin emulsion, and then the pyrethrin emulsion and silanized cellulose are mixed uniformly at a mass ratio of 1:1.9, and then placed in a CaCl 2 The solution was stirred to obtain a pyrethrin-loaded hydrogel, and then the pyrethrin-loaded hydrogel was placed in a freeze dryer for 9 hours, and finally ground to obtain a pyrethrin-loaded hydrogel powder.

[0034] The preparation method of silanized cellulose is as follows: 3.6 parts of cellulose and 99 parts of 0.1 mol / L sodium hydroxide solution are mixed by weight, the mixed raw materials are placed in 460 parts of anhydrous ethanol, 3.9 parts of vinyltriethoxysilane are added, and the mixture is stirred at a stirring rate of 290 rpm for 78 minutes until a uniform mixed suspension is formed, then the obtained suspension is transferred to a closed reaction container, the mixed solution is heated to 96°C, the temperature is increased at a heating rate of 4°C / min, the insulation time is 56 minutes, and constant temperature stirring is maintained at 96°C. After stirring, the mixture is centrifuged at a centrifugal rate of 8600 rpm for 6.5 minutes and solid powder is collected, then the solid powder is washed 3 times with anhydrous ethanol, and finally the solid powder is dried in a vacuum drying oven at 43°C for 9 hours to obtain silanized cellulose.

[0035] The preparation method of copolymer-coated neem oil microspheres is as follows: by weight, 2.6 parts of a mixture of high molecular weight polyvinyl alcohol and low molecular weight polyvinyl alcohol in a mass ratio of 10:1 are dissolved in 115 parts of deionized water, and stirred at 51°C for 78 minutes to obtain an aqueous phase; then 53 parts of polylactic acid-glycolic acid copolymer are dissolved in 12 parts of dichloromethane, ultrasonically treated for 6.5 minutes, and then 6.5 parts of neem oil and 1.8 parts of Tween are added. 80, and then continue ultrasonication for 11.5 minutes to obtain the oil phase; the oil phase is dripped into the water phase drop by drop, and after the dropwise addition is completed, an ultra-high speed homogenizer is used to stir at a stirring rate of 10900 rpm for 11.5 minutes under ice bath conditions to form an oil-in-water emulsion, and the obtained oil-in-water emulsion is continued to be stirred at room temperature for 13 hours to allow the dichloromethane to evaporate slowly to promote the solidification of the microspheres. After the solidification is completed, the obtained microsphere suspension is washed 3 times with deionized water, and then the microsphere suspension is collected, and then the suspension is centrifuged at 12900 rpm for 11.5 minutes, and then the microspheres are collected and freeze-dried in a freeze dryer for 27 hours to finally obtain copolymer-coated neem oil microspheres.

[0036] The molecular weight of the polylactic acid-glycolic acid copolymer is 74 kDa. The molecular weight of the high molecular weight polyvinyl alcohol is 158 kDa, and the degree of hydrolysis is 87.6%; the molecular weight of the low molecular weight polyvinyl alcohol is 42 kDa, and the degree of hydrolysis is 87.9%. The average diameter of the copolymer-coated neem oil microspheres is 7.1 μm.

[0037] The method for preparing the insecticidal composition of the present invention comprises the following steps: S1. The pyrethrin-loaded hydrogel powder and the copolymer-coated neem oil microspheres were placed in a stirring tank, deionized water was added, the stirring rate was 590 rpm, the stirring time was 23 min, until a uniform dispersion was formed, then lecithin and tea saponin were slowly added to the dispersion, and stirring was continued for 18 min until the solution was a milky uniform dispersion system; S2. Heat the solution obtained in S1 to 46°C at a heating rate of 2.9°C / min, maintain constant temperature and stirring for 39 minutes, then add Cnidium monnieri, matrine and gallic acid, maintain constant temperature and stirring for 26 minutes to allow the active ingredients to be fully dissolved and dispersed.

[0038] S3. At 46°C, chitosan was slowly added and stirring was continued for 39 minutes until a uniform stable colloidal system was formed. Subsequently, piperine and citric acid buffer were slowly added to the system and stirring was continued for 13 minutes. After cooling to room temperature, an insecticide composition was obtained.

[0039] Example 3 This embodiment provides an insecticidal composition, which includes the following components in parts by weight: 26 parts of pyrethrin-loaded hydrogel powder, 6.4 parts of copolymer-coated neem oil microspheres, 19 parts of lecithin, 6.8 parts of tea saponin, 12.2 parts of cnidium monnieri, 13.0 parts of matrine, 1.4 parts of gallic acid, 3.8 parts of chitosan, 1.1 parts of piperine, 68 parts of deionized water and some citric acid buffer, wherein the amount of citric acid buffer added is based on adjusting the pH of the insecticidal composition to 6.1; The preparation method of the pyrethrin-loaded hydrogel powder is as follows: by weight, 29 parts of sodium alginate and 29 parts of gelatin are dissolved in 124 parts of deionized water, and then stirred at 56°C at a stirring rate of 260 rpm for 168 min to obtain a uniform solution, and then 8.2 parts of pyrethrin are added to the solution, and the solution is homogenized at a stirring rate of 11200 rpm for 8.0 min to obtain a pyrethrin emulsion, and then the pyrethrin emulsion and silanized cellulose are mixed uniformly at a mass ratio of 1:2.8, and then placed in a 5% CaCl 2 The solution was stirred to obtain a pyrethrin-loaded hydrogel, and then the pyrethrin-loaded hydrogel was placed in a freeze dryer for 10 hours, and finally ground to obtain a pyrethrin-loaded hydrogel powder.

[0040] The preparation method of silanized cellulose is as follows: 4.2 parts of cellulose and 108 parts of 0.1 mol / L sodium hydroxide solution are mixed by weight, the mixed raw materials are placed in 520 parts of anhydrous ethanol, 4.8 parts of vinyltriethoxysilane are added, and the mixture is stirred at a stirring rate of 380 rpm for 96 minutes until a uniform mixed suspension is formed, then the obtained suspension is transferred to a closed reaction container, the mixed solution is heated to 102°C, the temperature is increased at a heating rate of 5°C / min, the heat preservation time is 62 minutes, and constant temperature stirring is maintained at 102°C. After stirring, the mixture is centrifuged at a centrifugal rate of 9200 rpm for 8.0 minutes and solid powder is collected, then the solid powder is washed 3 times with anhydrous ethanol, and finally the solid powder is dried in a vacuum drying oven at 46°C for 10 hours to obtain silanized cellulose.

[0041] The preparation method of copolymer-coated neem oil microspheres is as follows: by weight, 3.2 parts of a mixture of high molecular weight polyvinyl alcohol and low molecular weight polyvinyl alcohol in a mass ratio of 10:1 are dissolved in 130 parts of deionized water, and stirred at 52° C. for 96 minutes to obtain an aqueous phase; then 56 parts of polylactic acid-glycolic acid copolymer are dissolved in 15 parts of dichloromethane, ultrasonically treated for 8.0 minutes, and then 8.0 parts of neem oil and 2.1 parts of Tween are added. 80, and then continue ultrasonication for 13 minutes to obtain the oil phase; the oil phase is dripped into the water phase drop by drop, and after the dropwise addition is completed, an ultra-high speed homogenizer is used to stir at a stirring rate of 11800 rpm for 13 minutes under ice bath conditions to form an oil-in-water emulsion, and the obtained oil-in-water emulsion is continued to be stirred at room temperature for 16 hours to allow the dichloromethane to evaporate slowly to promote the solidification of the microspheres. After the solidification is completed, the obtained microsphere suspension is washed 3 times with deionized water, and then the microsphere suspension is collected, and then the suspension is centrifuged at 13800 rpm for 13 minutes, and then the microspheres are collected and freeze-dried in a freeze dryer for 31 hours to finally obtain copolymer-coated neem oil microspheres.

[0042] The molecular weight of the polylactic acid-glycolic acid copolymer is 83 kDa. The molecular weight of the high molecular weight polyvinyl alcohol is 170 kDa, and the degree of hydrolysis is 88.2%; the molecular weight of the low molecular weight polyvinyl alcohol is 54 kDa, and the degree of hydrolysis is 88.8%. The average diameter of the copolymer-coated neem oil microspheres is 9.2 μm.

[0043] The method for preparing the insecticidal composition of the present invention comprises the following steps: S1. The pyrethrin-loaded hydrogel powder and the copolymer-coated neem oil microspheres were placed in a stirring tank, deionized water was added, the stirring rate was 680 rpm, the stirring time was 26 min, until a uniform dispersion was formed, then lecithin and tea saponin were slowly added to the dispersion, and stirring was continued for 21 min until the solution was a milky uniform dispersion system; S2. Heat the solution obtained in S1 to 52°C at a heating rate of 3.8°C / min, maintain constant temperature and stirring for 48 minutes, then add Cnidium monnieri, matrine and gallic acid, maintain constant temperature and stirring for 32 minutes to allow the active ingredients to be fully dissolved and dispersed.

[0044] S3. At 52°C, chitosan was slowly added and stirring was continued for 48 minutes until a uniform stable colloidal system was formed. Subsequently, piperine and citric acid buffer were slowly added to the system and stirring was continued for 16 minutes. After cooling to room temperature, an insecticide composition was obtained.

[0045] Example 4 An insecticide composition, comprising the following components, measured by weight: 30 parts of pyrethrin-loaded hydrogel powder, 8.0 parts of copolymer-coated neem oil microspheres, 25 parts of lecithin, 8.0 parts of tea saponin, 15.0 parts of cnidium monnieri, 15.0 parts of matrine, 2.0 parts of gallic acid, 5.0 parts of chitosan, 1.5 parts of piperine, 80 parts of deionized water and a certain amount of citric acid buffer, wherein the amount of the citric acid buffer added is based on adjusting the pH of the insecticide composition to 6.5; The preparation method of the pyrethrin-loaded hydrogel powder is as follows: by weight, 35 parts of sodium alginate and 35 parts of gelatin are dissolved in 140 parts of deionized water, and then stirred at 60°C at a stirring rate of 300 rpm for 200 min to obtain a uniform solution, and then 12 parts of pyrethrin are added to the solution, and the solution is homogenized at a stirring rate of 12000 rpm for 10 min to obtain a pyrethrin emulsion, and then the pyrethrin emulsion and silanized cellulose are mixed uniformly at a mass ratio of 1:4.0, and then placed in a CaCl 2 The solution was stirred to obtain a pyrethrin-loaded hydrogel, and then the pyrethrin-loaded hydrogel was placed in a freeze dryer for 12 hours, and finally ground to obtain a pyrethrin-loaded hydrogel powder.

[0046] The preparation method of silanized cellulose is as follows: 5.0 parts of cellulose and 120 parts of 0.1 mol / L sodium hydroxide solution are mixed by weight, the mixed raw materials are placed in 600 parts of anhydrous ethanol, 6.0 parts of vinyltriethoxysilane are added, and the mixture is stirred for 120 minutes at a stirring rate of 500 rpm until a uniform mixed suspension is formed, then the obtained suspension is transferred to a closed reaction container, the mixed solution is heated to 110°C, the temperature is increased at a heating rate of 7°C / min, the heat preservation time is 70 minutes, and constant temperature stirring is maintained at 110°C. After stirring, the mixture is centrifuged at a centrifugal rate of 10000 rpm for 10.0 minutes and solid powder is collected, then the solid powder is washed with anhydrous ethanol for 3 times, and finally the solid powder is dried in a vacuum drying oven at 50°C for 12 hours to obtain silanized cellulose.

[0047] The preparation method of copolymer-coated neem oil microspheres is as follows: by weight, 4.0 parts of a mixture of high molecular weight polyvinyl alcohol and low molecular weight polyvinyl alcohol in a mass ratio of 10:1 are dissolved in 150 parts of deionized water, and stirred at 55° C. for 120 minutes to obtain an aqueous phase; then 60 parts of polylactic acid-glycolic acid copolymer are dissolved in 18 parts of dichloromethane, ultrasonically treated for 10 minutes, and then 10.0 parts of neem oil and 2.5 parts of Tween are added. 80, and then continue ultrasonication for 15 minutes to obtain the oil phase; the oil phase is dripped into the water phase drop by drop, and after the dropwise addition is completed, an ultra-high speed homogenizer is used to stir at a stirring rate of 13000 rpm for 15 minutes under ice bath conditions to form an oil-in-water emulsion, and the obtained oil-in-water emulsion is continued to be stirred at room temperature for 20 hours to allow the dichloromethane to evaporate slowly to promote the solidification of the microspheres. After the solidification is completed, the obtained microsphere suspension is washed with deionized water for 3 times, and then the microsphere suspension is collected, and then the suspension is centrifuged at 15000 rpm for 15 minutes, and then the microspheres are collected and freeze-dried in a freeze dryer for 36 hours to finally obtain copolymer-coated neem oil microspheres.

[0048] The molecular weight of the polylactic acid-glycolic acid copolymer is 95 kDa. The molecular weight of the high molecular weight polyvinyl alcohol is 186 kDa, and the degree of hydrolysis is 89%; the molecular weight of the low molecular weight polyvinyl alcohol is 70 kDa, and the degree of hydrolysis is 90%. The average diameter of the copolymer-coated neem oil microspheres is 12.0 μm.

[0049] A method for preparing an insecticide composition comprises the following steps: S1. The pyrethrin-loaded hydrogel powder and the copolymer-coated neem oil microspheres were placed in a stirring tank, deionized water was added, the stirring rate was 800 rpm, the stirring time was 30 min, until a uniform dispersion was formed, then lecithin and tea saponin were slowly added to the dispersion, and stirring was continued for 25 min until the solution was a milky uniform dispersion system; S2. Heat the solution obtained in S1 to 60°C, increase the temperature at a rate of 5°C / min, and maintain constant temperature stirring for 60 minutes. Subsequently, add Cnidium monnieri, matrine and gallic acid, and maintain constant temperature stirring for 40 minutes to allow the active ingredients to be fully dissolved and dispersed.

[0050] S3. At 60°C, chitosan was slowly added and stirring was continued for 60 minutes until a uniform stable colloidal system was formed. Subsequently, piperine and citric acid buffer were slowly added to the system and stirring was continued for 20 minutes. After cooling to room temperature, an insecticide composition was obtained.

[0051] Comparative Example 1 The method is basically the same as Example 1, except that the copolymer is not used to coat the neem oil microspheres, but an equal amount of neem oil is directly added.

[0052] Comparative Example 2 The method is basically the same as Example 1, except that the pyrethrin-loaded hydrogel powder is not freeze-dried but is dried using conventional hot air.

[0053] Comparative Example 3 It is basically the same as Example 1, except that chitosan is not added.

[0054] Comparative Example 4 The method is basically the same as Example 1, except that silanized cellulose is not used, but unmodified cellulose is directly used.

[0055] Comparative Example 5 The method is basically the same as Example 1, except that lecithin and tea saponin are not added.

[0056] Comparative Example 6 The method is basically the same as Example 1, except that no citric acid buffer is used.

[0057] Comparative Example 7 The method is basically the same as Example 1, except that the copolymer-coated neem oil microspheres are not subjected to ultrasonic treatment, and are not emulsified by ultra-high-speed homogenizer under ice bath conditions, but are emulsified by mechanical stirring.

[0058] Comparative Example 8 The method is substantially the same as Example 1, except that the molecular weight of the poly(lactic acid-co-glycolic acid) is reduced to 30 kDa.

[0059] Comparative Example 9 The method is basically the same as Example 1, except that the freeze-drying technique is not used to prepare the copolymer-coated neem oil microspheres, but spray drying is used.

[0060] Performance Test: Degradation residue test: The insecticide composition of the present invention and traditional chemical insecticides were applied to standard farmland soil, and soil samples were collected at fixed time intervals (0, 7, 14, 21, and 28 days). The degradation rate of the active ingredients was analyzed using high performance liquid chromatography (HPLC) to evaluate their environmental degradability.

[0061] Sustained-release performance: In a constant temperature and humidity environment (25°C, relative humidity 60%), the insecticidal composition of the present invention and the uncoated active ingredient were exposed separately, and samples were collected at fixed time points (0, 3, 7, 14, 21, and 28 days). The residual amount of the active ingredient was detected by gas chromatography-mass spectrometry (GC-MS) to evaluate the sustained-release effect.

[0062] Field persistence test: Under the same farmland conditions, the insecticidal composition of the present invention is sprayed separately, and the survival number of target pests is investigated regularly (every 3 days) after application, and the monitoring is continued until the pests recover to the level before application, so as to evaluate the persistence of the insecticidal composition.

[0063] Temperature and humidity stability test: The insecticidal composition of the present invention was stored under different environmental conditions (high temperature and high humidity: 40°C, 75% RH; room temperature: 25°C, 50% RH; low temperature and low humidity: 5°C, 30% RH), and samples were taken at fixed time intervals (0, 7, 14, and 28 days). High performance liquid chromatography (HPLC) was used to detect the degradation of the active ingredients to evaluate its environmental stability.

[0064] Pesticide penetration test: The insecticide composition of the present invention and traditional insecticides were applied to the front and back sides of plant leaves, respectively, and samples were taken at different time points (0, 6, 12, and 24 hours). Liquid chromatography-mass spectrometry (LC-MS) was used to detect the penetration concentration of the active ingredients inside the leaves to evaluate their penetration ability and bioavailability.

[0065] The properties of the insecticidal compositions of Examples 1 to 4 and Comparative Examples 1 to 9 are summarized in Table 1.

[0066] Table 1 Performance summary of the insecticide compositions of Examples 1 to 4 and Comparative Examples 1 to 9

[0067] Comparative Example 1: Neem oil microspheres were not coated with copolymers, resulting in neem oil being directly exposed to the environment, greatly increasing its degradation rate, significantly decreasing its sustained release, and shortening its field duration. However, due to the direct effect of neem oil, the permeability was improved, and the degradation rate was also accelerated. Comparative Example 2: Hot air drying was used instead of freeze drying, which reduced the specific surface area of ​​the hydrogel, affected the sustained release ability, made the hydrogel structure unstable, and accelerated degradation when the humidity changed, resulting in a decrease in overall stability. Comparative Example 3: Chitosan was not added, resulting in reduced colloid stability and affected the sustained release effect. Although the degradation rate did not change much, the field duration was shortened due to decreased adhesion. Comparative Example 4: Silylated cellulose was not used, which weakened the loading capacity of the hydrogel, making the active ingredients easier to release, the sustained release effect worsened, and the duration was slightly shorter, but it was still better than uncoated neem oil. Comparative Example 5 did not add lecithin and tea saponin, resulting in stratification of the aqueous phase and the oil phase, unstable emulsification, a significant decrease in sustained release, and a shortened duration. At the same time, due to the uneven distribution of the oil phase components, the absorption of the leaves was affected, and the permeability decreased. Comparative Example 6 did not use citric acid buffer, which caused the pH of the system to fluctuate greatly, resulting in accelerated degradation of some components and a decrease in overall stability. However, since the pH change may affect the release mechanism, the sustained release was slightly improved. Comparative Example 7 did not use ultrasonic treatment, but mechanical stirring was used for emulsification, resulting in uneven distribution of microsphere particle size, and the sustained release effect was not as good as in the embodiment. At the same time, due to the decrease in the quality of the microspheres, some components were released too quickly, resulting in accelerated degradation. Comparative Example 8 used low molecular weight PLGA (30 kDa), which accelerated the degradation rate, decreased sustained release, and shortened the duration, but because small molecules are easier to diffuse, the permeability was slightly improved. Comparative Example 9 used spray drying instead of freeze drying, which made the microsphere structure loose and the coverage rate decreased, resulting in faster release of the active ingredients. At the same time, the anti-hydrolysis ability of the microspheres decreased and the stability became worse.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that all equivalent structural changes made under the concept of the present invention and using the contents of the present invention specification and drawings should be covered within the scope of protection of the claims of the present invention.

Claims

1. An insecticidal composition, characterized in that: The insecticide composition comprises the following components in parts by weight: 20-30 parts of pyrethrin-loaded hydrogel powder, 4.0-8.0 parts of copolymer-coated neem oil microspheres, 10-25 parts of lecithin, 5.0-8.0 parts of tea saponin, 8.0-15.0 parts of cnidium monnieri, 10.0-15.0 parts of matrine, 0.5-2.0 parts of gallic acid, 2.0-5.0 parts of chitosan, 0.5-1.5 parts of piperine, 50-80 parts of deionized water and some citric acid buffer, wherein the amount of the citric acid buffer added is based on adjusting the pH value of the insecticide composition to 5.5-6.

5.

2. The insecticidal composition according to claim 1, characterized in that The pyrethrin-loaded hydrogel powder is made of sodium alginate, gelatin and silanized cellulose as a matrix, is cross-linked by Ca²⁺ to form a hydrogel loaded with pyrethrin, and is obtained by freeze-drying and grinding.

3. The insecticidal composition according to claim 1, characterized in that The copolymer-coated neem oil microspheres are prepared from polylactic acid-glycolic acid copolymer as a carrier and neem oil as an active ingredient through oil-in-water emulsification, high-speed homogenization, solvent volatilization, centrifugal purification and freeze drying.

4. The insecticidal composition according to claim 1, characterized in that The preparation method of the pyrethrin-loaded hydrogel powder is as follows: by weight, 20-35 parts of sodium alginate and 20-35 parts of gelatin are dissolved in 100-140 parts of deionized water, and then stirred at 50-60°C at a stirring rate of 200-300 rpm for 120-200 min to obtain a uniform solution, and then 2.5-12 parts of pyrethrin are added to the solution, and homogenized at a stirring rate of 10000-12000 rpm for 5.0-10 min to obtain a pyrethrin emulsion, and then the pyrethrin emulsion and silanized cellulose are mixed uniformly at a mass ratio of 1: (1.0-4.0), and then placed in a CaCl2 solution with a mass fraction of 5% and stirred to obtain a pyrethrin-loaded hydrogel, and then the pyrethrin-loaded hydrogel is placed in a freeze dryer for drying for 8-12 hours, and finally ground to obtain a pyrethrin-loaded hydrogel powder.

5. The insecticidal composition according to claim 4, characterized in that The preparation method of the silanized cellulose is as follows: by weight, 3.0-5.0 parts of cellulose and 90-120 parts of 0.1 mol / L sodium hydroxide solution are mixed, the mixed raw materials are placed in 400-600 parts of anhydrous ethanol, 3.0-6.0 parts of vinyl triethoxysilane are added, the stirring rate is 200-500 rpm, and the stirring is performed for 60-120 min until a uniform mixed suspension is formed, then the obtained suspension is transferred to a closed reaction container, the mixed solution is heated to 90-110°C, the temperature is increased at a heating rate of 3-7°C / min, the heat preservation time is 50-70 min, and the mixture is heated at 90-110°C. The mixture was stirred at a constant temperature of 8000-10000 rpm for 5.0-10.0 min and solid powder was collected. The solid powder was then washed with anhydrous ethanol for 3 times. Finally, the solid powder was dried in a vacuum drying oven at 40-50 ℃ for 8-12 h to obtain silanized cellulose.

6. The insecticidal composition according to claim 1, characterized in that The preparation method of the copolymer-coated neem oil microspheres is as follows: by weight, 2.0-4.0 parts of a mixture of high molecular weight polyvinyl alcohol and low molecular weight polyvinyl alcohol in a mass ratio of 10:1 are dissolved in 100-150 parts of deionized water, and stirred at 50-55° C. for 60-120 minutes to obtain an aqueous phase; then 50-60 parts of polylactic acid-glycolic acid copolymer are dissolved in 10-18 parts of dichloromethane, ultrasonically treated for 5-10 minutes, and then 5.0-10.0 parts of neem oil and 1.5-2.5 parts of Tween 80 are added, and then ultrasonicated for 10-15 minutes to obtain an oil phase; the oil phase is dripped into the aqueous phase drop by drop, and after the dripping is completed, an ultra-high-speed homogenizer is used to stir the aqueous phase at a stirring rate of 10000-13000 rpm under ice bath conditions for 10-15 minutes. min to form an oil-in-water emulsion, and the obtained oil-in-water emulsion was further stirred at room temperature for 10-20 h to allow the dichloromethane to evaporate slowly to promote the solidification of the microspheres. After the solidification was completed, the obtained microsphere suspension was washed with deionized water for 3 times, and then the microsphere suspension was collected, and then the suspension was centrifuged at 12000-15000 rpm for 10-15 min, and then the microspheres were collected and freeze-dried in a freeze dryer for 24-36 h to finally obtain copolymer-coated neem oil microspheres.

7. The insecticidal composition according to claim 6, characterized in that The molecular weight of the polylactic acid-glycolic acid copolymer is 65-95 kDa.

8. The insecticidal composition according to claim 6, characterized in that The molecular weight of the high molecular weight polyvinyl alcohol is 146-186 kDa, and the degree of hydrolysis is 87-89%; the molecular weight of the low molecular weight polyvinyl alcohol is 30-70 kDa, and the degree of hydrolysis is 87-90%.

9. The insecticidal composition according to any one of claims 1 to 8, characterized in that The average diameter of the copolymer-coated neem oil microspheres is 5.0-12.0 μm.

10. A method for preparing the insecticidal composition according to any one of claims 1 to 9, characterized in that: The following steps are involved: The pyrethrin-loaded hydrogel powder and copolymer-coated neem oil microspheres were placed in a stirring tank, and deionized water was added. The stirring rate was 500-800 rpm and the stirring time was 20-30 min until a uniform dispersion was formed. Subsequently, lecithin and tea saponin were slowly added to the dispersion and the stirring was continued for 15-25 min until the solution was a milky and uniformly dispersed system. Heat the solution obtained in the previous step to 40-60 °C, increase the temperature at a rate of 2-5 °C / min, and maintain constant temperature stirring for 30-60 min. Subsequently, add Cnidium monnieri, matrine and gallic acid, and maintain constant temperature stirring for 20-40 min to allow the active ingredients to be fully dissolved and dispersed. At 40-60 °C, chitosan was slowly added and stirred for 30-60 min until a uniform stable colloidal system was formed. Subsequently, piperine and citric acid buffer were slowly added to the system and stirred for 10-20 min. After cooling to room temperature, an insecticide composition was obtained.

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