Microbial-chemical synergistic prevention and control method for corn pests

Abstract

The present application provides a kind of microbial-chemical synergistic prevention and control method of corn pest.The steps include: preparing coated compound microbial agent, mixing efficient insecticidal microorganism and pathogenic biological control agent, using biological coating material to carry out coating treatment by in-situ polymerization method;Preparation of microcapsule preparation, low-toxicity chemical agent and coated compound microbial agent are respectively microencapsulated with temperature-sensitive material to obtain chemical agent microcapsule and microbial agent microcapsule;Precise application, combined with different growth stages of corn and occurrence law of target pest, two kinds of microcapsules and composite compatibility adjuvant are applied synergistically.The present application realizes the precise connection of rapid pest control of chemical agent and long-term protection of microbial agent by means of temperature-sensitive microcapsule differentiation design, achieves the effect of rapid pest control without inhibition, long-term prevention and control without lag, and takes into account the prevention and control effect and ecological safety.

Description

Technical Field

[0001] This invention relates to the field of agricultural pest control technology, specifically to a microbial-chemical synergistic control method for corn pests. Background Technology

[0002] Corn is one of my country's main food crops, and its yield and quality are directly related to national food security and agricultural economic development. However, corn cultivation faces serious damage from various pests, among which the corn borer and aphids are the two most widespread and damaging pests, affecting corn throughout its entire growth period. The corn borer larvae bore into the corn stalks, whorls, and ears, causing lodging, empty stalks, and underdeveloped kernels, resulting in yield reductions of over 30% in severe cases. Aphids, as adults and nymphs, pierce and suck sap from corn leaves, stalks, and ears, directly impacting corn growth and development and spreading corn viral diseases, further exacerbating the damage. Spider mites (red spider mites), as adults and nymphs, pierce and suck sap from corn leaves, causing yellow-white spots on affected leaves. In severe cases, entire leaves wither and fall off, leading to decreased photosynthetic efficiency, insufficient grain filling, and yield reductions of 20%-40%. Furthermore, their rapid reproduction rate (10-15 days per generation under suitable temperatures) and tendency to cause outbreaks pose a significant threat to corn production.

[0003] Currently, the control of corn pests mainly falls into three categories: single chemical control, single microbial control, and traditional microbial-chemical synergistic control. Single chemical control rapidly suppresses pest populations through the application of chemical agents, achieving high control efficiency. However, long-term use alone can lead to pesticide resistance in pests, and chemical residues pollute soil, water, and agricultural products, harming human and animal health, disrupting the ecological balance in fields, and failing to meet the needs of green agriculture development. Single microbial control, centered on insecticidal microorganisms such as Bacillus thuringiensis and Beauveria bassiana, has advantages such as being environmentally friendly, residue-free, and less prone to resistance development. However, it suffers from drawbacks such as slow onset of action, insufficient control during peak periods, and significant susceptibility to environmental factors, making it difficult to achieve effective control of corn pests alone. Traditional microbial-chemical synergistic control attempts to combine the advantages of both to achieve the goal of "rapid pest control + long-term protection," but it generally faces core technological bottlenecks: there is a significant antagonistic effect between chemical agents and microorganisms. Chemical agents inhibit the germination and metabolism of microorganisms, leading to reduced microbial activity and a shortened effective period. Conversely, the presence of microorganisms also affects the insecticidal effect of chemical agents, making true synergistic efficacy impossible. Existing technologies mostly adopt a passive adaptation mode of "simply reducing the amount of chemical agents" or "simple combination of microorganisms and chemical agents", which fails to fundamentally solve the compatibility problem between the two, resulting in poor synergistic control effect and difficulty in meeting the actual needs of corn production. Therefore, developing a method for the coordinated control of corn pests that can completely solve the problem of antagonism between chemical agents and microorganisms, achieve efficient synergy between the two, and take into account the effectiveness of control, ecological safety, and operability has become an urgent technical problem to be solved in the current corn planting field. Summary of the Invention

[0004] Technical Problem to be Solved: To address the aforementioned technical problems, the purpose of this invention is to provide a microbial-chemical synergistic control method for corn pests. Through microbial targeted isolation and encapsulation technology, direct contact between chemical agents and microorganisms is spatially isolated, eliminating the basis for antagonistic effects and ensuring that microorganisms and chemical agents each play their respective roles, thus providing a guarantee for subsequent synergistic control. Simultaneously, through the differentiated design of temperature-sensitive microcapsules, a connection is achieved between rapid pest control by chemical agents and long-term protection by microbial agents, avoiding direct contact and antagonism between the two, achieving the effect of rapid pest control without inhibition and long-term control without delay.

[0005] Technical solution: A microbial-chemical synergistic control method for corn pests, comprising the following steps: (1) Preparation of coated compound microbial agent: mix highly effective insecticidal microorganisms with pathogenic antibacterial agents, and use biological coating materials to coat them by in-situ polymerization to prepare coated compound microbial agent; (2) Preparation of microcapsule formulations: Low-toxic chemical agents and encapsulated compound bacterial agents are respectively encapsulated in microcapsules using temperature-sensitive materials to prepare chemical agent microcapsules and microbial agent microcapsules; (3) Precise application: At different growth stages of corn, combined with the occurrence patterns of target pests (corn borer, aphid, spider mite (red spider)), chemical agent microcapsules, microcapsules of microbial agents and compound compatible adjuvants are applied in combination. The temperature-sensitive properties are used to achieve the first slow release of chemical agents and the second slow release of microbial agents, so as to achieve the synergistic effect of rapid pest control and long-term prevention and control. Furthermore, the highly effective insecticidal microorganism is one or more of Bacillus thuringiensis, Beauveria bassiana, and Bacillus cereus.

[0006] Furthermore, the pathogenic antibacterial agent is Trichoderma harzianum, and / or Bacillus subtilis is added as an adjunct.

[0007] Furthermore, the mixing ratio of the highly effective insecticidal microorganism and the pathogenic antibacterial agent is: Bacillus thuringiensis: Beauveria bassiana: Bacillus subtilis: Trichoderma harzianum = (2-3):1:(1-2):1.

[0008] Furthermore, the bio-coating material is a chitosan-sodium alginate complex with a ratio of chitosan:sodium alginate = 1:1.5, and 0.02% glutaraldehyde is added as a crosslinking agent.

[0009] Furthermore, the low-toxicity chemical agent is one or more of thiamethoxam, azadirachtin, and chlorantraniliprole.

[0010] Furthermore, the temperature-sensitive material is poly(N-isopropylacrylamide) with a critical temperature of 25°C.

[0011] Furthermore, the chemical agent microcapsule encapsulation layer has a thickness of 0.5-1 μm and contains a rapid swelling agent, while the microbial agent microcapsule encapsulation layer has a thickness of 2-3 μm and contains a delayed swelling agent.

[0012] Furthermore, the rapid swelling aid is polyethylene glycol, and the delayed swelling aid is sodium carboxymethyl cellulose.

[0013] Furthermore, the composite compatibility adjuvant consists of Tween-80, trehalose, and a chitinase inhibitor.

[0014] Furthermore, the mass ratio of Tween-80, trehalose, and chitinase inhibitor is 10:5:3.

[0015] Furthermore, the precise application specifically refers to: S1. Corn seedling stage: Apply microbial inoculant microcapsules, diluted 500-600 times, at a rate of 100-110g per acre, focusing on spraying on the underside of the leaves, and adding a compound compatibility adjuvant; if there are ≥10 aphids / plant and / or ≥3 spider mites / leaf, apply chemical agent microcapsules in combination (thiamethoxam for aphids, azadirachtin for spider mites) to enhance the initial inhibition of spider mites by Trichoderma harzianum and reduce the initial insect population; S2. Corn jointing stage: Co-apply microbial inoculants and chemical pesticide microcapsules. Dilute the microbial inoculants 500-600 times and use 100-110g per acre. Use thiamethoxam + azadirachtin as the chemical pesticide microcapsules, with the addition of a compound compatibility adjuvant. If the monitored spider mite (red spider) population is ≥5 mites / leaf, increase the microbial inoculant microcapsule dosage to 120g / acre. By increasing the application of Trichoderma harzianum, targeted control of spider mites can be achieved, preventing rapid population proliferation. S3. Corn pollen shedding and silking stage: Apply chemical agent microcapsules (chlorantraniliprole) with an interval of 10-12 days between the previous application and the previous application. At the same time, apply microbial agent microcapsules (diluted 800 times for root irrigation and foliar spraying). Root irrigation can promote the colonization of Trichoderma harzianum in the rhizosphere and induce corn to develop mite resistance. Foliar spraying directly acts on spider mites. If the number of spider mites (red spiders) is ≥8 per leaf, supplement with microbial agent microcapsules (diluted 600 times) to prolong the effective period of Trichoderma harzianum and curb the outbreak of spider mites. S4. During the milk stage of corn: Monitor the aphid population density. If there are ≥10 aphids / plant or ≥6 spider mites / leaf, apply chemical microcapsules (thiamethoxam for aphids and azadirachtin for spider mites), with an interval of 12 days between the previous chemical microcapsule application and the application. At the same time, apply microcapsules of microbial agents (diluted 1000 times for foliar spraying). Furthermore, the corn pests mentioned are corn borers, aphids, and spider mites (red spiders).

[0016] Furthermore, the above methods are applicable to different planting patterns such as spring corn and summer corn, and the strain / pesticide ratio can be adjusted according to the types of pests in the region. Beneficial effects

[0017] 1. This invention uses a natural high-molecular biomaterial (chitosan-sodium alginate complex) to form a dense, breathable, and non-inhibitory isolation coating layer on the surface of microbial cells through in-situ polymerization. This isolates the cells from direct contact with chemical agents, thus preventing the inhibition of microbial activity by chemical agents. At the same time, the coating layer selectively allows oxygen and moisture to permeate, ensuring normal growth and metabolism of the cells and blocking the penetration of chemical agent molecules to avoid damage to the cells. 2. This invention employs a composite compatibility adjuvant (Tween-80 + trehalose + chitinase inhibitor), breaking through the single function of traditional adjuvants that only improve adhesion. It constructs a dual-action mechanism of protection and enhancement, mainly reflected in three aspects: First, Tween-80 enhances the adhesion and spread of the microbial agent and the pesticide, ensuring that the pesticide evenly covers the corn leaves and improving pest control efficiency; second, trehalose protects the microbial cells from damage by chemical agents and provides growth energy, further enhancing microbial activity; third, the chitinase inhibitor specifically inhibits the abnormal chitinase activity induced by chemical agents in microorganisms, preventing cell wall degradation. 3. This invention employs a microencapsulation process, encapsulating chemical agents and microbial agents separately using thermosensitive materials with the same critical temperature (25°C, matching the leaf surface temperature during the active period of corn pests). Through differentiated design of the encapsulation layers (thickness variation + adjuvant regulation), time-dependent slow release is achieved, eliminating the antagonistic effect between the two. Specifically: the chemical agent microcapsule encapsulation layer is thinner (0.5-1 μm) and contains a rapid swelling adjuvant (polyethylene glycol), enabling rapid response and slow release when the leaf surface temperature reaches 25°C, reaching peak insecticidal concentration within 24 hours and rapidly suppressing the pest population; the microbial agent microcapsule encapsulation layer is thicker (2-3 μm) and contains a delayed swelling adjuvant (sodium carboxymethyl cellulose), initiating slow release 24 hours later, by which time the chemical agent concentration has decreased to a safe range, avoiding antagonistic effects. 4. In this invention, the amount of chemical agents used is reduced to 50%-60% of the conventional amount, and agents with different mechanisms of action are used alternately to effectively avoid pesticide resistance in pests; at the same time, Bacillus cereus is used to degrade chemical agent residues, reducing environmental risks and achieving a dual improvement in ecological safety and control effectiveness. 5. The core of this invention is to explore and leverage the dual pest and disease control and biocontrol effects of Trichoderma harzianum, achieving simultaneous pest control and disease suppression: On the one hand, Trichoderma harzianum can target and control spider mites through parasitism and nutrient competition, reducing spider mite population density and minimizing their piercing-sucking damage; on the other hand, Trichoderma harzianum can colonize the surface and rhizosphere of corn plants, occupy ecological niches, and secrete antifungal metabolites, effectively inhibiting the infection and spread of fungal diseases such as corn leaf blight, breaking the vicious cycle of "insect-disease interaction" in cornfields, while simultaneously inducing systemic resistance in corn, comprehensively enhancing corn's resistance to pests and diseases; 6. This invention, through the synergistic effect of the above four technologies, forms a complete prevention and control system, achieving multiple synergistic effects: (1) Targeted isolation and synergy: Through microbial targeted isolation and coating technology, direct contact between chemical agents and bacteria is isolated in space, eliminating the basis for antagonistic effects, ensuring that microorganisms and chemical agents play their respective roles, and providing a guarantee for subsequent synergistic prevention and control; (2) Synergistic protection of adjuvants: The triple effect of compound compatible adjuvants further enhances the activity of microorganisms in the chemical agent environment, improves the adhesion of microbial agents and agents, protects the microbial cells from damage, promotes microbial growth and mycelial reproduction, and enhances the stability of synergistic prevention and control. (3) Time-series slow-release synergy: Through the differentiated design of thermosensitive microcapsule encapsulation, the rapid control of chemical agents and the long-term protection of microbial agents are achieved, avoiding direct contact between the two and antagonism, so as to achieve the effect of rapid control without inhibition and long-term prevention and control without lag. (4) Reduced dosage and alternating use: Reduced chemical dosage + alternating use + residual degradation can avoid pest resistance and reduce environmental risks, while ensuring the effectiveness of prevention and control, and achieve a dual improvement in ecological security and production efficiency. Attached Figure Description

[0018] Figure 1 This is a photograph of the corn growth process in Example 1; Figure 2 Comparative Example 1: Photographs of the corn growth process; Figure 3 Photos of corn growth without microbial-chemical synergistic control (natural growth). Detailed Implementation

[0019] This invention proposes a microbial-chemical synergistic control method for corn pests. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following will provide a more detailed description of the invention with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0020] Bacillus thuringiensis, accession number: ACCC11075, purchased from China Agricultural Microbial Culture Collection Center; Beauveria bassiana, accession number: ACCC32002, purchased from China Agricultural Microbial Culture Collection Center; Bacillus cereus, accession number: ACCC05302, purchased from China Agricultural Microbial Culture Collection Center; Bacillus subtilis, accession number: ACCC62258, purchased from China Agricultural Microbial Culture Collection Center; Trichoderma harzianum, accession number: ACCC32517, purchased from China Agricultural Microbial Culture Collection Center.

[0021] Example 1: Collaborative Prevention and Control in Spring Maize Fields A microbial-chemical synergistic control method for corn pests includes the following steps: Preparation of coated compound bacterial agent: 1.1 Mix Bacillus thuringiensis, Beauveria bassiana, Bacillus subtilis, and Trichoderma harzianum in a 2:1:1:1 ratio, add to sterile deionized water, stir well, and adjust the bacterial concentration to 1×10⁻⁶. 9 Add 0.05% trehalose to cfu / mL, and place in a shaker at 28℃ and 180r / min for 30min to obtain a bacterial suspension; 1.2 Preparation of coating material solution: Prepare a 1.5% chitosan solution (dissolved in 0.1 mol / L acetic acid solution) and a 2.0% sodium alginate solution (dissolved in sterile deionized water). Mix the two solutions at a chitosan:sodium alginate ratio of 1:1.5, stir for 30 min until homogeneous, and adjust the pH to 6.8. 1.3 In-situ polymerization coating: The bacterial suspension was slowly added to the coating material mixture at a volume ratio of 1:5 while stirring (stirring speed 120 r / min). The mixture was stirred at a constant temperature of 25℃ for 1 h to ensure uniform dispersion of the bacteria. 1.4 Crosslinking and curing: Slowly add 0.02% glutaraldehyde solution to the above system at a dropping rate of 1 mL / min. After the addition is complete, continue stirring at a constant temperature for 2 hours to complete the crosslinking and curing, forming coated microspheres. 1.5 Post-processing: Centrifuge the coated microspheres at 5000 r / min for 10 min, discard the supernatant, wash 3 times with sterile deionized water, vacuum dry at 35℃ until the moisture content is ≤8%, pulverize and pass through an 80 mesh sieve to obtain the coated compound bacterial agent (bacterial cell coating rate of 96.2%). (2) Chemical agents: ① Thiamethoxam, ② Thiamethoxam + azadirachtin, ③ Chlorantraniliprole; (3) Compound compatibility adjuvant: Tween-80 (0.1% of the total amount of the coated compound bacterial agent) + trehalose (0.05% of the total amount of the coated compound bacterial agent) + chitinase inhibitor (0.03% of the total amount of the coated compound bacterial agent), mixed evenly with the bacterial agent and the drug before use; (4) Preparation of microcapsule formulations: 4.1 Preparation of chemical agent microcapsules: ① The chemical agent and ethyl acetate were mixed at a mass ratio of 1:10 and ultrasonically dispersed for 10 min to obtain the oil phase; ② A 2.0 wt% PNIPAAM ethanol solution was prepared, 5% PEG-4000 was added, stirred and dissolved, and then 1.0 wt% Tween-80 was added and stirred until homogeneous to obtain the aqueous phase; ③ The oil phase and aqueous phase were mixed at a volume ratio of 1:4, and the oil phase was slowly added to the aqueous phase and stirred at 800 r / min for 30 min to emulsify; ④ 0.2 wt% glutaraldehyde was slowly added dropwise over 30 min; ⑤ The reaction was continued at 25℃ for 2 h; ⑥ The emulsion was broken, centrifuged at 6000 r / min for 10 min, and the supernatant was discarded; ⑦ The microcapsules were washed three times with sterile water and vacuum dried at 35℃ for 4 h; ⑧ The microcapsules were passed through a 100-mesh sieve to obtain chemical agent microcapsules with an encapsulation layer thickness of 0.7-0.9 μm. 4.2 Preparation of microcapsules for microbial agents: ① Pre-cooling: Take the coated compound bacterial agent and dilute it with sterile water to prepare 1.0×10 9 ① Pre-cool the bacterial suspension (cfu / mL) in an ice bath for 10 min; ② Prepare the aqueous phase: Prepare a 2.0 wt% PNIPAAM aqueous solution, add 3% sodium carboxymethyl cellulose, and stir evenly; then add 0.8 wt% Tween-80 as the aqueous phase; ③ Emulsify: Mix the pre-cooled bacterial suspension with the aqueous phase at a volume ratio of 1:2, and emulsify in an ice bath at 600 r / min for 20 min; ④ Phase transition and encapsulation: Slowly heat to 25℃ to induce a phase transition of PNIPAAM, forming an encapsulation layer on the surface of the bacteria; ⑤ Crosslinking: Slowly add 0.15 wt% glutaraldehyde, and crosslink and solidify for 1.5 h; ⑥ Post-treatment: Centrifuge at 5000 r / min for 10 min; wash 3 times with sterile water; vacuum dry at 30℃ for 3 h; pass through an 80-mesh sieve to obtain microbial agent microcapsules with an encapsulation layer thickness of 2.3-2.6 μm; (5) Precision application method S1. Corn seedling stage: Apply coated microbial inoculant microcapsules, diluted 500 times, at a rate of 100g per acre, and spray evenly on the back of corn leaves and the base of stems; add a compound compatibility adjuvant to improve the adhesion and stability of the inoculant; when the aphid population density was monitored to be 12 per plant and spider mite (red spider) 2 per leaf, apply chemical pesticide microcapsules (thiamethoxam, active ingredient 3g / acre) for rapid pest control; S2. Corn jointing stage: Co-application of encapsulated microbial inoculants and chemical pesticide microcapsules. The microbial inoculant microcapsules are diluted 500 times, with a dosage of 100g per acre, sprayed on the whorl and underside of the leaves of the corn. Simultaneous spraying of chemical pesticide microcapsules (thiamethoxam, 5g / acre of active ingredient + azadirachtin, 2g / acre of active ingredient) utilizes the temperature-sensitive properties to achieve slow release of the chemical pesticide first, followed by slow release of the microbial inoculant. Adding a compound compatibility adjuvant further eliminates antagonistic effects and rapidly suppresses the populations of corn borers and aphids. If 6 spider mites (red spiders) are detected per leaf, the dosage of microbial inoculant microcapsules is increased to 120g / acre. S3. Corn pollen shedding and silking stage: Apply chemical agent microcapsules (chlorantraniliprole, active ingredient 2g / mu), spray evenly on corn stalks and leaves (focus on spraying the underside of the middle and lower leaves); alternate with the previous application of chemical agent microcapsule preparation by 10 days; at the same time, apply encapsulated microbial agent microcapsule preparation (diluted 800 times for root irrigation + foliar spray), with a dosage of 130g per mu (80g for root irrigation + 50g for foliar spray). Root irrigation promotes the colonization of Trichoderma harzianum in the rhizosphere, and foliar spray directly acts on spider mites; S4. During the milk stage of corn: Aphid population density of 4 individuals / plant and spider mite (red spider) of 5 individuals / leaf were monitored. Apply coated microbial inoculant microcapsules (diluted 1000 times for foliar spraying) at a rate of 80g per acre to utilize long-term microbial control and avoid rebound.

[0022] Formulation performance test results: The chemical agent microcapsules and microbial agent microcapsules prepared in this example showed a droplet size of 175±10μm (measured by laser particle size analyzer) and a leaf retention time of 6.2±0.3h after spraying (high-speed photography tracking (field natural conditions)), significantly improving the uniformity of agent adhesion and the duration of pest control; the coating layer peeling rate of the coated compound microbial agent was only 4.2±0.4% (artificial shaking method (simulated rainfall washing 3 times)), under simulated rainfall conditions. The coating remains intact even after being washed away by rain; the loss rate of microcapsules under level 7 wind is 7.5±0.6% (wind tunnel simulation test (wind speed 15m / s)), demonstrating excellent anti-drift ability and suitability for large-scale field application; the survival rate of Bacillus thuringiensis colonization during the pollen shedding and silking stage reaches 83.2±2.1% (laser confocal microscopy), and the survival rate of Trichoderma harzianum colonization reaches 82.3±1.8%, indicating that the coating technology and microcapsule process of this invention have a protective effect on the colonization ability of microorganisms.

[0023] Example 2: Collaborative pest control in summer maize fields (summer maize has a short growth period and concentrated pest occurrence) A microbial-chemical synergistic control method for corn pests includes the following steps: (1) Preparation of coated compound bacterial agent: Bacillus thuringiensis, Beauveria bassiana, Bacillus subtilis and Trichoderma harzianum were mixed in a ratio of 3:1:2:1. Chitosan-sodium alginate complex (chitosan:sodium alginate = 1:1.5) was used, and 0.02% glutaraldehyde was added as a crosslinking agent. The mixed bacterial cells were coated by the same in-situ polymerization method as in Example 1 to prepare coated compound bacterial agent (bacterial cell coating rate of 95.8%). (2) Chemical agents: ① azadirachtin, ② azadirachtin + thiamethoxam ③ chlorantraniliprole; (3) Compound compatibility adjuvant: Tween-80 (0.1% of the total amount of the coated compound bacterial agent) + trehalose (0.05% of the total amount of the coated compound bacterial agent) + chitinase inhibitor (0.03% of the total amount of the coated compound bacterial agent), mixed evenly with the bacterial agent and the drug before use; (4) Preparation of microcapsule formulations: Chemical agents and encapsulated compound bacterial agents are respectively encapsulated with thermosensitive materials (as in Example 1) to prepare chemical agent microcapsules and microbial agent microcapsules. The encapsulation layer thickness of the chemical agent microcapsules is 0.7-0.9 μm and polyethylene glycol is added. The encapsulation layer thickness of the microbial agent microcapsules is 2.3-2.6 μm and sodium carboxymethyl cellulose is added. (5) Precision application method S1. Corn seedling stage: Spray with coated compound microcapsules of microbial agent, diluted 600 times, at a rate of 110g per mu, combining spraying and root irrigation (focusing on spraying the underside of leaves); add compound compatibility adjuvant; when the aphid population density is monitored at 13 per plant and spider mite (red spider) at 4 per leaf, spray with chemical microcapsules (azalea, active ingredient 2g / mu + thiamethoxam, active ingredient 2g / mu). S2. Corn jointing stage: Spray chemical pesticide microcapsules (azalea, active ingredient 3g / mu), add compound compatibility adjuvant; at the same time spray coated compound microbial agent microcapsule preparation (600 times diluted for foliar spray), 100g per mu, to achieve sequential release by utilizing temperature-sensitive slow-release characteristics, synergistically killing insects and strengthening microbial colonization; if 7 spider mites (red spiders) are detected per leaf, increase the dosage of microbial agent microcapsules to 120g / mu for targeted control of spider mites; S3. Silking and pollination stage of corn: The silking and pollination stage of summer corn is closely connected with the milk stage and has a short growth period. During this stage, older corn borer larvae are prone to bore into the stalks and tassels, and spider mites are prone to large-scale outbreaks, requiring precise control. Apply chemical pesticide microcapsules (chlorantraniliprole, active ingredient 3g / mu), and spray evenly on corn stalks, tassels, and leaves. Alternate between applications of chemical pesticide microcapsules and previous applications, with an interval of 12 days. At the same time, spray with a coated compound microcapsule preparation (diluted 800 times for foliar spraying), at a rate of 90g per mu, to consolidate the pest control effect and prevent older corn borer larvae from causing stalk breakage and affecting pollination. S4. During the milk stage of corn: When the aphid population density was monitored to be 4 aphids / plant and 6 spider mites / leaf, spray with coated compound microcapsules (diluted 1000 times for foliar spraying) at a rate of 100g per acre; when the corn borer population density was monitored to be 5 grains / plant, supplement with chemical agent microcapsules (chlorantraniliprole, active ingredient 2g / acre).

[0024] Formulation performance test results: The droplet size of the microcapsule formulation in this embodiment is 182±11μm, and the leaf surface retention time is 5.8±0.2h, ensuring rapid pest control in scenarios with short growth periods and concentrated pest occurrences in summer maize; the coating layer shedding rate is 4.5±0.3%, demonstrating strong erosion resistance; the loss rate under level 7 wind is 7.8±0.5%, reducing pesticide waste in the field; the microbial colonization survival rate during the pollen shedding and silking stage is 81.5±1.8% (of which Trichoderma harzianum accounts for 79.6±1.6%), ensuring the microbial activity required for long-term control, adapting to the concentrated control needs of summer maize, and especially meeting the timeliness requirements for rapid control of spider mites (red spider mites).

[0025] Comparative Example 1: Single microbial control program (no chemical agents) For Example 1, the compound bacterial agent of Example 1 (without coating treatment, Trichoderma harzianum ratio of 0.5) was used, without adding compound compatibility adjuvants, without applying any chemical agents, without using microcapsule sustained-release technology, and the application time and method were the same.

[0026] Comparative Example 2: Conventional chemical control measures (no microorganisms) For Example 1, conventional chemical agents were used for control: chlorantraniliprole (15g / mu of active ingredient) + imidacloprid (12g / mu of active ingredient) were sprayed during the corn jointing stage, and sprayed again after an interval of 7 days; imidacloprid (10g / mu of active ingredient) was sprayed during the aphid occurrence period.

[0027] Comparative Example 3: Traditional Microbial-Chemical Synergistic Control For Example 1, Bacillus thuringiensis and Beauveria bassiana without coating were used, along with low-toxicity chemical agents (13g / mu of imidacloprid and 15g / mu of chlorantraniliprole), without the addition of compound compatibility adjuvants, without the use of microencapsulation slow-release technology, and using conventional mixed spraying method.

[0028] Comparative Example 4: Single Microbial Control Program (No Chemical Agents) For Example 2, the compound bacterial agent of Example 2 (without coating treatment, Trichoderma harzianum ratio of 0.5) was used, without adding compound compatibility adjuvants, without applying any chemical agents, without using microcapsule sustained-release technology, and the application time and method were the same.

[0029] Comparative Example 5: Conventional chemical control measures (no microorganisms) For Example 2, conventional chemical agents were used for control: chlorantraniliprole (15g / mu of active ingredient) + imidacloprid (12g / mu of active ingredient) were sprayed during the corn jointing stage, and sprayed again after an interval of 7 days; imidacloprid (10g / mu of active ingredient) was sprayed during the aphid occurrence period. No microbial agents were used, and no coating, no compound compatibility adjuvants, and no microcapsule sustained-release technology were used.

[0030] Comparative Example 6: Traditional Microbial-Chemical Synergistic Control For Example 2, Bacillus thuringiensis and Beauveria bassiana without coating were used, along with low-toxicity chemical agents (14g / mu of imidacloprid and 15g / mu of chlorantraniliprole). No compound compatibility adjuvants were added, and microcapsule sustained-release technology was not used. The conventional mixed spraying method was adopted, and the application time and method were the same as in Example 2.

[0031] The sustained-release interval between chemical drug microcapsules and microbial agent microcapsules was determined to be 24-25 hours.

[0032] Prevention and control effectiveness testing: Table 1. Impact of different control programs on pest control and disease occurrence in spring maize.

[0033] Table 2. Effects of different control programs on pesticide dosage, residues, natural enemies, and yield.

[0034] Table 3 Comparison of microbial activity and duration of effectiveness under different control programs in spring maize

[0035] Table 4. Impact of different control programs on pest control and disease occurrence in summer maize.

[0036] Table 5. Effects of different control programs on pesticide application, residues, natural enemies, and yield of summer maize.

[0037] Table 6 Comparison of the activity and duration of microorganisms (including Bacillus thuringiensis) under different control programs in summer maize

[0038] Field trials have shown that after implementing this plan: (1) Control effect of spring maize in Example 1 Based on the data in Tables 1-3, it can be seen that Example 1, using the microbial-chemical synergistic control method of the present invention, exhibits the best control effect, ecological safety, and production benefits. 1. Significant pest and disease control effects: The corrected mortality rate of corn borer reached 95.3%, the corrected reduction rate of aphids reached 93.7%, and the corrected reduction rate of spider mites (red spiders) reached 92.8%. Compared with the traditional microbial-chemical synergistic control program (Comparative Example 3, corrected mortality rate of corn borer 78.5%, corrected reduction rate of aphids 79.3%, and corrected reduction rate of spider mites (red spiders) 71.2%), the control effects were improved by 21.4%, 18.2%, and 30.3% respectively, with an overall improvement of 23.3%. Compared with single microbial control technology (Comparative Example 1), the effects were improved by 25.1%, 27.9%, and 24.3% respectively, with an overall improvement of 25.8%, effectively solving the problems of insufficient pest control by single control and traditional synergistic control.

[0039] 2. Outstanding disease control results: The incidence rate of corn leaf blight was only 3.1%, which is 10.9 percentage points lower than Comparative Example 3 (14.0%), 15.2 percentage points lower than Comparative Example 1 (18.3%), and 3.4 percentage points lower than Comparative Example 2 (6.5%). This shows that the synergistic control scheme of the present invention can not only control pests, but also effectively inhibit the occurrence of corn leaf blight and improve the stress resistance of corn.

[0040] 3. Significant reduction in pesticide use and residue control: The total amount of chemical pesticides used was 12.0 g / mu, a reduction of 67.6% compared to conventional chemical control (Comparative Example 2, 37 g / mu) and a reduction of 57.1% compared to traditional synergistic control (Comparative Example 3, 28 g / mu); the pesticide residue in corn kernels at harvest was 0.0018 mg / kg, far below the national limit (0.01 mg / kg), a reduction of 45.5% compared to Comparative Example 3 (0.0033 mg / kg) and a reduction of 85% compared to Comparative Example 2 (0.012 mg / kg), meeting the requirements for agricultural product quality and safety.

[0041] 4. High ecological safety: The number of natural enemies such as ladybugs and lacewings in corn fields increased by 55% compared with conventional chemical control (Comparative Example 2) and by 20% compared with traditional synergistic control (Comparative Example 3), effectively protecting the ecological balance in the field and avoiding the damage to natural enemies caused by conventional chemical control.

[0042] 5. Significant production benefits: Corn grain yield increased by 21% compared with conventional control (Comparative Example 2), by 8% compared with traditional synergistic control (Comparative Example 3), and by 13 percentage points compared with single microbial control (Comparative Example 1), achieving a dual improvement in control effect and production benefits.

[0043] 6. Stable microbial activity: The germination rate of microbial cells reached 92%, which is 32% higher than that of traditional synergistic control (Comparative Example 3, 60%); the effective period lasted for 27 days, which is 7 days longer than that of Comparative Example 3 (20 days) and 12 days longer than that of Comparative Example 1 (15 days); the inhibition rate of chemical agents on microbial cells was 0, and the survival rate of Trichoderma harzianum colonization reached 82.3%, which is significantly higher than that of Comparative Example 1 (56.7%) and Comparative Example 3 (49.2%). This solves the industry pain point of chemical agents inhibiting microbial activity in traditional synergistic control and realizes the synergistic effect of microorganisms and chemical agents.

[0044] 7. Significant advantages in formulation performance: The microcapsule droplet size and leaf retention time of this embodiment are excellent, with low coating layer shedding rate, low wind loss rate, and high microbial colonization survival rate, providing solid formulation performance support for control effect and suitable for large-scale field application scenarios.

[0045] (2) Control effect of summer maize in Example 2 Based on the data in Tables 4-6, it can be seen that Example 2, which addresses the characteristics of short growth period and concentrated pest occurrence in summer maize, adopted an optimized synergistic control scheme, resulting in stable control effects consistent with the trend of Example 1, as detailed below: 1. Excellent pest and disease control results: The corrected mortality rate of corn borer reached 92.6%, the corrected reduction rate of aphids reached 91.5%, and the corrected reduction rate of spider mites (red spiders) reached 90.5%. Compared with the traditional synergistic control program (comparative example 6), the control effects of the three pests increased by 21.5%, 18.1%, and 30.4% respectively, with an overall improvement of 23.3%, and an overall improvement of 18.8% compared with the traditional synergistic program. The incidence rate of corn leaf blight was 4.2%, which was 11.1 percentage points lower than that of comparative example 6 (15.3%), 15.3 percentage points lower than that of comparative example 4 (19.5%), and 3.6 percentage points lower than that of comparative example 5 (7.8%), showing significant disease control effects.

[0046] 2. Reduced pesticide use and compliance with residue control standards: The total amount of chemical pesticides used was 12g / mu, a reduction of 67.6% compared to conventional chemical control (Comparative Example 5, 37g / mu) and a reduction of 58.6% compared to traditional synergistic control (Comparative Example 6, 29g / mu), meeting the development needs of reduced chemical pesticide use control; the pesticide residue in corn kernels was 0.0025mg / kg, far below the national limit (0.01mg / kg), a reduction of 30.6% compared to Comparative Example 6 (0.0036mg / kg) and a reduction of 78.3% compared to Comparative Example 5 (0.0115mg / kg), ensuring the quality and safety of corn products.

[0047] 3. Good ecological safety: The number of natural enemies in maize fields increased by 52% compared with conventional chemical control (comparative example 5) and by 18 percentage points compared with traditional collaborative control (comparative example 6), effectively maintaining the stability of the summer maize field ecosystem and reducing the damage of chemical agents to the ecological environment.

[0048] 4. Significant production benefits: Corn grain yield increased by 19% compared to conventional control (Comparative Example 5), 7 percentage points compared to traditional synergistic control (Comparative Example 6), and 12 percentage points compared to single microbial control (Comparative Example 4). It is adapted to the growth characteristics of summer corn and achieves a combination of rapid pest control and increased yield and quality.

[0049] 5. Stable microbial activity: The microbial cell germination rate reached 89%, which is 30% higher than that of traditional synergistic control (Comparative Example 6, 59%); the effective period was 25 days, which is 10 days longer than that of Comparative Example 6 (19 days) and 11 days longer than that of Comparative Example 4 (14 days); the inhibition rate of chemical agents on microbial cells was 0, and the retention rate of Bacillus thuringiensis cell activity was as high as 97.8%, which is much higher than that of Comparative Example 4 (60.5%) and Comparative Example 6 (49.8%). This further demonstrates the synergistic effect of the coating treatment, microcapsule sustained release and compatibility adjuvant of this invention, which effectively protects the microbial activity.

[0050] 6. Strong adaptability of formulation performance: In response to the concentrated occurrence of pests in summer maize, the performance indicators of the microcapsule formulation in this embodiment, such as droplet size and retention time, ensure that the agent takes effect quickly, covers evenly, has strong resistance to wind and erosion, and has a high survival rate of microbial colonization, providing a reliable guarantee for the concentrated control of short-growing-period maize.

[0051] Comparative Example 1 did not employ chemical agents, coating treatment, or microencapsulation slow-release technology; it only used uncoated compound microbial agents, resulting in significant shortcomings in control efficacy: the corrected mortality rate for corn borers was 70.2%, the corrected reduction rate for aphids was 65.8%, and the corrected reduction rate for spider mites (red spiders) was only 68.5%, representing decreases of 25.1%, 27.9%, and 24.3% respectively compared to Example 1, with an overall decrease of 25%-28%. The control effect significantly declined during the peak aphid outbreak, failing to effectively control the pest population. The incidence rate of corn leaf blight was as high as 18.3%, far exceeding the 3.1% in Example 1, indicating weak disease control capabilities. The microbial cell germination rate was only 60%, and the effective period was only 15 days, 12 days shorter than in Example 1. Furthermore, without the synergy of chemical agents, the control speed was slow, and the control capability during the peak period was insufficient. It is evident that a single microbial control program cannot meet the needs of efficient control of spring corn pests.

[0052] Comparative Example 2 did not use any microbial agents, but only conventional chemical agents for pest control. Although it achieved a certain level of pest control (corrected mortality rate of corn borer 88.3%, corrected reduction rate of aphids 86.5%, and corrected reduction rate of spider mites 76.3%), it had many drawbacks: the number of natural enemies in the cornfield was reduced by 55% compared to Example 1, seriously disrupting the ecological balance in the field; the pesticide residue in corn kernels at harvest was 0.012 mg / kg, which was higher than the national limit (0.01 mg / kg) and also higher than 0.0018 mg / kg in Example 1, posing a risk to the quality and safety of agricultural products; after two years of continuous application, the resistance index of corn borer to chlorantraniliprole increased by 1.8 times, which could easily lead to pesticide resistance in pests, and the control effect would continue to decline with long-term use; the corn yield increased by only 12%, which was 9 percentage points lower than that in Example 1, indicating poor production efficiency. This shows that conventional chemical control programs have high environmental risks and poor sustainability.

[0053] Comparative Example 3 used a conventional mixture of uncoated microbial inoculant and chemical pesticides for spraying, without adding a compound compatibility adjuvant or employing microencapsulation slow-release technology. The synergistic control effect was poor: the corrected mortality rate for corn borers was 78.5%, the corrected reduction rate for aphids was 79.3%, and the corrected reduction rate for spider mites (red spiders) was 71.2%, representing decreases of 16.8%, 14.4%, and 21.6% respectively compared to Example 1, with an overall decrease of 14.4%-16.8%. The chemical pesticide dosage was 28 g / mu, 133.3% higher than in Example 1, failing to achieve the pesticide reduction target. The pesticide residue in corn kernels was 0.0033 mg / kg, higher than the 0.0018 mg / kg in Example 1. Microbial cell germination... The efficacy rate was only 60%, 32% lower than that of Example 1, and the effective period was only 20 days, 7 days shorter than that of Example 1. The inhibition rate of chemical agents on microbial cells reached 18%, showing a significant antagonistic effect. The synergistic effect coefficient was only 1.4, far lower than 2.5 in Example 1, which fully demonstrates that the traditional synergistic control scheme cannot solve the antagonistic problem between chemical agents and microorganisms, resulting in poor synergistic effect and low control efficiency. Moreover, without the use of microencapsulation technology, the leaf retention time was only 2.3±0.1h, and the loss rate under level 7 wind reached 15.8±1.2%. Microorganisms were not protected by encapsulation, and the survival rate of the planted plants was only 52.6±2.3%, significantly lower than 83.2±2.1% in Example 1, leading to a shortened effective period and a further decline in control effect.

[0054] Comparative Example 4 uses the same control model as Comparative Example 1, but its shortcomings in controlling summer maize are more pronounced: the corrected mortality rate of maize borer is 68.3%, the corrected reduction rate of aphids is 63.7%, and the corrected reduction rate of spider mites (red spiders) is 65.3%, which are 24.3%, 27.8%, and 25.2% lower than in Example 2, respectively; the incidence rate of maize leaf spot is 19.5%, which is much higher than the 4.2% in Example 2; the microbial cell germination rate is only 59%, and the effective period is only 14 days, which is 11 days shorter than in Example 2; the retention rate of Bacillus thuringiensis cell activity is only 60.5%, with serious loss of activity; maize yield increases by only 7%, which is 12 percentage points lower than in Example 2. Moreover, the short growth period of summer maize and the concentrated occurrence of pests amplify the disadvantages of slow-acting single microbial control, making it impossible to quickly control pest populations and easily causing maize yield losses.

[0055] Comparative Example 5 and Comparative Example 2 used the same control mode, but the control effect on summer maize was poor: the corrected mortality rate of corn borer was 86.7%, the corrected reduction rate of aphids was 84.2%, and the corrected reduction rate of spider mites (red spiders) was 73.8%, which were 5.9% and 7.3% lower than those in Example 2, respectively; the total amount of chemical agents used was 37g / mu, which was 208.3% more than that in Example 2, indicating that the amount of agents used was too high; the pesticide residue in maize kernels was 0.0115mg / kg, which was close to the national limit standard and higher than that in Example 2 (0.0025mg / kg); the number of natural enemies in the maize field did not increase, and the ecological damage was obvious; the maize yield increased by only 11%, which was 8 percentage points lower than that in Example 2, and long-term use was likely to lead to pesticide resistance in pests, making it unsuitable for the needs of green control of summer maize.

[0056] Comparative Example 6 used the same control model as Comparative Example 3, but the synergistic control effect on summer maize was poor: the corrected mortality rate of corn borer was 76.2%, the corrected reduction rate of aphids was 77.5%, and the corrected reduction rate of spider mites (red spiders) was 69.4%, which were 16.4%, 14.0%, and 21.1% lower than in Example 2, respectively; the chemical pesticide dosage was 29 g / mu, which was 141.7% higher than in Example 2; the pesticide residue in maize kernels was 0.0036 mg / kg, which was higher than 0.0025 mg / kg in Example 2; the microbial cell germination rate was only 59%, which was 30% lower than in Example 2, and the effective period was only 19 days, which was lower than in Example 3. Example 2 shortened the treatment time by 10 days; the chemical agent inhibited the microbial cells by 17.5%, while the Bacillus thuringiensis cell activity retention rate was only 49.8%, showing a significant antagonistic effect and poor synergistic effect, failing to meet the needs of concentrated pest control and reduced-volume-increasing efficiency in summer maize; moreover, without coating treatment and microcapsule design, the leaf retention time was only 2.1±0.1h, and the loss rate under level 7 wind was 16.3±1.0%, indicating poor stability in field application; the microbial colonization survival rate was only 51.3±2.0%, a decrease of 30.2 percentage points compared to 81.5±1.8% in Example 2, indicating severe activity loss and failing to achieve long-term control.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A microbial-chemical synergistic control method for corn pests, characterized in that, Includes the following steps: (1) Preparation of coated compound microbial agent: mix highly effective insecticidal microorganisms with pathogenic antibacterial agents, and use biological coating materials to coat them by in-situ polymerization to prepare coated compound microbial agent; (2) Preparation of microcapsule formulations: Low-toxic chemical agents and encapsulated compound bacterial agents are respectively encapsulated in microcapsules using temperature-sensitive materials to prepare chemical agent microcapsules and microbial agent microcapsules; (3) Precise application: At different growth stages of corn, chemical agent microcapsules, microbial agent microcapsules and compound compatible adjuvants are applied in combination with the occurrence patterns of target pests.

2. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The highly effective insecticidal microorganism is one or more of Bacillus thuringiensis, Beauveria bassiana, and Bacillus cereus.

3. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The pathogenic antifungal agent is Trichoderma harzianum, and / or Bacillus subtilis is added as an auxiliary agent.

4. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The mixing ratio of the highly effective insecticidal microorganism and the pathogenic antibacterial agent is: Bacillus thuringiensis: Beauveria bassiana: Bacillus subtilis: Trichoderma harzianum = (2-3):1:(1-2):

1.

5. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The bio-coating material is a chitosan-sodium alginate complex with a ratio of chitosan:sodium alginate = 1:1.5, and 0.02% glutaraldehyde is added as a crosslinking agent.

6. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The low-toxicity chemical agent is one or more of thiamethoxam, azadirachtin, and chlorantraniliprole.

7. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The temperature-sensitive material is poly(N-isopropylacrylamide) with a critical temperature of 25°C.

8. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The chemical agent microcapsule has an encapsulation layer thickness of 0.5-1 μm and contains a rapid swelling agent, while the microbial agent microcapsule has an encapsulation layer thickness of 2-3 μm and contains a delayed swelling agent.

9. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The composite compatibility adjuvant consists of Tween-80, trehalose, and a chitinase inhibitor.

10. The microbial-chemical synergistic control method for corn pests according to claim 1, characterized in that, The precise application specifically refers to: S1. Corn seedling stage: Apply microbial inoculant microcapsules, diluted 500-600 times, at a rate of 100-110g per acre, with the addition of compound compatibility adjuvants; if there are ≥10 aphids / plant and / or ≥3 spider mites / leaf, apply chemical agent microcapsules in conjunction. S2. Corn jointing stage: Co-application of microbial agent microcapsules and chemical agent microcapsules. The microbial agent microcapsules are diluted 500-600 times, with a dosage of 100-110g per mu. The chemical agent microcapsules are a combination of thiamethoxam and azadirachtin, with the addition of a compound compatibility adjuvant. S3. Corn pollen shedding and silking stage: Apply chemical pesticide microcapsules, with an interval of 10-12 days between the previous application of chemical pesticide microcapsules, and apply microbial agent microcapsules at the same time; if the number of spider mites is ≥8 per leaf, supplement with microbial agent microcapsules; S4. During the milk stage of corn: Monitor the aphid population density. If there are ≥10 aphids / plant and / or ≥6 spider mites / leaf, apply chemical pesticide microcapsules and microcapsules of microbial agents at the same time.

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