Insecticidal and bactericidal method for plants based on intensive pulse light

Abstract

The invention relates to the technical field of plant protection, and discloses an intensive pulse light-based insecticidal and bactericidal method for plants, which comprises the following steps: preparing a liquid system containing nanoscale inorganic particles with high reflectivity and strong scattering ability, atomizing the liquid system to form liquid beads to be attached to the surfaces of the plants, and irradiating with intensive pulse light to obtain the insecticidal and bactericidal composition for the plants. Through the reflection and scattering of the liquid beads and the reflection effect of the particle interface, the strong light forms a multi-angle composite light field on the surface and the internal hidden part of the plant, so that the efficient physical inactivation of the polypide and pathogenic microorganisms is realized. The nanoparticles can be aluminum oxide, zirconium oxide or hollow silicon dioxide microspheres, and a dispersing agent, a stabilizing agent, a light absorption inhibitor and auxiliary liquid can be added into the liquid system to enhance the adhesiveness and light transmission performance of the liquid beads. The method does not need to use chemical pesticides, has the characteristics of uniform protection, efficient effect, no residue and environmental friendliness, and is suitable for green prevention and control of fruit trees, vegetables and other plants.

Description

Technical Field

[0001] This invention belongs to the field of plant protection technology, and in particular relates to a method for killing insects and bacteria on plant surfaces based on the principle of light reflection and scattering, which is especially suitable for the green protection of fruit trees, vegetables and ornamental plants. Background Technology

[0002] Currently, the most widely used methods of pest and fungicide control in agricultural production rely primarily on the spraying of chemical agents, such as organophosphates, carbamates, pyrethroid insecticides, and various chemical fungicides. While these chemical control methods can effectively control pests and diseases in the short term, their long-term use has led to significant environmental and food safety problems. Residues of chemical pesticides can cause excessive levels of harmful components in fruits, disrupt the balance of the ecosystem, and cause pollution of soil, water bodies, and non-target organisms, making it difficult for agricultural products to meet the safety standards for "green food" or "organic food."

[0003] Furthermore, traditional spray-type pesticides are limited by plant structure, making it difficult to apply evenly to areas such as the underside of leaves, the base of petioles, hidden parts of fruits, or internal cavities of plants. These areas are often key breeding grounds for pests and diseases, but existing pesticides often fail to reach them due to gravity settling, limited spray diffusion angles, or large contact angles. This results in uneven insecticidal and fungicidal effects, allowing pests and diseases to survive and reproduce in hidden areas, leading to incomplete control and high recurrence rates.

[0004] In recent years, some studies have attempted to replace chemical pesticides with physical methods (such as ultraviolet irradiation, plasma, and ozone treatment). However, these methods still suffer from problems such as limited range of action, light shading, high energy consumption, and plant epidermal burns, and have not yet formed a stable, low-cost, and widely applicable solution. Especially in the complex canopy structure of plants, light is often difficult to distribute evenly, leading to insufficient local protection.

[0005] Therefore, how to develop a green technology solution that can achieve uniform irradiation on the surface and hidden parts of plants, enhance the bactericidal and insecticidal effects by utilizing the reflection and scattering of light, and at the same time avoid environmental pollution and chemical residues has become a technical problem to be solved in the field of plant protection technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of environmental pollution and high residue risk associated with chemical pesticides in existing technologies, as well as the uneven action of traditional light and physical control methods in complex plant canopies. This invention provides a plant insecticidal and fungicidal method based on pulsed intense light. To achieve the above objective, the technical solution of this invention is as follows:

[0007] A method for insecticidal and fungicidal treatment of plants based on pulsed intense light, characterized by comprising the following steps:

[0008] S1. Prepare a liquid system, wherein the liquid system is a stable suspension containing a component that enhances the uniform distribution of the light field, and the component that enhances the uniform distribution of the light field is a nano-sized inorganic particle with high reflectivity and strong light scattering capability.

[0009] S2. Atomize the liquid system so that the liquid adheres to the plant surface in the form of droplets;

[0010] S3. Pulsed intense light is used to irradiate liquid droplets on the plant surface. By utilizing the reflection from the surface of the liquid droplets, the multi-angle scattering inside the liquid droplets, and the interfacial reflection of the light-reflecting components, the pulsed intense light forms a multi-directional light field distribution on the plant surface to kill insects and microorganisms attached to the plant surface.

[0011] Preferably, the component that enhances the uniform distribution of the light field is selected from hollow silica microspheres, zirconia nanoparticles, or alumina nanoparticles.

[0012] Preferably, the liquid system further contains a light absorption inhibitor selected from glycerol, dimethyl silicone oil, or a combination thereof. The light absorption inhibitor is used to reduce the absorption loss of the liquid system to pulsed intense light and to increase light transmittance.

[0013] Preferably, the wavelength range measured by an integrating sphere ultraviolet-visible-near-infrared spectrometer is 200–1100 nm, and the average reflectivity of the nanoscale inorganic particles in the liquid system to pulsed intense light is not less than 80%; the atomization process is achieved through an ultrasonic nozzle or an electrostatic atomization device, the viscosity of the suspension is controlled at 1.0–3.0 mPa·s, and the droplet size is 10–200 μm to ensure that the droplets form a uniformly distributed reflective layer on the plant surface; the pulsed intense light irradiation is achieved through a mobile light source, an array light source, or a robotic irradiation device to improve the coverage and irradiation uniformity.

[0014] Furthermore, the liquid system also contains an auxiliary liquid, which is glycerol or ethylene glycol, and the amount of the auxiliary liquid in the liquid system is 0.5–10 wt%. The auxiliary liquid is used to improve the uniformity of the liquid droplets, reduce the evaporation rate, enhance the adhesion of the liquid droplets, or improve the stability of the liquid droplets.

[0015] Furthermore, the wavelength range of the pulsed intense light is 200–1100 nm, the pulse width is 100 μs–10 ms, and the single-shot energy density is 0.5–10 J / cm².

[0016] Preferably, the preparation steps of the suspension containing alumina (Al2O3) nanoparticles include:

[0017] Step 1: Add dispersant and stabilizer to deionized water and stir until homogeneous to form a dispersion medium;

[0018] Step 2: Slowly add alumina nanoparticles while stirring, and treat with ultrasound for 10-30 minutes to ensure uniform dispersion of alumina particles.

[0019] St3, adjust the pH of the system to between 6 and 8 to reduce particle aggregation;

[0020] St4. Add an appropriate amount of thickener and / or surfactant to obtain a stable alumina nanoparticle suspension with stable viscosity and a settling velocity of less than 0.5 mm / 24h.

[0021] Further, in step St1, the dispersant is preferably polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP); the stabilizer is preferably sodium polyacrylate or lignin sulfonate; the surfactant is preferably alkyl glycoside, Tween-20, or organosilicon; the thickener is preferably xanthan gum or sodium carboxymethyl cellulose; in step St2, the alumina nanoparticles have an average particle size of 50–150 nm; and the alumina nanoparticle suspension accounts for 0.5–5 wt% of the total liquid system.

[0022] Preferably, the preparation steps of the suspension containing zirconium oxide nanoparticles include:

[0023] Ste1. A mixed solvent of ethanol and deionized water in a volume ratio of 1:2 to 4 is used as the dispersion medium.

[0024] Ste2, add 0.1-1.0 wt% of anionic dispersant to the dispersion medium and stir until homogeneous;

[0025] Ste3. Under stirring conditions, zirconium oxide nanoparticles are gradually added and ultrasonically dispersed for 10 to 30 minutes to ensure uniform dispersion of the particles.

[0026] Ste4. Adjust the pH of the system to 7-9 and add an interface regulator to improve the adhesion and stability of the droplets to the target surface, thereby obtaining a stable zirconia nanoparticle suspension.

[0027] Further, in step Ste2, the anionic dispersant is selected from one or more of sodium lignosulfonate, naphthalene sulfonate condensate, sodium polyacrylate, or sodium carboxymethyl cellulose; in step Ste4, the interface modifier is selected from one or more of silane coupling agents, organosilicon spreading agents, or aluminate coupling agents, and the amount of the interface modifier is 0.01–0.2 wt%; in step Ste3, the average particle size of the zirconia nanoparticles is 10–50 nm; and the zirconia nanoparticle suspension accounts for 0.2–3 wt% of the total liquid system.

[0028] Organosilicon surface modifiers are a specific type of surfactant used to regulate droplet wettability and reflectivity.

[0029] Preferably, the preparation steps of the suspension containing hollow silica microspheres include:

[0030] Step 1: Using ethanol or a mixture of ethanol and water as the dispersion medium, add polystyrene emulsion as template particles into the dispersion medium, and add ammonia water under stirring conditions to adjust the pH of the system to 8-11.

[0031] Step 2: Slowly add tetraethoxysilane dropwise while stirring, so that it hydrolyzes and condenses on the surface of the template particles to form a silica shell. After reacting for 1 to 3 hours, age the product.

[0032] Step 3: After centrifugation, washing and drying, the obtained composite particles are calcined to remove the template, resulting in hollow silica microspheres.

[0033] Step 4: Redisperse the obtained hollow silica microspheres in water or ethanol, add dispersant and stabilizer, adjust the pH of the system to 6-8, and obtain a stable hollow silica microsphere suspension after ultrasonic oscillation.

[0034] Further, in Step 1, the solid content of the polystyrene emulsion is 5–15 wt%, and the average particle size is 200–400 nm; in Step 2, the amount of tetraethoxysilane used is 50–150% of the mass of the polystyrene template, and the aging time is 2–6 hours; in Step 3, the calcination temperature is 500–600 °C, and the time is 1–3 hours; in Step 4, the average particle size of the hollow silica microspheres is 300–350 nm, and the shell thickness is 30–50 nm; the dispersant is selected from sodium lignosulfonate, sodium polyacrylate, polycarboxylate, polyvinylpyrrolidone, polyethylene glycol, or Tween-80; the stabilizer is selected from sodium carboxymethyl cellulose, polyethylene glycol, or polyvinylpyrrolidone; and the hollow silica microsphere suspension accounts for 0.5–4 wt% of the total liquid system.

[0035] In this invention, a plant insecticidal and bactericidal method based on pulsed intense light is used. The liquid droplets formed after atomization of the liquid system remain on the plant leaf surface for 10–30 minutes without evaporation, ensuring the full effect of the pulsed intense light. The propagation of the pulsed intense light within the droplets involves refraction, scattering, and reflection, forming a multi-angle composite light field distribution on the plant surface. This allows insects or bacteria to be simultaneously irradiated from multiple directions and killed. After irradiation with pulsed intense light, the uniformity of light on the plant surface increases by at least 30%, and the insect mortality rate or bacterial inhibition rate is at least 80%.

[0036] This invention relates to a plant insecticidal and bactericidal method based on pulsed intense light. By atomizing a liquid system into droplets that adhere to the plant surface, and combining this with nanoscale components that enhance the uniform distribution of the light field, the pulsed intense light undergoes refraction, scattering, and interface reflection within the droplets. This creates a multi-directional composite light field distribution on the plant surface and in concealed internal areas. This method effectively improves light uniformity, ensuring that insects and microorganisms attached to the plant surface are simultaneously killed by light from multiple directions, thus significantly enhancing insecticidal and bactericidal effects while avoiding the environmental pollution and residue risks associated with traditional chemical pesticides.

[0037] Furthermore, the combination of light absorption inhibitors, auxiliary liquids, and stabilizers contained in the liquid system of this invention improves the adhesion and uniformity of the droplets, allowing them to remain on the plant leaves for a sufficient time to fully utilize the effects of pulsed light. By optimizing the type, size, and suspension ratio of nanoparticles, the liquid system can achieve a low-viscosity, high-coverage spraying effect while ensuring reflective performance, thus providing an efficient, green, and sustainable plant protection solution for fruit trees, vegetables, and ornamental plants. Attached Figure Description

[0038] A brief explanation of the contents of each figure in the instruction manual and the markings in the figures is provided:

[0039] Figure 1 These are schematic diagrams of the insecticidal and bactericidal process of the suspension in Examples 1 and 2. In the diagrams, solid conical arrows represent the incident light path, and open indicator arrows represent the light path within the droplets and the outgoing light path.

[0040] Figure 2 This is a schematic diagram of the insecticidal and bactericidal process of the suspension in Example 3. In the diagram, the solid conical arrows represent the incident light path, and the open indicator arrows represent the light path inside the droplet and the outgoing light path.

[0041] Figure 3 This is a schematic diagram of the refraction and reflection path of pulsed intense light within a liquid droplet in Example 3. Detailed Implementation

[0042] The invention is further illustrated below with reference to the accompanying drawings, providing some non-limiting embodiments. However, it should be understood that these descriptions are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0043] Example 1: Preparation of alumina nanoparticle suspension and its application in insecticidal and fungicidal treatment of citrus trees

[0044] 1. Preparation of suspension

[0045] Take 1000 mL of deionized water and place it in a clean, stirred container. Add 1.0 wt% polyethylene glycol (PEG-400) as a dispersant and 0.5 wt% sodium polyacrylate as a stabilizer while stirring. After stirring until homogeneous, a uniform dispersion medium is obtained. Then, while stirring at 300 r / min, slowly add alumina nanoparticles with an average particle size of 100 nm and a purity of not less than 99.9%, ensuring that the added alumina nanoparticles account for 2.0 wt% of the total liquid system. Maintain uniform stirring during the addition process to prevent particle agglomeration.

[0046] The mixture was placed in an ultrasonic dispersion device and ultrasonically dispersed for 20 minutes at a power of 300 W and a frequency of 40 kHz to promote uniform dispersion of alumina particles. During the ultrasonic process, the temperature was controlled not to exceed 35 ℃ to prevent the dispersant from becoming ineffective due to localized heating.

[0047] After dispersion, the pH of the system was adjusted to 7.0 using dilute ammonia. 0.2 wt% sodium carboxymethyl cellulose was added and stirred for 10 min to stabilize the viscosity at approximately 2.2 mPa·s. Then, 0.1 wt% Tween-20 was added as a surfactant, and stirring was continued until homogeneous. After standing for 24 h, no significant sedimentation was observed (sedimentation rate less than 0.5 mm / 24 h), thus obtaining a stable and uniformly dispersed alumina nanoparticle suspension.

[0048] The prepared suspension is milky white and semi-transparent. The spectral reflectance test results show that the average reflectance in the wavelength range of 200 to 1100 nm is not less than 82%, which has excellent light reflection and scattering properties.

[0049] 2. Spraying of suspension and pulsed intense light irradiation

[0050] The above-mentioned alumina nanoparticle suspension was loaded into an ultrasonic atomizing nozzle (the spray particle size was controlled at 10-150 μm) and sprayed onto the leaves, branches and fruit surfaces of citrus seedlings and mature citrus trees. The droplets were evenly attached to the plant surface and the liquid film could remain for 10-30 minutes after it was formed.

[0051] After spraying, the plant surface is irradiated with a moving array of pulsed high-intensity light sources. The wavelength range of the pulsed high-intensity light is 200–1100 nm, the pulse width is 1 ms, and the energy density is 3 J / cm². The lighting device adopts an array-type high-intensity light source structure, with an irradiation distance of 25 cm–100 cm, and the irradiation angle can be automatically adjusted to adapt to different canopy structures. The irradiation operation adopts an intermittent mode of 2 s irradiation followed by a 30 s interval, repeated 3 times to ensure sufficient distribution of light energy at different levels of the plant canopy.

[0052] like Figure 1As shown, during the irradiation process, the liquid droplets attached to the leaf and fruit surfaces undergo multiple refractions, scattering, and interface reflections of the pulsed intense light, thus forming a multi-angle composite light field in hidden areas such as the citrus leaf surface, branch gaps, and under the fruit. Light energy is distributed in multiple directions on the plant surface, allowing insects, mycelia, and spores to be simultaneously irradiated with high-intensity light energy from multiple directions.

[0053] 3. Results Analysis

[0054] The uniformity of light distribution on the leaves of citrus trees treated with the suspension was increased by more than 30% compared to those without the suspension. Field statistics showed that under common citrus tree pest and disease conditions (such as black spot, anthracnose, and early-stage spider mite infestation), plants treated with the suspension in this embodiment, combined with pulsed high-intensity light irradiation, exhibited a significant reduction in the area of ​​lesion expansion and a marked decrease in the number of insects.

[0055] Test results showed that after one irradiation treatment, the visible insect mortality rate on citrus leaves exceeded 85%, and the rate of lesion development inhibition was no less than 80%. Simultaneously, no leaf scorching or light damage was observed, and the suspension dried naturally on the leaf surface without any pesticide residue. Table 1 lists the comparison results between the alumina nanoparticle suspension and the control liquid system (deionized water) (using the same batch of citrus seedlings as an example).

[0056] Table 1. Comparison of the effects of alumina nanoparticle suspension and control group in Example 1.

[0057] Handling method Improvement in illumination uniformity (%) Insect mortality rate (%) Lesion inhibition rate (%) Leaf scorch Liquid droplet adhesion time (min) control liquid system — 52.3 47.8 none 5–7 Using the suspension of this embodiment 30.8 89.6 84.2 none 22–28

[0058] The prepared alumina nanoparticle suspension exhibits high stability and uniform particle dispersion, forming a droplet layer on the leaf surface. This effectively enhances the reflection and scattering of pulsed intense light, resulting in more uniform light distribution. It is particularly suitable for areas of citrus trees with complex canopies and severe light shading. After irradiation by a pulsed intense light array, the light energy undergoes multiple reflections and scatterings at the droplet interface and particle surface, significantly increasing the light intensity against plant pathogens and pests, resulting in significant insecticidal and bactericidal effects. This method does not rely on chemical pesticides, posing no environmental pollution or chemical residue risks. Treatment does not affect fruit quality, meeting the application requirements of green protection and organic cultivation. Because the suspension contains components such as polyethylene glycol, sodium polyacrylate, and sodium carboxymethyl cellulose, the droplets adhere well to the leaf surface, reducing the evaporation rate and ensuring sufficient pulsed light exposure time, resulting in a stable and reliable overall protective effect.

[0059] In this embodiment, alumina nanoparticles enhance the spatial distribution of the light field primarily through high reflectivity and interface scattering effects during pulsed high-intensity light array irradiation. For example... Figure 1As shown, the refractive index difference between alumina particles and the liquid medium creates numerous microscale reflective interfaces on and within the liquid droplets. This results in multi-directional specular reflection and non-spectral scattering of incident light, thereby expanding the irradiation angle and reducing shadow areas. Particles with different orientations form a randomly distributed micro-reflective array, enabling multi-angle distribution of light energy on the plant surface, improving irradiation uniformity and localized illuminance. Simultaneously, alumina's high thermal conductivity helps to quickly disperse the instantaneous heat generated by light energy, preventing localized overheating or scorching of the leaf surface. Through these combined effects, alumina nanoparticle suspensions significantly improve the utilization rate and protective uniformity of pulsed light, achieving highly efficient physical inactivation of insects and pathogenic microorganisms.

[0060] This embodiment is merely an illustration of a preferred embodiment of the technical solution of the present invention. By controlling the particle size of alumina nanoparticles, suspension concentration, atomized particle size, and light energy parameters, the protection needs of citrus orchards of different ages and planting densities can be adapted. Reasonable variations in the process and application methods are all within the protection scope of the present invention.

[0061] Example 2: Preparation of Zirconia Nanoparticle Suspension and Its Application in Insecticide and Fungicide Application in Citrus Trees

[0062] 1. Preparation of suspension

[0063] Take 1000 mL of a solvent prepared by mixing ethanol and deionized water at a volume ratio of 1:3 and place it in a clean stirring container. Start stirring (300 r / min). While stirring, add 0.5 wt% sodium lignosulfonate as an anionic dispersant to the mixed solvent to fully dissolve it and form a homogeneous dispersion medium.

[0064] Subsequently, zirconium oxide nanoparticles (ZrO2) with an average particle size of 30 nm and a purity ≥99.9% were slowly added, at a concentration of 1.5 wt% of the total liquid system. The mixture was stirred continuously during addition to ensure thorough dispersion of the particles. The resulting mixture was then placed in an ultrasonic dispersion apparatus at a power of 300 W and a frequency of 40 kHz for 20 min to promote uniform particle dispersion. The temperature was maintained below 35 ℃ during the ultrasonic process.

[0065] After dispersion, the pH of the system was adjusted to 8.0 using dilute ammonia to enhance the charged stability of the particle surface. Subsequently, 0.1 wt% of a silane coupling agent (KH-550) was added as an interface regulator to improve the adhesion and stability of the droplets to the plant surface. After stirring for another 10 min, the mixture was allowed to stand for 24 h. No significant sedimentation was observed (sedimentation rate less than 0.5 mm / 24 h), resulting in a stable suspension of zirconia nanoparticles.

[0066] The resulting suspension is a milky white, slightly bluish, uniform liquid. Spectral reflectance measurement shows an average reflectance of 85.3% within the wavelength range of 200–1100 nm, indicating strong light reflection and scattering properties. Furthermore, the system viscosity is 2.0 mPa·s, making it suitable for atomized spraying.

[0067] 2. Spraying of suspension and pulsed intense light irradiation

[0068] The aforementioned zirconia nanoparticle suspension was loaded into an electrostatic atomizing device (spray voltage 12 kV, liquid flow rate 1.2 mL / min) and sprayed onto citrus trees, allowing the suspension to be evenly distributed as droplets on both sides of the leaves, branches, and fruit surfaces. The atomized particle size was controlled between 20 and 180 μm. After spraying, the droplets formed a uniform film with good adhesion, and the liquid film residence time could reach 25 min at room temperature. Due to the introduction of the silane coupling agent (KH-550) into the liquid system, the droplets formed a weak polar binding force and electrostatic adsorption effect on the plant surface, thereby significantly prolonging the residence time of the liquid film.

[0069] After spraying, if Figure 1 As shown, a pulsed high-intensity light array was used for irradiation. The wavelength range of the pulsed high-intensity light was 200–1100 nm, the pulse width was 0.8 ms, the energy density was 3.5 J / cm², and the irradiation distance was 30 cm. An array-type synchronous irradiation device was used to create superimposed coverage of light energy in different directions of the tree canopy. Each tree was irradiated three times, each time for 2 seconds, with an interval of 40 seconds.

[0070] During irradiation, the zirconia nanoparticles suspended on the leaf and fruit surfaces efficiently reflect and scatter the pulsed intense light, enabling the light energy to form a multi-angle distribution field between the leaves, fruit surfaces, and the intersections of branches. Through the reflection and scattering of multiple interfaces, the uniformity of light distribution in hidden areas is significantly improved.

[0071] 3. Results Analysis

[0072] The citrus trees treated in this embodiment showed significant protective effects under typical pest and disease stress conditions (such as black spot disease, anthracnose, and early-stage spider mite infestation). Field observation and subsequent testing revealed that lesion development on leaves and fruit surfaces was significantly inhibited, and pest activity was markedly reduced. Light distribution analysis showed that the uniformity of light on citrus leaves treated with zirconium oxide nanoparticle suspension increased by approximately 33% compared to the control liquid system (deionized water), and the area of ​​the shaded zone decreased by approximately 40%. The improvement rate of light uniformity was calculated using the variance normalization method of leaf light intensity distribution, and the change in shaded area was quantitatively analyzed using an image recognition algorithm; both were based on comparative measurements under the same irradiation conditions. The fungicidal and insecticidal effects on citrus leaves under different treatment methods were statistically analyzed, and the results are shown in Table 2.

[0073] Table 2. Comparison of the effects of zirconium oxide nanoparticle suspension in Example 2 with the control group.

[0074] Handling method Improvement in illumination uniformity (%) Insect mortality rate (%) Lesion inhibition rate (%) Leaf scorch Liquid droplet adhesion time (min) control liquid system — 50.1 46.7 none 6–8 Using the suspension from Example 2 33.2 91.5 86.8 none 25–28

[0075] As shown in Table 2, after treatment with zirconium oxide nanoparticle suspension and pulsed light, the mortality rate of insects on citrus leaves reached 91.5%, and the lesion inhibition rate reached 86.8%, both of which were significantly higher than the control group without the enhanced liquid system, demonstrating excellent insecticidal and fungicidal performance.

[0076] like Figure 1 As shown, during pulsed high-intensity light array irradiation, zirconia nanoparticles, due to their high refractive index (approximately 2.1), form a significant interfacial refractive index difference in the liquid medium (approximately 1.35–1.4), causing strong reflection of incident light at the particle interface. A large number of dispersed particles constitute a dense array of microscale reflective surfaces, causing some light to undergo multiple reflections and non-mirror scattering within the liquid droplets, thereby expanding the light field distribution range. The particle size and concentration are controlled at the nanoscale, resulting in a hemispherical diffusion of the scattering angle, which is beneficial for the shielded areas to receive indirect light. Therefore, zirconia particles mainly improve the overall illumination uniformity through a synergistic mechanism of interfacial reflection and scattering. Furthermore, the high thermal conductivity of zirconia accelerates the diffusion of instantaneous heat energy, preventing the formation of local hot spots, thus combining high reflectivity with anti-burn properties. Under the combined effect, zirconia nanoparticles construct a stable composite light field through the interfacial reflection-scattering synergistic mechanism, significantly improving the utilization rate of pulsed high-intensity light and achieving efficient photo-energy inactivation of insects and pathogenic microorganisms.

[0077] Zirconia nanoparticles possess high refractive index and thermal stability, exhibiting strong reflection and scattering capabilities for pulsed high-intensity light. This enables multi-angle propagation of high-intensity light energy within complex plant canopies, significantly improving light uniformity and coverage. The addition of sodium lignosulfonate dispersant and silane coupling agent to the suspension system enhances its stability and adhesion, allowing droplets to remain on leaf surfaces for an extended period, facilitating the full application of light energy to insects and pathogenic microorganisms. This method eliminates the need for chemical pesticides, produces no harmful residues, and has no impact on citrus fruit quality, demonstrating excellent ecological safety and environmental friendliness. Through the multi-angle composite light field, insects and fungal spores are simultaneously exposed to high-energy light from different directions, achieving highly efficient physical killing. Furthermore, the short duration and concentrated energy of the pulsed light prevent leaf tissue burns.

[0078] The zirconium oxide nanoparticle suspension described in this embodiment can achieve similar enhanced reflection and protective effects by adjusting the zirconium oxide particle size (10-50 nm), mass fraction (0.2-3 wt%), and solvent ratio (ethanol:water = 1:2-1:4) according to different crop types, leaf structures, and light conditions. This falls within the scope of equivalent substitution of the technical solution of this invention.

[0079] Example 3: Preparation of a suspension containing hollow silica microspheres and its application in insecticidal and fungicidal treatment of citrus trees.

[0080] 1. Preparation of suspension

[0081] (1) Preparation of hollow silica microspheres

[0082] Take 10 g of polystyrene (PS) emulsion with a solid content of 10 wt% and an average particle size of approximately 300 nm, add it to 200 mL of anhydrous ethanol, place it in a 500 mL three-necked flask, and connect it to a reflux condenser. Start stirring (400 r / min), add 10 mL of ammonia water (25 wt%), and adjust the pH of the system to 10. Then slowly add 10 mL of tetraethoxysilane (TEOS), and react at room temperature (25 ℃) for 2 h to promote the hydrolysis and condensation of TEOS on the surface of PS particles to form a SiO2 shell. After the reaction is complete, continue aging for 4 h to enhance the density of the shell.

[0083] The resulting suspension was centrifuged (8000 r / min, 10 min), washed three times alternately with ethanol and deionized water, and then vacuum-dried at 60 °C for 12 h to obtain polystyrene-silica core-shell composite microspheres. These composite microspheres are core-shell structured microspheres with polystyrene microspheres as the core and a silica shell coating on their surface. The samples were then placed in a muffle furnace and calcined in air at 550 °C for 2 h to remove the internal polystyrene template. After calcination and cooling to room temperature, hollow silica microspheres with a particle size of 300–350 nm and a shell thickness of approximately 40 nm were obtained. Transmission electron microscopy showed that the obtained hollow structure was intact and uniformly distributed, with no obvious collapse or breakage.

[0084] (2) Preparation of hollow silica microsphere suspension

[0085] 2.0 g of the obtained hollow silica microspheres were added to a mixed solvent of 400 mL of ethanol and deionized water (volume ratio 1:3). 0.5 wt% polyvinylpyrrolidone (PVP) and 0.2 wt% sodium carboxymethyl cellulose (CMC-Na) were added as dispersing and stabilizing agents. The mixture was ultrasonically dispersed for 20 min under magnetic stirring (300 W, 40 kHz), with the system temperature controlled below 30 °C. The pH was then adjusted to 7.0 with dilute ammonia to obtain a stable suspension. This liquid was milky white and transparent, with a sedimentation rate of less than 0.4 mm / 24 h and an average reflectance of 87.5% in the 200–1100 nm wavelength range, exhibiting excellent optical properties and dispersion stability.

[0086] 2. Spraying and pulsed intense light irradiation

[0087] The suspension was loaded into an ultrasonic atomizing nozzle (spray particle size 15–180 μm) and sprayed evenly onto the surface of leaves, fruits, and branches of citrus trees. After spraying, the droplets formed a uniform film on the surface, which adhered and remained for approximately 25 minutes.

[0088] like Figure 2 As shown, a pulsed high-intensity light array was used for processing, with a pulse wavelength range of 200–1100 nm, a single pulse width of 1.2 ms, an energy density of 3 J / cm², and an illumination distance of 30 cm. An array-style surround illumination method was employed. Each illumination session lasted 2 s, with a 30 s interval, and was repeated 3 times.

[0089] The shell-cavity structure of hollow silica microspheres significantly enhances local light flux through multiple scattering, refraction, and reflection, while also improving light coverage in complex parts of the plant (such as the underside of leaves and the base of fruit stalks).

[0090] 3. Results Analysis

[0091] Citrus trees treated in this embodiment showed significant protective effects under typical pest and disease stress conditions (such as black spot disease, anthracnose, and early-stage spider mite infestation). After light exposure, the uniformity of light on citrus leaves increased by approximately 35%, and the average illuminance in the shaded areas of the fruit increased by 42%. Comparative experiments showed that plants treated with this suspension exhibited a 90.3% insect mortality rate and an 85.7% anthracnose inhibition rate, significantly superior to the control group (deionized water) and the non-hollow silica group (ordinary SiO2 particle suspension). Simultaneously, no scorching or browning was observed on the plant surface. No visible residue remained after drying; the suspension components are environmentally friendly, biodegradable, and do not affect the appearance or taste of the fruit. The fungicidal and insecticidal effects on citrus leaves under different treatment methods were statistically analyzed, and the results are shown in Table 3.

[0092] Table 3. Comparison of the effects of hollow silica microsphere suspension in Example 3 with the control group.

[0093] Handling method Improvement in illumination uniformity (%) Insect mortality rate (%) Lesion inhibition rate (%) Leaf scorch Liquid droplet adhesion time (min) Deionized water control group — 42.1 37.8 none 2–3 Ordinary silica microparticle suspension 18.4 67.5 63.2 none 5–8 Hollow silica microsphere suspension 35.0 90.3 85.7 none 20-25 Conventional insecticide comparison — 91.0 83.5 Mild drug stains —

[0094] This embodiment introduces hollow silica microspheres into a pulsed light insecticidal and fungicidal system, significantly enhancing the multiple scattering of light and resulting in a more uniform energy distribution. Compared to traditional solid granules or chemical agents, this system significantly improves plant protection while achieving a residue-free and pollution-free green control approach, demonstrating excellent environmental compatibility and potential for widespread application.

[0095] In this embodiment, the droplets formed after the hollow silica microsphere suspension was sprayed exhibited a significant light scattering enhancement effect under pulsed intense light irradiation. For example... Figure 2 , 3 As shown, due to the refractive index difference between the hollow silica shell and the internal cavity, incident light undergoes multi-level interface reflection, refraction, and scattering within the droplet, with some light rays being deflected and redistributed to the outer area of ​​the droplet. This process effectively increases the effective illumination flux per unit area of ​​the leaf and fruit surfaces, and provides compensatory illumination to areas originally blocked by the plant structure (such as the underside of leaves and the base of fruit stalks). This achieves the redistribution and diffusion of light energy within the irradiated area, improving overall light uniformity and spatial coverage.

[0096] Based on this, the multi-angle distributed reflected and scattered light can create a superimposed irradiation effect on the surface of insects and pathogens, causing the insect epidermis and microbial cell membranes to rapidly heat up or structurally damage under the action of multi-directional light energy, thereby improving the insecticidal and antibacterial efficiency. Through the multi-directional distribution of light energy and local energy homogenization, this mechanism effectively avoids tissue damage caused by local overheating, achieving controllable and uniform strong light action. Therefore, the hollow silica microsphere suspension in this embodiment not only improves the utilization rate of pulsed light energy, but also achieves efficient and green physical control effects without relying on chemical agents.

[0097] The above embodiments should be understood as illustrative only and not as limiting the scope of protection of the present invention. After reading the description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A method for insecticidal and fungicidal treatment of plants based on pulsed intense light, characterized in that, Includes the following steps: S1. Prepare a liquid system, wherein the liquid system is a stable suspension containing a component that enhances the uniform distribution of the light field, and the component that enhances the uniform distribution of the light field is a nano-sized inorganic particle with high reflectivity and strong light scattering capability. S2. Atomize the liquid system so that the liquid adheres to the plant surface in the form of droplets; S3. Pulsed intense light is used to irradiate liquid droplets on the plant surface. By utilizing the reflection from the surface of the liquid droplets, the multi-angle scattering inside the liquid droplets, and the interface reflection effect of the components that enhance the uniform distribution of the light field, the pulsed intense light forms a multi-directional light field distribution on the plant surface to kill insects and microorganisms attached to the plant surface.

2. The insecticidal and bactericidal method according to claim 1, characterized in that, The component that enhances the uniform distribution of the light field is selected from alumina nanoparticles, zirconia nanoparticles, or hollow silica microspheres.

3. The insecticidal and bactericidal method according to claim 1, characterized in that, The liquid system also contains a light absorption inhibitor, which is selected from glycerol, dimethyl silicone oil or a combination thereof, and the amount of the light absorption inhibitor in the liquid system is 0.1 to 5 wt%.

4. The insecticidal and bactericidal method according to claim 1, characterized in that, The average reflectivity of the nanoscale inorganic particles in the liquid system to pulsed intense light is not less than 80%; the atomization process is achieved by an ultrasonic nozzle or an electrostatic atomization device; the viscosity of the suspension is controlled at 1.0–3.0 mPa·s; and the droplet size is 10–200 μm; the pulsed intense light irradiation is achieved by a mobile light source, an array light source, or a robotic light irradiation device.

5. The insecticidal and bactericidal method according to claim 2, characterized in that, The preparation steps of the suspension containing alumina nanoparticles include: Step 1: Add dispersant and stabilizer to deionized water and stir until uniform to form a dispersion medium; Step 2: Slowly add alumina nanoparticles while stirring, and use ultrasonic treatment to make the alumina particles evenly dispersed. St3, adjust the pH of the system to between 6 and 8 to reduce particle aggregation; St4. Add an appropriate amount of thickener and / or surfactant to obtain a stable alumina nanoparticle suspension with stable viscosity and a settling velocity of less than 0.5 mm / 24h.

6. The insecticidal and bactericidal method according to claim 5, characterized in that, In step St1, the dispersant is preferably polyethylene glycol or polyvinylpyrrolidone; the stabilizer is preferably sodium polyacrylate or lignin sulfonate; the surfactant is selected from alkyl glycosides, Tween-20, or organosilicon; the thickener is selected from xanthan gum or sodium carboxymethyl cellulose; in step St2, the alumina nanoparticles have an average particle size of 50–150 nm; and the alumina nanoparticle suspension accounts for 0.5–5 wt% of the total liquid system.

7. The insecticidal and bactericidal method according to claim 2, characterized in that, The preparation steps of the suspension containing zirconium oxide nanoparticles include: Ste1. A mixed solvent of ethanol and deionized water in a volume ratio of 1:2 to 4 is used as the dispersion medium. Ste2, add 0.1-1.0 wt% of anionic dispersant to the dispersion medium and stir until homogeneous; Ste3. Under stirring conditions, zirconium oxide nanoparticles are gradually added and ultrasonically dispersed for 10 to 30 minutes to ensure uniform dispersion of the particles. Ste4. Adjust the pH of the system to 7-9 and add an interface regulator to improve the adhesion and stability of the droplets to the target surface, thereby obtaining a stable zirconia nanoparticle suspension.

8. The insecticidal and bactericidal method according to claim 7, characterized in that, In step Ste2, the anionic dispersant is selected from one or more of sodium lignosulfonate, naphthalene sulfonate condensate, sodium polyacrylate, or sodium carboxymethyl cellulose; in step Ste4, the interface modifier is selected from one or more of silane coupling agents, organosilicon spreading agents, or aluminate coupling agents, and the amount of the interface modifier is 0.01–0.2 wt%; in step Ste3, the average particle size of the zirconia nanoparticles is 10–50 nm; and the zirconia nanoparticle suspension accounts for 0.2–3 wt% of the total liquid system.

9. The insecticidal and bactericidal method according to claim 2, characterized in that, The preparation steps of the suspension containing hollow silica microspheres include: Step 1: Using ethanol or a mixture of ethanol and water as the dispersion medium, add polystyrene emulsion as template particles into the dispersion medium, and add ammonia water under stirring conditions to adjust the pH of the system to 8-11. Step 2: Slowly add tetraethoxysilane dropwise while stirring, so that it hydrolyzes and condenses on the surface of the template particles to form a silica shell. After reacting for 1 to 3 hours, age the product. Step 3: After centrifugation, washing and drying, the obtained composite particles are calcined to remove the template, resulting in hollow silica microspheres. Step 4: Redisperse the obtained hollow silica microspheres in water or ethanol, add dispersant and stabilizer, adjust the pH of the system to 6-8, and obtain a stable hollow silica microsphere suspension after ultrasonic oscillation.

10. The insecticidal and bactericidal method according to claim 9, characterized in that, In Step 1, the solid content of the polystyrene emulsion is 5–15 wt%, and the average particle size is 200–400 nm. In Step 2, the amount of tetraethoxysilane used is 50–150% of the mass of the polystyrene template, and the aging time is 2–6 hours. In Step 3, the calcination temperature is 500–600℃, and the time is 1–3 hours. In Step 4, the average particle size of the hollow silica microspheres is 300–350 nm, and the shell thickness is 30–50 nm. The dispersant is selected from sodium lignosulfonate, sodium polyacrylate, polycarboxylate, polyvinylpyrrolidone, polyethylene glycol, or Tween-80. The stabilizer is selected from sodium carboxymethyl cellulose, polyethylene glycol, or polyvinylpyrrolidone. The hollow silica microsphere suspension accounts for 0.5–4 wt% of the total liquid system.

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