Preparation method of cowpea fruit fly repellent and application thereof

Abstract

The application provides a preparation method of a cowpea leafhopper repellent and application thereof, and belongs to the technical field of green prevention and control of agricultural pests. The preparation method is as follows: activated biochar obtained by microwave pyrolysis of straw powder and activated by phosphoric acid is mixed with intercalated montmorillonite-PVA compound obtained by intercalating aluminum ions into montmorillonite and modifying the intercalated montmorillonite with polyvinyl alcohol, and then the mixture is modified with KH-550 to obtain a supported controlled-release carrier; linalool, geraniol and methyl salicylate are loaded on the supported controlled-release carrier to prepare a core; trans-2-hexenal and trans-2-octenal are loaded on the core to prepare a core-shell structure microsphere; the core-shell structure microsphere is coated with poly-N-isopropyl acrylamide to prepare a multi-stage controlled-release microsphere; and the multi-stage controlled-release microsphere is used to prepare the cowpea leafhopper repellent for preventing and controlling cowpea leafhoppers. The application improves the loading capacity and adsorption stability of active components, and improves the compatibility with the wax layer of cowpea leaves. The preparation of the application shows fast effect and long persistence.

Description

Technical Field

[0001] The invention relates to the field of green pest control technology, and in particular to a method for preparing a cowpea thrips repellent and its application. Background Technology

[0002] cowpea( Vigna unguiculata Cowpea thrips is an important vegetable crop, with a large planting area and high year-round supply demand in both greenhouse cultivation and open-field production. However, cowpea thrips ( Megalurothrips usitatus Bagnall As one of the dominant pests of cowpeas, thrips are characterized by overlapping generations, rapid reproduction, strong concealment, and rapid development of pesticide resistance, which has long severely restricted the green and safe production of cowpeas. Currently, field control still relies mainly on chemical pesticides (such as neonicotinoids and pyrethroids). However, thrips easily develop resistance and often hide in parts of the flower and leaf that are difficult for pesticides to reach, resulting in low control efficacy. This not only leads to frequent increases in pesticide use, causing serious pesticide residues and environmental pollution, but also kills natural enemy insects, disrupts the ecological balance of farmland, and goes against the current trend of green agriculture.

[0003] Green pest control technologies based on insect behavior have become a research hotspot. Studies have shown that using plant-derived volatile organic compounds (VOCs) and their analogues (such as aldehydes and terpenes) to interfere with the olfactory receptors of pests is a highly promising strategy. Among them, monomeric compounds such as trans-2-hexenal, linalool, and trans-2-octenal have significant repellent activity against various thrips. However, existing technologies mostly use single active ingredients or simple physical mixtures, lacking a systematic design targeting the synergistic repellency mechanism of cowpea thrips, resulting in short-lasting effects and poor stability in the field. Aldehydes are easily oxidized and volatilized, and terpenes are easily photodegraded, making it difficult for conventional formulations to achieve efficient, long-lasting, and targeted control.

[0004] Currently, most commonly used controlled-release carriers employ ordinary charcoal, inorganic clay, or single polymer materials. These carriers exhibit poor compatibility with the waxy layer on cowpea leaves, resulting in insufficient adhesion and easy erosion by rainwater. Furthermore, their limited adsorption capacity prevents high loading, thus restricting the effectiveness of repellents. In addition, most existing products only achieve uniform release, failing to match the high-temperature periods of thrips' diurnal activity, leading to wasted or insufficient supply of active ingredients and a lack of intelligent environmental response. Therefore, a novel supported controlled-release composite material with high loading capacity, stratified release, and environmental responsiveness is urgently needed to achieve efficient, long-lasting, targeted, and green control of cowpea thrips. Summary of the Invention

[0005] To address the above problems, this invention provides a method for preparing cowpea thrips repellent and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a cowpea thrips repellent, the method comprising the following steps: S1. Preparation of supported controlled-release vectors Biochar activation and modification: After pyrolysis, straw powder is activated by microwave and phosphoric acid to obtain activated biochar; Clay intercalation modification: Montmorillonite was intercalated with aluminum ions and modified with polyvinyl alcohol to obtain intercalated montmorillonite-PVA composite. Silane coupling agent modification: After mixing activated biochar with intercalated montmorillonite-PVA composite, the mixture was modified with γ-aminopropyltriethoxysilane to obtain a supported controlled-release carrier. S2, Preparation of multi-level controlled-release microspheres Core preparation: Linalool, geraniol, and methyl salicylate were used to prepare a microemulsion; The supported controlled-release carrier was added to the microemulsion for dispersion, adsorbed under vacuum conditions, then sonicated, and then sodium alginate aqueous solution was added, followed by calcium chloride aqueous solution to form the core. Shell encapsulation: Trans-2-hexenal and trans-2-octenal are mixed to prepare a stabilized aldehyde mixture; The obtained core was dispersed in a gelatin aqueous solution and ultrasonically dispersed to form a uniform suspension. Then, a stabilized aldehyde mixture was slowly added dropwise, along with an emulsifier. The system was stirred at room temperature, and the pH of the system was adjusted so that trans-2-hexenal and trans-2-octenal were uniformly coated on the surface of the core to form a shell, thus obtaining core-shell structured microspheres. Outer coating: Prepare a PNIPAM solution by taking poly-N-isopropylacrylamide, then add the obtained core-shell structured microspheres for dispersion and stirring, so that PNIPAM is uniformly coated on the shell surface to form an environmentally responsive coating. Then add a crosslinking agent and an initiator, crosslink and cure to prepare multi-level controlled-release microspheres. S3. Preparation of cowpea thrips repellent Multi-stage controlled-release microspheres were added to deionized water, along with polycarboxylate and sodium dodecylbenzenesulfonate. The mixture was then ultrasonically dispersed, and a thickener was added to the resulting aqueous suspension to obtain the cowpea thrips repellent.

[0007] Furthermore, in step S1, the specific process of biochar activation and modification is as follows: Straw powder was placed in a microwave reactor and pyrolyzed at 780-820W and 430-470℃ for 18-22 minutes under nitrogen protection to rapidly form a porous structure. Then it was transferred to an ultrasonic reactor and phosphoric acid aqueous solution was added at 480-520W and 38-42kHz. The mixture was ultrasonically treated for 9-12 minutes, cooled to room temperature, washed with deionized water until neutral, and dried to constant weight to obtain activated biochar. The weight-to-volume ratio of straw powder to phosphoric acid aqueous solution is 300g:340~380mL; The concentration of the phosphoric acid aqueous solution is 24~26 wt%; Straw powder is made by drying cowpea straw and then crushing it.

[0008] Furthermore, in step S1, the specific process of clay intercalation modification is as follows: Montmorillonite was added to an aqueous solution of aluminum chloride and stirred at 58-62°C for 4.8-5.2 hours. Then, an aqueous solution of polyvinyl alcohol was added and stirred until homogeneous. The mixture was allowed to stand and cool to room temperature, and then centrifuged to obtain the intercalated montmorillonite-PVA composite. The weight-to-volume ratio of montmorillonite to aluminum chloride aqueous solution and polyvinyl alcohol aqueous solution is 60g: 95~105mL: 95~105mL. The concentration of aluminum chloride aqueous solution is 0.95~1.1 mol / L; The concentration of the polyvinyl alcohol aqueous solution is 2.9~3.1wt%.

[0009] Furthermore, the specific process of silane coupling agent modification in step S1 is as follows: Activated biochar was mixed with intercalated montmorillonite-PVA composite. Anhydrous ethanol was added to the resulting mixture, and the mixture was ultrasonically dispersed to form a uniform suspension. Then, γ-aminopropyltriethoxysilane was added, and the mixture was stirred in a water bath at 75-85°C for 2.5-3 hours to allow the silanol groups formed by the hydrolysis of the silane coupling agent to undergo a condensation reaction with the hydroxyl groups on the surface of the support. After the condensation reaction was completed, the mixture was vacuum dried and pulverized to obtain the supported controlled-release support. The weight ratio of activated biochar to intercalated montmorillonite-PVA complex and γ-aminopropyltriethoxysilane is 200:48~52:4.9~5.1.

[0010] Furthermore, in step S2, the specific process of kernel preparation is as follows: Take 15-15.5 parts by weight of linalool, 15-15.5 parts by weight of geraniol and 16.5-17 parts by weight of methyl salicylate, add water and mix well, then add 0.65-0.75 parts by weight of vitamin E and 0.65-0.75 parts by weight of Tween-60, and ultrasonically emulsify to prepare a microemulsion. The supported controlled-release carrier was added to the microemulsion for dispersion, stirred and adsorbed under vacuum, then sonicated, and then sodium alginate aqueous solution was added, followed by calcium chloride aqueous solution to form the core. The weight ratio of the supported controlled-release carrier to linalool is 250:15~15.5.

[0011] Furthermore, in step S2, the specific preparation process of the shell encapsulation is as follows: Take 1.9~2.1 parts by weight of trans-2-hexenal and 1.9~2.1 parts by weight of trans-2-octenal, mix with water, then add 0.95~1.05 parts by weight of tert-butylhydroquinone and 8~8.4 parts by weight of β-cyclodextrin, stir in a water bath at 38~42℃ for 1~1.5h to obtain a stabilized aldehyde mixture; The core was dispersed in a gelatin aqueous solution and ultrasonically dispersed to form a uniform suspension. Then, a stabilized aldehyde mixture was slowly added dropwise, along with Tween-80. The system was stirred at room temperature, and the pH of the system was adjusted so that trans-2-hexenal and trans-2-octenal were uniformly coated on the surface of the core to form a shell, thus obtaining core-shell structured microspheres. The weight ratio of the supported controlled-release carrier used to prepare the core to trans-2-hexenal is 250:1.9~2.1.

[0012] Furthermore, in step S2, the specific preparation process of the outer coating is as follows: Prepare a PNIPAM solution by adding poly(N-isopropylacrylamide) and deionized water, then add core-shell structured microspheres for dispersion, and stir in a water bath at 58-62℃ for 1-1.5h to uniformly coat the shell surface with PNIPAM and form an environmentally responsive coating. Then add N,N-methylenebisacrylamide and ammonium persulfate, and crosslink and cure in a water bath at 63-66℃ for 1.5-1.7h. After cooling to room temperature, centrifuge, wash with anhydrous ethanol, and dry to obtain multi-level controlled-release microspheres. The weight ratio of the supported controlled-release carrier used to prepare the core to poly(N-isopropylacrylamide) is 250:7.8~8.2.

[0013] Furthermore, in step S3, the weight ratio of the multi-level controlled-release microspheres to polycarboxylate, sodium dodecylbenzenesulfonate and thickener is 250:1.2~1.3:0.7~0.8:0.45~0.55.

[0014] An application of a cowpea thrips repellent, using the aforementioned cowpea thrips repellent to control cowpea thrips.

[0015] Furthermore, the above-mentioned cowpea thrips repellent was diluted with water and sprayed onto cowpea plants to control cowpea thrips.

[0016] The beneficial effects of the preparation method of the cowpea thrips repellent of the present invention and its application are as follows: This invention achieves a combination of barrier protection and gradient release by synergistically activating biochar and modifying clay, followed by silane coupling agent modification, and constructing a three-tiered controlled-release structure (core, shell, and outer membrane) during loading. The outer PNIPAM thermosensitive coating adjusts its permeability according to environmental temperature changes, reducing the volatilization of active components at low temperatures and increasing the release rate at high temperatures. It undergoes a hydrophilic-hydrophobic transition at 32℃, thereby controlling the release rate of active components. The shell layer, composed of β-cyclodextrin, forms an inclusion protection for aldehyde components, reducing oxidative decomposition. The porous structure and interlayer gaps of the core-modified composite carrier facilitate the slow permeation and release of long-acting components. These three elements synergistically form a sustained-release, efficacy-maintaining, and controlled-release system. The results of the examples show that the formulation of this invention still has good preventive and therapeutic effects 28 days after application. This invention improves the carrier performance by synergistically activating biochar and modifying clay, followed by modification with a silane coupling agent. After microwave and phosphoric acid activation, the biochar forms a porous structure with a high specific surface area and introduces -OH and -COOH active groups. After aluminum ion intercalation and PVA modification, the interlayer spacing of montmorillonite is expanded and its hydrophobicity is improved. After modification with KH-550 silane coupling agent, it is beneficial to enhance the carrier's loading and stabilizing effect on active components and improve its compatibility with the waxy layer of cowpea leaves, thereby helping to reduce the loss caused by rainwater erosion. The multi-level structural design of this invention also enables the orderly release of active components; the long-acting components such as linalool and geraniol loaded in the core can be slowly released through the porous channels of the carrier, ensuring long-term repellency; the short-acting components such as trans-2-hexenal wrapped in the shell can be released quickly and exert an initial repellency effect; the outer temperature-sensitive membrane can dynamically adjust the release rate according to the temperature of the cowpea growth environment, thereby helping to achieve rapid onset of action 1 day after drug administration and continuous effectiveness 28 days after drug administration; This invention uses linalool, geraniol, methyl salicylate, trans-2-hexenal and trans-2-octenal as the active ingredients of cowpea thrips repellent, which can synergistically enhance the repellency effect. This invention uses cowpea straw to prepare biochar, realizing the resource utilization of agricultural waste. It has better compatibility with cowpea crops and is free from foreign object stress. Attached Figure Description

[0017] Figure 1 These are comparative photos of the corresponding avoidance effects in each group of Embodiment 1 of the present invention; Figure 2 These are the results of the corresponding insect population reduction rates in each group in Example 1 of this invention; Figure 3 These are the corresponding prevention and control effect results for each group in Example 1 of the present invention; Figure 4 These are the results of the corresponding insect population reduction rates in Example 1 and Comparative Examples 1-6 of this invention; Figure 5These are the corresponding prevention and control effects in Embodiment 1 and Comparative Examples 1-6 of the present invention. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] Example 1: A method for preparing a cowpea thrips repellent and its application This embodiment describes a method for preparing a cowpea thrips repellent and its application, specifically including the following steps: S1. Preparation of supported controlled-release vectors Biochar activation and modification: After drying cowpea straw, it is pulverized to 100 mesh to obtain straw powder; 300g of straw powder was placed in a microwave reactor and pyrolyzed for 20min under nitrogen protection at a reactor power of 800W and an internal temperature of 450℃ to rapidly form a porous structure. Then, it was transferred to an ultrasonic reactor, where 350mL of a 25wt% phosphoric acid aqueous solution was added at 500W and 40kHz. The mixture was ultrasonically treated at room temperature for 10min to etch porous channels and introduce hydroxyl (-OH) and carboxyl (-COOH) active groups. After cooling to room temperature, the mixture was washed with deionized water until neutral and dried at 105℃ to constant weight to obtain activated biochar.

[0020] Clay intercalation modification: 60g of montmorillonite was selected as an auxiliary carrier, and 100mL of 1.0mol / L aluminum chloride aqueous solution was added. The mixture was stirred in a 60℃ water bath for 5h to achieve aluminum ion intercalation, improve the interlayer structure of montmorillonite, and enhance its loading capacity for hydrophobic active components (linalool and geraniol). Subsequently, 100mL of 3wt% polyvinyl alcohol (PVA) aqueous solution was added, and the mixture was stirred evenly in a 60℃ water bath. After standing and cooling to room temperature, the mixture was centrifuged to obtain the intercalated montmorillonite-PVA composite (MP).

[0021] Silane coupling agent modification: 200g of activated biochar (AC) and 50g of intercalated montmorillonite-PVA complex (MP) were mixed. 400mL of anhydrous ethanol was added to the resulting mixture, and the mixture was ultrasonically dispersed for 30min to form a uniform suspension. Then, 5g of γ-aminopropyltriethoxysilane (KH-550) was added, and the mixture was stirred in an 80℃ water bath for 2.5h. This allowed the silanol groups formed by the hydrolysis of the silane coupling agent to undergo a condensation reaction with the hydroxyl groups on the surface of the carrier, forming a hydrophobic film on the carrier surface. The modified carrier not only improves the adsorption stability of aldehydes and terpenes, but also enhances the compatibility between the carrier and the waxy layer of cowpea leaves, reducing carrier loss caused by rainwater erosion. After the condensation reaction was completed, the carrier was vacuum dried and pulverized to 150 mesh to obtain the modified composite carrier (AC-MP-KH), which is the supported controlled-release carrier.

[0022] This invention employs a three-step process of biochar activation modification, clay intercalation modification, and silane coupling agent modification to synergistically modify the carrier, thereby enhancing the adsorption capacity and compatibility of the prepared carrier with aldehydes and terpenes, while also strengthening the adhesion between the carrier and cowpea leaves.

[0023] S2, Preparation of multi-level controlled-release microspheres Core preparation: Take 15.4g linalool, 15.2g geraniol and 16.6g methyl salicylate and add 250mL deionized water to mix well. Then add 0.7g vitamin E as an antioxidant and 0.7g Tween-60. Ultrasonic emulsify for 20min (power 400W, frequency 30kHz) to prepare microemulsion.

[0024] 250g of modified composite carrier (AC-MP-KH) was added to the microemulsion for dispersion. Under vacuum conditions (vacuum degree -0.1MPa, temperature 50℃), the mixture was stirred and adsorbed for 2h. Then, it was ultrasonically treated for 30min (power 200W, frequency 15kHz) to allow the active component to fully fill the porous channels of the carrier and the montmorillonite layer, forming a carrier-long-lasting active component core. Then, 250mL of 1.5wt% sodium alginate aqueous solution was added and stirred for 30min. Then, 250mL of 0.3mol / L calcium chloride aqueous solution was added dropwise to form spherical particles. The particles were centrifuged and washed with a small amount of deionized water to obtain the core.

[0025] Shell encapsulation: Take 2g of trans-2-hexenal and 2g of trans-2-octenal and mix with 40mL of deionized water, then add 1g of tert-butylhydroquinone (TBHQ) as an antioxidant, and then add 8g of β-cyclodextrin (β-CD). Stir in a 40℃ water bath for 1h to allow the cyclodextrin to form an encapsulation protection for the aldehyde components, reduce oxidative decomposition, and obtain a stabilized aldehyde mixture.

[0026] All cores were dispersed in 500 mL of 1 wt% gelatin aqueous solution and ultrasonically dispersed at room temperature for 15 min to form a uniform suspension. Then, a stabilized aldehyde mixture was slowly added dropwise, and 0.75 g of Tween-80 was added as an emulsifier. The mixture was stirred at room temperature for 30 min, and the pH of the system was adjusted to 6.8 so that trans-2-hexenal and trans-2-octenal were uniformly coated on the surface of the core to form a shell. The core-shell structured microspheres were obtained by centrifugation.

[0027] Outer coating: 8g of thermosensitive poly(N-isopropylacrylamide) (PNIPAM) was used as the coating material and 750mL of deionized water was added to prepare a PNIPAM solution. Then, the obtained core-shell structured microspheres were added and dispersed. The mixture was stirred in a 60℃ water bath for 1h to uniformly coat the shell surface with PNIPAM, forming an environmentally responsive coating. 0.2g of crosslinking agent N,N-methylenebisacrylamide (MBA) and 0.15g of initiator ammonium persulfate (APS) were added. The mixture was crosslinked and cured in a 65℃ water bath for 1.5h. After cooling to room temperature, the mixture was centrifuged, washed 2-3 times with anhydrous ethanol, and dried at 105℃ to constant weight to obtain core-shell-membrane three-level structured controlled-release microspheres, referred to as multi-level controlled-release microspheres.

[0028] This invention designs sustained-release formulations as microspheres with a three-tiered structure of core, shell, and outer membrane, which helps to achieve faster onset of action, longer duration of action, and environmentally responsive release of active components, while reducing the adverse effects of easy oxidation of aldehydes and easy volatility of alcohols.

[0029] S3. Preparation of cowpea thrips repellent 250g of multi-stage controlled-release microspheres were added to 500mL of deionized water, along with 1.25g of polycarboxylate and 0.75g of sodium dodecylbenzenesulfonate. The mixture was ultrasonically dispersed for 20min. 0.5g of xanthan gum was then added to the resulting aqueous suspension as a thickener to adjust its viscosity, improve its adhesion to the waxy layer of cowpea leaves, and reduce runoff caused by rainwater. The resulting aqueous suspension was designated as the cowpea thrips repellent, labeled Q1.

[0030] S4. Application of cowpea thrips repellent Dilute cowpea thrips repellent Q1 with water 1000-2000 times and spray it on cowpea plants to control cowpea thrips, as follows: Cowpea thrips repellent Q1 was diluted 1000 times with water and stirred evenly. The resulting diluted solution was used as the spraying agent for the experimental group. Meanwhile, 25% thiamethoxam water-dispersible granules were diluted 5000 times with water and stirred evenly. The resulting diluted chemical solution was used as the spraying agent for the control group. Water was used as the spraying agent for the blank group.

[0031] Experiments were conducted on cowpea experimental fields, with randomized groups. Before treatment, there was no significant difference in insect population density among the groups. Each group was 5 mu (approximately 0.33 hectares), and each group was isolated by an 80-mesh insect-proof net. Each group was replicated three times. During the cowpea seedling stage, vine extension stage, or pre-flowering stage (pre-flowering stage in this example), each group was sprayed with the appropriate pesticide using a drone at a rate of 50 L / mu (approximately 250 L / mu). After spraying, the number of thrips was counted at five points along the diagonal of each experimental field, with 30 cowpea plants counted at each point. The counts were taken at 1 day, 7 days, 14 days, and 28 days post-treatment. The insect population reduction rate and control effect were calculated, and the average of the five-point counts from the three replicates was calculated. Comparative photos of the repellency effect for each group (at 28 days) are also provided. Figure 1 As shown.

[0032] Insect repellency rate (%) = (Number of insects before pesticide application - Number of insects after pesticide application) / Number of insects before pesticide application × 100%; Control effect (%) = (Pest population reduction rate in the treated area - Pest population reduction rate in the blank area) / (1 - Pest population reduction rate in the blank area) × 100%.

[0033] Table 1. Overview of Avoidance Effects for Each Group

[0034] Note: Compared to the blank group. This means P < 0.01. ns represents P < 0.05, and ns represents P > 0.05. The above data on insect population reduction rate and control effect are expressed as the average of three replicates, and significance was tested using one-way ANOVA.

[0035] From Table 1 and Figures 1 to 3 It can be seen that the cowpea thrips repellent prepared by this invention has good cowpea thrips repellency and sustained-release effects. Its initial control effect on cowpea thrips is similar to that of chemical treatment, and its control effect 14 days after application is significantly better than that of existing chemical treatment.

[0036] Examples 2-5: Preparation method of cowpea thrips repellent Examples 2-5 are methods for preparing cowpea thrips repellents. Their steps are basically the same as in Example 1, differing only in the amount of raw materials and some process parameters, as detailed in Table 2. Table 2. Summary of process parameters for the preparation methods and applications of cowpea thrips repellents in Examples 2-5. ,

[0037] The contents and types of raw materials used in other parts of Examples 2 to 5 are the same as those in Example 1, and will not be repeated here.

[0038] Comparative Example 1: A method for preparing a cowpea thrips repellent and its application This comparative example illustrates a method for preparing a cowpea thrips repellent and its application, specifically including the following steps: S1. Preparation of supported controlled-release vectors Biochar activation and modification: After drying cowpea straw, it is pulverized to 100 mesh to obtain straw powder; 300g of straw powder was placed in a microwave reactor and pyrolyzed at 800W and 450℃ for 20min under nitrogen protection to rapidly form a porous structure. Then it was transferred to an ultrasonic reactor and 350mL of 25wt% phosphoric acid aqueous solution was added at 500W and 40kHz. The mixture was ultrasonically treated for 10min, cooled to room temperature, washed with deionized water until neutral, and dried at 105℃ to constant weight to obtain activated biochar.

[0039] Silane coupling agent modification: 200g activated biochar (AC) and 50g montmorillonite were added to 400mL anhydrous ethanol and ultrasonically dispersed for 30min to form a uniform suspension. Then, 5g of γ-aminopropyltriethoxysilane (KH-550) was added and stirred in an 80℃ water bath for 2.5h. After vacuum drying and pulverizing to 150 mesh, the modified composite carrier (AC-MP-KH) was obtained, which is the supported controlled-release carrier.

[0040] S2, Preparation of multi-level controlled-release microspheres The modified composite carrier (AC-MP-KH) prepared using this comparative example was used to fabricate multi-level controlled-release microspheres, following the method described in Example 1.

[0041] S3. Preparation of cowpea thrips repellent Using the multi-level controlled-release microspheres prepared in this comparative example, cowpea thrips repellent was made entirely according to the method of Example 1 and labeled as DQ1.

[0042] S4. Application of cowpea thrips repellent The cowpea thrips repellent DQ1 was diluted 1000 times with water and sprayed onto cowpea seedlings. The pest population reduction rate and control effect were calculated at 1, 7, 14, and 28 days after application. The results are shown in Tables 3 and 4. Figures 4 to 5 .

[0043] Comparative Example 2: A method for preparing a cowpea thrips repellent and its application This comparative example illustrates a method for preparing a cowpea thrips repellent and its application, specifically including the following steps: S1. Preparation of supported controlled-release vectors Biochar preparation: After drying cowpea stalks, they are pulverized to 100 mesh to obtain stalk powder; 300g of straw powder was placed in a microwave reactor and pyrolyzed at 800W and 450℃ for 20min under nitrogen protection to rapidly form a porous structure and obtain biochar.

[0044] Clay intercalation modification: 60g of montmorillonite was selected as an auxiliary carrier, and 100mL of 1.0mol / L aluminum chloride aqueous solution was added. The mixture was stirred in a 60℃ water bath for 5h to achieve aluminum ion intercalation, improve the interlayer structure of montmorillonite, and enhance its loading capacity for hydrophobic active components (linalool and geraniol). Subsequently, 100mL of 3wt% polyvinyl alcohol (PVA) aqueous solution was added, and the mixture was stirred evenly in a 60℃ water bath. After standing and cooling to room temperature, the mixture was centrifuged to obtain the intercalated montmorillonite-PVA composite (MP).

[0045] Silane coupling agent modification: 200g of biochar (AC) and 50g of intercalated montmorillonite-PVA complex (MP) were mixed, 400mL of anhydrous ethanol was added, and the mixture was ultrasonically dispersed for 30min to form a uniform suspension. Then, 5g of γ-aminopropyltriethoxysilane (KH-550) was added, and the mixture was stirred in an 80℃ water bath for 2.5h. After vacuum drying and pulverizing to 150 mesh, the modified composite carrier (AC-MP-KH) was obtained, which is the supported controlled-release carrier.

[0046] S2, Preparation of multi-level controlled-release microspheres The modified composite carrier (AC-MP-KH) prepared using this comparative example was used to fabricate multi-level controlled-release microspheres, following the method described in Example 1.

[0047] S3. Preparation of cowpea thrips repellent Using the multi-level controlled-release microspheres prepared in this comparative example, cowpea thrips repellent was made entirely according to the method of Example 1 and labeled as DQ2.

[0048] S4. Application of cowpea thrips repellent The cowpea thrips repellent DQ2 was diluted 1000 times with water and sprayed onto cowpea seedlings. The pest population reduction rate and control effect were calculated at 1, 7, 14, and 28 days after application. The results are shown in Tables 3 and 4. Figures 4 to 5 .

[0049] Comparative Example 3: A method for preparing a cowpea thrips repellent and its application This comparative example illustrates a method for preparing a cowpea thrips repellent and its application, specifically including the following steps: S1. Preparation of supported controlled-release vectors Biochar activation and modification: After drying cowpea straw, it is pulverized to 100 mesh to obtain straw powder; 300g of straw powder was placed in a microwave reactor and pyrolyzed at 800W and 450℃ for 20min under nitrogen protection to rapidly form a porous structure. Then, it was transferred to an ultrasonic reactor and 350mL of 25wt% phosphoric acid aqueous solution was added at 500W and 40kHz. The mixture was ultrasonically treated for 10min to etch porous channels and introduce hydroxyl (-OH) and carboxyl (-COOH) active groups. After cooling to room temperature, the mixture was washed with deionized water until neutral and dried at 105℃ to constant weight to obtain activated biochar.

[0050] Clay intercalation modification: 60g of montmorillonite was selected as an auxiliary carrier, and 100mL of 1.0mol / L aluminum chloride aqueous solution was added. The mixture was stirred in a 60℃ water bath for 5h to achieve aluminum ion intercalation, improve the interlayer structure of montmorillonite, and enhance its loading capacity for hydrophobic active components (linalool and geraniol). Subsequently, 100mL of 3wt% polyvinyl alcohol (PVA) aqueous solution was added, and the mixture was stirred evenly in a 60℃ water bath. After standing and cooling to room temperature, the mixture was centrifuged to obtain the intercalated montmorillonite-PVA composite (MP).

[0051] Mixing: Take 200g of activated biochar (AC) and mix it with 50g of intercalated montmorillonite-PVA complex (MP) to obtain the supported controlled-release carrier.

[0052] S2, Preparation of multi-level controlled-release microspheres Following the method of Example 1, the loaded controlled-release carrier prepared in this comparative example was used instead of the modified composite carrier (AC-MP-KH) of Example 1 to sequentially prepare the core, encapsulate the shell, and coat the outer layer to prepare multi-level controlled-release microspheres.

[0053] S3. Preparation of cowpea thrips repellent Using the multi-level controlled-release microspheres prepared in this comparative example, cowpea thrips repellent was made entirely according to the method of Example 1 and labeled as DQ3.

[0054] S4. Application of cowpea thrips repellent The cowpea thrips repellent DQ3 was diluted 1000 times with water and sprayed onto cowpea seedlings. The pest population reduction rate and control effect were calculated at 1, 7, 14, and 28 days after application. The results are shown in Tables 3 and 4. Figures 4 to 5 .

[0055] Comparative Example 4: A method for preparing a cowpea thrips repellent and its application This comparative example illustrates a method for preparing a cowpea thrips repellent and its application, specifically including the following steps: S1. Preparation of supported controlled-release vectors The modified composite carrier (AC-MP-KH) was prepared entirely according to the method in Example 1, which is the supported controlled-release carrier.

[0056] S2. Preparation of controlled-release microspheres Microsphere preparation: Take 15.4g linalool, 15.2g geraniol, 16.6g methyl salicylate, 2g trans-2-hexenal and 2g trans-2-octenal and add 290mL water to mix well. Then add 0.7g vitamin E and 1g tert-butylhydroquinone (TBHQ) as antioxidants, and then add 0.7g Tween-60. Ultrasonic emulsify for 20min (power 400W, frequency 30kHz) to prepare microemulsion.

[0057] 250g of the supported controlled-release carrier was dispersed in a microemulsion and stirred for 2 hours under vacuum (vacuum degree -0.1MPa, temperature 50℃). Then, it was sonicated for 30 minutes (power 200W, frequency 15kHz). Next, 250mL of 1.5wt% sodium alginate aqueous solution was added and stirred for 30 minutes. Then, 250mL of 0.3mol / L calcium chloride aqueous solution was added dropwise to form spherical particles with a particle size of 150μm. The particles were centrifuged and washed with a small amount of deionized water to obtain microspheres.

[0058] Outer coating: Take 8g of thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and add 750mL of deionized water to prepare PNIPAM solution. Then add all the microspheres and disperse. Stir in a 60℃ water bath for 1h. Then add 0.2g of crosslinking agent N,N-methylenebisacrylamide (MBA) and 0.15g of initiator ammonium persulfate (APS). Crosslink and cure in a 65℃ water bath for 1.5h. Cool to room temperature, centrifuge, wash 2-3 times with anhydrous ethanol, and dry at 105℃ to constant weight to obtain controlled-release microspheres.

[0059] S3. Preparation of cowpea thrips repellent The controlled-release microspheres prepared in this comparative example were used instead of the multi-stage controlled-release microspheres of Example 1. The cowpea thrips repellent was prepared in complete accordance with the method of Example 1 and labeled as DQ4.

[0060] S4. Application of cowpea thrips repellent The cowpea thrips repellent DQ4 was diluted 1000 times with water and sprayed onto cowpea seedlings. The pest population reduction rate and control effect were calculated at 1, 7, 14, and 28 days after application. The results are shown in Tables 3 and 4. Figures 4 to 5 .

[0061] Comparative Example 5: A method for preparing a cowpea thrips repellent and its application This comparative example illustrates a method for preparing a cowpea thrips repellent and its application, specifically including the following steps: S1. Preparation of supported controlled-release vectors The modified composite carrier (AC-MP-KH) was prepared entirely according to the method in Example 1, which is the supported controlled-release carrier.

[0062] S2. Preparation of controlled-release microspheres Microsphere preparation: 15.4g linalool, 15.2g geraniol, 16.6g methyl salicylate, 2g trans-2-hexenal and 2g trans-2-octenal were mixed with 300mL water, then 0.7g vitamin E and 1g tert-butylhydroquinone (TBHQ) were added as antioxidants, followed by 0.7g Tween-60. The mixture was ultrasonically emulsified for 20min (400W power, 30kHz frequency). 100g β-cyclodextrin (β-CD) was added to the resulting microemulsion, and the mixture was stirred in a 40℃ water bath for 1h to obtain a mixture.

[0063] 250g of the supported controlled-release carrier was dispersed in 500mL of 1wt% gelatin aqueous solution and ultrasonically dispersed at room temperature for 15min to form a uniform suspension. Then, the above mixture was slowly added dropwise, and 0.75g of Tween-80 was added as an emulsifier. The mixture was stirred at room temperature for 30min, the pH of the system was adjusted to 6.8, and the microspheres were obtained by centrifugation.

[0064] Outer coating: Take 8g of thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and add 750mL of deionized water to prepare PNIPAM solution. Then add all the microspheres and disperse. Stir in a 60℃ water bath for 1h. Then add 0.2g of crosslinking agent N,N-methylenebisacrylamide (MBA) and 0.15g of initiator ammonium persulfate (APS). Crosslink and cure in a 65℃ water bath for 1.5h. Cool to room temperature, centrifuge, wash 2-3 times with anhydrous ethanol, and dry at 105℃ to constant weight to obtain controlled-release microspheres.

[0065] S3. Preparation of cowpea thrips repellent The controlled-release microspheres prepared in this comparative example were used instead of the multi-stage controlled-release microspheres of Example 1. The cowpea thrips repellent was prepared in complete accordance with the method of Example 1 and labeled as DQ5.

[0066] S4. Application of cowpea thrips repellent The cowpea thrips repellent DQ5 was diluted 1000 times with water and sprayed onto cowpea seedlings. The pest population reduction rate and control effect were calculated at 1, 7, 14, and 28 days after application. The results are shown in Tables 3 and 4. Figures 4 to 5 .

[0067] Comparative Example 6: A method for preparing a cowpea thrips repellent and its application This comparative example illustrates a method for preparing a cowpea thrips repellent and its application, specifically including the following steps: S1. Preparation of supported controlled-release vectors The modified composite carrier (AC-MP-KH) was prepared entirely according to the method in Example 1, which is the supported controlled-release carrier.

[0068] S2, Preparation of core-shell structured microspheres Core preparation: Take 15.4g linalool, 15.2g geraniol and 16.6g methyl salicylate and add 250mL water to mix well. Then add 0.7g vitamin E as an antioxidant and 0.7g Tween-60. Ultrasonic emulsify for 20min (power 400W, frequency 30kHz) to prepare microemulsion.

[0069] 250g of modified composite carrier (AC-MP-KH) was added to the microemulsion for dispersion. Under vacuum conditions (vacuum degree -0.1MPa, temperature 50℃), the mixture was stirred and adsorbed for 2h. Then, it was ultrasonically treated for 30min (power 200W, frequency 15kHz) to allow the active component to fully fill the porous channels of the carrier and the montmorillonite layer, forming a carrier-long-lasting active component core. Then, 250mL of 1.5wt% sodium alginate aqueous solution was added and stirred for 30min. Then, 250mL of 0.3mol / L calcium chloride aqueous solution was added dropwise to prepare spherical particles with a particle size of 150μm. The particles were centrifuged and washed with a small amount of deionized water to obtain the core.

[0070] Shell encapsulation: Take 2g of trans-2-hexenal and 2g of trans-2-octenal and mix with 40mL of deionized water, then add 1g of tert-butylhydroquinone (TBHQ) as an antioxidant, and then add 8g of β-cyclodextrin (β-CD). Stir in a 40℃ water bath for 1h to allow the cyclodextrin to form an encapsulation protection for the aldehyde components, reduce oxidative decomposition, and obtain a stabilized aldehyde mixture.

[0071] All cores were dispersed in 500 mL of 1 wt% gelatin aqueous solution and ultrasonically dispersed at room temperature for 15 min to form a uniform suspension. Then, a stabilized aldehyde mixture was slowly added dropwise, and 0.75 g of Tween-80 was added as an emulsifier. The mixture was stirred at room temperature for 30 min, and the pH of the system was adjusted to 6.8 so that trans-2-hexenal and trans-2-octenal were uniformly coated on the surface of the core to form a shell. The core-shell structured microspheres were obtained by centrifugation.

[0072] S3. Preparation of cowpea thrips repellent The core-shell structured microspheres prepared in this comparative example were used instead of the multi-level controlled-release microspheres of Example 1. The cowpea thrips repellent was prepared in complete accordance with the method of Example 1 and labeled as DQ6.

[0073] S4. Application of cowpea thrips repellent The cowpea thrips repellent DQ6 was diluted 1000 times with water and sprayed onto cowpea seedlings. The insect repellency rate and repellency effect were calculated at 1, 7, 14, and 28 days after application. The results are shown in Tables 3 and 4. Figures 4 to 5 .

[0074] Table 3. Summary of the mean insect avoidance rates for each control group

[0075] Note: Compared to the blank group. This means P < 0.01. ns represents P < 0.05, and ns represents P > 0.05.

[0076] Table 4. Summary of the mean avoidance effects for each pair of pairs.

[0077] Note: Compared to the blank group. This means P < 0.01.

[0078] From Table 3 to Table 4 and Figures 4 to 5 It can be seen that the cowpea thrips repellent prepared by this invention has a good sustained-release effect; changing the process conditions will lead to a decrease in the sustained-release effect to varying degrees.

[0079] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a cowpea thrips repellent, characterized in that, The preparation method includes the following steps: S1. Preparation of supported controlled-release vectors Biochar activation and modification: After pyrolysis, straw powder is activated by microwave and phosphoric acid to obtain activated biochar; Clay intercalation modification: Montmorillonite was intercalated with aluminum ions and modified with polyvinyl alcohol to obtain intercalated montmorillonite-PVA composite. Silane coupling agent modification: After mixing activated biochar with intercalated montmorillonite-PVA composite, the mixture was modified with γ-aminopropyltriethoxysilane to obtain a supported controlled-release carrier. The weight ratio of activated biochar to intercalated montmorillonite-PVA composite and γ-aminopropyltriethoxysilane is 200:48~52:4.9~5.

1. S2, Preparation of multi-level controlled-release microspheres Core preparation: Take 15-15.5 parts by weight of linalool, 15-15.5 parts by weight of geraniol and 16.5-17 parts by weight of methyl salicylate and add 240-260 parts by volume of deionized water to prepare a microemulsion; wherein, the ratio of parts by weight to parts by volume is g:mL. The supported controlled-release carrier was added to the microemulsion for dispersion, adsorbed under vacuum conditions, then sonicated, and then sodium alginate aqueous solution was added, followed by calcium chloride aqueous solution to form the core. Shell encapsulation: Take 1.9~2.1 parts by weight of trans-2-hexenal and 1.9~2.1 parts by weight of trans-2-octenal and add 38~42 parts by volume of deionized water to prepare a stabilized aldehyde mixture; wherein, the ratio of parts by weight to parts by volume is g:mL. The obtained core was dispersed in a gelatin aqueous solution and ultrasonically dispersed to form a uniform suspension. Then, a stabilized aldehyde mixture was slowly added dropwise, along with an emulsifier. The system was stirred at room temperature, and the pH of the system was adjusted so that trans-2-hexenal and trans-2-octenal were uniformly coated on the surface of the core to form a shell, thus obtaining core-shell structured microspheres. Outer coating: Take 7.8~8.2 parts by weight of poly-N-isopropylacrylamide and add 750~850 parts by volume of deionized water to prepare PNIPAM solution, then add the obtained core-shell structured microspheres for dispersion and stirring, so that PNIPAM is uniformly coated on the shell surface to form an environmentally responsive coating, then add crosslinking agent and initiator, crosslink and cure to prepare multi-level controlled-release microspheres; The weight ratio of the supported controlled-release carrier to poly(N-isopropylacrylamide) used to prepare the core was 250:7.8~8.

2. S3. Preparation of cowpea thrips repellent Multi-stage controlled-release microspheres were added to deionized water, along with polycarboxylate and sodium dodecylbenzenesulfonate. The mixture was then ultrasonically dispersed, and a thickener was added to the resulting aqueous suspension to obtain the cowpea thrips repellent.

2. The method for preparing cowpea thrips repellent according to claim 1, characterized in that, In step S1, the specific process of biochar activation and modification is as follows: Straw powder was placed in a microwave reactor and pyrolyzed at 780-820W and 430-470℃ for 18-22 minutes under nitrogen protection to rapidly form a porous structure. Then it was transferred to an ultrasonic reactor and phosphoric acid aqueous solution was added at 480-520W and 38-42kHz. The mixture was ultrasonically treated for 9-12 minutes, cooled to room temperature, washed with deionized water until neutral, and dried to constant weight to obtain activated biochar. The weight-to-volume ratio of straw powder to phosphoric acid aqueous solution is 300g:340~380mL; The concentration of the phosphoric acid aqueous solution is 24~26 wt%; Straw powder is made by drying cowpea straw and then crushing it.

3. The method for preparing cowpea thrips repellent according to claim 1 or 2, characterized in that, In step S1, the specific process of clay intercalation modification is as follows: Montmorillonite was added to an aqueous solution of aluminum chloride and stirred at 58-62°C for 4.8-5.2 hours. Then, an aqueous solution of polyvinyl alcohol was added and stirred until homogeneous. The mixture was allowed to stand and cool to room temperature, and then centrifuged to obtain the intercalated montmorillonite-PVA composite. The weight-to-volume ratio of montmorillonite to aluminum chloride aqueous solution and polyvinyl alcohol aqueous solution is 60g: 95~105mL: 95~105mL. The concentration of aluminum chloride aqueous solution is 0.95~1.1 mol / L; The concentration of the polyvinyl alcohol aqueous solution is 2.9~3.1wt%.

4. The method for preparing cowpea thrips repellent according to claim 1 or 2, characterized in that, In step S1, the specific process of silane coupling agent modification is as follows: Activated biochar was mixed with intercalated montmorillonite-PVA composite. Anhydrous ethanol was added to the resulting mixture, and the mixture was ultrasonically dispersed to form a uniform suspension. Then, γ-aminopropyltriethoxysilane was added, and the mixture was stirred in a water bath at 75-85°C for 2.5-3 hours to allow the silanol groups formed by the hydrolysis of the silane coupling agent to undergo a condensation reaction with the hydroxyl groups on the surface of the carrier. After the condensation reaction was completed, the mixture was vacuum dried and pulverized to obtain the supported controlled-release carrier.

5. The method for preparing cowpea thrips repellent according to claim 1 or 2, characterized in that, In step S2, the specific process of kernel preparation is as follows: Take 15-15.5 parts by weight of linalool, 15-15.5 parts by weight of geraniol and 16.5-17 parts by weight of methyl salicylate, add water and mix well, then add 0.65-0.75 parts by weight of vitamin E and 0.65-0.75 parts by weight of Tween-60, and ultrasonically emulsify to prepare a microemulsion. The supported controlled-release carrier was added to the microemulsion for dispersion, stirred and adsorbed under vacuum, then sonicated, and then sodium alginate aqueous solution was added, followed by calcium chloride aqueous solution to form the core. The weight ratio of the supported controlled-release carrier to linalool is 250:15~15.

5.

6. The method for preparing cowpea thrips repellent according to claim 1 or 2, characterized in that, In step S2, the specific preparation process of the shell encapsulation is as follows: Take 1.9~2.1 parts by weight of trans-2-hexenal and 1.9~2.1 parts by weight of trans-2-octenal, mix with water, then add 0.95~1.05 parts by weight of tert-butylhydroquinone and 8~8.4 parts by weight of β-cyclodextrin, stir in a water bath at 38~42℃ for 1~1.5h to obtain a stabilized aldehyde mixture; The core was dispersed in a gelatin aqueous solution and ultrasonically dispersed to form a uniform suspension. Then, a stabilized aldehyde mixture was slowly added dropwise, along with Tween-80. The system was stirred at room temperature, and the pH of the system was adjusted so that trans-2-hexenal and trans-2-octenal were uniformly coated on the surface of the core to form a shell, thus obtaining core-shell structured microspheres. The weight ratio of the supported controlled-release carrier used to prepare the core to trans-2-hexenal is 250:1.9~2.

1.

7. The method for preparing cowpea thrips repellent according to claim 1 or 2, characterized in that, In step S2, the specific preparation process of the outer coating is as follows: Prepare a PNIPAM solution by adding poly(N-isopropylacrylamide) and deionized water. Then, add core-shell microspheres for dispersion and stir in a water bath at 58-62°C for 1-1.5 hours to uniformly coat the shell surface with PNIPAM and form an environmentally responsive coating. Then, add N,N-methylenebisacrylamide and ammonium persulfate and crosslink and cure in a water bath at 63-66°C for 1.5-1.7 hours. After cooling to room temperature, centrifuge, wash with anhydrous ethanol, and dry to obtain multi-level controlled-release microspheres.

8. The method for preparing cowpea thrips repellent according to claim 1 or 2, characterized in that, In step S3, the weight ratio of multi-level controlled-release microspheres to polycarboxylate, sodium dodecylbenzenesulfonate and thickener is 250:1.2~1.3:0.7~0.8:0.45~0.

55.

9. An application of cowpea thrips repellent, characterized in that, The cowpea thrips repellent prepared by any one of the preparation methods described in claims 1-8 is used to control cowpea thrips.

10. The application of the cowpea thrips repellent according to claim 9, characterized in that, The cowpea thrips repellent was diluted with water and sprayed onto cowpea plants to control cowpea thrips.

Images