Slow-release insecticide for landscaping and preparation method thereof

Abstract

The invention relates to the technical field of biopesticides, and provides a slow-release insecticide for landscaping and a preparation method thereof.The slow-release insecticide is prepared from, by weight, 5%-20% of clothianidin, 1%-5% of cyromazine, 1.5%-2.5% of metalaxyl hymexazol, 0.8%-1.2% of humic acid, 5%-8% of chitosan, 3%-4% of polylactic acid, 1.5%-2.5% of nanometer titania, 0.5%-0.8% of plant source auxiliaries and the balance water; compared with existing insecticides, a'stepped release 'system (clothianidin rapidly controls insects in the early stage and cyromazine is long-acting and stable in the later stage) is formed through a nano slow release technology (chitosan nanoparticles and PLA microspheres), synergistic prevention and control of overground and underground insects are effectively achieved, the instantaneous concentration of the insecticide in the environment is reduced, and the resistance selection pressure is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of biopesticides, and in particular to a slow-release insecticide for landscaping and a preparation method thereof. Background Art

[0002] In the field of landscaping, the application of pesticides faces diverse demands and new challenges. In existing technologies, clothianidin and cyromazine are mostly used to control pests such as aphids. While they have achieved certain results in pest control, they still face the following prominent problems:

[0003] Insecticide combinations of clothianidin and cyromazine, available in emulsifiable concentrates and suspensions, are suitable for use against agricultural pests such as leafminers and fruit flies. However, in landscaping settings, the pests are complex (such as aphids, spider mites, and scale insects). A single combination ratio is insufficient to address the varying resistance profiles of multiple target pests. Existing literature lacks data on resistance management for garden pests, and the combination ratio is not optimized. This results in significant fluctuations in effectiveness in practice. The risk of resistance is high, and a single ingredient can easily lead to the development of pest resistance, resulting in a short effective period.

[0004] Poor sustained-release performance makes it unsuitable for garden environments. Researchers have proposed the use of clothianidin chitosan microspheres, produced through spray drying, to extend the drug's effectiveness to over 30 days. However, in gardening environments, the micron-sized microspheres are easily lost due to rain or irrigation, resulting in insufficient sustained-release performance and a duration that is unlikely to last the entire growing season. Furthermore, without considering the sensitivity of garden plants to residual pesticides (such as the risk of clogging leaf stomata), the toxicity of clothianidin to non-target organisms (such as bees and birds) remains unresolved.

[0005] The single function is not conducive to ecological restoration; most of the existing garden pesticides focus on a single insecticidal function, and rarely involve the common dual prevention and control needs of insects and diseases in landscaping (such as the coordinated prevention and control of aphids and sooty mold disease).

[0006] In addition, it is precisely because of the frequent application of pesticides in garden soil that the microbial community is unbalanced, and the existing pesticides do not introduce soil repair functions (such as the addition of humic acid), it is impossible to achieve long-term health maintenance of the ecosystem.

[0007] Therefore, the related technology about the insecticide of landscaping in the prior art still needs to be further improved. Summary of the Invention

[0008] In response to the shortcomings of the existing technology, the present invention proposes a slow-release insecticide for landscaping and a preparation method, which solves the technical problems in the existing technology such as high resistance risk, short effectiveness, poor slow-release performance, single function and inability to carry out ecological restoration.

[0009] The technical solution of the present invention is achieved as follows:

[0010] The invention provides a slow-release insecticide for landscaping. The slow-release insecticide comprises the following components by weight: 5-20% of clothianidin, 1-5% of cyromazine, 1.5-2.5% of metalaxyl, 0.8-1.2% of humic acid, 5-8% of chitosan, 3-4% of polylactic acid, 1.5-2.5% of nano titanium dioxide, 0.5-0.8% of a plant-derived additive, and the balance is water.

[0011] On the basis of this technical solution, it is further preferred that the following components are included in weight percentage: 15% clothianidin, 5% cyromazine, 2% metalaxyl, 0.9% humic acid, 7.5% chitosan, 3% polylactic acid, 2.5% nano titanium dioxide, 0.6% plant-based additives, and the balance is water.

[0012] On the basis of this technical solution, more preferably, the deacetylation degree of the chitosan is 86-95%.

[0013] On the basis of this technical solution, more preferably, the molecular weight of the polylactic acid is 25,000-50,000.

[0014] On the basis of this technical solution, more preferably, the molecular weight of chitosan is 50,000-80,000.

[0015] On the basis of this technical solution, it is further preferred that the plant-derived adjuvant includes azadirachtin and peppermint oil, and the weight ratio of the two is 1:1.5-2.

[0016] In another aspect, the present invention provides a method for preparing the slow-release insecticide for landscaping according to any one of the first aspects, comprising the following steps:

[0017] S1. Chitosan was dissolved in acetic acid to obtain a chitosan solution; clothianidin was dissolved in ethyl acetate and added to the chitosan solution. A 0.6-1.0% CaCl2 solution was added dropwise with stirring at 800-1200 rpm. The cross-linking reaction was allowed to proceed for 3-5 h, and the chitosan nanoparticles were filtered.

[0018] S2. Polylactic acid was dissolved in dichloromethane, cyromazine was added, sheared at 900-1200 rpm, and ultrasonically emulsified for 10-20 min. A 1-2% Span-80 aqueous solution was added, and dichloromethane was removed by vacuum distillation to obtain polylactic acid microspheres.

[0019] S3. The chitosan nanoparticles obtained in step S1, the polylactic acid microspheres obtained in step S2, metalaxyl, humic acid, nano-titanium dioxide and plant-derived additives are mixed, water is added, and shear emulsification is performed at 1000-1500 rpm for 25-35 minutes. The pH is adjusted to 5.5-6.5 to obtain a slow-release insecticide.

[0020] On the basis of this technical solution, more preferably, the particle size of the polylactic acid microspheres in step S2 is 250-400 nm.

[0021] On the basis of this technical solution, it is further preferred that the particle size of the chitosan nanoparticles in step S1 is 60-90 nm, and the encapsulation efficiency is >92%.

[0022] On the basis of this technical solution, it is further preferred that the mass concentration of the chitosan solution in step S1 is 1.2-1.8%, and the power of the ultrasound in step S2 is 400-500W.

[0023] On the basis of this technical solution, it is further preferred that the temperature of the shear emulsification in step S3 is controlled at 20-25°C.

[0024] The slow-release insecticide for landscaping and its preparation method provided by the present invention have the following beneficial effects compared with the prior art:

[0025] Compared with the simple combination of existing technologies, the present invention embeds clothianidin into chitosan nanoparticles. The nanoscale particle size can directly penetrate through the stomata of plant leaves or the epidermis of roots. The systemic efficiency is increased by more than 30% compared with micron-sized chitosan microspheres (6.73-25.03μm). It is prepared by the reverse emulsion-ionic crosslinking method to avoid carrier degradation caused by high temperature. The 24-hour release rate is controlled at around 30%, which not only ensures the rapid knockdown of sucking pests (such as aphids), but also reduces the toxicity of instantaneous exposure to the agent to pollinating insects such as bees.

[0026] At the same time, cyromazine is encapsulated in polylactic acid microspheres. The biodegradation rate of PLA matches the generation cycle (30 generations) of dipteran pests such as leafminers. This avoids overdosage and extends the effective period by 50% compared to conventional suspension concentrates, solving the current problem of persistent underground flies in the garden. PLA can be completely degraded into carbon dioxide and water, and its residual content in the soil is 60% lower than that of traditional carriers, making it highly compatible with the landscaping demand for soil ecological protection.

[0027] In addition, the chitosan nanoparticles of clothianidin (interfering with nerve conduction) and the polylactic acid microspheres of cyromazine (inhibiting chitin synthesis) are combined to form a dual target, delaying the development of resistance; the addition of carbendazim (inhibiting pathogen cell wall synthesis) and humic acid (promoting root growth and enhancing stress resistance) further reduces the possibility of pests developing resistance through metabolic pathways, forming a "insecticide + antibacterial" synergistic and synergistic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 The sustained release of the insecticide at different particle sizes in Example 1 and Comparative Example 6 is shown. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] While existing insecticides include cyromazine compounding, they haven't addressed its poor solubility in organic solvents (PLA microspheres typically rely on readily soluble ingredients like acetamiprid). In landscaping applications, cyromazine requires stable encapsulation through nanoencapsulation or emulsification techniques. However, existing technologies lack relevant process parameters (such as mixed solvent optimization and emulsification-solvent evaporation methods), resulting in low microsphere encapsulation rates (<70%), impacting their effectiveness.

[0032] This invention provides a slow-release insecticide for landscaping and its preparation method. The insecticide contains clothianidin and cyromazine in an optimal ratio of 15% + 5%. It achieves dual slow-release through chitosan nanoparticles encapsulating clothianidin and PLA microspheres encapsulating cyromazine, extending its effective duration to 45 days. Metalaxyl is further added to the biocompatibility to control soilborne diseases, and humic acid is introduced to promote soil microbial remediation. The preparation method utilizes an emulsification-solvent volatilization method, optimizing the encapsulation efficiency of cyromazine (≥70%) using a mixed solvent. Combined with root irrigation or drip irrigation, the insecticide is adaptable to the complex needs of garden environments. The insecticide has a control efficacy of >90% against underground pests (such as the larvae of the non-rapeseed blue-eyed maggot), an acute toxicity LC50 of >1000 mg / kg for bees, and a degradation rate of the active ingredient in soil of ≥80%. By integrating dual slow-release nanoparticles with microspheres, pest and disease control, and ecological restoration, this invention significantly improves its long-lasting effectiveness, resistance management, and environmental friendliness in garden settings, offering broad application value.

[0033] Example 1

[0034] A slow-release insecticide for landscaping, comprising: clothianidin (purity 98%), cyromazine (purity 97%), metalaxyl (purity 95%), chitosan (deacetylation degree 90%, molecular weight 50,000), polylactic acid (molecular weight 50,000), nano-titanium dioxide (anatase type, particle size 25 nm); plant-derived adjuvants: azadirachtin (purity 1%), and peppermint oil (food grade).

[0035] The preparation method comprises the following steps:

[0036] S1. Preparation of chitosan nanoparticles: Weigh 5 g of chitosan and dissolve it in 333 mL of 1% acetic acid. Stir magnetically (400 rpm) for 2 h until completely dissolved to obtain a 1.5% chitosan solution. Weigh 10 g of clothianidin technical drug and dissolve it in 100 mL of ethyl acetate. Stir until dissolved to obtain a clothianidin solution.

[0037] The clothianidin solution was slowly dripped into the chitosan solution (volume ratio 1:5). Under stirring at 1000 rpm, 50 mL of 0.8% CaCl2 solution was added dropwise at a rate of 1.5 mL / min. Stirring was continued for 4 h to carry out the cross-linking reaction.

[0038] After the reaction, the precipitate was collected by centrifugation (8000 rpm, 10 min), washed three times with deionized water, and freeze-dried to obtain chitosan nanoparticles with a particle size of 90 nm (encapsulation efficiency of 93.2%).

[0039] Preparation of PLA microspheres: 6 g PLA was dissolved in 100 mL of dichloromethane and stirred until dissolved to obtain a 6% PLA solution. 2 g cyromazine technical was added to the PLA solution and stirred until dissolved.

[0040] The above mixture was added to 200 mL of deionized water containing 1.5% Span-80 and ultrasonically emulsified (power 400 W) for 15 min to form a W / O emulsion;

[0041] The emulsion was transferred to a rotary evaporator and distilled under reduced pressure at 35°C for 30 min to remove dichloromethane. The precipitate was collected by centrifugation (5000 rpm, 8 min) and dried to obtain polylactic acid microspheres with an average particle size of 300 nm (drug loading 25.6%).

[0042] S3. Compounding: To 500 mL of deionized water, the prepared nanoparticles (containing 10 g of clothianidin), microspheres (containing 3.3 g of cyromazine), 2 g of metalaxyl, 1 g of humic acid, 2 g of nano-titanium dioxide, 0.2 g of azadirachtin, and 0.4 g of peppermint oil were added in sequence.

[0043] The mixed solution was transferred to a high-speed shear emulsifier and emulsified at 1200 rpm for 30 min (temperature 22°C). After emulsification, the pH was adjusted to 6.0, and deionized water was added to a total mass of 100 g to obtain a slow-release insecticide.

[0044] Example 2

[0045] A slow-release insecticide for landscaping, which differs from Example 1 in that it comprises: 15 g of clothianidin, 5 g of cyromazine, 2 g of metalaxyl, 0.9 g of humic acid, 7.5 g of chitosan, 3 g of polylactic acid, 2.5 g of nano-titanium dioxide, 0.6 g of a plant-derived adjuvant, 550 mL of water, and chitosan nanoparticles with a particle size of 60 nm.

[0046] Example 3

[0047] A slow-release insecticide for landscaping, which differs from Example 1 in that it comprises: 20 g of clothianidin, 2 g of cyromazine, 2.5 g of metalaxyl, 1.2 g of humic acid, 8 g of chitosan, 4 g of polylactic acid, 2.5 g of nano-titanium dioxide, 0.8 g of a plant-derived adjuvant, and 600 mL of water; the shear emulsification temperature is controlled at 30°C.

[0048] Comparative Example 1

[0049] A landscaping insecticide is provided, which differs from Example 1 in that chitosan and polylactic acid are not added to encapsulate clothianidin and cyromazine.

[0050] Comparative Example 2

[0051] A garden insecticide, which differs from Example 2 in that cyromazine and polylactic acid are not added.

[0052] Comparative Example 3

[0053] A garden insecticide, which differs from Example 2 in that clothianidin and chitosan are not added.

[0054] Comparative Example 4

[0055] A garden insecticide, which differs from Example 3 in that clothianidin and chitosan are not added.

[0056] Comparative Example 5

[0057] A garden insecticide, which differs from Example 2 in that metalaxyl and humic acid are not added.

[0058] Comparative Example 6

[0059] A garden insecticide, which differs from Example 2 in that the particle size of the chitosan-coated clothianidin is 6 μm.

[0060] Comparative Example 7

[0061] A garden insecticide, which differs from Example 2 in that the chitosan has a deacetylation degree of 80%.

[0062] Table 1 Control effects of examples and comparative examples

[0063]

[0064] The results show that when Example 1 is compared with Comparative Example 1, Example 3 is compared with Comparative Example 3, and Example 2 is compared with Comparative Examples 2 and 4-7, Example 2 has significantly better control effects on different aphids and leaf miners than Comparative Examples 2 and 4-7, and also shows good effects on root rot and bee toxicity, meeting the ecological requirements of landscaping. Analyzing the reasons, Example 2 maintains a control effect of more than 80% on aphids and leaf miners, and a root rot control effect of more than 90% through the dual sustained-release technology of nano-microspheres, process parameter optimization, and humic acid synergistic repair. However, the control effect of the comparative example decreases to varying degrees due to the high parameters. This may be due to the lack of nano-carriers and bactericidal ingredients, resulting in low control efficiency and no disease prevention function. This also shows that the existing insecticides do not meet the standards for control effect, duration of effect, and environmental friendliness due to the lack of sustained-release design and process optimization.

[0065] like Figure 1As shown in the table, the sustained release of the insecticides at different particle sizes is compared with that of Comparative Example 6. It can be seen that the sustained release rate of Comparative Example 6 is significantly greater than that of Examples 1-2. This shows that compared with the existing micron-sized chitosan microspheres, the nanoscale microspheres prepared by the reverse emulsion-ionic crosslinking method avoid carrier degradation caused by high temperature, and the 24h release rate is controlled at about 30%. This ensures rapid knockdown of sucking pests and reduces the toxicity of instantaneous exposure to the agent to pollinating insects such as bees. At the same time, combined with Table 1, it can be seen that particle size control and emulsification temperature also play a major role in the control effect.

[0066] In summary, the present invention provides a sustained-release insecticide for landscaping and its preparation method. It utilizes chitosan nanoparticles (50-100 nm) to encapsulate clothianidin, PLA microspheres (200-400 nm) to encapsulate cyromazine, and a combination of metalaxyl and humic acid. Clothianidin kills piercing-sucking pests by interfering with acetylcholine receptors, while cyromazine inhibits chitin synthesis to control dipteran pests. The two create a 3:1 synergistic effect, with metalaxyl blocking soil-borne diseases spread by sickle species, and humic acid enhancing rhizosphere activity. The nanocarrier achieves a stepped sustained-release mechanism (thianidin releases 30% within 24 hours, cyromazine releases <15% within 7 days), with a 45-day duration and a 50% reduction in bee toxicity. The formulation is suitable for targeted spraying, under-tree injection, and soil treatment on street trees and lawns. Furthermore, chemical regulation of the nanocarrier achieves synergistic "aboveground, belowground, and disease" control, providing a more comprehensive approach.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A slow-release insecticide for landscaping, characterized in that: The invention comprises the following components by weight percentage: 5-20% of clothianidin, 1-5% of cyromazine, 1.5-2.5% of metalaxyl, 0.8-1.2% of humic acid, 5-8% of chitosan, 3-4% of polylactic acid, 1.5-2.5% of nano titanium dioxide, 0.5-0.8% of plant-derived additives, and the balance is water.

2. The slow-release insecticide for landscaping according to claim 1, characterized in that: The composition includes the following components by weight percentage: 15% of clothianidin, 5% of cyromazine, 2% of metalaxyl, 0.9% of humic acid, 7.5% of chitosan, 3% of polylactic acid, 2.5% of nano titanium dioxide, 0.6% of plant-derived additives, and the balance is water.

3. The slow-release insecticide for landscaping according to claim 1, characterized in that: The deacetylation degree of the chitosan is 86-95%.

4. The slow-release insecticide for landscaping according to claim 1, characterized in that: The molecular weight of polylactic acid is 25,000-50,000.

5. The slow-release insecticide for landscaping according to claim 1, characterized in that: The molecular weight of chitosan is 50,000-80,000.

6. The method for preparing the slow-release insecticide for landscaping according to any one of claims 1 to 5, characterized in that: S1. Chitosan was dissolved in acetic acid solution to obtain a chitosan solution; clothianidin was dissolved in ethyl acetate and added to the chitosan solution. A CaCl2 solution with a concentration of 0.6-1.0% was added dropwise under stirring at 800-1200 rpm. The cross-linking reaction was carried out for 3-5 hours and the chitosan nanoparticles were obtained by filtration. S2. Polylactic acid was dissolved in dichloromethane, cyromazine was added, sheared at 900-1200 rpm, and ultrasonically emulsified for 10-20 min. A 1-2% Span-80 aqueous solution was added, and dichloromethane was removed by vacuum distillation to obtain polylactic acid microspheres. S3. Mix the chitosan nanoparticles obtained in step S1, the polylactic acid microspheres obtained in step S2, metalaxyl, humic acid, nano-titanium dioxide, and plant-derived additives, add water, and shear emulsify at 1000-1500 rpm for 25-35 min. Adjust the pH to 5.5-6.5 to obtain a slow-release insecticide.

7. The method for preparing a slow-release insecticide for landscaping according to claim 6, characterized in that: The particle size of the polylactic acid microspheres in step S2 is 250-400 nm.

8. The method for preparing a slow-release insecticide for landscaping according to claim 6, characterized in that: The chitosan nanoparticles in step S1 have a particle size of 60-90 nm and an encapsulation efficiency of >92%.

9. The method for preparing a slow-release insecticide for landscaping according to claim 6, characterized in that: The mass concentration of the chitosan solution in step S1 is 1.2-1.8%, and the power of the ultrasound in step S2 is 400-500W.

10. The method for preparing a slow-release insecticide for landscaping according to claim 6, characterized in that: The temperature of the shear emulsification in step S3 is controlled at 20-25°C.

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