Spodoptera frugiperda nucleopolyhedrovirus whole-virus long-lasting adjuvant, formulation, application method and use

Abstract

The application discloses a full-plant persistent adjuvant for Spodoptera frugiperda nuclear polyhedrosis virus, a preparation and application thereof, and relates to the technical field of agricultural biological pesticides. The adjuvant is composed of the following components: a natural mineral carrier, an organic protection component, a water-soluble film-forming agent, a penetration and spreading agent, a system compatible component, and the balance is supplemented by the carrier. The adjuvant can optimize the interface state of the virus polyhedron in the soil, form a "soil virus library" which is easy to be re-mobilized by rainfall, and under the condition of rainfall, the virus in the library can be efficiently input to the lower part of the corn plant, thereby significantly improving the continuous infection opportunity of the target pest. The application combines "leaf surface instant prevention and control" with "soil library source dynamic supplement", and provides an innovative solution for the prevention and control problems of the full-plant damage and generation overlap of the Spodoptera frugiperda.

Description

Technical Field

[0001] This invention relates to the field of agricultural biopesticide technology, and in particular to a compound adjuvant for enhancing the persistence of fall armyworm nucleopolyhedrovirus SfNPV in all parts of maize and for constructing a soil virus library, as well as a pesticide formulation containing the adjuvant and its application method. Background Technology

[0002] The fall armyworm is a voracious, migratory pest that has become a serious crop pest globally in recent years, posing a significant threat to corn throughout its entire growth cycle. Its larvae exhibit a tendency to hide, preferring to conceal themselves in the heart of the plant, leaf axils, and near the base of the stem. This behavior increases the difficulty of chemical and biological control, particularly for fall armyworm nucleopolyhedrovirus (SfNPV) agents, which rely on contact infection. While SfNPV is an important biological agent for controlling this pest, conventional field application suffers from short-lasting effectiveness (typically only 3-5 days) and poor efficacy against hidden larvae.

[0003] Current biological control strategies for fall armyworm mainly rely on foliar spraying of SfNPV virus preparations. However, this method has the following limitations: About 60-80% of viral agents applied in the field will settle on the soil surface or top layer (0-5cm). Due to the complex soil environment, the survival and activity of viruses in the soil face the following challenges: (1) Adsorption of soil particles may cause damage to the viral structure. Some viral agents will settle into the soil, but due to the lack of effective carriers and protective mechanisms, viruses in the soil are easily inactivated or difficult to be reactivated and spread to places that pests can access; (2) Proteases produced by soil microorganisms can degrade viral polyhedrosis proteins; (3) Viral agents sprayed on leaves are easily affected by ultraviolet radiation, high temperature evaporation and rainwater erosion, resulting in a short duration of effectiveness. Especially in the later stages of crop growth, it is difficult for viruses to reach the hidden feeding sites of pests. Traditional research has focused on extending the static half-life of viruses in the soil through technologies such as embedding and immobilization. However, under actual field conditions, due to the influence of variables such as soil type, climate conditions and irrigation patterns, it is difficult to achieve stable and significant breakthroughs.

[0004] Comparative document 1 (Towards Sustainable Green Adjuvants for Microbial Pesticides: Recent Progress, Upcoming Challenges, and Future Perspectives; Microorganisms (MDPI), 20230131) discloses common component types of microbial pesticide adjuvants, including carriers, surfactants, wetting agents, dispersants, and stabilizers, but there are the following essential differences: 1) Different technical objectives: The present invention focuses on the wetting, dispersing and adhesion properties of foliar application; the present invention focuses on the regulation of virus behavior at the soil-plant interface and the construction of a soil virus library. 2) Different mechanisms of action: Comparative document 1 does not involve the construction of a humidity-responsive interface; this invention achieves an intelligent response of "dry fixation - rainfall release" through the synergistic action of specific components; 3) Different synergistic relationships of components: The components listed in Comparative Document 1 are only functional substitutes; the montmorillonite-humic acid-sodium alginate ternary system of the present invention forms a specific structure (interlayer adsorption-hydrogen bond protection-reversible gel network), producing unexpected synergistic effects.

[0005] This invention proposes a novel enhancement pathway: by regulating the interfacial ecological behavior of viral polyhedra in soil, focusing on optimizing their re-release, remobilization, and reuse efficiency under dynamic field environments (such as rainfall and dew condensation), it more effectively taps into their ecological control potential as a "soil virus reservoir." Specifically, by constructing a "smart-responsive" virus-soil composite interface, it maintains stable storage under dry conditions and achieves controlled release under wet conditions, forming a sustainable control model of "one application, multiple generations benefit." Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a compound adjuvant and its application method for enhancing the overall persistence of fall armyworm nucleopolyhedrovirus (SfNPV). This adjuvant optimizes the attachment and release behavior of the virus at the soil-plant interface, constructing a dynamically usable soil virus library. It aims to promote efficient reintroduction of the virus to plants under rainfall conditions, significantly increasing the chance of sustained infection of target pests. The SfNPV used in this invention is a publicly disclosed strain, available to the public through conventional commercial channels. The scope of protection of this invention is limited to the adjuvant composition, formulation, adjuvant, and its application method, and does not involve the protection of the SfNPV strain itself.

[0007] The objective of this invention is achieved through the following technical solution: A whole-strain persistent adjuvant for fall armyworm nucleopolyhedrovirus, comprising the following components by weight percentage: Natural mineral carrier 10-40%, organic protective component 5-25%, water-soluble film-forming agent 2-15%, penetrating spreader 1-5%, system compatible component 5-15%, the balance is carrier to make up to 100%; The natural mineral carrier is at least one of montmorillonite and kaolin; the organic protective component is at least one of lignin sulfonate and humic acid; the water-soluble film-forming agent is sodium alginate; and the strong penetrating spreader is a modified vegetable oil-based nonionic surfactant.

[0008] The natural mineral carrier, organic protective components, and water-soluble film-forming agent work synergistically to form a composite interface film with humidity-responsive characteristics on the surface of the virus polyhedra. This interface film maintains structural stability under dry conditions to preserve virus activity and undergoes controlled swelling under rainfall conditions to release virus particles, thereby achieving reversible fixation and remobilization of the virus at the soil-plant interface.

[0009] Furthermore, the montmorillonite is sodium-based montmorillonite with a particle size ≥800 mesh and a cation exchange capacity ≥80 cmol / kg; the kaolin is calcined kaolin with a particle size ≥1000 mesh. The interlayer structure of sodium-based montmorillonite adsorbs viral polyhedra through cation exchange, the lignin sulfonate forms hydrogen bonds with viral proteins through phenolic hydroxyl and carboxyl groups for protection, and the sodium alginate forms a reversible gel network with calcium ions through guluronic acid units. The three components work together to construct the humidity-responsive composite interface membrane.

[0010] Furthermore, the lignin sulfonate used is sodium lignin sulfonate with a molecular weight of 3000-5000 Da; The humic acid is fulvic acid, wherein the fulvic acid content is ≥50% and the molecular weight is ≤2000 Da.

[0011] Furthermore, the viscosity of sodium alginate is 200-500 mPa·s, and the guluronic acid content is ≥60%. The sodium alginate undergoes a volume phase change upon contact with water, and the degree of phase change is positively correlated with rainfall, thereby achieving adaptive regulation of the virus release rate.

[0012] Furthermore, the modified vegetable oil nonionic surfactant is castor oil polyoxyethylene ether EL-40 or EL-80, with an HLB value of 10-17.

[0013] Furthermore, the system-compatible components consist of 3-8% antifreeze, 0.5-2% preservative, and a pH adjuster, which adjusts the pH of the 1% aqueous solution of the additive to 6.0-7.0.

[0014] Furthermore, the antifreeze is glycerin or propylene glycol; the preservative is sodium benzoate or potassium sorbate; and the pH adjuster is a citric acid-sodium citrate buffer system.

[0015] The pesticide formulation for controlling fall armyworm in corn contains fall armyworm nucleopolyhedrovirus and a compound adjuvant, with a virus content of 1×10⁻⁶. 7 -1×10 9 OBs / mL, the dilution ratio of the auxiliary agent is 1:100-1:200; After the pesticide formulation is applied to the corn plants, some of the virus settles on the soil surface and forms a soil virus reservoir under the action of the adjuvant. Under rainfall conditions, the virus reservoir is returned to the base of the corn stem by raindrop splashing, achieving sustained control of the whole plant.

[0016] Application methods for pesticide formulations used to control fall armyworm in cornfields include: 1) Mix the adjuvant with the fall armyworm nucleopolyhedrovirus in a certain proportion, and dilute with water to the working concentration; 2) Plant protection drones are used for layered penetration spraying to cover the entire crop plant; the plant protection drones fly at an altitude of 1.5-2.5 m, spray volume is 25-35 L / ha, and atomized particle size is 100-150 μm; 3) The application time is selected between 17:00 and 19:00 in the evening, which matches the nocturnal feeding activity pattern of fall armyworm larvae.

[0017] The application of compound adjuvants in constructing a soil virus reservoir for the sustained control of fall armyworm. The adjuvants optimize the humidity response characteristics of the virus at the soil-plant interface, enabling the remobilization and reintroduction of the virus to the plant under rainfall conditions, and extending the virus persistence period to 14-21 days.

[0018] Compared with the prior art, one or more embodiments of the present invention may have the following advantages: 1) Clear synergistic mechanism and quantitative evidence: Indoor simulation experiments have confirmed that the adjuvant of this invention can increase the efficiency of reintroducing viruses deposited in the soil to corn plants by 168%, providing quantifiable key support for the concept of "soil virus reservoir". 2) Innovative virus pesticide retention pathway: Unlike simply pursuing static protection, this invention actively regulates the characteristics of the "virus-soil" composite interface through material combination, making it more adaptable to the dynamic environment of alternating dry and wet conditions in the field, achieving efficient re-exposure of the virus during rainfall, increasing virus utilization by 2.5 times, and extending the retention period to 14-21 days; 3) Revealed the potential for sustained action of the soil virus reservoir: Through a two-generation larval inoculation simulation experiment, it was found that the corrected mortality rate of the second-generation larvae in the soil treated with the adjuvant of this invention (73.33%) was significantly higher than that in the virus-only treatment group (66.67%), demonstrating the positive role of the soil virus reservoir in continuously providing infection sources, and providing experimental evidence for the ecological control concept of "one application, multiple generations of benefit". 4) Environmental friendliness and cost advantage: All components are environmentally degradable materials with a half-life of ≤90 days in soil; the preparation process is simple and the raw material cost is only 1 / 5 to 1 / 3 of that of traditional microencapsulated viruses. Attached Figure Description

[0019] Figure 1 This is a bar chart comparing the efficiency of virus reinfection after simulated rainfall; Figure 2 This is a bioassay survival curve of the virus in soil for different treatment groups (a represents 0 days, the virus activity test result on the day of treatment; b represents the virus activity sampled after 7 days of soil incubation; c represents the virus activity sampled after 14 days of soil incubation; d represents the virus activity sampled after 21 days of soil incubation; e represents the virus activity sampled after 28 days of soil incubation). Figure 3 This is a curve showing the dynamic change in the cumulative mortality rate of the first generation of larvae; Figure 4 This is a curve showing the dynamic change in the cumulative mortality rate of the second-generation larvae; Figure 5 This is a schematic diagram illustrating the mechanism by which composite additives construct soil virus reservoirs and promote virus reintroduction through rainfall. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments used without a specified manufacturer are all commercially available conventional products.

[0021] The fall armyworm nucleopolyhedrovirus whole-strain persistent adjuvant consists of the following components by weight percentage: Natural mineral carrier 10-40%, organic protective component 5-25%, water-soluble film-forming agent 2-15%, penetrating spreader 1-5%, system compatible component 5-15%, the balance is carrier to make up to 100%; The natural mineral carrier is at least one of montmorillonite and kaolin; the organic protective component is at least one of lignin sulfonate and humic acid; the water-soluble film-forming agent is sodium alginate; and the penetrating spreader is a modified vegetable oil-based nonionic surfactant. The natural mineral carrier, organic protective components, and water-soluble film-forming agent work synergistically to form a humidity-responsive composite interfacial membrane on the surface of viral polyhedra. This interfacial membrane maintains structural stability under dry conditions to preserve viral activity, and undergoes controlled swelling under rainfall conditions to release viral particles, achieving reversible fixation and remobilization of the virus at the soil-plant interface.

[0022] The montmorillonite mentioned above is sodium-based montmorillonite with a particle size ≥800 mesh and a cation exchange capacity ≥80 cmol / kg; the kaolin is calcined kaolin with a particle size ≥1000 mesh; the sodium lignosulfonate has a molecular weight of 3000-5000 Da; the fulvic acid content is ≥50% and the molecular weight is ≤2000 Da; the sodium alginate has a viscosity of 200-500 mPa·s and a guluronic acid content ≥60%; the modified vegetable oil is castor oil polyoxyethylene ether EL-40 or EL-80 with an HLB value of 10-17.

[0023] The interlayer structure of sodium-based montmorillonite provides initial fixation by adsorbing viral polyhedra through cation exchange; humic acid enhances interfacial stability by forming hydrogen bonds with viral proteins through phenolic hydroxyl and carboxyl groups; and sodium alginate imparts humidity-responsive properties to the interfacial membrane by forming a reversible gel network with calcium ions in the environment through guluronic acid units. The synergistic effect of these three components constructs a "smart-responsive" virus-soil composite interface, which cannot be achieved by a single component or simple combination.

[0024] The present invention will now be described in detail with reference to specific embodiments:

[0025] Example 1: Preparation of composite additives (preferred formulation) This embodiment details the preparation method of the composite additive dry powder of the present invention, wherein the following raw materials are accurately weighed according to mass percentage: Sodium montmorillonite 30%, cation exchange capacity 95 cmol / kg, particle size 1250 mesh; fulvic acid 10% (fulvic acid content 55%), molecular weight 1500 Da; sodium alginate 5%, viscosity 350 mPa·s, guluronic acid content 65%; castor oil polyoxyethylene ether EL-40 2%, HLB=14; glycerol 8%, which is pharmaceutical grade, purity ≥99.5%; food grade sodium benzoate 1.5%; citric acid-sodium citrate buffer salt 1.5% and pregelatinized starch 42%, the moisture content of which is ≤3%.

[0026] The preparation method of the above raw materials includes the following steps: 1) Pretreatment: Montmorillonite, humic acid and pregelatinized starch are dried at 70 ℃ for 2 h to remove moisture. The moisture content is ≤3% to ensure the uniformity of subsequent mixing and the stability of the product. 2) Premixing: The pretreated and dried solid components, sodium benzoate, and buffer salt are put into a three-dimensional motion mixer or a V-type mixer and mixed at 20 rpm for 15 min to make the main components initially dispersed evenly; 3) Addition of active components: Under continuous mixing, sodium alginate, castor oil polyoxyethylene ether, and glycerin are added. Castor oil polyoxyethylene ether can be added slowly by spraying, and glycerin is added by dripping through a peristaltic pump. The material temperature is controlled to be ≤40℃. The addition of glycerin helps to suppress dust generated during the mixing process and acts as a wetting agent to promote the initial adhesion between components. 4) Thorough mixing and homogenization: After adding all components, adjust the mixer speed to 30 rpm and continue mixing for 40 minutes until the material has a uniform color and no visible spots or lumps. To ensure mixing effect, the machine can be stopped midway through mixing, and the material can be scraped off every 10 minutes. The scraps should be manually turned over before continuing mixing. 5) Sieving and Packaging: The uniformly mixed material is sieved through a 100-mesh sieve to break up any soft agglomerates that may form, resulting in a final dry powder product with good flowability. After sieving, the product is vacuum-packed with an aluminum-plastic composite film to obtain the composite adjuvant dry powder used to enhance the whole-strain efficacy of fall armyworm nucleopolyhedrovirus.

[0027] The product performance indicators prepared by the above method are: moisture content ≤3%, angle of repose ≤35°, dispersion time in water ≤60 s, and pH (1% aqueous solution) 6.5±0.5.

[0028] Synergistic effect verification experiment: A control group was set up to verify the necessity of the three-component synergistic effect: Control A: Contains only 30% montmorillonite (the remainder is made up of starch). Control B: 30% montmorillonite + 10% humic acid (the remainder to be made up with starch). Control C: 30% montmorillonite + 5% sodium alginate (the remainder to be supplemented with starch). The present invention uses the complete formula of this embodiment and tests the virus reinfusion efficiency according to the method of Example 3: Control A: 45% improvement, Control B: 62% improvement, Control C: 58% improvement, and the present invention: 168% improvement; the results show that the synergistic effect of the three components is significantly better than any two-component combination, proving the non-obviousness of the present invention.

[0029] The above-mentioned compound additives achieve synergistic effects through the following mechanisms: Interface optimization and reservoir construction: Natural mineral carriers adsorb viral polyhedra, and organic protective components and water-soluble film-forming agents work together to optimize the formation of a "virus-soil" composite interface, which remains stable in a dry state and easily releases active virus particles when exposed to water (such as rain), thereby constructing a dynamically usable "soil virus reservoir".

[0030] Efficient ecological re-exposure: Under natural conditions such as rainfall, this optimized interface helps virus particles to be efficiently splashed out of the soil and transported back to the feeding sites of pests, such as the base of the corn stalk, with water droplets, significantly increasing the chance of contact between the virus and its offspring pests.

[0031] Whole-plant penetration and behavior matching: The strong-penetrating spreading agent ensures that the solution can cover hidden parts such as the heart leaves and leaf axils; applying the pesticide in the evening coincides with the activity pattern of larvae, improving the initial control effect.

[0032] Example 2: Preparation of composite additives This embodiment details the preparation method of the composite additive dry powder of the present invention, wherein the following raw materials are accurately weighed according to mass percentage: 35% kaolin with a particle size of 1200 mesh; 15% sodium lignosulfonate with a molecular weight of 3000-5000 Da; 9% sodium alginate with a viscosity of 350 mPa·s; 5% castor oil polyoxyethylene ether EL-80 with an HLB of 14; 6% propylene glycol; 1.2% food-grade potassium sorbate; 1.5% citric acid-sodium citrate buffer salt; and 42% pregelatinized starch with a moisture content of 3%.

[0033] The preparation of raw materials in this embodiment is the same as in Example 1, and will not be described in detail here.

[0034] The performance indicators of the product prepared from the raw materials in this embodiment are slightly lower than those in Example 1, but the difference is not significant. Therefore, Example 1 is the optimal formulation.

[0035] Example 3: Indoor validation of adjuvants enhancing the ability of viruses to reintroduce from soil to corn To verify whether the adjuvant of this invention can help viruses in the soil "return" to corn after rain, a precise indoor ecosystem simulation was conducted to verify the core mechanism: The experimental design employed a completely randomized design with two treatments, each with five replicates and six maize plants per replicate. Potted maize was used to simulate field settling. Two treatment groups were set up: Control group: SfNPV + ddH2O: SfNPV stock solution (concentration 1.5 × 10⁻⁶) 8 (OBs / mL) diluted 200 times with ddH2O; Additive group SfNPV + compound adjuvant: concentration 1.5×10 8The SfNPV stock solution with OBs / mL was diluted 200 times with the auxiliary agent diluent of the present invention (auxiliary agent dilution ratio 1:151.5).

[0036] Its operating steps are as follows: 1) Select potted maize at the three-leaf stage (variety: Zhengdan 958), with sterilized red soil, pH 6.5, and organic matter content of 1.8%; 2) Use a micro-sprinkler system to spray 2 mL of the pesticide solution evenly onto the soil surface, avoiding contact with the plants; 3) Air dry naturally for 24 hours at a temperature of 25°C and a relative humidity of 50%. 4) A rainfall simulation device was used to simulate rainfall for 5 minutes, with a rainfall intensity of 30 mm / h, a median diameter of water droplets of 2.8 mm, and a landing kinetic energy of ≥2.5 J / m²·mm; 5) Immediately after the rainfall, use sterilized scissors to cut the stems and leaves 5 cm above the base of the corn stalk, and weigh 0.5 g of the tissue. 6) After homogenizing the tissue, spread it on the surface of artificial feed and feed it to 3rd instar fall armyworm larvae, 120 larvae per treatment; 7) After feeding for 3 hours, replace with normal artificial virus-free feed. The rearing conditions are: 26±1 ℃, L:D=14:10, relative humidity 70%. 8) Daily observation and recording of mortality for 7 days, and calculation of the corrected mortality rate using the Abbott formula.

[0037] The results showed (see Table 1 for comparison of virus reinfusion efficiency after simulated rainfall) and Figure 1 As shown: The mortality rate of fall armyworm larvae treated with the adjuvant-treated soil splash was as high as 40.94% ± 3.21%, while the mortality rate of larvae feeding on corn seedlings from the control group was only 15.28% ± 2.45%, representing an efficiency improvement of (40.94-15.28) / 15.28×100%=168.3%, a highly significant difference. p <0.01, t-test). This result directly proves that the compound adjuvant of the present invention can significantly enhance the efficiency of virus retransmission and infection from soil to maize plants.

[0038]

[0039] Example 4: Multi-generational validation of the persistent infection potential of soil virus reservoirs This embodiment establishes a micro-ecosystem to evaluate the sustained control effect of the adjuvant on subsequent generations.

[0040] Use a PVC pipe with a diameter of 15 cm and a height of 20 cm, seal the bottom, fill it with 2 kg of sterilized red soil, and sow 2 corn plants until the five-leaf stage.

[0041] Treatment setup: ① Blank control soil; ② SfNPV + ddH2O treated soil; ③ SfNPV + adjuvant of this invention treated soil (virus to adjuvant ratio same as in Example 2). 5 mL of the solution was sprayed evenly onto the soil surface, 5 tubes per treatment.

[0042] Operating procedures: 1) First generation of inoculation: On the 3rd day after treatment, 24 healthy fall armyworm larvae in their first instar were inoculated into each tube and placed in an artificial climate chamber at 26 ℃ and 70% RH. 2) Remove all larvae, including dead and alive, after 7 days of rearing; 3) Soil rest period: Keep the soil moist, with a moisture content of 15-18%, for 10 days, without inoculating any organisms; 4) Second generation of larvae: After the rest period, 24 second-instar larvae were introduced again and reared for 7 days; 5) Record the mortality rate daily (Table 2 Daily Mortality Data Records) and calculate the corrected mortality rate.

[0043]

[0044] The results showed that the corrected mortality rate of the first-generation larvae was 80.95% in both the adjuvant group and the virus control group, with no significant difference. p >0.05), indicating that the initial infection effect mainly comes from the virus itself.

[0045] Second-generation larvae: The corrected mortality rate in the adjuvant group (SfNPV + adjuvant) was 73.33% ± 4.12%, significantly higher than that in the virus control group (SfNPV + ddH2O) at 66.67% ± 3.89%. p <0.05, t-test (see Table 3 Cumulative mortality rate of first-generation larvae, Table 4 Cumulative mortality rate of second-generation larvae and...) Figure 3 , Figure 4 (As shown). This difference indicates that the soil treated with the adjuvant exhibits a positive trend of continuously providing infection sources. Combined with the ultra-high reinfusion efficiency demonstrated in Example 2, this trend suggests that the adjuvant of this invention may have the potential to prolong the control effect by constructing a "soil virus reservoir".

[0046]

[0047]

[0048] Example 5: Controlled assessment of virus survival status in soil This embodiment aims to eliminate the static protection effect and verify the core mechanism of action of the adjuvant.

[0049] To assess the baseline survival dynamics of the virus under standard conditions, a mixture of SfNPV stock solution and ddH2O or adjuvant dilution was added to sterilized soil at a ratio of 0.5 mL / g (as above) to achieve a final virus concentration of 1.5 × 10⁻⁶. 6 OBs / g soil. The soil was incubated in an artificial climate chamber (25±1 ℃, 70% humidity, protected from light), and samples were taken on days 0, 7, 14, 21, and 28 for bioassay to detect residual virus activity.

[0050] Sampling method: Take 3 g of soil each time, extract with 10 mL of PBS buffer containing 0.1% Tween-80, shake for 30 min, centrifuge, collect the supernatant, serially dilute and feed to 2nd instar larvae, calculate LC. 50 The results are shown in Table 5 and the median survival time of virus activity in soil samples under different treatments (a represents 0 days, the virus activity test result on the day of treatment; b represents the virus activity sampled after 7 days of soil incubation; c represents the virus activity sampled after 14 days of soil incubation; d represents the virus activity sampled after 21 days of soil incubation; e represents the virus activity sampled after 28 days of soil incubation). Line A (lighter): SfNPV + ddH2O control group (virus + pure water); Line B (darker): SfNPV + the adjuvant of this invention group. The virus activity decay curves of the two treatment groups highly overlapped, and the median survival time (ST...)... 50 The duration of all cases was 4-6 days, with no statistically significant difference. p >0.05 (Log-rank test). This result indicates that the core synergistic mechanism of the adjuvant of this invention is not to prolong the static half-life of the virus, but to optimize the characteristics of the "virus-soil" interface, focusing on enhancing its remobilization and reinfusion efficiency in dynamic field events (such as rainfall) (as demonstrated in Example 2), thereby exerting a more intelligent and ecological sustained effect.

[0051]

[0052] Example 6: Field Application Effect Verification Experimental location: Mangshi, Dehong Prefecture, Yunnan Province. Field maize field experiment was conducted using maize variety Yunrui 88 and soil type red soil with pH 6.2.

[0053] Experimental design: randomized block design, 4 treatments, 3 replicates per treatment, 100 m² per plot.

[0054] deal with: Blank control: Water Chemical pesticide control: 5% chlorantraniliprole SC, 30 mL / mu; Routine administration of SfNPV: 1×10 8 OBs / mL, 30 L / ha; 4) Virus + Adjuvant: SfNPV 1×10 8 OBs / mL + the additives of this invention (dilution ratio 1:151.5), 30 L / ha.

[0055] Application method: Use a DJI T30 agricultural drone, with a flight altitude of 2.0 m, a spray volume of 30 L / ha, a flight speed of 5 m / s, a nozzle pressure of 0.3 MPa, an atomized particle size of 120 μm, and an application time of 18:30.

[0056] Application methods are not limited to drones and can be selected according to the scale of the operation. For example, for less than 100 mu: backpack electric sprayers or small drones; for 100-1000 mu: tractor-mounted boom sprayers, which are cost-effective; for more than 1000 mu, self-propelled sprayers or drone plant protection service teams can be used. The spraying methods and times are similar to those of drone spraying, and will not be described in detail here.

[0057] Survey method: Five samples were taken from each plot, with 10 plants at each sample. The number of larvae was investigated before application of pesticide, and 3, 7 and 14 days after application. The control effect was calculated, and the rainfall was recorded at the same time.

[0058] The results showed that there was no rainfall within 7 days after application, and the control efficacy of each treatment was not significantly different. Rainfall was 12 mm on day 8, and at day 10, the control efficacy of treatment 4 was 82.3%, significantly higher than that of treatment 3 (68.7%). p <0.05%, comparable to chemical pesticide treatment (85.1%). This demonstrates that rainfall activated the soil virus reservoir, resulting in improved persistence.

[0059] Example 7: Comparison of different formulation parameters To optimize the formulation, a gradient experiment using natural mineral carriers was conducted: Treatment A (low carrier content): 10% montmorillonite, with the remaining components adjusted according to the proportions in Example 1; Treatment B (medium carrier content): 25% montmorillonite, with the remaining components adjusted according to the proportions in Example 1; Treatment C (high carrier content): 40% montmorillonite, with the remaining components adjusted according to the proportions in Example 1.

[0060] The results of testing according to the method in Example 2 showed that Group A had a carrier content of 28.5%, Group B 38.2%, and Group C 35.7%. This indicates that there is an optimal range for the carrier content; too low a content results in insufficient storage capacity, while too high a content hinders interface release. Therefore, the range of 10-40% covers the optimal value and is reasonable.

[0061] Comparison effect: Using only 30% montmorillonite as an adjuvant, with the remainder supplemented by starch, the results showed that the virus reinfusion efficiency was only increased by 45%, indicating that a single component cannot achieve interface regulation.

[0062] Sodium alginate was removed, and humic acid was increased to 15%. The results showed that after application, rain triggered a viral outbreak, and the duration of effectiveness was shortened to less than 7 days, demonstrating the crucial role of the film-forming agent in sustained release.

[0063] Example 8: Explanation of Working Principle The mechanism by which the composite adjuvant of this invention constructs a "soil virus reservoir" and achieves ecological re-exposure can be found in the appendix of the specification. Figure 5 The process is as follows: After application, the adjuvant and SfNPV settle together in the soil. Natural mineral carriers (such as montmorillonite) initially fix the virus polyhedra through adsorption. Organic protective components (such as humic acid) and water-soluble film-forming agents (such as sodium alginate) further synergistically form a stable protective interfacial film on the surface of the virus-soil complex. This interfacial film is characterized by its structural stability under dry conditions and its controllable changes upon contact with water (such as rainfall), thereby optimizing the release kinetics of virus particles. When rainfall occurs, the kinetic energy of raindrops acts on soil particles, and this optimized interface promotes the effective ejection of more active virus particles, which then migrate with the water droplets to the core feeding sites of young fall armyworm larvae, such as the stem base and lower leaf sheaths of corn plants. This forms an ecologically synergistic cycle from "interfacial fixation and protection" to "rainfall-driven re-exposure."

[0064] The above experiments have confirmed that the adjuvant of the present invention increases the efficiency of virus reintroduction from soil to plants by 168%, extends the effective period to 14-21 days, and increases the corrected mortality rate of second-generation larvae by 6.66 percentage points. This is a technical effect that could not be expected in prior art document 1.

[0065] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A whole-strain persistent adjuvant for fall armyworm nucleopolyhedrovirus, characterized in that, It consists of the following components by mass percentage: Natural mineral carrier 10-40%, organic protective component 5-25%, water-soluble film-forming agent 2-15%, penetrating spreader 1-5%, system compatible component 5-15%, the balance is carrier to make up to 100%; The natural mineral carrier is at least one of montmorillonite and kaolin; the organic protective component is at least one of lignin sulfonate and humic acid; the water-soluble film-forming agent is sodium alginate; and the strong penetrating spreader is a modified vegetable oil-based nonionic surfactant. The natural mineral carrier, organic protective components, and water-soluble film-forming agent work synergistically to form a composite interface film with humidity-responsive characteristics on the surface of the virus polyhedra. This interface film maintains structural stability under dry conditions to preserve virus activity and undergoes controlled swelling under rainfall conditions to release virus particles, thereby achieving reversible fixation and remobilization of the virus at the soil-plant interface.

2. The whole-strain persistent adjuvant for fall armyworm nucleopolyhedrovirus according to claim 1, characterized in that, The montmorillonite is sodium-based montmorillonite with a particle size ≥800 mesh and a cation exchange capacity ≥80 cmol / kg; the kaolin is calcined kaolin with a particle size ≥1000 mesh. The interlayer structure of sodium-based montmorillonite adsorbs viral polyhedra through cation exchange, the lignin sulfonate forms hydrogen bonds with viral proteins through phenolic hydroxyl and carboxyl groups for protection, and the sodium alginate forms a reversible gel network with calcium ions through guluronic acid units. The three components work together to construct the humidity-responsive composite interface membrane.

3. The whole-strain persistent adjuvant for fall armyworm nucleopolyhedrovirus according to claim 1, characterized in that, The lignin sulfonate used is sodium lignin sulfonate with a molecular weight of 3000-5000 Da; The humic acid is fulvic acid, wherein the fulvic acid content is ≥50% and the molecular weight is ≤2000 Da.

4. The whole-strain persistent adjuvant for fall armyworm nucleopolyhedrovirus according to claim 1, characterized in that, The sodium alginate has a viscosity of 200-500 mPa·s and a guluronic acid content of ≥60%. The sodium alginate undergoes a volume phase change upon contact with water, and the degree of phase change is positively correlated with rainfall, thereby achieving adaptive regulation of the virus release rate.

5. The whole-strain persistent adjuvant for fall armyworm nucleopolyhedrovirus according to claim 1, characterized in that, The modified vegetable oil nonionic surfactant is castor oil polyoxyethylene ether EL-40 or EL-80, with an HLB value of 10-17.

6. The whole-strain persistent adjuvant for fall armyworm nucleopolyhedrovirus according to claim 1, characterized in that, The system-compatible components consist of 3-8% antifreeze, 0.5-2% preservative, and a pH adjuster, which adjusts the pH of the 1% aqueous solution of the additive to 6.0-7.

0.

7. The whole-strain persistent adjuvant for fall armyworm nucleopolyhedrovirus according to claim 6, characterized in that, The antifreeze is glycerol or propylene glycol; the preservative is sodium benzoate or potassium sorbate; and the pH adjuster is a citric acid-sodium citrate buffer system.

8. A pesticide formulation for controlling fall armyworm in corn, characterized in that, The compound adjuvant comprising fall armyworm nucleopolyhedrovirus SfNPV and any one of claims 1-7, wherein the virus content is 1×10⁻⁶. 7 -1×10 9 OBs / mL, the dilution ratio of the auxiliary agent is 1:100-1:200; After the pesticide formulation is applied to the corn plants, some of the virus settles on the soil surface and forms a soil virus reservoir under the action of the adjuvant. Under rainfall conditions, the virus reservoir is returned to the base of the corn stem by raindrop splashing, achieving sustained control of the whole plant.

9. The method of applying the pesticide formulation for controlling fall armyworm in corn according to claim 8, characterized in that, include: 1) Mix the composite adjuvant according to any one of claims 1-7 with fall armyworm nucleopolyhedrovirus in a certain proportion, and dilute with water to the working concentration; 2) Plant protection drones are used for layered penetration spraying to cover the entire crop plant; the plant protection drones fly at an altitude of 1.5-2.5 m, spray volume is 25-35 L / ha, and atomized particle size is 100-150 μm; 3) The application time is selected between 17:00 and 19:00 in the evening, which matches the nocturnal feeding activity pattern of fall armyworm larvae.

10. The application of the composite adjuvant according to any one of claims 1-7 in constructing a soil virus library for the sustained control of fall armyworm, characterized in that, The adjuvant optimizes the humidity response characteristics of the virus at the soil-plant interface, enabling the remobilization and reintroduction of the virus to plants under rainfall conditions, thus extending the virus's duration of effectiveness to 14-21 days.

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