A nano liquid spray film forming agent for planting fruits against diseases and pests and a preparation method thereof

Abstract

The application relates to the field of agricultural technology, and discloses a nano liquid-state spraying film-forming agent for disease and pest resistance of fruit planting and a preparation method thereof. The nano liquid-state spraying film-forming agent has good disease and pest resistance effect, has good film-forming property after being sprayed on the leaf blades or fruit surfaces and being air-dried, can well adhere the pesticide on the leaf blades, can improve the utilization rate of the pesticide, and can be used as a long-acting slow-release disease and pest resistance agent. The material preparation method is simple, the raw material cost is low, the material can be preserved for 1-3 months in long-term application, the pesticide residue problem can be solved, and the material can be used for producing green organic food. The nano liquid-state spraying film-forming agent can realize safety, environmental protection and functionality, is harmless to human bodies and the environment while ensuring the fruit preservation effect, and is suitable for orchards, comprehensive fruit and vegetable gardens and the like in humid areas.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of agricultural technology, and particularly relates to a nano-liquid spray film-forming agent for disease and pest resistance of fruit and vegetable planting and a preparation method thereof, which is a nano-liquid spray film-forming agent capable of simultaneously playing a role of disease and pest resistance and promoting crop growth. BACKGROUND

[0002] Mango planting industry in China has a long history and broad development prospects. China's mangoes are mainly planted in the tropical and subtropical regions of the south, especially in Guangdong, Guangxi Zhuang Autonomous Region, Yunnan, Hainan, Fujian and Sichuan provinces. According to statistics, there are more than 300 kinds of mango diseases and pests reported at home and abroad, and nearly 90 new mango diseases and pests have been added in the past 10 years, about 20 of which can cause serious economic losses. There are 1-2 important diseases and pests during the mango sprouting period, flowering period, fruit setting period, etc., which lead to a 10%-30% decrease in yield, seriously affecting the development of the mango industry. Anthracnose is the most common and most harmful fungal disease in mango production. Mango anthracnose is a common disease caused by a fungus, and its main pathogen is Colletotrichum gloeosporioides. This disease can affect mango leaves, flowers, fruits and branches. Small water spots appear on the surface of the fruit at the initial stage, which gradually expand into circular or irregular black spots. These spots may grow larger and merge over time, causing the fruit surface to appear concave or pitted, and the fruit to rot in severe cases. The pathogen of bacterial angular leaf spot is Xanthomonas campestris pv. Mangiferaeindicae. Bacterial angular leaf spot is a disease caused by a bacterium. The symptoms of this disease include black or dark brown spots on the leaves, which gradually enlarge to form angular or irregular patches. Mango fruits infected with the disease show water-stained black spots, with a yellow halo around the edge of the lesion, and in severe cases, the fruit cracks, leading to a decrease in fruit quality, affecting yield and quality, and making it difficult to sell. Mango thrips cause great harm to young fruits, and the larvae will suck the sap of young fruits, causing the fruits to fail to grow normally and reducing the commodity rate. Thrips occur in multiple generations in a year, with overlapping generations, and cause serious damage in fruit orchards with uneven sprouting and in hot and dry weather.

[0003] At present, more than 10 species of thrips have been reported, including Thrips flavus Schrank, Thrips hawaiiensis (Morgan) and so on. Among them, Scirtothrips dorsalis Hood and Thrips hawaiiensis are dominant species. Thrips can cause great damage to the leaves, flower spikes and fruits of mango, and can induce smoke coal disease, flow disease and other diseases, which seriously reduce the yield and quality of mango. Bactrocera dorsalis Hendel is one of the most harmful pests during the fruiting period of mango. Adult females lay eggs in fruits, and the larvae that hatch from the eggs will eat the fruit, causing the fruit to rot and deteriorate. Bactrocera dorsalis mainly feeds on fruits, which is the main factor restricting the export of fresh mangoes. Female flies lay eggs in fruits, and the larvae that hatch from the eggs will eat the fruit, causing the fruit to rot, crack and fall off. During the storage and transportation of fruits, rotting may occur, and maggots may be found in the rotten fruits.

[0004] Mango trees will encounter various diseases during cultivation. During the growth of mangoes, fruits are easily attacked by various diseases. If these diseases are not timely prevented and controlled, they will seriously affect the yield and quality of mangoes. Mango disease control needs to combine agricultural measures and chemical control methods, timely detect and identify diseases, and take scientific and effective control measures to ensure the healthy growth and high yield of mangoes. The application of nano liquid spray film-forming agent in agriculture provides an efficient and environmentally friendly plant protection method. The current research status of nano pesticides shows that significant progress has been made in this field, especially in improving the effectiveness of pesticides, reducing the amount of use, and enhancing the ability to control crop diseases. However, there are also some technical and safety challenges in the research and application of nano pesticides. The durability of nano pesticides may be a concern compared to traditional pesticides. Due to the small particle size and large specific surface area of nano pesticides, they have a high coverage on plant leaves or harmful organisms, which helps to improve the bioavailability of pesticides and reduce the amount of pesticide use. However, this high efficiency may also lead to an increase in the persistence of nano pesticides in the environment, thereby increasing the potential risk to non-target organisms and ecosystems. Currently, nano materials can be used to construct long-acting slow-release systems to match the release characteristics of pesticides with the occurrence patterns of harmful organisms, prolong the duration of efficacy, and reduce the dosage and frequency of pesticide application.

[0005] The application of nano liquid spray film-forming agent on fruits is an effective control method. In-depth research and technological progress provide a feasible solution to the sustainable development of pesticides and the problems exposed in the application of traditional pesticides. Therefore, in-depth research and utilization of nano liquid spray film-forming agent in agriculture is a problem that needs to be solved at present. SUMMARY

[0006] Therefore, the fruit disease prevention needs to combine agricultural measures and chemical control means, timely find and identify diseases, and take scientific and effective control measures to ensure the healthy growth and high yield and quality of fruits. Therefore, the application discloses a nano liquid spray film-forming agent for planting fruits and resisting diseases and pests and a preparation method thereof, which can not only avoid the defects that the effect of nano pesticides is not as persistent as traditional pesticides, and more frequent spraying or higher concentration is needed to maintain the same control effect, but also avoid the defects that pesticides and fertilizers have problems of waste of pesticides, environmental pollution, and short duration of drug effect.

[0007] Further, in order to improve the performance and application effect of the nano pesticide, the polyurethane is combined with the polysaccharide nanoparticles to form a film-forming spray for the fruit, which can provide effective protection measures, improve the quality of the fruit, and has the advantages of environmental protection and controlled release effect, and is an innovative and efficient agricultural technology.

[0008] It should be noted that the polysaccharide compound is a biodegradable polymer, has good biocompatibility and low toxicity, and is widely used in the agricultural field as a carrier or additive of pesticides. In agriculture, it can be used as a plant growth regulator, a soil conditioner and a pesticide carrier, can improve the disease resistance of plants, and promote the growth of crops. Polyurethane is a multifunctional synthetic material, has excellent physical properties and chemical stability, can form a thin film with good wrapping and protection, covers the surface of plants or fruits, prevents pathogenic microorganisms, pests and external factors, and helps to protect the growth and development of crops. The polyurethane film has strong durability and weather resistance, can remain on the surface of plants or soil for a long time, provides sustained protection effect, and reduces the need for frequent pesticide application. The polyurethane material has biodegradability and can be degraded by microorganisms under certain conditions, reduces pollution to the environment, and meets the concept of green agriculture. Polyurethane has the advantages of wrapping, durability, controlled release, biodegradability and synergistic effect in agriculture, can be combined with polysaccharide compounds to form a composite material, has the synergistic effects of antibacterial, antioxidant and growth promotion, and helps to improve crop yield and quality. It can be used as an important agricultural material to improve crop yield, protect the environment and promote sustainable agricultural development.

[0009] In order to achieve the above object, the application adopts the following technical scheme:

[0010] The first object of the application is to provide a nano liquid spray film-forming agent for planting fruits and resisting diseases and pests, which mainly comprises the following raw materials in mass percentage:

[0011] Polymer compound 2-20%, crosslinking agent 0.5-5%, surfactant 0.1-5%, insecticide 0.1-10%, fungicide 0.1-10%, isocyanate 0.5-3%, polyol 0.5-7.5%, hydrophilic chain extender 0.1-3%, neutralizing agent 0.1-5%, antioxidant 0.1-5%, light stabilizer 0.1-1%, organic solvent 0.01-10%, water balance.

[0012] Optionally, the nano-liquid spray film forming agent mainly comprises the following raw materials in mass percentage:

[0013] Polymer compound 2-20%, crosslinking agent 0.5-5%, surfactant 0.1-5%, insecticide 0.1-10%, fungicide 0.1-10%, isocyanate 0.5-3%, polyol 0.5-7.5%, hydrophilic chain extender 0.1-3%, neutralizing agent 0.1-5%, antioxidant 0.1-5%, light stabilizer 0.1-1%, organic solvent 0.01-10%, water balance.

[0014] Further, the nano-liquid spray film forming agent mainly comprises the following raw materials in mass percentage:

[0015] Polymer compound 5%, crosslinking agent 1.2%, surfactant 0.2%, insecticide 0.4%, fungicide 0.15%, isocyanate 0.8%, polyol 1.5%, hydrophilic chain extender 0.2%, neutralizing agent 0.7%, antioxidant 0.5%, light stabilizer 0.1%, organic solvent 0.01%, water balance.

[0016] Further, the polymer compound is one or a combination of several of chitosan, sodium alginate, quaternary ammonium chitosan, oxidized carboxymethyl chitosan, quaternary ammonium alginate, and quaternary ammonium cellulose.

[0017] Further, the organic solvent is one or a combination of several of methanol, ethanol, propanol, and acetonitrile.

[0018] Further, the crosslinking agent is any one of trimethylolpropane, sodium tripolyphosphate, genipin, glutaraldehyde, and diethylenetriamine.

[0019] Further, the surfactant is any one of lecithin, saponin, Tween 80, and polyethylene glycol.

[0020] Further, the isocyanate is any one of 4,4'-diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and 1,6-hexane diisocyanate.

[0021] Further, the polyol is any one of castor oil-based polyol, soybean oil-based polyol, fructose-based polyol, lactic acid-based polyol, and polycaprolactone.

[0022] Further, the neutralizing agent is any one of ammonia water, potassium hydroxide.

[0023] Further, the hydrophilic chain extender is any one of dimethylol propionic acid, citric acid, succinic acid, glycerol, 1,4-butanediol, 1,3-propanediol, glycerol.

[0024] Further, the insecticide is any one of lambda-cyhalothrin, emamectin benzoate, acetamiprid, ivermectin, spinosad, methoxychlor, trichlorphon, and the fungicide is any one of azoxystrobin, kasugamycin, prochloraz, pyraclostrobin, copper hydroxide, fluazinam.

[0025] A second object of the present application is to provide a preparation method of the nano liquid spray film-forming agent for disease and pest resistance of fruit planting.

[0026] A preparation method of a nano liquid spray film-forming agent for disease and pest resistance of fruit planting, comprising the following steps:

[0027] (1) dissolving a polysaccharide compound in a solution to prepare a solution; then adding a surfactant, a fungicide and an insecticide to fully stir and mix to obtain a liquid medicine;

[0028] It should be noted that the solution includes deionized water, low-concentration saline, 1% acetic acid water, dilute ethanol, dilute isopropyl alcohol, dilute hydrochloric acid (pH < 6), and different solutions can be selected according to the type of polysaccharide compound, such as chitosan (1% acetic acid water, 1% acetic acid water, etc. Acidic solution), quaternary ammonium fiber (35-60℃, 1% acetic acid water, etc. Acidic solution), oxidized carboxymethyl chitosan (neutral or alkaline, low-concentration saline), quaternary ammonium alginate (dilute ethanol), quaternary ammonium chitosan (dilute solution of ethanol, isopropyl alcohol) and the like

[0029] (2) using a dropwise method, slowly dropping a crosslinking agent solution into the liquid medicine of step (1) in stirring through a syringe or dropper to form nanoparticles; or using an ultrasonic method, using ultrasonic self-assembly to uniformly disperse the polysaccharide compound molecules in the solution to form nanoparticles; continue to stir the mixed solution, maintain 30-40℃, and perform crosslinking reaction to form a stable nano solution;

[0030] (3) mixing isocyanate and polyol in proportion, heating to react to generate a prepolymer; cooling the prepolymer, adding a hydrophilic chain extender to perform chain extension reaction to form an aqueous polyurethane prepolymer; adding a neutralizing agent to adjust the pH value to 6.0-6.9, and gradually adding the neutralized prepolymer into water, high-speed stirring for 2h to form a stable aqueous dispersion; after all reactions are completed, completely removing residual solvents at 40℃ through a rotary evaporator;

[0031] (4) Polyurethane is added as an additive to the nano solution with pesticide as the core and sugar as the carrier prepared in step (2) to increase the adhesion of the final product to the surface of plants and pests, enhance the drug loading performance, targeted adhesion, and stability of the active ingredients, and greatly reduce environmental pollution by enhancing the physical and chemical properties of the product.

[0032] Furthermore, the method of using the nano-liquid spray film-forming agent for disease and pest resistance in fruit cultivation disclosed in this invention is as follows:

[0033] Properly protect the plant surface from pests and diseases by directly spraying the prepared pest-resistant nano-liquid spray film-forming agent onto the surface of the plant and pests. After the sprayed liquid dries, a composite film forms, covering the fruit surface. The mass ratio of the pest-resistant nano-liquid spray film-forming agent to water in this invention is 1:50-500.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1) This invention provides a nano-liquid spray film-forming agent for fruit that simultaneously provides disease and insect resistance. It exhibits excellent film-forming properties and long-lasting protective effects while reducing the use of pesticides and fertilizers, thus lowering environmental pollution. The nanoparticles have a controlled-release function, allowing for the slow release of phytoprotective agents, extending the duration of the protective effect and reducing the need for frequent spraying. The addition of polyurethane enhances the adhesion of the spray liquid, enabling it to form a more uniform and stable film layer on the fruit surface, improving the protective effect. Furthermore, its application does not pollute the environment, aligning with the development trend of green agriculture.

[0036] Polyurethane-polysaccharide composite films can form on the surface of fruits, providing a protective film. This protective film can reduce water evaporation and respiration on the fruit surface, prevent pathogens, climatic factors and mechanical damage from harming the fruit, delay fruit aging and decay, and help improve fruit quality and shelf life.

[0037] 2) The nano-liquid spray film-forming agent in this invention uses a water-soluble solvent system, which reduces the emission of volatile organic compounds and achieves low VOCs emissions; low-toxicity or non-toxic raw materials are selected to improve the biocompatibility and safety of the product; renewable resources and bio-based raw materials are used to reduce the environmental burden and increase degradability; the composition and structure are designed to ensure degradability in the natural environment; and the coating has breathability, waterproofness and antibacterial properties, with advantages such as good comprehensive prevention and control effect, strong durability and convenient operation, and is suitable for the prevention and control of diseases and pests and the promotion of growth of various crops. Detailed Implementation

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of them. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0039] The special word "embodiment" in this application is not necessarily interpreted as superior or better than other embodiments as explained by "exemplary". In the performance index test of the embodiments of the present application, unless otherwise specified, the conventional test method in the art is adopted. It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the disclosure of the present application.

[0040] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as generally understood by those skilled in the art to which the present application belongs; as the test methods and technical means not specially noted in the present application refer to the experimental methods and technical means generally used by those skilled in the art.

[0041] In order to better illustrate the content of the present application, a large number of specific details are given in the specific embodiments below. Those skilled in the art should understand that the present application can also be implemented without some specific details. In the embodiments, some methods, means, instruments, equipment and the like which are well known to those skilled in the art are not described in detail, in order to highlight the main idea of the present application.

[0042] The technical features disclosed in the embodiments of the present application can be combined in any way without conflict, and the technical solutions obtained belong to the disclosure of the embodiments of the present application.

[0043] The present application discloses a kind of nano liquid spray film forming agent for planting fruit disease and pest resistance and preparation method thereof.

[0044] In order to better understand the present application, the present application is further specifically described by the following embodiments, but it should not be understood as limiting the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above disclosure are also considered to fall within the scope of protection of the present application.

[0045] Example 1

[0046] 1) 50.0 g of chitosan was dissolved in 1000 mL of water, 2.0 g of polyethylene glycol was added under stirring, 4.0 g of kasugamycin and 4.0 g of acetamiprid dissolved in 4 mL of acetonitrile were added to the above solution and stirred for 0.5 h, 5 mL of glutaraldehyde solution was slowly added dropwise to the stirred drug solution by syringe, and stirred for 2 h to form nanoparticles.

[0047] 2) In a reaction kettle, 4.0 g of 4,4'-diphenylmethane diisocyanate and 3.0 g of castor oil-based polyol were mixed in proportion, and a prepolymer was generated by heating reaction. After cooling the prepolymer, 7.0 g of citric acid was added to perform chain extension reaction, forming an aqueous polyurethane prepolymer. Subsequently, 7 mL of ammonia water was added to adjust the pH value to 6.0-6.9, and all reactions were completed, after which the solvent was evaporated at 40°C by a rotary evaporator.

[0048] 3) The nanosolution obtained in step 1) and the polyurethane of step 2) were uniformly mixed, thereby obtaining a nanoliquid spray film-forming agent.

[0049] Example 2

[0050] 1) 50.0 g of sodium alginate was dissolved in 1000 mL of water, and 0.8 g of Tween 80 was added under stirring. 4.0 g of azoxystrobin and 4.0 g of lambda cyhalothrin dissolved in 4 mL of acetonitrile were added to the above solution, stirred for 0.5 h, and then 7.4 mL of sodium tripolyphosphate was added and ultrasonicated for 0.5 h. Ultrasonic self-assembly was used to uniformly disperse the polysaccharide compound molecules in the solution to form nanoparticles.

[0051] 2) In a reaction kettle, 6.0 g of dicyclohexylmethane diisocyanate and 3.0 g of polycaprolactone were mixed in proportion, and a prepolymer was generated by heating reaction. After cooling the prepolymer, 8.2 g of 1,4-butanediol was added to perform chain extension reaction, forming an aqueous polyurethane prepolymer. 7.0 mL of ammonia water was added to adjust the pH value to 6.0-6.9, and all reactions were completed, after which the solvent was evaporated at 40°C by a rotary evaporator.

[0052] 3) The nanosolution obtained in step 1) and the polyurethane of step 2) were uniformly mixed, thereby obtaining a nanoliquid spray film-forming agent.

[0053] Example 3

[0054] 1) 62.0 g of quaternary ammonium cellulose was dissolved in 1000 mL of water, and 3.2 g of lecithin was added under stirring. 4.0 g of pyraclostrobin and 4.0 g of emamectin benzoate dissolved in 4 mL of methanol were added to the above solution, stirred for 0.5 h, and then 5 mL of trimethylolpropane was added and ultrasonicated for 1 h. Ultrasonic self-assembly was used to uniformly disperse the polysaccharide compound molecules in the solution to form nanoparticles.

[0055] 2) In a reaction kettle, 4.0 g of adipic acid diisocyanate and 3.0 g of castor oil-based polyol were mixed in proportion, and a prepolymer was generated by heating reaction. After cooling the prepolymer, 8.2 g of 1,3-propanediol was added to perform chain extension reaction, forming an aqueous polyurethane prepolymer. 15.0 mL of potassium hydroxide was added to adjust the pH value to 6.0-6.9, and all reactions were completed, after which the solvent was evaporated at 40°C by a rotary evaporator.

[0056] 3) The nanosolution obtained in step 1) and the polyurethane of step 2) are mixed homogeneously, i.e. a nanoliquid spray film forming agent is obtained.

[0057] Example 4

[0058] 1) 50.0 g of chitosan is dissolved in 1000 mL of water, 3.0 g of saponin is added under stirring. 4.0 g of methoxychlor and 4.0 g of prochloraz dissolved in 4 mL of propanol are added to the above solution and stirred for 0.5 h. 6.4 mL of diethylene triamine is slowly added dropwise to the stirred solution through a syringe, and stirred for 2 h to form nanoparticles.

[0059] 2) 7.7 g of adipic acid diisocyanate and 6.3 g of fructose-based polyol are mixed in a reaction kettle in proportion, and a prepolymer is generated by heating reaction. After cooling the prepolymer, 7.5 g of glycerol is added to perform chain extension reaction, and an aqueous polyurethane prepolymer is formed. 7.0 mL of ammonia water is added to adjust the pH value to 6.0-6.9, and all reactions are completed, after which the solvent is evaporated at 40°C by a rotary evaporator.

[0060] 3) The nanosolution obtained in step 1) and the polyurethane of step 2) are mixed homogeneously, i.e. a nanoliquid spray film forming agent is obtained.

[0061] Example 5

[0062] 1) 50.0 g of quaternized alginic acid is dissolved in 1000 mL of water, 5.0 g of saponin is added under stirring. 4.0 g of polyoxin and 4.0 g of copper hydroxide dissolved in 7 mL of ethanol are added to the above solution and stirred for 0.5 h, and 5 mL of genipin is added to perform ultrasonic for 1 h, and the polysaccharide compound molecules are uniformly dispersed in the solution by ultrasonic self-assembly to form nanoparticles.

[0063] 2) 4.0 g of 4,4'-diphenyl methane diisocyanate and 3.8 g of lactic acid-based polyol are mixed in a reaction kettle in proportion, and a prepolymer is generated by heating reaction. After cooling the prepolymer, 12.0 g of glycerol is added to perform chain extension reaction, and an aqueous polyurethane prepolymer is formed. 7.0 mL of ammonia water is added to adjust the pH value to 6.0-6.9, and all reactions are completed, after which the solvent is evaporated at 40°C by a rotary evaporator.

[0064] 3) The nanosolution obtained in step 1) and the polyurethane of step 2) are mixed homogeneously, i.e. a nanoliquid spray film forming agent is obtained.

[0065] Example 6

[0066] 1) Dissolve 50.0 g of chitosan in 1000 mL of water, and add 2.0 g of Tween 80 under stirring. Add 4.0 g of ivermectin and 4.0 g of fluazinam dissolved in 5 mL of acetonitrile to the above solution, and stir for 0.5 h. Slowly drop 5 mL of trimethylolpropane into the stirred solution through a syringe, and stir for 2 h to form nanoparticles.

[0067] 2) Mix 4.0 g of dicyclohexylmethane diisocyanate and 3.0 g of polycaprolactone in a reaction kettle, and heat to react to form a prepolymer. After cooling the prepolymer, add 8.2 g of 1,4-butanediol to perform chain extension, and form an aqueous polyurethane prepolymer. Add 7.0 mL of ammonia water to adjust the pH to 6.0-6.9, and evaporate the solvent at 40°C by a rotary evaporator after all reactions are completed.

[0068] 3) Uniformly mix the nanoparticle solution obtained in step 1) and the polyurethane of step 2) to obtain a nano liquid spray film forming agent.

[0069] Example 7

[0070] 1) Dissolve 40.0 g of oxycarbomethyl chitosan in 1000 mL of water, and add 2.8 g of polyethylene glycol under stirring. Add 4.0 g of dipterex and 4.0 g of fluazinam dissolved in 5 mL of methanol to the above solution, and stir for 0.5 h. Slowly drop 5 mL of glutaraldehyde solution into the stirred solution through a syringe, and stir for 2 h to form nanoparticles.

[0071] 2) Mix 4.0 g of dicyclohexylmethane diisocyanate and 3.0 g of soybean oil-based polyol in a reaction kettle, and heat to react to form a prepolymer. After cooling the prepolymer, add 8.2 g of dimethylolpropionic acid to perform chain extension, and form an aqueous polyurethane prepolymer. Add 7.0 mL of ammonia water to adjust the pH to 6.0-6.9, and evaporate the solvent at 40°C by a rotary evaporator after all reactions are completed.

[0072] 3) Uniformly mix the nanoparticle solution obtained in step 1) and the polyurethane of step 2) to obtain a nano liquid spray film forming agent.

[0073] Example 8

[0074] 1) Dissolve 60.0 g of quaternary ammonium cellulose in 1000 mL of water, and add 2.2 g of Tween 80 under stirring. Add 4.0 g of spinosad and 4.0 g of pyraclostrobin dissolved in 5 mL of acetonitrile to the above solution, and stir for 0.5 h. Add 5 mL of genipin to perform ultrasonic for 1 h, and use ultrasonic self-assembly to uniformly disperse the polysaccharide compound molecules in the solution to form nanoparticles.

[0075] 2) In a reaction kettle, 4.0 g of dicyclohexyl methane diisocyanate and 3.0 g of castor oil based polyol were mixed in proportion, heated to react to form a prepolymer. After cooling the prepolymer, 8.2 g of succinic acid was added to carry out chain extension reaction to form an aqueous polyurethane prepolymer. 7.0 mL of ammonia water was added to adjust the pH value to 6.0-6.9, and all reactions were completed, and the solvent was removed by rotary evaporator at 40°C.

[0076] 3) The nano solution obtained in step 1) and the polyurethane of step 2) were uniformly mixed to obtain a nano liquid spray film forming agent.

[0077] In order to further prove the beneficial effects of the present application and better understand the present application, the technical features disclosed in the present application are further illustrated by the following experiments, but it should not be understood as limiting the present application. Other improvements without creative work made by those skilled in the art according to the above disclosure are also considered to fall within the scope of protection of the present application.

[0078] Experiment 1: Control effect of nano liquid spray film forming agent on B. dorsalis

[0079] 1) Method of applying pesticide to crops and test method

[0080] The field efficacy test was carried out in Yangdong District, Guangdong Province. The prepared nano liquid spray film forming liquid of embodiments 1-8 was sprayed on the surface of mango fruits to form a uniform film covering. After the spray liquid was dried, a polyurethane-chitosan composite film was formed and covered on the surface of the mango fruits. Selective test: 20 healthy female insects of 20-25 days old at the peak of oviposition were randomly selected and introduced into the test cage (30 cm x 30 cm x 30 cm) with adult insect feed and water, and the test insects were allowed to adapt for 24 h. The positive control group was sprayed with commercially available B. dorsalis control pesticide. The control group was sprayed with an equal amount of water. After natural air drying, the mangoes in the treatment group and the control group were placed in one test cage, and the test was repeated 3 times. The mangoes in the test cage were taken out after 24 h, and the number of oviposition holes and the amount of oviposition on the fruits were checked and recorded, and the oviposition repellency rate of each pesticide was calculated.

[0081] Investigation method:

[0082] Non-selective test: The prepared nano liquid spray film forming liquid was sprayed on the surface of mango fruits to form a uniform film covering, and after natural air drying, it was placed in a preservation box with temperature control at (26±1)℃ and humidity control at 60%±10%. The control group was sprayed with an equal amount of water, and the mangoes in the treatment group and the control group were placed in different test cages, and the test was repeated 3 times. The number of oviposition holes and the amount of oviposition on the fruits were checked and recorded, and the oviposition repellency rate was calculated.

[0083] Selectivity test: mangoes in treatment group and control group were put into the same test cage, and other conditions were the same as in the non-selectivity test. The oviposition repellency rate was calculated.

[0084] The calculation formula of oviposition repellency rate is as follows:

[0085]

[0086] (2) Test results

[0087] Table 1 Effect of anti-disease and insect prevention and control of nano liquid spray film forming agent

[0088]

[0089]

[0090] Experiment two: effect of nano liquid spray film forming agent on thrips control

[0091] (1) Preparation method and test method

[0092] Field efficacy test was carried out in Yangdong District, Guangdong Province. The nano liquid spray film forming agent obtained from cases 1-8 was used to form a uniform film. After the spray liquid was dried, a polyurethane-chitosan composite film was formed on the surface of the mango tree to achieve the control effect. The positive control selected a certain brand of registered pesticide for thrips control on the market, which was diluted 50 times and sprayed on the branches to achieve the control effect. The control group was not treated. The insect population base was investigated before treatment, and the thrips population was investigated 7 and 14 days after treatment. The investigation method was as follows: 3 trees were selected in each plot, and 1 flower cluster with consistent growth period was randomly selected in each of the 5 directions of each tree. The flower cluster was lightly tapped 3 times, and the thrips number was collected and counted using a tray (paved with coordinate paper). The insect population reduction rate and control effect were calculated, and the calculation formulas were as follows: ① and ②.

[0093]

[0094] (2) Test results

[0095] Table 2 Control effect of nano liquid spray film forming agent on thrips 7 days after treatment

[0096]

[0097]

[0098] Table 3 Control effect of nano liquid spray film forming agent on thrips 14 days after treatment

[0099]

[0100] Experiment three: control effect of nano liquid spray film forming agent on anthracnose disease

[0101] (1) Preparation method and test method

[0102] The mango samples were treated as follows. The nano liquid spray film forming agent obtained in Example 1-8 was diluted 50 times and sprayed on the mango fruits after the disease was contracted, and then dried at 25°C. The nano liquid spray film forming agent obtained in Example 1-8 was allowed to form a uniform thin film covering. After the spray liquid was dried, a polyurethane-chitosan composite film was formed on the surface of the mango samples to achieve the control effect. The positive control was a certain brand of registered pesticide for controlling anthracnose disease on the market, which was diluted to the same multiple and sprayed on the samples to achieve the control effect. The blank control group (CK): water was sprayed on the mango fruits after the disease was contracted, and then dried. The treated mangoes were placed in a (25±1) °C storage for 7 days, and 12 mangoes were extracted from each group for mixed determination. The anthracnose spots and the inhibition of anthracnose by different treatments were observed. According to the anthracnose spot area ratio, it was divided into 4 levels: no spot was 0 level; spot area ratio less than 10% was 1 level, spot area ratio 10%-20% was 2 level, spot area ratio 20%-50% was 3 level; and spot area ratio greater than 50% was 4 level.

[0103] Calculation formula:

[0104]

[0105] (2) Test results

[0106] Table 4 Anthracnose disease occurrence 7 days after the first treatment of nano liquid spray film forming agent

[0107]

[0108] Experiment four: control effect of nano liquid spray film forming agent on bacterial angular leaf spot

[0109] (1) Preparation method and test method

[0110] The field efficacy test was carried out in Yangdong District, Guangdong Province, with initial occurrence of bacterial angular leaf spot. The method was carried out in accordance with the test guidelines of GB / T 17980.98-2004, and a backpack electric sprayer was used for spraying. The test agent was the nano liquid spray film forming agent prepared according to the ratio of Example 1-9, and water was used as the control. Each treatment plot had 5 plants, and there were 3 repetitions. The spraying was started in mid-October 2018, and the spraying was carried out once every 7 days, for a total of 3 times. Fifteen and 30 days after the last spraying, 3 plants were investigated at the fixed point in each plot, 5 branches were selected according to different directions of the mango crown layer for each plant, the total leaf number and the number of diseased leaves at each level were recorded, the disease index was calculated, and the control effect of the agent was calculated.

[0111] Disease severity was rated as follows, 0: no lesion; 1: lesion area was less than 5% of the whole leaf area; 3: lesion area was 6-15% of the whole leaf area; 5: lesion area was 16-25% of the whole leaf area; 7: lesion area was 26-50% of the whole leaf area; 9: lesion area was more than 50% of the whole leaf area. The formula for calculating the efficacy of the drug was:

[0112]

[0113] Table 5 Field control effect of nano liquid spray film forming agent on bacterial angular spot of mango

[0114]

[0115] The foregoing description of the disclosed embodiments enables a person skilled in the art to carry out or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the present application will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A nano liquid spray film forming agent for planting fruits resistant to diseases and pests, characterized by, The nano liquid spray film forming agent mainly comprises the following raw materials in percentage by mass: polysaccharide compound 2-20%, crosslinking agent 0.5-5%, surfactant 0.1-5%, insecticide 0.1-10%, fungicide 0.1-10%, isocyanate 0.1-5%, polyol 0.5-10%, hydrophilic chain extender 0.1-5%, neutralizing agent 0.1-10%, antioxidant 0.1-7%, light stabilizer 0.1-6%, organic solvent 0.01-20%, and water in balance; The preparation method of the nano liquid spray film forming agent for disease and pest resistance of fruit planting comprises the following steps: (1) dissolving polysaccharide compound in a solution to prepare a solution; then adding surfactant, fungicide and insecticide and stirring uniformly to obtain a liquid medicine; (2) using dropwise addition method, slowly adding crosslinking agent solution into the liquid medicine of step (1) through a syringe or dropper to form nanoparticles; or using ultrasonic method, uniformly dispersing polysaccharide compound molecules in the solution by ultrasonic self-assembly to form nanoparticles; continuing to stir the mixed solution, maintaining at 30-40℃, and performing crosslinking reaction to form a stable nano solution; (3) mixing isocyanate and polyol according to a proportion, heating and reacting to generate a prepolymer; cooling the prepolymer, adding a hydrophilic chain extender to perform chain extension reaction, forming a water-based polyurethane prepolymer; adding a neutralizing agent to adjust the pH value to 6.0-6.9, and gradually adding the neutralized prepolymer into water, and stirring at high speed for 2h to form a stable water-based dispersion; after all reactions are completed, completely removing residual solvent at 40℃ through a rotary evaporator; (4) adding polyurethane as an additive into the nano solution prepared in step (2) with pesticide as a core and sugar-based carrier to increase the adhesion of the final product on the surface of plants and harmful organisms, enhance the material drug loading performance, targeted adhesion, effective ingredient stability, and greatly reduce environmental pollution by enhancing the physical and chemical properties of the product.

2. The nano liquid spray film forming agent for planting fruits against diseases and pests according to claim 1, characterized in that, The nano liquid spray film forming agent mainly comprises the following raw materials in percentage by mass: polysaccharide compound 2-20%, crosslinking agent 0.5-5%, surfactant 0.1-5%, insecticide 0.1-10%, fungicide 0.1-10%, isocyanate 0.5-3%, polyol 0.5-7.5%, hydrophilic chain extender 0.1-3%, neutralizing agent 0.1-5%, antioxidant 0.1-5%, light stabilizer 0.1-1%, organic solvent 0.01-10%, and water in balance.

3. The nano liquid spray film forming agent for planting fruit resistance to diseases and pests according to claim 1 or 2, characterized in that, The nano liquid spray film forming agent mainly comprises the following raw materials in percentage by mass: polysaccharide compound 5%, crosslinking agent 1.2%, surfactant 0.2%, insecticide 0.4%, fungicide 0.15%, isocyanate 0.8%, polyol 1.5%, hydrophilic chain extender 0.2%, neutralizing agent 0.7%, antioxidant 0.5%, light stabilizer 0.1%, organic solvent 0.01%, and water in balance.

4. The nano liquid spray film forming agent for planting fruits against diseases and pests according to claim 1, characterized by, The polysaccharide compound is one or a combination of several of chitosan, sodium alginate, quaternary ammonium chitosan, oxidized carboxymethyl chitosan, quaternary ammonium alginate, and quaternary ammonium cellulose, and the organic solvent is one or a combination of several of methanol, ethanol, propanol, and acetonitrile.

5. The nano liquid spray film forming agent for planting fruits against diseases and pests according to claim 1, characterized in that, The crosslinking agent is any one of trimethylolpropane, sodium tripolyphosphate, genipin, glutaraldehyde, and diethylenetriamine, and the surfactant is any one of lecithin, saponin, Tween 80, and polyethylene glycol.

6. The nano liquid spray film forming agent for planting fruits against diseases and pests according to claim 1, characterized by, The isocyanate is any one of 4,4'-diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and 1,6-hexane diisocyanate, and the polyol is any one of castor oil-based polyol, soybean oil-based polyol, fructose-based polyol, lactic acid-based polyol, and polycaprolactone.

7. The nano liquid spray film forming agent for planting fruits against diseases and pests according to claim 1, characterized by, The neutralizing agent is any one of ammonia and potassium hydroxide.

8. The nano liquid spray film forming agent for planting fruits against diseases and pests according to claim 1, characterized by, The hydrophilic chain extender is any one of dimethylol propanoic acid, citric acid, succinic acid, glycerol, 1,4-butanediol, 1,3-propanediol, and glycerol.

9. The nano liquid spray film forming agent for planting fruits against diseases and pests according to claim 1, characterized by, The insecticide is any one of lambda-cyhalothrin, emamectin benzoate, acetamiprid, ivermectin, spinosad, methoxychlor, and trichlorphon, and the fungicide is any one of azoxystrobin, kasugamycin, prochloraz, pyraclostrobin, copper hydroxide, and fluazinam.

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