Microbial agent for preventing and treating nematode diseases as well as preparation method and application of microbial agent

Abstract

The invention provides a microbial agent for preventing and treating nematode diseases as well as a preparation method and application thereof, and relates to the technical field of organic fertilizers, the microbial agent is mainly prepared from the following raw materials in percentage by mass: 60-75% of microbial thalli; 25%-40% of an additive; wherein the microbial thalli are prepared from purpureocillium lilacinum, bacillus subtilis, brevibacillus laterosporus, bacillus mucilaginosus and lactobacillus sporogenes. Through the collaborative design of a specific strain combination and a functional additive, the stress resistance and colonization ability of the microbial inoculum in a complex soil environment can be effectively improved, meanwhile, an efficient synergistic mechanism of fungi and bacteria is established, the microbial inoculum can adapt to complex soil types, and the control effect on nematodes can be effectively improved. The invention fundamentally solves the industrial obstacles of poor environmental adaptability, short lasting period, single function and the like of biological agents, and provides a solution for large-scale application for chemical pesticide substitution.

Description

Technical Field

[0001] The present invention relates to the technical field of organic fertilizers, and in particular to a microbial agent for preventing and treating nematodes, a preparation method and application thereof. Background Art

[0002] Soil nematode diseases have become a major biotic stress constraining agricultural production. Root-knot nematodes, in particular, can severely reduce the yields of cash crops like vegetables and fruit trees. Currently, control relies primarily on chemical nematicides (such as avermectin and thiazolinone). However, long-term use of these pesticides can lead to significant problems, including excessive pesticide residues, imbalances in the soil microbiome, and increased pesticide resistance in nematodes.

[0003] Biological control has become an alternative due to its environmental compatibility. Among them, Pseudomonas lilacinus, a fungus that parasitizes nematode eggs, has been widely used. However, single-bacterial preparations suffer from unstable efficacy and poor environmental adaptability. Recent research has explored composite microbial agents (combining Pseudomonas lilacinus with Bacillus subtilis, or combining Bacillus subtilis, Pseudomonas lilacinus, and Bacillus gelatinus). For example, Chinese invention patent application CN109355236A discloses a composite microbial agent for nematode control that combines Bacillus subtilis, Lactobacillus casei, Bacillus gelatinus, and Paecilomyces lilacinus. However, inappropriate strain combinations can lead to insufficient synergistic effects. For example, Bacillus subtilis rapidly consumes nutrients and inhibits fungal growth, or spore conversion is low, resulting in a loss of viable bacteria count exceeding 40% during storage. Existing composite microbial agents for soil nematode control perform poorly in complex soil environments, and technical bottlenecks in nematode control remain to be overcome. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a microbial agent for preventing and controlling nematode diseases. Through the coordinated design of specific bacterial species combinations and functional additives, the agent can effectively improve the stress resistance and colonization ability of the agent in complex soil environments; at the same time, an efficient synergistic mechanism between fungi and bacteria is established, which can not only adapt to complex soil types, but also effectively improve the nematode control effect.

[0005] In order to achieve the purpose of the present invention, the present invention provides a microbial agent for preventing and treating nematodes, which is prepared from the following raw materials in terms of mass percentage: Microbial cells 60%-75%; Additives 25%-40%; The microbial cells are prepared from Bacillus lilacinus, Bacillus subtilis, Brevibacillus laterosporus, Bacillus gelatinus and Spore Lactobacillus; and the additives are prepared from humic acid, sodium alginate and chitosan.

[0006] Furthermore, the mass ratio of humic acid, sodium alginate and chitosan in the additive is (20-25): (1-3): (0.1-0.5).

[0007] Furthermore, the mass ratio of humic acid, sodium alginate and chitosan in the additive is 25:2:0.3.

[0008] Furthermore, the humic acid is any one of mineral-derived humic acid, biochemical humic acid or natural humic acid.

[0009] Furthermore, the total viable count of the microbial cells is ≥ 2×10 10 CFU / g; Furthermore, the total viable count of the microorganisms in the seriously diseased area is ≥5×10 10 CFU / g.

[0010] The present invention also provides a method for preparing the above-mentioned microbial agent for preventing and treating nematodes, comprising the following steps: S1. Activate and culture Bacillus lilacinus, Bacillus subtilis, Brevibacillus laterosporus, Bacillus jelly-like and Spore Lactobacillus respectively; S2. collecting the spore suspension of Bacillus lilacinus, the spore suspension of Bacillus subtilis, the spore suspension of Brevibacillus laterosporus, the spore suspension of Bacillus gelatinus, and the spore suspension of Lactobacillus sporogenes respectively; S3. Drying the spore suspension of Pseudomonas lilacinus, the spore suspension of Bacillus subtilis, the spore suspension of Brevibacillus laterosporus, the spore suspension of Bacillus jelly-like, and the spore suspension of Lactobacillus sporogenes in step S2 separately to obtain Pseudomonas lilacinus spore powder, Bacillus subtilis spore powder, Brevibacillus laterosporus spore powder, Bacillus jelly-like, and Lactobacillus sporogenes spore powder, and mixing them to prepare microbial cells; S4, preparing humic acid, sodium alginate and chitosan into solutions respectively, mixing them in sequence, drying and granulating them to obtain a granular additive; S5. Mix and stir the microbial cells prepared in step S3 and the additive obtained in step S4 to obtain a microbial agent for preventing and treating nematodes.

[0011] Furthermore, in step S3, the spore powder of Pseudomonas lilacinus, the spore powder of Bacillus subtilis, the spore powder of Brevibacillus laterosporus, the spore powder of Bacillus gelatinosa and the spore powder of Lactobacillus sporogenes are mixed in a mass ratio of (15-40): (15-20): (12-20): (1-8): (1-5).

[0012] Furthermore, the spore powder of Pseudomonas lilacinus, the spore powder of Bacillus subtilis, the spore powder of Brevibacillus laterosporus, the spore powder of Bacillus gelatinosa and the spore powder of Lactobacillus sporogenes are mixed in a mass ratio of 30:16:16:5:3.

[0013] Furthermore, in step S4, the particle size of the additive is 0.5 mm-1 mm.

[0014] Furthermore, in step S4, humic acid is passed through a 200-mesh sieve and dissolved in a 1 wt% sodium hydroxide solution, and the pH is adjusted to 7.0; sodium alginate is dissolved in sterile water to prepare an aqueous solution with a concentration of 2 wt%; chitosan is prepared into a chitosan solution with a concentration of 1 wt% using 1 wt% acetic acid; and the chitosan solution is added last during the mixing process.

[0015] Furthermore, in step S3, the drying temperature is 15°C-35°C.

[0016] Furthermore, in step S5, the mixing and stirring time is ≥5h.

[0017] The present invention also provides the use of the microbial agent for preventing and controlling nematodes in preventing and controlling soil nematodes.

[0018] Compared with the prior art, the present invention has the following technical effects: Through the coordinated design of specific bacterial strain combinations and functional additives, the stress resistance and colonization ability of bacterial agents in complex soil environments can be effectively improved. At the same time, an efficient synergistic mechanism between fungi and bacteria is established, which can not only adapt to complex soil types, but also effectively improve the prevention and control effect of nematodes. This fundamentally solves the industrialization obstacles of biological agents such as poor environmental adaptability, short duration of effectiveness, and single function, and provides a scalable application solution for replacing chemical pesticides. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0020] In a first aspect, the present invention provides a microbial agent for preventing and treating nematodes, which is mainly prepared from the following raw materials, calculated by mass percentage: Microbial cells 60%-75%; Additives 25%-40%; The microbial cells are prepared from Bacillus lilacinus, Bacillus subtilis, Brevibacillus laterosporus, Bacillus gelatinus and Lactobacillus spores.

[0021] In this invention, a composite system of fungi and four Bacillus species achieves synergistic control. The bacterial combination covers three mechanisms: parasitism, inhibition, and growth promotion, overcoming the limited functionality of a single bacterium. The synergistic effect of multiple bacterial species significantly improves nematode control and is suitable for sandy, clay, and other complex soil types. Additives provide physical protection for the bacteria.

[0022] In the microbial agent provided by the present invention, the bacterial body accounts for more than 60%, which can ensure the number of active microorganisms and meet the effective concentration in the field; and the additive accounts for more than 25%, which can ensure the effective protection of the additive for the bacterial body.

[0023] In some embodiments, the additive is prepared from humic acid, sodium alginate and chitosan in a mass ratio of (20-25): (1-3): (0.1-0.5).

[0024] In some embodiments, the mass ratio of humic acid, sodium alginate and chitosan in the above additive is 25:2:0.3; Humic acid, as a carrier, has strong adsorption capacity. Within the above ratio range, it can slowly release nutrients and buffer soil pH fluctuations, while ensuring colonization space for bacteria. Sodium alginate has good film-forming properties and can wrap bacteria, allowing the bacteria to resist drought or ultraviolet rays to adapt to complex environments, and can form an effective gel layer under the above mass ratio. In the case of excessive sodium alginate, the sodium alginate particles will be too hard, thereby affecting the release of bacteria. The cationic properties of chitosan can enhance the adsorption of bacteria on the nematode epidermis, thereby improving the parasitic efficiency of the bacteria and playing an auxiliary role in inhibiting nematodes. In the process of selecting the ratio, the amount of chitosan can be selected as a trace amount to prevent excessive chitosan from inhibiting fungal growth.

[0025] In some embodiments, the humic acid is any one of mineral-derived humic acid, biochemical humic acid, or natural humic acid. Humic acid itself contains carboxyl and phenolic hydroxyl groups, which can provide protection for bacteria. Mineral-derived humic acid is relatively low in cost and is more suitable for industrialization needs.

[0026] In some embodiments, the total viable count of microorganisms is ≥ 2×10 10 CFU / g. In the critically ill area, the total viable bacteria count is required to be ≥5×10 10 CFU / g.

[0027] In a second aspect, the present invention provides a method for preparing a microbial agent for preventing and treating nematodes, comprising the following steps: S1. Activate and culture Bacillus lilacinus, Bacillus subtilis, Brevibacillus laterosporus, Bacillus jelly-like and Spore Lactobacillus respectively; S2. collecting the spore suspension of Bacillus lilacinus, the spore suspension of Bacillus subtilis, the spore suspension of Brevibacillus laterosporus, the spore suspension of Bacillus gelatinus, and the spore suspension of Lactobacillus sporogenes respectively; S3. Drying the spore suspension of Pseudomonas lilacinus, the spore suspension of Bacillus subtilis, the spore suspension of Brevibacillus laterosporus, the spore suspension of Bacillus jelly-like, and the spore suspension of Lactobacillus sporogenes in step S2 separately to obtain spore powder of Pseudomonas lilacinus, spore powder of Bacillus subtilis, spore powder of Brevibacillus laterosporus, spore powder of Bacillus jelly-like, and spore powder of Lactobacillus sporogenes, and mixing them to prepare microbial cells; S4, preparing humic acid, sodium alginate and chitosan into solutions respectively, mixing them in sequence, drying and granulating them to obtain a granular additive; S5. Mix and stir the microbial cells prepared in step S3 and the additive obtained in step S4 to obtain a microbial agent for preventing and treating nematodes.

[0028] Cultivating each strain separately avoids competitive inhibition between different strains when mixed in liquid form, ensuring independent high activity of each bacterium; collecting spore or spore suspensions separately during the preparation process can effectively ensure the survival rate of subsequent drying; after the strains are dried, mixing them in the form of dry powder can avoid bacteria secreting antibiotics and inhibiting fungi during liquid mixing. In addition, dry mixing can eliminate physiological antagonism and retain the activity of each bacterium.

[0029] Humic acid, sodium alginate, and chitosan are not simply physically mixed, but rather form a functional composite structure through intermolecular forces, ultimately forming a carrier. Humic acid itself contains a large number of carboxyl and hydroxyl groups, forming the final skeleton network; sodium alginate can form a hydrogen bond network with the carboxyl and hydroxyl groups in humic acid, and after release, it can gel with calcium ions in the soil and form "microcapsules"; the amino groups in chitosan can electrostatically self-assemble with the carboxyl groups in sodium alginate, forming a positive charge on the particle surface and providing protection. In this process, the chitosan solution needs to be added last to avoid premature acidification of the sodium alginate and ensure the formation of a composite structure of "humic acid core-sodium alginate gel layer-chitosan shell", which can make this carrier have sustained release, stress resistance, and targeting properties, thereby effectively slowing down and targeting nematodes, thereby improving the killing effect on nematodes.

[0030] In fact, the bacteria and the carrier are mixed to form a "core-shell-bacteria" structure, and the bacteria are physically adsorbed in the gaps of the carrier.

[0031] In some embodiments, in step S3, the spore powder of Pseudomonas lilacinus, the spore powder of Bacillus subtilis, the spore powder of Brevibacillus laterosporus, the spore powder of Bacillus gelatinosa, and the spore powder of Lactobacillus sporogenes are mixed in a mass ratio of (15-40): (15-20): (12-20): (1-8): (1-5).

[0032] In some embodiments, the spore powder of Pseudomonas lilacinus, the spore powder of Bacillus subtilis, the spore powder of Brevibacillus laterosporus, the spore powder of Bacillus gelatinosa, and the spore powder of Lactobacillus sporogenes are mixed in a mass ratio of 30:16:16:5:3; By limiting the ratio of each bacterial species, the amount of each species used should not be too much, to prevent them from competing for growth and squeezing each other's living space, which would reduce the killing effect on nematodes. In addition, the amount of each bacterial species used should also be considered to maximize the synergistic effect between them. Under this ratio, the synergistic effect of Bacillus subtilis and Brevibacillus laterosporus can be maximized, effectively enhancing the inhibitory and killing effect on nematodes; at the same time, Bacillus gelatinosa and Sporolactobacillus are added in trace amounts as auxiliary bacteria. Bacillus gelatinosa can solubilize phosphorus and fix nitrogen, promote healthy root growth, and indirectly enhance crop resistance. Excessive use of Bacillus gelatinosa will compete for root colonization sites; while Sporolactobacillus can regulate soil pH, inhibit pathogenic bacteria, and create a good living environment for functional bacteria. Excessive use of Sporolactobacillus may lead to soil acidification.

[0033] In some embodiments, in step S3, the drying temperature is 15° C.-35° C. Low-temperature drying can prevent high temperatures from killing spores or spores, thereby maximizing the survival rate of the bacteria.

[0034] In a third aspect, the present invention also provides the use of a microbial agent for preventing and controlling nematodes in preventing and controlling soil nematodes.

[0035] The following is elaborated with reference to specific embodiments: Example 1 a. Culture of Psoralea corylifolia PDA medium (potato 200 g / L, glucose 20 g / L, agar 15 g / L) was used for constant culture at 25°C and 70%-80% humidity for 6 days until the spores matured. The colonies were then scraped with sterile water and passed through a 200-mesh sieve to remove the mycelium to obtain a spore suspension.

[0036] b. Culture of Bacillus subtilis and Brevibacillus laterosporus Bacillus subtilis and Brevibacillus laterosporus were cultured in LB liquid medium (10 g / L tryptone, 5 g / L yeast extract, 10 g / L sodium chloride) at 37°C and 180 rpm for 48 h, and spores were collected.

[0037] c. Culture of jelly-like Bacillus The culture was carried out using a modified silicate medium (sucrose 5 g / L, potassium dihydrogen phosphate 0.5 g / L, magnesium sulfate 0.5 g / L, silicate powder 10 g / L) at 30°C and 150 rpm for 72 h, and the spores were collected.

[0038] d. Sporolactobacillus MRS medium (10 g / L peptone, 10 g / L beef extract, 20 g / L glucose, 5 g / L sodium acetate) was used for culture at 37°C under anaerobic conditions (nitrogen was added to maintain the oxygen concentration <0.5%) for 36 h, and spores were collected.

[0039] e. Preparation of microbial cells The collected spores and spores were dried at 30°C in a low-temperature air flow. After drying, 30g of spore powder of Psoralea lilacinus, 16g of spore powder of Bacillus subtilis, 16g of spore powder of Brevibacillus laterosporus, 5g of spore powder of Bacillus jelly-like, and 3g of spore powder of Lactobacillus sporogenes were weighed, wherein the mass ratio of the spore powder of Psoralea lilacinus, the spore powder of Bacillus subtilis, the spore powder of Brevibacillus laterosporus, the spore powder of Bacillus jelly-like, and the spore powder of Lactobacillus sporogenes was 30:16:16:5:3. The spore powders and spore powders were mixed and stirred at 200 rpm for 3 hours to obtain a composite bacterial cell dry powder, which was used as a microbial cell.

[0040] f. Preparation of vector Weigh 27.5g of mineral-derived humic acid, 2.2g of sodium alginate, and 0.3g of chitosan. The mass ratio of humic acid, sodium alginate, and chitosan is approximately 25:2:0.3. Dissolve the mineral-derived humic acid in a 1wt% sodium hydroxide solution at 25°C, and gradually add hydrochloric acid to adjust the pH to 7.0. Dissolve the sodium alginate in a sterile aqueous solution to prepare a 2wt% sodium alginate aqueous solution. Prepare a 1wt% chitosan solution with a 1wt% acetic acid solution.

[0041] The mineral humic acid solution and the sodium alginate solution were mixed and stirred until uniform to obtain a mixed solution; then the chitosan solution was added to the mixed solution and stirred for 20 minutes, followed by spray drying (inlet 60°C / outlet 40°C) to obtain a granular additive, and the prepared additive was sieved to obtain a carrier with a particle size of 1 mm.

[0042] g. Preparation of composite bacterial agent The carrier obtained in step f and the microbial cells obtained in step e were mixed and stirred for 5 hours to obtain the microbial agent.

[0043] Example 2 Based on Example 1, the difference is that the amount of each microbial cell in step e and the amount of each substance of the additive in step f are changed. The remaining steps are consistent with Example 1, as follows: Weigh 25.6 g of Purple Sporangium lilacinum spore powder, 25.6 g of Bacillus subtilis spore powder, 20.4 g of Brevibacillus laterosporus spore powder, 1.7 g of Bacillus jelly-like spore powder, and 1.7 g of Sporolactobacillus spore powder. Now, the mass ratio of Purple Sporangium lilacinum spore powder, Bacillus subtilis spore powder, Brevibacillus laterosporus spore powder, Bacillus jelly-like spore powder, and Sporolactobacillus spore powder is close to 15:15:12:1:1.

[0044] Weigh 23.7 g of mineral-source humic acid, 1.2 g of sodium alginate, and 0.1 g of chitosan. At this time, the mass ratio of mineral-source humic acid, sodium alginate, and chitosan is close to 20:1:0.1.

[0045] Example 3 Based on Example 1, the difference is that the amount of each microbial cell in step e and the amount of each substance of the additive in step f are changed. The remaining steps are consistent with Example 1, as follows: Weigh 25.8 g of Psoralea corylifolia spore powder, 12.9 g of Bacillus subtilis spore powder, 12.9 g of Brevibacillus laterosporus spore powder, 5.2 g of Bacillus jelly-like spore powder and 3.2 g of Spore Lactobacillus spore powder. Now, the mass ratio of Psoralea corylifolia spore powder, Bacillus subtilis spore powder, Brevibacillus laterosporus spore powder, Bacillus jelly-like spore powder and Spore Lactobacillus spore powder is close to 40:20:20:8:5.

[0046] Weigh 35 g of mineral-source humic acid, 4.2 g of sodium alginate and 0.8 g of chitosan. At this time, the mass ratio of mineral-source humic acid, sodium alginate and chitosan is close to 25:3:0.5.

[0047] Comparative Example 1 According to the cultivation method of Example 1, the purpurogenous fungus was cultured and spore powder was collected, and 70 g of the spore powder was weighed; at the same time, the carrier (additive) prepared in the same manner as in Example 1 was added, and the mass of the added carrier was also the same as that in Example 1.

[0048] Comparative Example 2 Based on Example 1, the difference is that step c and step d in Example 1 are not used, and the cell composition and amount of the microbial cells in step e are changed. The remaining steps are consistent with Example 1, as follows: Weigh 33.8 g of Psoralea corylifolia spore powder, 18.1 g of Bacillus subtilis spore powder, and 18.1 g of Brevibacillus laterosporus spore powder. At this time, the mass ratio of Psoralea corylifolia spore powder, Bacillus subtilis spore powder, and Brevibacillus laterosporus spore powder is close to 30:16:16.

[0049] Comparative Example 3 Based on Example 1, the difference is that only step f is changed, that is, the ratio between the various substances in the additive is changed, and the remaining steps are consistent with Example 1, as follows: Weigh 22.5 g of mineral humic acid, 6 g of sodium alginate and 1.5 g of chitosan. At this time, the mass ratio of humic acid, sodium alginate and chitosan is close to 15:4:1.

[0050] Comparative Example 4 Based on Example 1, the difference is that step f is not adopted and the carrier prepared in step f of Example 1 is not added in step g, and the remaining steps are consistent with Example 1.

[0051] Experimental Example 1: Nematode Control Effect Test Soil treatment: Take nematode-infected soil (root-knot nematode eggs ≥ 2000 / 100g) and distribute it into pots (2kg / pot).

[0052] Groups: Set up control group 1, which was treated with water only; Experimental group: The microbial agents prepared in the example and comparative examples were mixed into the soil at a mass ratio of 0.5% (5 g / kg). Tomato seedlings were planted and cultured in a greenhouse at 25°C for 30 days. The mortality rate of second-instar larvae, egg mass reduction rate, and plant biomass were tested. The experimental results are shown in Table 1.

[0053] Table 1 Nematode prevention effect test

[0054] Experimental Example 2: Environmental adaptability and sustained-release performance test Soil preparation: sandy soil (sand content > 85%, organic matter < 1%), clay (clay content > 40%, organic matter 2-3%), and continuously planted diseased soil (tomatoes planted for 3 consecutive years, pH 5.5-6.5, containing ≥ 2000 root-knot nematode eggs / 100g). Each soil type is packaged at 1 kg / pot.

[0055] Drought group: normal soil, after drying, the moisture content was reduced to 10%.

[0056] Ultraviolet group: UV-B irradiation (30W / m 2 , 6 hours per day).

[0057] Control group 2: soil without any bacterial agent added.

[0058] Experimental group: The microbial agents prepared in the examples and comparative examples were added in equal amounts to sandy soil, clay soil, diseased soil from continuous cropping, and soil from the drought group and UV group, respectively; Then, samples were taken on the 7th, 14th and 30th days to determine the number of viable bacteria in the soil and the residual amount of sodium alginate. The experimental results are shown in Tables 2 to 5.

[0059] Table 2 Number of viable bacteria and residual amount of sodium alginate in sandy soil

[0060] Table 3 Number of viable bacteria and residual amount of sodium alginate in clay

[0061] Table 4 Number of viable bacteria and residual amount of sodium alginate in diseased soil after continuous cropping

[0062] Table 5 The number of viable bacteria and the amount of sodium alginate residue in the soil of the drought group and the ultraviolet group

[0063] The above experimental results demonstrate that the microbial agent prepared by the present invention overcomes the limitation of poor nematode control effectiveness of a single bacterial strain; by using multiple bacterial strains and a carrier (additive) in synergy, the control efficacy is significantly enhanced. The residual amount of sodium alginate demonstrates the sustained-release effect of the carrier (additive) structure of the present invention, making the prepared microbial agent adaptable to different soil types and complex environments, thereby improving its control performance against soil nematodes.

Claims

1. A microbial agent for preventing and treating nematodes, characterized in that: In terms of mass percentage, it is prepared from the following raw materials: Microbial cells 60%-75%; Additives 25%-40%; The microbial cells are prepared from Bacillus lilacinus, Bacillus subtilis, Brevibacillus laterosporus, Bacillus jelly-like and Spore Lactobacillus; the additives are prepared from humic acid, sodium alginate and chitosan; The mass ratio of humic acid, sodium alginate and chitosan is (20-25): (1-3): (0.1-0.5).

2. The microbial agent for preventing and treating nematodes according to claim 1, characterized in that: In the additive, the mass ratio of humic acid, sodium alginate and chitosan is 25:2:0.

3.

3. The microbial agent for preventing and treating nematodes according to claim 2, characterized in that: The humic acid is any one of mineral humic acid, biochemical humic acid or natural humic acid.

4. The microbial agent for preventing and treating nematodes according to claim 1, characterized in that: The total viable count of the microbial cells is ≥2×10 10 CFU / g.

5. A method for preparing a microbial agent for controlling nematodes according to any one of claims 1 to 4, characterized in that: The steps include: S1. Activate and culture Bacillus lilacinus, Bacillus subtilis, Brevibacillus laterosporus, Bacillus jelly-like and Spore Lactobacillus respectively; S2. collecting the spore suspension of Bacillus lilacinus, the spore suspension of Bacillus subtilis, the spore suspension of Brevibacillus laterosporus, the spore suspension of Bacillus gelatinus, and the spore suspension of Lactobacillus sporogenes respectively; S3. Drying the spore suspension of Pseudomonas lilacinus, the spore suspension of Bacillus subtilis, the spore suspension of Brevibacillus laterosporus, the spore suspension of Bacillus jelly-like, and the spore suspension of Lactobacillus sporogenes in step S2 separately to obtain Pseudomonas lilacinus spore powder, Bacillus subtilis spore powder, Brevibacillus laterosporus spore powder, Bacillus jelly-like, and Lactobacillus sporogenes spore powder, and mixing them to prepare microbial cells; S4, preparing humic acid, sodium alginate and chitosan into solutions respectively, mixing them in sequence, drying and granulating them to obtain a granular additive; S5. Mix and stir the microbial cells prepared in step S3 and the additive obtained in step S4 to obtain a microbial agent for preventing and treating nematodes.

6. The method for preparing the microbial agent for preventing and treating nematodes according to claim 5, characterized in that: In the step S3, the spore powder of Pseudomonas lilacinus, the spore powder of Bacillus subtilis, the spore powder of Brevibacillus laterosporus, the spore powder of Bacillus gelatinus and the spore powder of Lactobacillus sporogenes are mixed in a mass ratio of (15-40): (15-20): (12-20): (1-8): (1-5).

7. The method for preparing the microbial agent for preventing and treating nematodes according to claim 6, characterized in that: The spore powder of Purpureus lilacinus, the spore powder of Bacillus subtilis, the spore powder of Brevibacillus laterosporus, the spore powder of Bacillus gelatinosa and the spore powder of Lactobacillus sporogenes are mixed in a mass ratio of 30:16:16:5:

3.

8. The method for preparing the microbial agent for preventing and treating nematodes according to claim 7, characterized in that: In step S3, the drying temperature is 15°C-35°C.

9. Use of the microbial agent for controlling nematodes according to any one of claims 1 to 4 in controlling soil nematodes.

Images