Method for preventing and treating watermelon fusarium wilt by using green bactericide

Abstract

The invention relates to the technical field of agricultural planting, in particular to a method for preventing and treating watermelon fusarium wilt by using a green bactericide, which comprises the following steps: preparing the green bactericide which comprises the following components in percentage by mass: 18-25% of composite plant source active component consisting of water lettuce extract, enteromorpha polysaccharide and field horsetail flavone; 20%-30% of an antagonistic bacterium compound preparation, wherein the antagonistic bacterium compound preparation comprises bacillus pumilus and trichoderma; 38%-45% of a nano-carrier, wherein a chitosan-sodium alginate compound is used as an embedding material; and the balance of auxiliary components. Applying the green bactericide to watermelon plants; through component optimization and a synergistic effect, compared with the prior art, the composition has the remarkable advantages that the safety is high, all the components are from natural plants or microorganisms, no chemical pesticide residue exists, the composition is healthy to human bodies and environmentally friendly, and the problems of drug resistance and soil pollution caused by chemical agents can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agricultural planting technology, in particular to a method for preventing and treating watermelon fusarium wilt by using green fungicide. BACKGROUND

[0002] Watermelon fusarium wilt is a soil-borne vascular disease caused by Fusarium oxysporum f. sp. Niveum, which is one of the main diseases in the process of watermelon planting. The disease has the characteristics of hidden onset and wide transmission path, and can be transmitted through soil, seeds, irrigation water, etc. It is particularly serious in the continuous cropping plot. At the early stage of the disease, the leaves of the watermelon plant gradually wilt from the base upwards, the symptoms are obvious at noon, and the symptoms can be temporarily restored in the morning and evening. In the later stage, the whole plant wilts and dies, the vascular bundle turns brown and rots, which seriously affects the yield and quality of watermelon. Generally, the yield of the plot is reduced by 20%-30%, and in severe cases, it can be reduced by more than 80% or even be absolutely lost, causing great economic losses to the watermelon industry.

[0003] At present, the prevention and treatment of watermelon fusarium wilt still mainly relies on chemical fungicides, such as benomyl, thiophanate-methyl and other benzimidazole agents. Although these agents can inhibit the reproduction of the pathogen in the short term and alleviate the occurrence of the disease, long-term use has obvious drawbacks: first, it is easy to cause the pathogen to develop drug resistance, which makes the control effect decrease year by year and requires increasing the amount of pesticide; second, the chemical agents accumulate in the soil and destroy the soil micro-ecological balance, leading to soil compaction and decline in soil fertility; third, the agents are absorbed by fruits or spread through surface runoff, causing excessive pesticide residues in agricultural products and environmental pollution, and threatening human health and ecological safety.

[0004] Therefore, the development of safe and efficient, environmentally friendly green control technology has become a demand to solve the problem of watermelon fusarium wilt prevention and treatment. SUMMARY

[0005] The present application relates to a method for preventing and treating watermelon fusarium wilt by using green fungicide.

[0006] The present application provides the following technical scheme:

[0007] A method for preventing and treating watermelon fusarium wilt by using green fungicide, comprising the following steps:

[0008] Preparation of green fungicide, the fungicide contains, based on the total mass of the fungicide being 100%, 18%-25% of complex plant source active ingredient, which is composed of water lily extract, ulva polysaccharide and vitexicano flavone in a mass ratio of 3-5:2-3:1-1.2; 20%-30% of antagonistic bacteria complex preparation, including bacillus pumilus and trichoderma; 38%-45% of nano carrier, taking chitosan-sodium alginate complex as embedding material; and the rest of auxiliary ingredients.

[0009] The green fungicide is applied to the watermelon plant.

[0010] As a further technical solution, the preparation method of the green bactericide comprises:

[0011] Extraction of composite plant active ingredients: extract water lotus, green algae, and ask Jing respectively; mix the extracts according to the mass ratio to obtain composite plant active ingredients;

[0012] The volume ratio of ethanol to water in the ethanol-water mixed solution is 7:3.

[0013] Preparation of antagonistic bacteria composite preparation: Bacillus pumilus and Trichoderma sp. are inoculated into LB liquid fermentation medium respectively, and cultured at 30°C for 48 hours. The bacterial cells are collected by centrifugation. The bacterial cells are mixed according to the ratio of viable bacteria 1:1, and freeze-dried at -40°C to obtain the antagonistic bacteria composite preparation.

[0014] Embedding of nano-carrier: chitosan is dissolved in 1% acetic acid solution to obtain a chitosan solution with a mass fraction of 8%. The chitosan solution and 2% sodium alginate solution are mixed according to the mass ratio of 1:2, and the above-mentioned composite plant active ingredients and antagonistic bacteria composite preparation are added and ultrasonically dispersed for 10-14 minutes. Nanoparticles are formed by high-pressure homogenization, and freeze-dried at -25°C for standby.

[0015] Product preparation: mix the nano-carrier particles with the auxiliary ingredients, granulate and dry to obtain the green bactericide.

[0016] As a further technical solution, in the extraction of composite plant active ingredients: the water lotus extract is obtained by low-temperature supercritical carbon dioxide extraction, the ethanol mass concentration of the ethanol-water mixed solution as the entraining agent is 65%-70%, and the extraction time is 90-100 minutes; the extraction of green algae polysaccharide adopts enzyme-assisted method: the green algae is crushed, 0.1% cellulase solution is added, the solid-liquid ratio is 1:10, and the enzyme is hydrolyzed at 50°C for 2 hours. After enzyme inactivation, the supernatant is collected by centrifugation and concentrated and dried; the extraction of ask Jing flavonoids adopts microwave-assisted extraction: the microwave power is 400W, the extraction time is 15 minutes, and after filtration and spray drying, the solvent is 70% ethanol solution.

[0017] As a further technical solution, in the antagonistic bacteria composite preparation, the total concentration of viable bacteria is ≥1×10 8 CFU / mL.

[0018] As a further technical solution, in the embedding of nano-carrier: the high-pressure homogenization parameters are pressure 20MPa and cycle 3 times.

[0019] As a further technical solution, the auxiliary ingredients are composed of poly naphthalene formaldehyde sulfonic acid sodium salt and sodium dodecyl sulfate according to the mass ratio of 2:1.

[0020] As a further technical solution, the application mode of the green bactericide is combined root irrigation and foliar spraying, 500-800 mL of the green bactericide with a concentration of 500-800 times liquid is applied to each watermelon plant during root irrigation, and the green bactericide is diluted 1000-1200 times and uniformly sprayed on the front and back of the leaves during foliar spraying.

[0021] The green bactericide is mixed and diluted with clean water during dilution.

[0022] As a further technical solution, the root irrigation frequency is once every 7-10 days, and the root irrigation is continuously performed 2-3 times; the foliar spraying frequency is once every 5-7 days, and the foliar spraying is continuously performed 3-4 times.

[0023] As a further technical solution, when the green bactericide is applied, environmental adaptability adjustment is performed according to the soil pH value, when the soil pH value is less than 6.0, 0.8%-1% of calcium carbonate powder based on the mass of the green bactericide is added to the green bactericide; when the soil pH value is greater than 7.5, 0.5%-0.8% of citric acid powder based on the mass of the green bactericide is added to the green bactericide.

[0024] As a further technical solution, the green bactericide is applied to the watermelon seedling stage, the vine stretching stage and the initial fruiting stage, 1-1.5 kg of the green bactericide is applied to each mu of land in the watermelon seedling stage, 2-2.5 kg of the green bactericide is applied to each mu of land in the vine stretching stage, and 2.5-3 kg of the green bactericide is applied to each mu of land in the initial fruiting stage.

[0025] Compared with the prior art, the green bactericide has the following beneficial effects:

[0026] The components of the green bactericide of the present application are complementary to each other, providing multiple safeguards for preventing and treating watermelon fusarium wilt: first, among the composite plant source active ingredients, the water lettuce extract contains alkaloids, flavones and other substances, which can destroy the cell membrane permeability of the pathogenic bacteria and inhibit the mycelium growth; the enteromorpha polysaccharide can enhance the immunity of the watermelon plant and promote the activity of the body's disease resistance related enzymes such as peroxidase and polyphenol oxidase; the vitex negundo flavone can interfere with the metabolic process of the pathogenic bacteria and inhibit spore germination, and the three are mixed in a specific ratio to form a broad-spectrum bacteriostatic effect.

[0027] The bacillus pumilus and trichoderma in the antagonistic bacteria composite preparation can directly inhibit the reproduction of the pathogenic bacteria by competing for the living space and nutrients of the pathogenic bacteria, secreting antibacterial peptides and chitinase and other substances, and can also improve the rhizosphere microenvironment and promote the growth of the plant.

[0028] The nano carrier has good biocompatibility and slow release, can protect the composite plant source active ingredients and the antagonistic bacteria from damage by the external environment such as ultraviolet rays and soil pH, and can also control the slow release of the effective components and prolong the action time.

[0029] The auxiliary component can enhance the adhesion and dispersion of the fungicide on the leaf and root surface, and improve the absorption efficiency of the active ingredient; and the calcium carbonate or citric acid added according to the soil pH value can adjust the stability of the fungicide, so that the fungicide can play a role in both acidic and alkaline soils.

[0030] The components of the present application are not simply superimposed, but form a comprehensive prevention and control system of bacteriostasis, immunity and synergistic effect through synergistic effect: the active ingredients of plant origin and the antagonistic bacteria form a double defense line of chemical bacteriostasis and biological antagonism: the active ingredients of plant origin quickly inhibit the activity of the pathogenic bacteria, creating conditions for the colonization of the antagonistic bacteria; the antagonistic bacteria consolidate the bacteriostasis effect and reduce the risk of recurrence of the pathogenic bacteria through continuous competition and secretion of active substances.

[0031] The embedding effect of the nano-carrier enhances the stability of the system: on the one hand, it avoids the degradation of the active ingredients of plant origin due to light and oxidation, prolonging the effective period; on the other hand, it protects the antagonistic bacteria from surviving in complex soil environment, improves the colonization rate, and solves the problem of easy inactivation of traditional biological agents.

[0032] The environmental adaptability adjustment of the auxiliary component further improves the action efficiency: the auxiliary component promotes the adhesion and penetration of the active ingredients on the plant surface, ensuring that the pesticide uniformly contacts the target; and the adjustment of the soil pH value avoids the damage of extreme acidity and alkalinity to the active ingredients and the antagonistic bacteria, ensuring the consistency of the prevention and control in different environments.

[0033] Compared with the prior art, the present application has the following advantages: high safety: all components are derived from natural plants or microorganisms, without chemical pesticide residues, friendly to human health and environment, and can avoid the problems of drug resistance and soil pollution caused by chemical pesticides. Stable prevention and control effect: multiple action mechanisms are superimposed, not only can quickly control existing diseases, but also can reduce the recurrence rate of diseases by enhancing the immunity of plants and improving the rhizosphere environment, and the prevention and control effect can reach more than 85%, which is better than conventional chemical fungicides. Growth promotion: the components such as ulvan and antagonistic bacteria can promote the development and nutrient absorption of watermelon root system, increase plant height, stem diameter and single fruit weight, increase yield while preventing diseases, and realize the dual benefits of prevention and control and yield increase. In summary, the present application provides a new way for green prevention and control of watermelon fusarium wilt, and is suitable for popularization and application in sustainable agricultural production. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The flow chart for preparing the green fungicide. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0036] The present application provides a method for preventing and treating watermelon fusarium wilt by using a green fungicide, comprising: preparing the green fungicide and applying the fungicide to watermelon plants.

[0037] The green fungicide comprises, based on the total mass of 100%, 18%-25% of a composite plant source active ingredient, 20%-30% of an antagonistic bacteria composite preparation, 38%-45% of a nano carrier and the balance of an auxiliary ingredient. The composite plant source active ingredient is composed of water lily extract, Enteromorpha polysaccharide and Vitex negundo flavone at a mass ratio of 3-5:2-3:1-1.2; the antagonistic bacteria composite preparation comprises Bacillus pumilus and Trichoderma; the nano carrier takes a chitosan-sodium alginate complex as an embedding material; and the auxiliary ingredient is composed of poly naphthalene formaldehyde sulfonate sodium salt and sodium dodecyl sulfate at a mass ratio of 2:1.

[0038] Preparation of the green fungicide

[0039] Extraction of the composite plant source active ingredient

[0040] Water lily extract: low-temperature supercritical carbon dioxide extraction is adopted, an ethanol-water mixed solution (65%-70% ethanol mass concentration) is used as a entraining agent, and the extraction time is 90-100 minutes.

[0041] Enteromorpha polysaccharide: enzyme-assisted extraction is adopted. After the Enteromorpha is crushed, 0.1% cellulase solution is added, the solid-liquid ratio is 1:10, enzyme hydrolysis is carried out at 50°C for 2 hours, after enzyme inactivation, the supernatant is obtained by centrifugation, and concentration and drying are carried out to obtain the Enteromorpha polysaccharide.

[0042] Vitex negundo flavone: microwave-assisted extraction is adopted, the microwave power is 400W, the extraction time is 15 minutes, 70% ethanol solution is used as a solvent, and after filtration, spray drying is carried out to obtain the Vitex negundo flavone.

[0043] The above three extracts are mixed at a mass ratio of 3-5:2-3:1-1.2 to obtain the composite plant source active ingredient.

[0044] Preparation of the antagonistic bacteria composite preparation

[0045] Bacillus pumilus and Trichoderma are inoculated into LB liquid fermentation medium respectively, constant temperature oscillation culture is carried out at 30°C for 48 hours, the bacterial bodies are collected by centrifugation, the bacterial bodies are mixed at a viable bacterial number ratio of 1:1, freeze-drying is carried out at-40°C to obtain the antagonistic bacteria composite preparation, and the total concentration of viable bacteria is ≥1×10 8 CFU / mL.

[0046] Embedding of nanocarriers

[0047] Chitosan was dissolved in acetic acid solution with a mass concentration of 1% to obtain a chitosan solution with a mass fraction of 8%; the chitosan solution was mixed with a sodium alginate solution with a mass concentration of 2% at a mass ratio of 1:2, and the above-mentioned complex plant source active ingredient and antagonistic bacteria complex preparation was added and ultrasonically dispersed for 10-14 minutes; nanometer particles were formed by high-pressure homogenization at a pressure of 20 MPa for 3 cycles, and freeze-dried at -25°C for standby use.

[0048] Product preparation

[0049] The nanocarrier particles were mixed with auxiliary ingredients (sodium polyphthalaldehyde sulfonate and sodium dodecyl sulfate at a mass ratio of 2:1), granulated and dried to obtain a green bactericide.

[0050] Application of the green bactericide

[0051] Application method: root irrigation and foliar spraying were combined.

[0052] Root irrigation: 500-800 mL of the green bactericide (mixed with water and diluted) with a concentration of 500-800 times was applied to each watermelon plant.

[0053] Foliar spraying: the green bactericide was diluted 1000-1200 times (mixed with water) and then uniformly sprayed on the front and back of the leaves.

[0054] Application frequency:

[0055] Root irrigation: once every 7-10 days, and continuous root irrigation for 2-3 times.

[0056] Foliar spraying: once every 5-7 days, and continuous spraying for 3-4 times.

[0057] Environmental adaptability adjustment:

[0058] When the soil pH value is < 6.0, 0.8%-1% of calcium carbonate powder by mass of the green bactericide is added.

[0059] When the soil pH value is > 7.5, 0.5%-0.8% of citric acid powder by mass of the green bactericide is added.

[0060] Application period and dosage:

[0061] Watermelon seedling stage: 1-1.5 kg per mu was applied.

[0062] Vine stretching stage: 2-2.5 kg per mu was applied.

[0063] Early results: 2.5-3 kg per mu was applied.

[0064] The method provided by the application can efficiently prevent and treat watermelon fusarium wilt through the synergistic effect of the composite plant source active ingredients and antagonistic bacteria and the slow-release effect of the nano carrier.

[0065] The following is a specific embodiment

[0066] Embodiment 1

[0067] Preparation of the green bactericide

[0068] The composite plant source active ingredients are water lettuce extract, Enteromorpha polysaccharide and Vitex negundo flavone, which are mixed at a mass ratio of 3:2:1 and account for 18% of the total mass of the bactericide.

[0069] The antagonistic bacteria composite preparation is composed of Bacillus pumilus and Trichoderma (the ratio of live bacteria is 1:1), which accounts for 20% of the total mass (the total concentration of live bacteria is 1.2x10 8 CFU / mL).

[0070] The nano carrier is a chitosan-sodium alginate compound (the mass ratio of chitosan solution to sodium alginate solution is 1:2), which accounts for 45% of the total mass.

[0071] The auxiliary ingredients are poly (naphthalene formaldehyde) sodium sulfonate and sodium dodecyl sulfate, which are mixed at a mass ratio of 2:1 and account for 17% of the total mass.

[0072] The extraction and preparation parameters are as follows: the ethanol concentration for water lettuce extraction is 65%, the extraction time is 90 minutes; the microwave extraction time for Vitex negundo flavone is 10 minutes; the ultrasonic dispersion time for the nano carrier is 10 minutes, and the high-pressure homogenization cycle is 3 times at 20 MPa.

[0073] Application method

[0074] Irrigation of roots: 800 times of liquid, 500 mL per plant, once every 10 days, for 2 times.

[0075] Leaf surface spraying: 1200 times of liquid, once every 7 days, for 3 times.

[0076] The soil pH value is 6.5 (no adjustment is needed), 1 kg per mu is applied during the seedling stage, 2 kg is applied during the vine stretching stage, and 2.5 kg is applied during the initial fruiting stage.

[0077] Embodiment 2

[0078] Preparation of the green bactericide

[0079] The composite plant source active ingredients are water lettuce extract, Enteromorpha polysaccharide and Vitex negundo flavone, which are mixed at a mass ratio of 4:2.5:1.1 and account for 22% of the total mass.

[0080] The antagonistic bacteria composite preparation accounts for 25% of the total mass (the total concentration of live bacteria is 1.5x10 8 CFU / mL).

[0081] The nano carrier accounts for 42% of the total mass.

[0082] Auxiliary ingredients: 11% of the total mass.

[0083] Extraction and preparation parameters: water lily extraction ethanol concentration 68%, time 95 minutes; willow flavonoids microwave extraction 12 minutes; nanocarrier ultrasonic dispersion 12 minutes.

[0084] Application method

[0085] Irrigation: 600 times liquid, 600 mL per plant, once every 8 days, for 3 times in a row.

[0086] Leaf spraying: 1100 times liquid, once every 6 days, for 4 times in a row.

[0087] Soil pH value 5.8 (add 0.8% calcium carbonate), 1.2 kg per mu at seedling stage, 2.2 kg at vine stretching stage, and 2.8 kg at initial fruiting stage.

[0088] Example 3

[0089] Green bactericide preparation

[0090] Composite plant source active ingredients: mass ratio 5:3:1.2, 25% of the total mass.

[0091] Antagonistic bacteria composite preparation: 30% of the total mass (total concentration of live bacteria 2.0 x 10 8 CFU / mL).

[0092] Nanocarrier: 38% of the total mass.

[0093] Auxiliary ingredients: 7% of the total mass.

[0094] Extraction and preparation parameters: water lily extraction ethanol concentration 70%, time 100 minutes; willow flavonoids microwave extraction 14 minutes; nanocarrier ultrasonic dispersion 14 minutes.

[0095] Application method

[0096] Irrigation: 500 times liquid, 800 mL per plant, once every 7 days, for 3 times in a row.

[0097] Leaf spraying: 1000 times liquid, once every 5 days, for 4 times in a row.

[0098] Soil pH value 7.8 (add 0.5% citric acid), 1.5 kg per mu at seedling stage, 2.5 kg at vine stretching stage, and 3 kg at initial fruiting stage.

[0099] Example 4

[0100] Green bactericide preparation

[0101] Composite plant-derived active ingredients: mass ratio 3.5:2.2:1.0, 20% of the total mass.

[0102] Antagonistic bacteria composite preparation: 22% of the total mass (total live bacteria concentration 1.3 x 10 8 CFU / mL).

[0103] Nano-carrier: 44% of the total mass.

[0104] Auxiliary ingredients: 14% of the total mass.

[0105] Extraction and preparation parameters: water lily extraction ethanol concentration 66%, time 92 minutes; huangqin flavone microwave extraction 11 minutes; nano-carrier ultrasonic dispersion 11 minutes.

[0106] Application method

[0107] Irrigation roots: 700 times liquid, 700 mL per plant, once every 9 days, for 2 times in a row.

[0108] Leaf surface spraying: 1150 times liquid, once every 6 days, for 3 times in a row.

[0109] Soil pH value 6.2 (no adjustment needed), 1.1 kg per mu at seedling stage, 2.1 kg at vine stretching stage, and 2.6 kg at early fruiting stage.

[0110] Example 5

[0111] Green fungicide preparation

[0112] Composite plant-derived active ingredients: mass ratio 4.5:2.8:1.1, 23% of the total mass.

[0113] Antagonistic bacteria composite preparation: 28% of the total mass (total live bacteria concentration 1.8 x 10 8 CFU / mL).

[0114] Nano-carrier: 40% of the total mass.

[0115] Auxiliary ingredients: 9% of the total mass.

[0116] Extraction and preparation parameters: water lily extraction ethanol concentration 69%, time 98 minutes; huangqin flavone microwave extraction 13 minutes; nano-carrier ultrasonic dispersion 13 minutes.

[0117] Application method

[0118] Irrigation roots: 550 times liquid, 750 mL per plant, once every 8 days, for 3 times in a row.

[0119] Leaf surface spraying: 1050 times liquid, once every 5 days, for 4 times in a row.

[0120] Soil pH 8.0 (add 0.8% citric acid), seedling stage 1.4 kg per mu, vine stage 2.4 kg, initial fruit stage 2.9 kg.

[0121] Comparative Example 1

[0122] The method of Example 2 was used, except that the composite plant-derived active ingredient lacked apigenin (only water lettuce extract: Enteromorpha polysaccharide was 4:2.5), and the proportions and preparation, application parameters of the remaining components were the same.

[0123] Comparative Example 2

[0124] The method of Example 2 was used, except that no nano-carrier was used, and the composite plant-derived active ingredient, antagonistic bacteria composite preparation, and auxiliary ingredients were mixed and granulated directly, and the remaining parameters were the same.

[0125] Test

[0126] Watermelon wilt prevention and control effect test

[0127] Experimental method

[0128] According to GB / T 17980.101-2024 "Guidelines for Pesticide Field Trials (I) Fungicides for Prevention and Control of Watermelon Wilt", select a high-risk area for watermelon wilt, plant "Jingxin No. 1" watermelon, set up 9 treatment groups (Examples 1-5, Comparative Examples 1-2, water control group, conventional chemical fungicide control group (50% carbendazim wettable powder 500 times liquid)), 3 repeats for each group, 20 m 2 2 area per plot, plant 30 plants.

[0129] At the seedling stage of watermelon, each group was treated according to the method, and the disease was investigated 30 days after the onset of the disease. The grading standard was: 0 level (no disease), 1 level (1-25% leaf wilt), 2 level (26-50% leaf wilt), 3 level (51-75% leaf wilt), 4 level (76-100% leaf wilt or whole plant death).

[0130] Disease index and control effect were calculated:

[0131] Disease index = Σ (number of plants at each level x relative level value) / (total number of plants x highest level value) x 100 Control effect = (control group disease index - treatment group disease index) / control group disease index x 100%; The results are as follows:

[0132] Table 1

[0133] Treatment group Disease index (%) Control effect (%) Example 1 8.2±1.1 85.3±2.3 Example 2 6.5±0.9 88.7±1.8 Example 3 5.8±0.8 90.0±1.5 Example 4 7.6±1.0 86.5±2.1 Example 5 6.1±0.8 89.5±1.6 Comparative Example 1 18.5±2.2 64.2±3.5 Comparative Example 2 22.3±2.5 57.5±4.0 Water control group 55.8±3.0 - Conventional fungicide group 12.6±1.5 77.4±2.8

[0134] As can be seen from Table 1, the control effects of Examples 1-5 are all above 85%, which are significantly higher than those of Comparative Examples 1-2 and the conventional fungicide group, indicating that the green fungicide of the application has excellent control effect on watermelon fusarium wilt.

[0135] Comparative Example 1 lacks scutellarein, and the synergistic antibacterial effect of the composite plant-derived active ingredient is weakened (scutellarein can enhance the inhibition of fusarium wilt fungus), resulting in a decrease of more than 30% in the control effect.

[0136] Comparative Example 2 does not use a nano carrier, and the active ingredient is released too quickly to continuously inhibit bacteria, and is easily affected by environmental factors (such as rainwater washing), with a control effect of only 57.5%, which is much lower than that of the examples.

[0137] Watermelon growth index and yield test

[0138] Experimental method

[0139] Under the planting conditions of Test 1, the plant height, stem diameter (at 10 cm from the ground), single fruit weight and yield per mu were measured at the mature stage of watermelon, 10 plants were randomly selected for each group, and the average value was taken. Referring to the crop growth index determination method in GB / T8321.10-2018 "Guidelines for the Rational Use of Pesticides (Ten)", the results are as follows:

[0140] Table 2

[0141] Treatment group Plant height (cm) Stem diameter (cm) Single fruit weight (kg) Yield per mu (kg) Example 1 185±5.2 2.8±0.2 4.2±0.3 3850±80 Example 2 192±4.8 3.0±0.1 4.5±0.2 4020±70 Example 3 198±4.5 3.1±0.1 4.6±0.2 4150±65 Example 4 188±5.0 2.9±0.2 4.3±0.3 3920±75 Example 5 195±4.6 3.0±0.1 4.5±0.2 4080±68 Comparative Example 1 162±6.0 2.5±0.2 3.6±0.4 3200±90 Comparative Example 2 155±6.5 2.4±0.3 3.4±0.4 3050±95 Water control group 140±7.0 2.2±0.3 3.0±0.5 2700±100 Conventional fungicide group 170±5.5 2.6±0.2 3.8±0.3 3400±85

[0142] As can be seen from Table 2, the plant height, stem diameter, single fruit weight and yield per mu of Examples 1-5 are all significantly higher than those of the comparative examples and the control group, indicating that the green fungicide of the application not only can control diseases, but also can promote the growth of watermelon.

[0143] Comparative Example 1 lacks scutellarein, and the growth regulation effect of the plant-derived active ingredient is weakened (scutellarein can promote cell division), resulting in a decrease in growth index and yield.

[0144] Comparative Example 2 does not use a nano carrier, and the utilization rate of the active ingredient is low, and the absorption of watermelon may be affected due to uneven release, resulting in the worst growth index and yield.

[0145] Safety test (leaf phytotoxicity and soil microbial influence)

[0146] Experimental method

[0147] Leaf phytotoxicity: 7 days after the last leaf spraying, whether the watermelon leaves of each group appear yellowing, spots, wilting and other phytotoxicity was observed, and the classification of GB / T19378-2003 "Guidelines for Environmental Impact Test of Pesticide Registration" was referred to (0 level: no phytotoxicity; 1 level: slight phytotoxicity <10% of leaves affected).

[0148] Soil microorganism: soil samples were collected after harvest, and the number of bacteria, fungi and actinomycetes in the soil was determined by plate counting method (3 replicates for each treatment), and the results were as follows:

[0149] Table 3

[0150]

[0151] As can be seen from Table 3, the leaves of Examples 1-5 have no phytotoxicity, and the number of soil microorganisms is close to that of the water control group, indicating that the green bactericide of the present application has high safety and small impact on soil microecology.

[0152] Although Comparative Example 1 has no phytotoxicity, the promoting effect on soil microorganisms is weaker than that of the examples because of incomplete components (the composite plant source components can synergistically nourish microorganisms).

[0153] Comparative Example 2 has no nano carrier, and the effective components directly contact the leaves, which may cause slight phytotoxicity (level 1), and the components are released too quickly, which destroys the balance of soil microorganisms and leads to a decrease in the number of microorganisms.

[0154] The conventional fungicide group has level 1 phytotoxicity, and significantly inhibits soil microorganisms, and has much lower safety than the present application.

[0155] The preferred embodiments of the present application disclosed above are only used to help illustrate the present application. The preferred embodiments do not describe all the details, and the present application is not limited to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present application.

Claims

1. A method for controlling watermelon fusarium wilt by using green bactericide, characterized in that, The method comprises the following steps: Preparation of the green bactericide, which comprises, based on the total mass of the bactericide: 18-25% of a composite plant-derived active ingredient consisting of water lettuce extract, Enteromorpha polysaccharide and Vitex negundo flavone at a mass ratio of 3-5:2-3:1-1.2; 20-30% of an antagonistic bacteria composite preparation comprising Bacillus pumilus and Trichoderma; 38-45% of a nano-carrier taking chitosan-sodium alginate complex as embedding material; and the balance of auxiliary ingredients; The green bactericide is applied to watermelon plants.

2. The method of claim 1, wherein, The preparation method of the green bactericide comprises: Extraction of the composite plant-derived active ingredient: water lettuce, Enteromorpha and Vitex negundo are extracted respectively, and the extracts are mixed at a mass ratio to obtain the composite plant-derived active ingredient; The volume ratio of ethanol to water in the ethanol-water mixed solution is 7:3; Preparation of the antagonistic bacteria composite preparation: Bacillus pumilus and Trichoderma are inoculated into LB liquid fermentation medium respectively, and are cultured at 30°C for 48 hours under constant temperature oscillation, and the bacterial bodies are collected by centrifugation; the bacterial bodies are mixed at a viable bacterial number ratio of 1:1, and are freeze-dried at-40°C to obtain the antagonistic bacteria composite preparation; Embedding of the nano-carrier: chitosan is dissolved in a 1% acetic acid solution to obtain a chitosan solution with a mass fraction of 8%, the chitosan solution is mixed with a 2% sodium alginate solution at a mass ratio of 1:2, the composite plant-derived active ingredient and the antagonistic bacteria composite preparation are added, and ultrasonic dispersion is performed for 10-14 minutes; nano-particles are formed by high-pressure homogenization, and are freeze-dried at-25°C for standby; Product preparation: the nano-carrier particles are mixed with the auxiliary ingredients, granulated, dried, and the green bactericide is obtained.

3. The method of claim 2, wherein, In the extraction of the composite plant-derived active ingredient: the water lettuce extract is obtained by low-temperature supercritical carbon dioxide extraction, the mass concentration of ethanol in the ethanol-water mixed solution as the entraining agent is 65-70%, and the extraction time is 90-100 minutes; the extraction of Enteromorpha polysaccharide adopts an enzymatic hydrolysis auxiliary method: after the Enteromorpha is crushed, a 0.1% cellulase solution is added, the solid-liquid ratio is 1:10, and enzymatic hydrolysis is performed at 50°C for 2 hours; after enzyme inactivation, the supernatant is obtained by centrifugation and concentrated and dried; the extraction of Vitex negundo flavone adopts microwave-assisted extraction: the microwave power is 400W, the extraction time is 15 minutes, and after filtration and spray drying, the solvent is 70% ethanol solution.

4. The method of claim 2, wherein, The total concentration of viable bacteria in the antagonistic bacteria compound preparation is ≥1×10 8 CFU / mL.

5. The method of claim 2, wherein, In the embedding of the nano-carrier: the high-pressure homogenization parameters are a pressure of 20MPa and 3 cycles.

6. The method of claim 1, wherein, The auxiliary ingredients are composed of polyoxymethylene formaldehyde sodium sulfonate and sodium dodecyl sulfate at a mass ratio of 2:

1.

7. The method of claim 1, wherein, The application mode of the green bactericide is a combination of root irrigation and foliar spraying: when the roots are irrigated, 500-800mL of the green bactericide with a concentration of 500-800 times the liquid is applied to each watermelon plant, and when the leaves are sprayed, the green bactericide is diluted by 1000-1200 times and uniformly sprayed on the front and back of the leaves; When diluted, the green bactericide is mixed and diluted with water.

8. The method of claim 7, wherein, The root irrigation frequency is once every 7-10 days, and the roots are irrigated continuously for 2-3 times; the foliar spraying frequency is once every 5-7 days, and the leaves are sprayed continuously for 3-4 times.

9. The method of claim 1, wherein, When the green bactericide is applied, environmental adaptability adjustment is made according to the soil pH value, when the soil pH value is < 6.0, 0.8%-1% of calcium carbonate powder by mass of the green bactericide is added to the green bactericide; when the soil pH value is > 7.5, 0.5%-0.8% of citric acid powder by mass of the green bactericide is added to the green bactericide.

10. The method of claim 1, wherein, The green bactericide is applied to the watermelon seedling stage, the vine stretching stage and the initial fruiting stage, 1-1.5 kg per mu is applied to the watermelon seedling stage, 2-2.5 kg per mu is applied to the vine stretching stage, and 2.5-3 kg per mu is applied to the initial fruiting stage.

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