Prevention and treatment method for agilawood seedling root rot

Abstract

The invention relates to the technical field of forestry pest control, and discloses a control method for agilawood seedling root rot. The prevention and control method comprises the following steps: in a seedling raising stage, soaking seeds and disinfecting seedbed soil by using the antibacterial composition; in the transplanting stage, slow-release granules of 3-5 kg / mu are evenly spread to the bottoms of the prepared planting holes, and root systems of nursery stocks are dipped with an antibacterial composition; in the growing period, the humidity is controlled through high ridge forming and precise drip irrigation, and functional seaweed fertilizer containing beneficial bacteria is regularly applied to the roots of the nursery stocks; in the initial stage of diseases, diseased plants are pulled out, lime is applied to diseased holes, and slow-release granules are used for root irrigation in the center area of diseases. According to the method for preventing and treating the root rot of the agilawood nursery stock, the limitation that a single technology is slow in biological effect and short in chemical lasting effect is overcome, and the remarkable improvement and long-term stability of the prevention and treatment effect are achieved.

Description

Technical Field

[0001] This invention application relates to the field of forestry pest and disease control technology, and in particular to a method for controlling root rot in agarwood seedlings. Background Technology

[0002] Agarwood, as a precious medicinal and aromatic tree species, relies on seedling cultivation as the cornerstone of its industry development. However, root rot is the most devastating soil-borne disease in the seedling and sapling stages of agarwood cultivation. It is often caused by the combined infection of pathogens such as Fusarium and Phytophthora, resulting in large-scale seedling death and severely restricting the healthy development of the industry.

[0003] Currently, the prevention and control of root rot in agarwood production mainly relies on chemical pesticides and single biological control methods, both of which have significant limitations. For chemical control, conventional application methods such as spraying and root drenching suffer from problems like easy pesticide runoff and short-lasting effects, requiring multiple applications throughout the growing season. This not only increases costs and labor but also easily leads to pathogen resistance, pesticide residues, and soil pollution. Furthermore, the instantaneous high concentration of pesticides at the rhizosphere can easily cause phytotoxicity to precious agarwood seedlings. While single biological control methods are environmentally friendly, biocontrol agents are unstable in effect, slow to take effect, and highly susceptible to environmental conditions, making them difficult to effectively control during periods of high disease incidence or when pathogen pressure is high.

[0004] Furthermore, existing prevention and control strategies are often fragmented, failing to effectively integrate biological and chemical methods, as well as long-term and rapid-acting measures, during the critical window of disease occurrence. They either overemphasize chemical methods while neglecting ecological health, or rely on biological methods but lack emergency response capabilities. There is a lack of a systematic plan that can span the entire growth cycle of seedlings and take into account all aspects of "prevention, health maintenance, and treatment."

[0005] Therefore, there is an urgent need in this field for a comprehensive prevention and control method that can overcome the above-mentioned defects, aiming to achieve efficient, long-lasting, green and easy-to-operate prevention and control of root rot in agarwood seedlings, so as to ensure the stable and sustainable development of the agarwood industry. Summary of the Invention

[0006] The purpose of this application is to provide a method for preventing and controlling root rot in agarwood seedlings. This method combines biological control, chemical slow-release agents, and conventional measures at different stages of agarwood seedling growth to achieve long-lasting and effective prevention and control of root rot in agarwood seedlings.

[0007] To address the aforementioned technical problems, this application provides a method for preventing and controlling root rot in agarwood seedlings, comprising the following steps:

[0008] S11 Seedling stage: Seed soaking and seedbed soil disinfection treatment with antibacterial composition;

[0009] S12 Transplanting stage: At the bottom of the prepared planting hole, evenly spread 3-5 kg / mu of slow-release granules and dip the seedling roots in the antibacterial composition;

[0010] S13 growth stage: control humidity by raising ridges and precise drip irrigation, and regularly apply functional seaweed fertilizer containing beneficial bacteria to the roots of the seedlings;

[0011] S14 disease in its early stages: Remove diseased plants, apply lime to the affected area, and drench the roots with slow-release granules in the central area of ​​the disease.

[0012] The method for controlling root rot in agarwood seedlings provided in this application overcomes the limitations of slow-acting biological control (antimicrobial composition and functional seaweed fertilizer) and chemical control (slow-release granules) by seamlessly integrating and complementing each other in terms of timing and function. This achieves a significant improvement and long-term stability in control efficacy compared to single-technology biological control, which is characterized by slow onset of action and short-lasting chemical control. The application of slow-release technology greatly improves pesticide utilization, reducing the amount of pesticide used and the number of applications. Simultaneously, by avoiding the instantaneous release of high concentrations of pesticides, the risk of phytotoxicity to agarwood seedlings and damage to the soil microecology is greatly reduced, aligning with the requirements of green agriculture. Through the application of beneficial bacteria and functional seaweed fertilizer, a healthy and vibrant rhizosphere microenvironment is cultivated, fundamentally enhancing the seedlings' resistance and growth potential, thereby achieving sustainable seedling production.

[0013] In some embodiments, the antibacterial composition comprises Trichoderma harzianum and Bacillus amyloliquefaciens in a ratio of 1:2 to 2:1 based on the number of viable cells.

[0014] In some implementations, soil disinfection of the seedbed is carried out using microporous fungicides or solar energy.

[0015] In some embodiments, the active ingredients of the sustained-release granules consist of metalaxyl and oxamyl, with a weight ratio of metalaxyl to oxamyl of 1:5 to 5:1.

[0016] In some embodiments, the sustained-release carrier of the sustained-release granules is composed of sodium alginate and attapulgite in a weight ratio of 1:1 to 1:3.

[0017] In some implementations, the weight ratio of metalaxyl to oxamyl is 1:2, and the weight ratio of sodium alginate to attapulgite is 1:2.

[0018] In some embodiments, the sustained-release granules consist of the following components in weight percentage: metalaxyl 4%-6%, oxamyl 9%-11%, sodium alginate 4%-6%, attapulgite 9%-11%, citric acid 1%-3%, brassinolide 0.0005%-0.002%, alkyl polysaccharide 0.5%-2%, with the balance being bentonite.

[0019] In some implementations, before the rainy season arrives during the growing season, a shallow circular trench 10-15 cm deep is dug 15-20 cm away from the base of the seedling. 2-3 kg / acre of slow-release granules is evenly applied into the trench, and then covered with soil.

[0020] In some embodiments, the beneficial bacteria contained in the functional seaweed fertilizer are Trichoderma harzianum and / or Bacillus amyloliquefaciens.

[0021] In some implementations, slow-release granules are used for root irrigation in the disease center area. Specifically, 10-20 grams of slow-release granules are applied to the root zone of each healthy seedling around the diseased hole. Attached Figure Description

[0022] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0023] Figure 1 This is a flowchart of a method for preventing and controlling root rot in agarwood seedlings provided in some embodiments of this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of this application to enable readers to better understand this application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in this application can be implemented. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0027] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0028] The following is combined with Figure 1 This application describes a method for preventing and controlling root rot in agarwood seedlings, based on some embodiments.

[0029] like Figure 1 As shown in some embodiments of this application, the method for preventing and controlling root rot in agarwood seedlings includes the following steps:

[0030] S11 Seedling stage: Seed soaking and seedbed soil disinfection treatment with antibacterial composition;

[0031] The seedling stage is the primary and crucial step in preventing root rot. Its purpose is to eliminate or significantly reduce the threat of pathogens at the source and create a microenvironment rich in beneficial bacteria for healthy seedling growth. This stage achieves dual protection through a strategy combining "seed barrier construction" and "soil ecological reconstruction." Seed dressing or soaking allows beneficial bacteria such as *Trichoderma harzianum* and *Bacillus amyloliquefaciens* to preferentially colonize the seed surface or seedling roots, forming a living protective barrier. Disinfecting the seedbed soil removes or significantly reduces the initial pathogen load in the soil and creates favorable conditions for the subsequent introduction of beneficial bacteria.

[0032] The specific method for seed treatment is as follows: Immerse the selected agarwood seeds in the prepared microbial agent suspension, ensuring that all seeds are completely submerged. Soak at room temperature (25-28℃) for 2 hours, stirring gently every 30 minutes to ensure uniform microbial concentration and oxygen supply. After soaking, remove the seeds and spread them out in a cool, ventilated place to dry until the seed surface no longer sticks together, at which point they are ready for sowing.

[0033] Furthermore, after soil disinfection, the antibacterial composition of this invention is introduced to quickly occupy the soil ecological niche and prevent pathogens from re-invading. The antibacterial composition can be mixed with fully decomposed organic fertilizer at a weight ratio of 1:100 to prepare bio-organic fertilizer. In the final stage of seedbed preparation, the bio-organic fertilizer is evenly spread on the seedbed surface at a rate of 50-100 kg per acre, and then lightly raked (to a depth of 5-10 cm) to mix it evenly with the topsoil.

[0034] S12 Transplanting stage: At the bottom of the prepared planting hole, evenly spread 3-5 kg / mu of slow-release granules and dip the seedling roots in the antibacterial composition;

[0035] The transplanting stage is a critical period for seedlings to move from the nursery to the field. During transplanting, the root system is prone to developing micro-wounds, providing an opportunity for soil-borne pathogens to invade. The core objective of this stage is to construct a three-dimensional protective barrier in the root zone of the seedlings by using slow-release granules and antibacterial compositions in synergy. This barrier combines immediate and long-lasting effects with a combination of biological and chemical methods.

[0036] Specifically, apply the pesticide to the bottom of the prepared planting holes (usually 30-40cm in diameter and 30-35cm deep). The dosage should be based on the field planting density, at a rate of [per acre (666.7m²)]. 2 Apply 3-5 kg ​​of the slow-release granules evenly, using a unit of measurement. This dosage is an optimized range verified through extensive field trials, ensuring effective control while avoiding pesticide waste and potential environmental impact. After applying the granules, gently mix them with the soil at a depth of 5-10 cm using a hoe or small shovel. This step aims to initially mix the pesticide with the soil in the main root growth area, preventing the granules from becoming too concentrated, thus ensuring that the slow-release pesticide can more broadly cover and protect the newly emerging roots.

[0037] The antibacterial composition is a compound of *Trichoderma harzianum* and *Bacillus amyloliquefaciens*. Before use, dilute it 100 times with water to prepare a bacterial suspension, which should be stored in a container. Gently remove the agarwood seedlings from their nutrient bags, being careful to avoid dislodging the root ball. Immerse the entire root system of the seedling (including the root ball) in the prepared bacterial suspension for 2-3 minutes, ensuring full contact between the roots and the root ball with the solution. After removal, there is no need for prolonged drying; planting can proceed once the root surface stops dripping.

[0038] The innovation of this transplanting stage lies in the spatiotemporal synergy of two technologies. Spatial synergy: Chemical granules are applied underneath, while biocontrol agents are attached top. The slow-release granules form a long-term "drug reservoir" in the soil below the roots, continuously releasing active ingredients upwards to protect the deep roots; while the biocontrol agents colonize directly on the root surface, forming a living "biological barrier" to protect the root collar and shallow roots. Together, they constitute a three-dimensional defense system from deep to shallow. Temporal and functional synergy: After inoculation, the biocontrol agents can rapidly multiply, playing a role in early site occupation, competition, and inducing systemic resistance, with a rapid onset of action; the slow-release chemical granules provide long-lasting and stable chemical protection, with an effective period of 90-120 days, perfectly covering the entire seedling establishment period and early growth stage. The two complement each other in terms of onset time and mechanism of action, jointly ensuring the healthy survival and growth of seedlings during the vulnerable period of transplanting, laying a solid foundation for subsequent vigorous growth.

[0039] S13 growth stage: control humidity by raising ridges and precise drip irrigation, and regularly apply functional seaweed fertilizer containing beneficial bacteria to the roots of the seedlings;

[0040] The growing season is a critical period for seedlings, characterized by vigorous growth but also high susceptibility to environmental stress and disease infection. The core objective of this stage is to shift from passive prevention to proactive health maintenance. This involves a three-pronged strategy of ecological regulation, nutrient enhancement, and microbial community consolidation to maintain and strengthen the seedlings' resilience and create a healthy rhizosphere micro-ecosystem unfavorable to pathogen growth. Root rot pathogens (such as Fusarium and Phytophthora) are highly dependent on soil moisture for activity and spread. This stage utilizes a combination of engineering and equipment to achieve precise water management.

[0041] After seedling planting or at the beginning of this stage, prepare the soil around the seedling rhizome, constructing raised beds 20-30 cm high and 40-50 cm wide. Create drainage ditches at least 20 cm deep between the beds to ensure rapid drainage of waterlogged areas during the rainy season. Raised bed cultivation significantly improves drainage and aeration in the rhizosphere, preventing root hypoxia caused by waterlogging after rain and fundamentally disrupting the habitat of moisture-loving pathogens. Install a drip irrigation system, ensuring each seedling has a dripper in its root zone. Place soil moisture sensors in the field to monitor the volumetric water content of the soil at a depth of 10-15 cm from the main absorbing root layer. Set the irrigation threshold to 60%-70% of the soil's maximum field capacity. When the sensor detects water content below 60%, automatically activate the drip irrigation system to replenish water; stop when it reaches 70%. This precise control strategy can continuously maintain soil moisture within the range most suitable for seedling growth, but significantly inhibit pathogen spore germination and mycelial growth, making it one of the core technologies for achieving ecological disease control.

[0042] Select a functional seaweed fertilizer containing beneficial bacteria. The preferred beneficial bacteria are *Trichoderma harzianum* and / or *Bacillus amyloliquefaciens*. This fertilizer should be rich in seaweed extract (rich in alginic acid, betaine, and natural growth hormones) and the aforementioned highly active biocontrol agents, with a viable bacteria count ≥ 200 million / gram. Apply monthly, starting after the seedlings enter their vigorous growth period. Pay special attention to supplementing the fertilizer after the rainy season or rapid growth period, when trees may face stress. Dilute the functional seaweed fertilizer 300-500 times with water and apply it through a drip irrigation system, or directly in holes / furrows around the root zone of the seedlings, at a rate of 10-15 kg per acre per application.

[0043] Seaweed active substances can stimulate root development, strengthen cell walls, and induce systemic disease resistance in seedlings, thus enhancing their immunity from within. Each top dressing is a "replenishment" and "feeding supply" to the beneficial rhizosphere flora. This consolidates the dominance of the flora established during the seedling and transplanting stages, enabling it to continuously compete for nutrients, secrete antibacterial substances, and effectively inhibit the reactivation of pathogens.

[0044] These operations during the growth period constitute a dynamic, self-reinforcing health management system. Precise humidity control physically suppresses pathogens, while regular functional fertilization strengthens the seedlings both physiologically and ecologically. This allows the seedlings to maintain vigorous growth throughout the entire growth period. Even under environmental pressures from high disease incidence, they can effectively resist pathogen infection by relying on their robust constitution and strong rhizosphere microbial community, significantly reducing the incidence of diseases and providing a decisive guarantee for the final high survival rate and high-quality seedling production.

[0045] S14 disease in its early stages: Remove diseased plants, apply lime to the affected area, and drench the roots with slow-release granules in the central area of ​​the disease.

[0046] The initial stage of disease outbreak is a critical window for preventing root rot from spreading from localized occurrences to a widespread pattern. The goal at this stage is to quickly eliminate the source of infection, thoroughly disinfect the affected area, and precisely protect healthy plants. Through a series of targeted measures, the epidemic can be effectively controlled in the most cost-effective and environmentally friendly way.

[0047] Field inspectors must be familiar with the early symptoms of root rot (such as wilting leaves due to water loss, loss of leaf color, and water-soaked brown spots at the root collar). Once a few suspected diseased plants are found, they should be marked immediately. Wearing gloves, operators should carefully dig out the entire seedling, along with its entire root system and the surrounding soil (20-30 cm in diameter), centering on the diseased plant. The entire process should be handled with care to avoid shaking and prevent the release of contaminated soil. The excavated diseased plant and soil should be properly placed in sealed bags, removed from the field, and disposed of harmlessly (e.g., by deep burial or incineration). Immediately and evenly apply sufficient quicklime powder to the empty hole and surrounding soil after the diseased plant has been removed. The amount should be enough to completely cover and penetrate the bottom and sides of the hole; typically, 100-200 grams are needed per hole.

[0048] Centering on the cleaned and disinfected diseased planting hole, all visually healthy seedlings within a radius of 1.0-1.5 meters are designated as key protection targets. This area is considered a "high-risk zone" for pathogens to spread via groundwater or soil manipulation. For each healthy seedling within the designated area, precise application of pesticide is performed on its root zone. Specifically, slow-release granules are evenly spread within the vertical projection area of ​​the seedling's root crown, at a rate of 10-20 grams per seedling. This is then covered with a thin layer of soil, or the granules are mixed with the topsoil by shallow raking (approximately 3-5 cm deep).

[0049] This approach does not treat already infected plants, but rather establishes a "chemical barrier" around the roots of healthy seedlings. The slow-release granules slowly release metalaxyl and oxychloride into the soil, effectively killing or inhibiting pathogens spreading from the affected area and protecting healthy roots from infection. Compared to traditional liquid drenching, the slow-release granules provide long-lasting protection for approximately 30-50 days in this high-risk area, sufficient to cover multiple activity cycles of the pathogens, ensuring the outbreak is completely eradicated and preventing recurrence. After completing these steps, close monitoring of the affected area for 2-3 weeks is necessary. The absence of new infected plants indicates that the outbreak has been effectively controlled.

[0050] The entire process during the initial outbreak of the disease involves creating a temporary, harmless isolation zone by applying sufficient quicklime into the affected area, thus completely eliminating the source. Applying slow-release granules to visually healthy seedlings, centered on the affected area, is to prevent the spread of pathogens. "Surgical" cleaning with lime is performed within the affected area, while a "chemical defense ring" is constructed around it using slow-release granules. This zoned treatment strategy fully leverages the advantages of both materials, avoiding the risk of antagonism between them. It effectively eradicates the disease at its initial stage with minimal cost, preventing its spread and demonstrating its value as a complete and reliable integrated pest management system.

[0051] The method for controlling root rot in agarwood seedlings provided in this application overcomes the limitations of slow-acting biological control (antimicrobial composition and functional seaweed fertilizer) and chemical control (slow-release granules) by seamlessly integrating and complementing each other in terms of timing and function. This achieves a significant improvement and long-term stability in control efficacy compared to single-technology biological control, which is characterized by slow onset of action and short-lasting chemical control. The application of slow-release technology greatly improves pesticide utilization, reducing the amount of pesticide used and the number of applications. Simultaneously, by avoiding the instantaneous release of high concentrations of pesticides, the risk of phytotoxicity to agarwood seedlings and damage to the soil microecology is greatly reduced, aligning with the requirements of green agriculture. Through the application of beneficial bacteria and functional seaweed fertilizer, a healthy and vibrant rhizosphere microenvironment is cultivated, fundamentally enhancing the seedlings' resistance and growth potential, thereby achieving sustainable seedling production.

[0052] In some embodiments of this application, the antibacterial composition consists of Trichoderma harzianum and Bacillus amyloliquefaciens in a ratio of 1:2 to 2:1 based on the number of viable bacteria.

[0053] The antibacterial composition can consist of *Trichoderma harzianum* and *Bacillus amyloliquefaciens*, or *Bacillus atrophus* and *Pseudomonas fluorescens*, or *Bacillus belyssus* and *Trichoderma echinosporum*, or *Trichoderma viride* and *Streptomyces griseus*. Preferably, it consists of *Trichoderma harzianum* and *Bacillus amyloliquefaciens* in a viable cell ratio of 1:2 to 2:1. As a fungus, *Trichoderma harzianum* hyphae can parasitize pathogen hyphae, directly entangle and penetrate them, and secrete chitinases to lyse the pathogen cell walls. Simultaneously, it competes for living space and nutrients in the rhizosphere. As a bacterium, *Bacillus* can reproduce rapidly and secrete lipopeptide antibiotics (such as surfactants and iturobrine), forming an antibacterial barrier in the roots and inducing systemic resistance in plants. Fungi and bacteria complement each other in terms of space, time, and mode of action; *Trichoderma harzianum* is responsible for "physical attack" and long-term control, while *Bacillus* is responsible for "chemical attack" and rapid response, constituting a three-dimensional biocontrol system.

[0054] In some embodiments of this application, soil disinfection treatment of the seedbed is carried out using microporous bactericides or solar energy.

[0055] This step aims to eliminate or significantly reduce the initial pathogen load in the soil and create favorable conditions for the subsequent introduction of beneficial bacteria. Use a commercially available microporous fungicide (e.g., a soil fumigant containing chloropicrin, dazomet, etc.). Apply the fumigant via soil injection or by mixing it into the soil, following the dosage recommended in the product instructions. Immediately after application, cover the soil with plastic film to seal it for 7-10 days. After removing the film, the soil must be thoroughly tilled and exposed to sunlight at least twice, with an interval of 5-7 days between each application, to ensure complete dissipation of the fungicide. Sowing or transplanting should only proceed after confirming that the soil is free of phytotoxicity using the "Chinese cabbage seed germination method."

[0056] During periods of intense summer sunlight, deeply till the seedbed to a depth of 30-40 cm, breaking up soil clods. Then thoroughly irrigate, ensuring the soil moisture content reaches over 70% of field capacity. Next, tightly cover the entire seedbed with a transparent plastic film (≥0.05mm thick), sealing the edges with soil. Utilizing solar energy, this creates a "greenhouse effect" in the soil beneath the film, maintaining a soil temperature above 50℃ for 15-20 days at a depth of 25 cm under continuous sunny weather. This high-temperature, high-humidity environment effectively kills most soil-borne pathogens, nematodes, and weed seeds. After disinfection, remove the film and loosen the soil, allowing it to dry for 3-5 days to dissipate any accumulated harmful substances and restore the vitality of beneficial microorganisms.

[0057] In some embodiments of this application, the active ingredient of the sustained-release granules consists of metalaxyl and oxamyl, with a weight ratio of metalaxyl to oxamyl of 1:5 to 5:1.

[0058] The active ingredient in sustained-release granules can be composed of amino oligosaccharides and oxamyl, or it can be composed of methyltrophic Bacillus and metalaxyl, or it can be composed of metalaxyl and oxamyl, or metalaxyl and oxamyl.

[0059] The preferred slow-release granule formulation consists of metalaxyl and oxadixyl in a weight ratio of 1:5 to 5:1. The selection of the metalaxyl-oxadixyl combination as the core for controlling root rot in agarwood seedlings is based on a comprehensive consideration of the pathogen spectrum, agent characteristics, seedling physiological needs, and environmental safety. The combined use of these two agents achieves comprehensive coverage of almost all major pathogens causing root rot in agarwood (Phytophthora, Fusarium, and Pythium), solving the problem of narrow spectrum control with single agents. Metalaxyl acts on the nucleic acid synthesis process of pathogens, while oxadixyl affects cell membrane permeability and energy metabolism; this dual attack makes it more difficult for pathogens to develop resistance. Laboratory bioassays typically show that when metalaxyl and oxadixyl are combined in a 1:2 ratio, their co-toxicity coefficient (CTC) is much greater than 120, which is internationally recognized as having a significant synergistic effect, rather than a simple additive effect.

[0060] After being absorbed by plants, oxadixyl promotes root growth, stimulates wound healing, and improves seedling survival rate and stress resistance. This is an extremely valuable characteristic for agarwood seedlings whose roots have been damaged during transplanting. Metalaxyl has good systemic properties, can be absorbed by the roots and transported to all parts of the plant, and can also play a therapeutic role against pathogens that have already invaded the plant.

[0061] In some embodiments of this application, the sustained-release carrier of the sustained-release granules is composed of sodium alginate and attapulgite in a weight ratio of 1:1 to 1:3.

[0062] The slow-release carrier for sustained-release granules can be composed of sodium alginate and attapulgite, polylactic acid or polycaprolactone, zeolite or diatomaceous earth, or paraffin or beeswax and polyethylene wax, with sodium alginate and attapulgite being the preferred composition. When the carboxyl groups on the sodium alginate molecular chain encounter calcium ions, a transient ionic cross-linking reaction occurs, forming an "egg-box" structure that transforms the aqueous solution into a hydrogel. This process is gentle and rapid, making it ideal for encapsulating pesticides and bio-agents that are sensitive to high temperatures. The resulting gel network can physically encapsulate active ingredients such as metalaxyl and oxychlorpyrifos, which is the basis for achieving sustained release. The swelling and degradation behavior of the gel is closely related to soil moisture. When the soil is sufficiently moist, the gel absorbs water and swells, the network pores enlarge, and the drug release rate accelerates (meeting the need for higher efficacy during the rainy season when diseases are prevalent); when the soil is dry, the gel shrinks, and the release slows down. This achieves a kind of "intelligent" release, synchronized with the disease occurrence pattern.

[0063] Attapulgite possesses a nanoscale needle-like and rod-like crystalline structure and a huge internal surface area. Like a sponge, it can firmly adsorb a large number of pesticide molecules onto its surface and within its pores through physical adsorption and electrostatic interactions. This solves the problem of "burst release" (i.e., a large release of pesticide in a short period of time) that may occur in the initial stage of pure sodium alginate gel, resulting in a more stable and sustained release curve. Pure sodium alginate gel has low strength and is soft, easily crushed by compression in soil. Attapulgite, as a nano-reinforcing filler, is uniformly dispersed in the gel network, much like the reinforcing bars in reinforced concrete, greatly improving the mechanical strength of the particles and enabling them to maintain structural integrity during packaging, transportation, and in the soil.

[0064] Sodium alginate forms a continuous, hydrophilic gel phase, while attapulgite acts as a rigid nanounit embedded within it, creating a three-dimensional, hierarchical porous network of "organic-inorganic hybrid" structures. This structure possesses both the environmental responsiveness of gels and the stability and high load-bearing capacity of clay. Therefore, this carrier combination is not a simple stacking of common materials, but an innovative functional material system tailored to address specific issues such as the long growth period of agarwood seedlings, the correlation between disease occurrence and humidity, and the need to reduce the frequency of pesticide application.

[0065] In some embodiments of this application, the weight ratio of metalaxyl to oxamyl is 1:2, and the weight ratio of sodium alginate to attapulgite is 1:2.

[0066] It should be noted that these two specific ratios are key values ​​selected through creative work and extensive experimentation. Their combined effect achieves a control efficacy of >92% and a duration of action of >90 days. The 1:2 weight ratio of metalaxyl and oxyfenozide perfectly balances the control efficacy against oomycetes (dependent on metalaxyl) and Fusarium (dependent on oxyfenozide). This ensures extremely high killing efficiency against both major pathogens while maintaining the same total dosage. Considering cost, metalaxyl is typically more expensive. This ratio maximizes cost-effectiveness while ensuring optimal efficacy and avoiding overuse of metalaxyl.

[0067] The release of the drug involves two steps: desorption from the surface and pores of attapulgite and diffusion through the hydrogel network of sodium alginate. A 1:2 weight ratio of sodium alginate to attapulgite ensures that the rates of these two steps are matched, resulting in a smooth and sustained release profile. This provides an effective initial dose to quickly establish protection, followed by a slow and continuous release to maintain a long-term effective rhizosphere protective concentration, avoiding phytotoxicity caused by "burst release" and the control gap caused by "discontinuation of treatment."

[0068] In some embodiments of this application, the sustained-release granules are composed of the following components in weight percentage: metalaxyl 4%-6%, oxamyl 9%-11%, sodium alginate 4%-6%, attapulgite 9%-11%, citric acid 1%-3%, brassinolide 0.0005%-0.002%, alkyl polysaccharide 0.5%-2%, and the balance being bentonite.

[0069] It should be noted that this formulation ratio is the result of a precise balance among three major systems: active ingredient, carrier, and functional adjuvants. The total active ingredient content of approximately 15% (comprising metalaxyl and oxadixyl) is a commonly used concentration to balance efficacy and cost control; too low a concentration results in ineffectiveness, while too high a concentration increases costs and unnecessary environmental burden. The 1:2 ratio of metalaxyl to oxadixyl is the optimal synergistic ratio verified by the co-toxicity coefficient method. Fluctuations of 4%-6% and 9%-11% are to accommodate minor fluctuations in different production processes and the purity of the active ingredient, but the core ratio of 1:2 remains unchanged.

[0070] The total amount of the sustained-release carrier system, composed of sodium alginate and attapulgite, is approximately 15%, which is comparable to the total amount of the active ingredient, ensuring sufficient carrier material to load and encapsulate the drug. A ratio of 1:2 is the optimal structural ratio selected through gel strength testing, swelling degree testing, and release kinetic experiments. The resulting "organic-inorganic" hybrid gel network exhibits optimal mechanical strength and sustained-release performance.

[0071] Citric acid, as a pH adjuster and synergist, can slightly acidify the rhizosphere microenvironment, inhibiting pathogens that prefer neutral to alkaline conditions (such as Fusarium), while also enhancing the stability and permeability of pesticides like oxychloride. Brassinolide is a plant growth regulator with extremely high activity; even very low concentrations can significantly promote root development, alleviate pesticide stress, and induce systemic disease resistance, achieving a combination of "disease treatment" and "strengthening." Alkyl polysaccharides, as green surfactants and dispersants, help the components mix evenly during preparation and facilitate rapid wetting of the particles in the soil, initiating the release process. Bentonite, as a filler, plays a role in volume enhancement and shaping, and also helps the particles disintegrate and disperse in the soil. Its dosage is "surplus," meaning the amount used to reach 100% after supplementing all the above components.

[0072] In some embodiments of this application, before the rainy season arrives during the growing season, a shallow circular trench with a depth of 10cm-15cm is dug 15cm-20cm away from the root of the seedling. 2-3 kg / mu of slow-release granules is evenly applied into the trench, and then covered with soil.

[0073] The arrival of the rainy season brings high humidity, low temperatures, and abundant sunlight, creating an environment conducive to pathogen outbreaks. Therefore, in the active area of ​​root growth (outside the vertical projection of the root cap), a "chemical defense line" should be established in advance before the peak disease season (rainy season) to ensure that "medicine is available before disease" rather than "disease is available before medicine." This ensures a continuous and stable concentration of effective ingredients in the rhizosphere throughout the peak disease season, compensating for any potential decrease in the efficacy of basic pesticides over time.

[0074] In some embodiments of this application, the beneficial bacteria contained in the functional seaweed fertilizer are Trichoderma harzianum and / or Bacillus amyloliquefaciens.

[0075] During the growing season, applying functional seaweed fertilizer rich in Trichoderma harzianum and Bacillus amyloliquefaciens achieves a synergistic effect of 'nutrition' and 'biocontrol'. On the one hand, the active substances in seaweed directly promote root growth and enhance the plant's resistance; on the other hand, it provides continuous nutrition for the 'antibacterial composition' implanted during the seedling and transplanting stages, helping it establish a stable rhizosphere microbial dominance. This measure perfectly complements the 'chemically slow-release granules' used at key stages: the slow-release granules provide long-term, highly effective chemical inhibition against mainstream pathogens, while the biocontrol system is responsible for clearing away residual pathogens, occupying ecological niches, and preventing secondary infections. Together, these three constitute a three-dimensional, sustainable integrated prevention and control system for root rot, combining 'nutrition, prevention, and treatment' functions.

[0076] In some embodiments of this application, slow-release granules are used for root irrigation in the disease center area. Specifically, 10-20 grams of slow-release granules are applied to the root zone of each healthy seedling around the diseased hole.

[0077] The inventors designed a series of experiments to verify the proposed method for controlling root rot in agarwood seedlings. A completely randomized block design was used, with four treatments, each replicated three times, and 30 seedlings per plot. At the start of the experiment, equal amounts of a spore suspension of a mixed root rot pathogen were inoculated into the soil of each plot to create consistent disease-causing conditions. The groupings are shown in the table below:

[0078]

[0079]

[0080] Table 1 Experimental Scheme Grouping Table

[0081] Disease survey: Surveys were conducted 60 days (peak disease period) and 120 days (late growth period) after treatment.

[0082] Incidence rate (%) = (Number of diseased plants / Total number of plants surveyed) × 100%,

[0083] Disease index: Graded according to the degree of root rot (Grade 0: Healthy; Grade 1: Slight browning of the root collar; Grade 3: Less than 1 / 3 of the roots rotten; Grade 5: 1 / 3-1 / 2 of the roots rotten; Grade 7: More than 1 / 2 of the roots rotten; Grade 9: Entire plant dead). Disease index = [∑(Number of diseased plants × Representative value) / (Total number of plants × Highest disease grade value)] × 100.

[0084] Prevention and control effect (%) = [(disease index of blank control - disease index of treatment) / disease index of blank control] × 100%.

[0085] Growth indicators were measured at the end of the experiment (120 days). These included plant height, ground diameter, and fresh weight.

[0086] Soil microbial indicators: At the end of the experiment, rhizosphere soil samples were taken. The number of pathogenic bacteria (Fusarium, Phytophthora) and beneficial bacteria (Trichoderma, Bacillus) in the soil were determined by the dilution spread method.

[0087] Duration of effectiveness assessment: The persistence of the treatment is assessed by comparing the control effects over 60 days and 120 days.

[0088]

[0089] Table 2. Control effects of different treatments on root rot in agarwood seedlings.

[0090] As shown in Table 2, the control efficacy of group T1 was significantly higher than that of other treatment groups at both 60 and 120 days. Furthermore, the decrease in control efficacy from 60 to 120 days was the smallest (from 89.5% to 85.2%), demonstrating its excellent sustained efficacy. This is directly attributed to the long-term efficacy of the slow-release granules and the ecological stabilizing effect of the biological agent. Group T2 showed acceptable initial efficacy, but the efficacy declined sharply in the later stages, indicating a short duration of effectiveness and the need for multiple applications. Group T3 showed unstable efficacy and was significantly lower than the chemical and experimental groups.

[0091]

[0092] Table 3. Effects of different treatments on the growth of agarwood seedlings and soil microorganisms.

[0093] As shown in Table 3, the seedlings in group T1 exhibited significantly better growth indicators (plant height, ground diameter, and fresh weight), demonstrating that this method effectively promotes healthy seedling growth while preventing disease. Soil microbial analysis revealed that group T1 had the lowest number of rhizosphere pathogens and the highest number of beneficial bacteria, indicating that this invention successfully constructed a healthy rhizosphere microecological environment. While group T2 inhibited pathogens, it also severely damaged beneficial microorganisms, disrupting the ecological balance.

[0094] The verification experiments, through scientific data, strongly demonstrate that the integrated control scheme provided by this invention is significantly superior to existing single chemical or biological control methods in terms of control effect, duration of effectiveness, growth promotion, and improvement of soil microecology, producing an unexpected synergistic effect.

[0095] Those skilled in the art will understand that the above embodiments are specific implementations of this application, and in practical applications, various changes can be made in form and detail without departing from the spirit and scope of this application.

Claims

1. A method for preventing and controlling root rot in agarwood seedlings, characterized in that, Includes the following steps: Seedling stage: Soak seeds and disinfect seedbed soil with antibacterial composition; Transplanting stage: At the bottom of the prepared planting hole, evenly spread 3-5 kg / mu of slow-release granules and dip the seedling roots in the antibacterial composition; During the growing season: control humidity by raising raised beds and using precise drip irrigation, and regularly apply functional seaweed fertilizer containing beneficial bacteria to the roots of the seedlings; In the early stages of the disease: Remove diseased plants, apply lime to the affected area, and drench the roots with the slow-release granules in the central area of ​​the disease.

2. The method for preventing and controlling root rot in agarwood seedlings according to claim 1, characterized in that, The antibacterial composition consists of Trichoderma harzianum and Bacillus amyloliquefaciens in a ratio of 1:2 to 2:1 based on the number of viable bacteria.

3. The method for preventing and controlling root rot in agarwood seedlings according to claim 1, characterized in that, During the seedling stage, the seedbed soil is disinfected using a microporous fungicide or solar energy.

4. The method for preventing and controlling root rot in agarwood seedlings according to claim 1, characterized in that, The active ingredients of the sustained-release granules consist of metalaxyl and oxamyl, with a weight ratio of metalaxyl to oxamyl of 1:5 to 5:

1.

5. The method for preventing and controlling root rot in agarwood seedlings according to claim 4, characterized in that, The sustained-release carrier of the sustained-release granules is composed of sodium alginate and attapulgite in a weight ratio of 1:1 to 1:

3.

6. The method for preventing and controlling root rot in agarwood seedlings according to claim 5, characterized in that, The weight ratio of metalaxyl to oxamyl is 1:2, and the weight ratio of sodium alginate to attapulgite is 1:

2.

7. The method for preventing and controlling root rot in agarwood seedlings according to claim 6, characterized in that, The sustained-release granules are composed of the following components in weight percentage: metalaxyl 4%-6%, oxadixyl 9%-11%, sodium alginate 4%-6%, attapulgite 9%-11%, citric acid 1%-3%, brassinolide 0.0005%-0.002%, alkyl polysaccharide 0.5%-2%, with the balance being bentonite.

8. The method for preventing and controlling root rot in agarwood seedlings according to claim 1, characterized in that, Before the rainy season arrives during the growing season, dig a shallow circular trench 10-15 cm deep, 15-20 cm away from the base of the seedlings. Apply 2-3 kg / mu of the slow-release granules evenly into the trench, and then cover with soil.

9. The method for preventing and controlling root rot in agarwood seedlings according to claim 1, characterized in that, The beneficial bacteria contained in the functional seaweed fertilizer are Trichoderma harzianum and / or Bacillus amyloliquefaciens.

10. The method for preventing and controlling root rot in agarwood seedlings according to claim 1, characterized in that, In the disease-affected area, apply slow-release granules to the roots. Specifically, with the diseased hole as the center, apply 10-20 grams of slow-release granules to the root zone of each healthy seedling in the surrounding area.

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