A plant-derived biological control agent for controlling cucumber mosaic virus disease

Abstract

A plant-derived biocontrol agent for controlling cucumber mosaic virus disease includes one or more of the following: Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, or Mentha haplocalyx. Research in this invention shows that Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, and Mentha haplocalyx have certain inhibitory effects on cucumber mosaic virus, with Alternanthera philoxeroides showing the most significant inhibitory effect. This invention provides more options for controlling cucumber mosaic virus disease.

Description

Technical Field

[0001] This invention relates to the field of biological control technology for plant diseases, and more specifically, to a plant-derived biological control agent for controlling cucumber mosaic virus. Background Technology

[0002] Cucumber mosaic virus (CMV) is a typical member of the genus Cucumber mosaic virus in the family Bromoviridae, and is listed as one of the world's top ten plant viruses. CMV has a wide range of harmful effects, being one of the plant viruses with the most host plants, the widest distribution, and the greatest economic importance. Statistics show that in China, CMV infection can reduce tomato yields by approximately 25% to 50% and pepper yields by 20%. Diseases caused by CMV pose a serious threat to crops and other economic crops, causing enormous economic losses. The diseases caused by CMV are becoming increasingly serious but difficult to control, resulting in severe economic losses to crop production worldwide.

[0003] Plant-derived biocontrol agents are active ingredients extracted from cultivated or wild plants. Their effective components are typically some, or even most, of the organic matter in the plant organism. Compared to chemically synthesized pesticides, plant-derived biocontrol agents are environmentally friendly, safe for non-target organisms, less likely to induce resistance, have specific modes of action, promote crop growth and enhance disease resistance, are diverse in type, and have multiple development pathways. Therefore, plant-derived biocontrol agents have received widespread attention and application in the fields of melons, fruits, vegetables, specialty crops (tea, mulberry, traditional Chinese medicine, flowers, etc.), and organic agriculture. Chinese patent CN105707136A discloses a biocontrol agent for cucumber mosaic virus disease, including Astragalus membranaceus, Isatis indigotica, Artemisia capillaris, Lonicera japonica, Forsythia suspensa, Coptis chinensis, Atractylodes macrocephala, Taraxacum mongolicum, and Zanthoxylum bungeanum. Currently, there are still relatively few plant-derived biocontrol agents for cucumber mosaic virus disease, therefore, more plant-derived biocontrol agents for cucumber mosaic virus need to be provided for selection. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects and deficiencies in the prior art and to provide new uses for any one or more of Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata or Mentha haplocalyx in the fight against cucumber mosaic virus or in the preparation of biocontrol agents against cucumber mosaic virus, thereby providing more plant-derived biocontrol agents against cucumber mosaic virus.

[0005] The second objective of this invention is to provide a plant-derived biological control agent for the prevention and control of cucumber mosaic virus disease.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] Alternanthera philoxeroides (Mart.) Griseb., also known as drought-tolerant alternanthera, is a perennial herb belonging to the genus Alternanthera in the family Amaranthaceae. Its stems are creeping at the base and ascending obliquely upwards, hollow and branched. Leaves are opposite, oblong, with an acute or obtuse apex and a gradually narrowing base, covered with appressed hairs on the upper surface and ciliate margins. The flower heads are solitary in the leaf axils of the upper stem, spherical, with oblong, white, pinkish-white, and glossy perianth segments. Originally from Brazil, Alternanthera philoxeroides has escaped into the wild after being introduced to my country and is now a significant invasive plant; it is widely distributed on both the northern and southern slopes of the Qinling Mountains in China. Alternanthera philoxeroides prefers warm climates and is highly cold-resistant; it is adaptable and can grow in both water and on land. It primarily reproduces asexually. The whole plant is used medicinally; it has a bitter and slightly sweet taste and is cold in nature; it has the effects of clearing heat and promoting diuresis, cooling the blood and detoxifying.

[0008] Bidens pilosa L., a plant in the Asteraceae family, is a type of beggar-ticks. It is distributed in East China, Central China, South China, and Southwest China. It possesses detoxifying and swelling-reducing, heat-clearing and analgesic, blood-activating and stasis-removing, qi-regulating and stagnation-reducing effects. It is commonly used for gastroenteritis, abdominal pain due to heatstroke, bacterial dysentery, fever from colds, acute laryngitis, urinary tract infections, leukorrhea, hemorrhoids, rectal prolapse, hematochezia, diabetes, snake bites, frozen shoulder, traumatic injuries, and arthritis.

[0009] *Emilia sonchifolia* (L.) DC. in Wight is an annual or perennial herbaceous plant belonging to the Asteraceae family. It has vertical roots and an erect stem, glabrous or sparsely pubescent, and grayish-green in color. The leaves are relatively thick, with a large, broadly ovate-triangular terminal lobe with irregular teeth; the lateral lobes are oblong with wavy teeth. The upper surface is dark green, often turning purple on the lower surface. The middle stem leaves are sparsely arranged, smaller, and sessile; the upper leaves are few and linear. The flower heads droop before flowering and become erect after flowering; the peduncles are slender, without bracts, and the involucre is cylindrical; the involucral bracts are yellowish-green, about the same length as the florets, and glabrous on the back. The florets are pink or purple with slender tubes; the pappus is abundant, white, and soft. It is found wild in South China, Central China, and Southwest China. The herb *Cinnamomum camphora* is neutral in nature, bitter and slightly pungent in taste, and has the effects of cooling the blood and detoxifying. It is mainly eaten for its tender shoots and leaves, which can be stir-fried, used in soups, or as a hot pot ingredient. It has a crisp texture and tastes similar to garland chrysanthemum. It has the effects of clearing heat and detoxifying, promoting blood circulation and removing blood stasis, and can also treat urinary tract infections, pharyngitis, and boils.

[0010] Houttuynia cordata Thunb. is a medicinal herb listed in the Chinese Pharmacopoeia. The herbal source is the dried aerial parts of the herb, *Houttuynia cordata*, belonging to the Saururaceae family. It is harvested in summer when the stems and leaves are lush and the flower spikes are abundant. Impurities are removed, and it is then sun-dried. The stems of *Houttuynia cordata* are flattened cylindrical, twisted, 20–35 cm long, and 0.2–0.3 cm in diameter; the surface is brownish-yellow with several longitudinal ridges, distinct nodes, and residual fibrous roots on the lower nodes; it is brittle and easily broken. The leaves are alternate, rolled and wrinkled, becoming heart-shaped when flattened, 3–5 cm long and 3–4.5 cm wide; the apex is acuminate, and the margin is entire; the upper surface is dark yellowish-green to dark brown, and the lower surface is grayish-green or grayish-brown; the petiole is slender, and the base is fused with the stipules to form a sheath. The spike-like inflorescences are terminal and yellowish-brown. When crushed, it has a fishy odor. *Houttuynia cordata* is pungent in taste, cold in nature, and enters the lung meridian. It can clear heat and detoxify, reduce swelling and heal sores, promote diuresis and remove dampness, clear heat and stop dysentery, and strengthen the stomach and aid digestion. It is used to treat lung abscesses, carbuncles and boils, hemorrhoids with bleeding, and spleen and stomach heat accumulation caused by excess heat, heat toxicity, dampness, and febrile diseases. Modern pharmacological experiments have shown that it has antibacterial, antiviral, immune-enhancing, and diuretic effects.

[0011] Peppermint (Mentha canadensis Linnaeus), also known as Yindan grass or night-blooming jasmine, is a perennial herb belonging to the genus Mentha in the Lamiaceae family. It has opposite leaves, small, pale purple, labiate flowers, and produces small, dark purplish-brown berries after flowering. It prefers warm, humid, and sunny locations, and is commonly found in mountain wetlands. The entire plant has a fragrant aroma and is an aromatic crop with special economic value. Peppermint is one of the commonly used traditional Chinese medicines. It is a pungent and cooling diaphoretic and antipyretic, used to treat influenza, headaches, red eyes, fever, sore throat, and swollen gums. Externally, it can treat neuralgia, itchy skin, rashes, and eczema. Peppermint is often used as a tea substitute to refresh the mind and improve eyesight.

[0012] This invention involves grinding wild plants such as Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, and Mentha haplocalyx into a crude juice. Diseased leaves of Cucumber Mosaic Virus (CMV) are then ground together with the crude juice in a specific ratio and inoculated onto healthy zucchini leaves of uniform growth. The experiment was repeated three times, with a control group included. Symptoms were observed and statistically analyzed on leaves taken from the same location 7-12 days after inoculation. The results showed that Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, and Mentha haplocalyx all had a certain inhibitory effect on CMV, with Alternanthera philoxeroides showing the most significant inhibitory effect. The virus concentration in plants under different treatments was calculated using ELISA, and the inhibition rate of CMV by each wild plant was calculated. The results showed that Alternanthera philoxeroides treatment had a significant inhibitory effect on CMV, with an inhibition rate of 76.20%. Other plants such as Bidens pilosa, Houttuynia cordata, and Mentha haplocalyx all had certain inhibitory effects on CMV (10.06–53.72%). The ELISA results were consistent with the symptom manifestations of zucchini after treatment, indicating that Alternanthera philoxeroides had a significant inhibitory effect on CMV.

[0013] Furthermore, *Alternanthera philoxeroides* was subjected to ultrasonic water extraction and alcohol precipitation to obtain an extract. To clarify the effect of the *Alternanthera philoxeroides* extract solution on CMV-inoculated zucchini, the extract and CMV-infected leaves were ground in a specific ratio and then inoculated onto healthy zucchini leaves of uniform growth. The results showed that after inoculation with the *Alternanthera philoxeroides* extract, the zucchini leaves did not show mosaic symptoms, only slight yellowing at the leaf edges; while the CMV control leaves showed chlorosis and more severe mosaic symptoms, with curled leaf edges and more severe symptoms. These experimental results are consistent with the results of the crude juice experiment of *Alternanthera philoxeroides*, indicating that the extract is the component in the crude juice that inhibits CMV. Therefore, *Alternanthera philoxeroides*, *Bidens pilosa*, *Bidens trifoliata*, *Houttuynia cordata*, and mint can serve as new plant sources for the control of cucumber mosaic virus disease, providing more options for CMV prevention and control.

[0014] Therefore, this invention first protects the following new applications of the aforementioned wild plants:

[0015] The use of any one or more of Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, or Mentha haplocalyx in the treatment of cucumber mosaic virus or in the preparation of biological control agents against cucumber mosaic virus.

[0016] The use of any one or more of Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, or Mentha haplocalyx in the control of cucumber mosaic virus disease or in the preparation of biological control agents for the control of cucumber mosaic virus disease.

[0017] Furthermore, the *Alternanthera philoxeroides*, *Bidens trifoliata*, *Houttuynia cordata*, *Houttuynia cordata*, or mint are crude juices obtained by grinding their fresh plants.

[0018] Furthermore, the hollow lotus herb is an extract of hollow lotus herb, which is prepared by water extraction and alcohol precipitation.

[0019] Furthermore, the preparation method of the Hollow Lotus extract is as follows: fresh Hollow Lotus is ground and added to deionized water (solid-to-liquid ratio 1:4-5 g / mL), and ultrasonically extracted intermittently 2-3 times, each time for 15-25 min. The solution is then centrifuged, and 2-4 times the volume of anhydrous ethanol is added to the supernatant. The ethanol is precipitated overnight at 2-6℃. Subsequently, the precipitate is centrifuged and dried to obtain the extract.

[0020] This invention also provides a plant-derived biological control agent for controlling cucumber mosaic virus disease, wherein the biological control agent contains one or more of the following as active ingredients: Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, or Mentha haplocalyx; the plant-derived biological control agent may use one or more of the following as the sole active ingredient or in combination with other known active ingredients to exert its effect.

[0021] Furthermore, the *Alternanthera philoxeroides*, *Bidens trifoliata*, *Houttuynia cordata*, *Houttuynia cordata*, or mint are crude juices obtained by grinding their fresh plants.

[0022] Furthermore, the hollow lotus herb is an extract of hollow lotus herb, which is prepared by water extraction and alcohol precipitation.

[0023] Furthermore, the preparation method of the Hollow Lotus extract is as follows: fresh Hollow Lotus is ground and added to deionized water (solid-to-liquid ratio 1:4-5 g / mL), and ultrasonically extracted intermittently 2-3 times, each time for 15-25 min. The solution is then centrifuged, and 2-4 times the volume of anhydrous ethanol is added to the supernatant. The ethanol is precipitated overnight at 2-6℃. Subsequently, the precipitate is centrifuged and dried to obtain the extract.

[0024] Furthermore, the biocontrol agent also includes excipients acceptable for use in biocontrol agents.

[0025] The present invention also provides the application of any of the above-described plant-derived biocontrol agents in the treatment of cucumber mosaic virus or in the prevention and control of cucumber mosaic virus disease.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention demonstrates that Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, and Mentha haplocalyx all exhibit certain inhibitory effects on cucumber mosaic virus, with Alternanthera philoxeroides showing the most significant inhibitory effect. Therefore, this invention provides new uses for any one or more of Alternanthera philoxeroides, Bidens trifoliata, Rhododendron simsii, Houttuynia cordata, or Mentha haplocalyx in combating or controlling cucumber mosaic virus disease, offering more options for the prevention and control of cucumber mosaic virus disease. Attached Figure Description

[0028] Figure 1 Symptoms of CMV inoculation with Alternanthera philoxeroides treated with it. a: Blank control; b: Alternanthera philoxeroides treatment; c: CMV control.

[0029] Figure 2 Symptoms of zucchini inoculated with CMV after treatment with Bidens trifoliata. a: Blank control; b: Bidens trifoliata treatment; c: CMV control.

[0030] Figure 3 Symptoms of zucchini inoculated with CMV after treatment with *Ichthyophthirius multifiliis* (a red spot treatment group). a: Blank control; b: *Ichthyophthirius multifiliis* treatment group; c: CMV control group.

[0031] Figure 4 Symptoms of CMV inoculation in zucchini after treatment with Houttuynia cordata. a: CMV control; b: Houttuynia cordata treatment; c: Blank control.

[0032] Figure 5Symptoms of zucchini inoculated with CMV after peppermint treatment. a: Blank control; b: Peppermint treatment; c: CMV control.

[0033] Figure 6 ELISA results for CMV resistance in different plants. Note: Different letters indicate significant differences between different treatments (P < 0.05).

[0034] Figure 7 Symptoms of CMV inoculation in zucchini after treatment with Alternanthera philoxeroides extract. a: Blank control; b: Alternanthera philoxeroides extract treatment group; c: CMV control. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0036] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0037] Example 1: Inhibitory effect of crude juices from various wild plants on CMV

[0038] I. Materials and Methods

[0039] 1. Experimental materials

[0040] Zucchini seeds and various wild plants: Alternanthera philoxeroides, Bidens pilosa, Amaranthus praecox, Houttuynia cordata, and mint.

[0041] 2. Experimental Methods

[0042] After grinding the aforementioned wild plants into coarse juice, CMV-infected leaves were ground with the coarse juice at a ratio of 1:8. The resulting juice was then used to inoculate healthy zucchini cotyledons with uniform growth. The experiment was repeated three times, with a control group included. Leaves from the same location were selected 7-12 days after inoculation for symptom observation and statistical analysis.

[0043] 3. ELISA testing application effect

[0044] The virus concentration in different treated plants was calculated using ELISA. The CMV inhibition rate was calculated using the following formula: Inhibition rate (%) = (Control OD) / (Control OD) / Control OD. 492 Value - Processing Group OD 492 Value) / Reference OD 492 Value × 100%.

[0045] Statistical data are expressed as mean ± standard error (SE) of three replicates. Analysis of variance was performed using Duncan's multiple range test, with different letters indicating statistical significance at the 0.05 level.

[0046] II. Experimental Results

[0047] 1. The anti-CMV effect of Hollow Lotus Seed Grass

[0048] The anti-CMV effect of Hollow Lotus Seed Grass Figure 1 As shown, the leaves of the Hollow Lotus treatment group did not show mosaic or wrinkling, and the growth was good. Figure 1 b); CMV control leaves showed chlorosis and more severe mosaic patterns, with curled leaf edges and more severe symptoms. Figure 1 c); The blank control plants showed good growth ( Figure 1 a) This indicates that Alternanthera philoxeroides has a significant inhibitory effect on CMV.

[0049] 2. The anti-CMV effect of Bidens trifoliata

[0050] The anti-CMV effect of Bidens pilosa Figure 2 As shown, the leaves of the Bidens trifoliata treatment showed slightly wrinkled edges, no mosaic symptoms, and slight yellowing of the leaf edges. The leaves were also smaller than the blank control. Figure 2 b); CMV control leaves showed chlorosis and more severe mosaic patterns, with curled leaf edges and more severe symptoms. Figure 2 c); The blank control plants showed good growth ( Figure 2 a) This indicates that Bidens trifoliata has a certain inhibitory effect on CMV, and also has a certain inhibitory effect on the growth of zucchini.

[0051] 3. The effect of Red Spot Anti-CMV

[0052] The effect of Yidianhong against CMV is as follows Figure 3 As shown, the leaves treated with the red spot treatment exhibited less variegation than the control. Figure 3 b); CMV control leaves showed chlorosis and more severe mosaic patterns, with curled leaf edges and more severe symptoms. Figure 3 c); The blank control plants showed good growth ( Figure 3 a) This indicates that *Ipomoea aquatica* has a certain inhibitory effect on CMV.

[0053] 4. The anti-CMV effect of houttuynia cordata

[0054] The anti-CMV effect of houttuynia cordata is as follows Figure 4 As shown, the CMV control leaves turned pale green, the diseased leaves had curled edges, and the leaves were smaller. Figure 4 a) After treatment with houttuynia cordata, symptoms such as mosaic and chlorosis appeared on the leaf surface, but the symptoms were milder than those of the CMV control. Figure 4 b); The blank control plants showed good growth ( Figure 4 c). This indicates that Houttuynia cordata has a certain inhibitory effect on CMV.

[0055] 5. Peppermint's effect against CMV

[0056] Peppermint's anti-CMV effects are as follows Figure 5 As shown, after treatment, peppermint leaves exhibited mosaic and chlorosis symptoms, but the symptoms were not as pronounced as in the CMV control, and the leaves were smaller. Figure 5 b); The CMV control group showed more severe chlorosis and mosaic symptoms. Figure 5 c); The blank control group showed good leaf growth. Figure 5 a) This indicates that peppermint has a certain inhibitory effect on CMV, and at the same time, peppermint has a certain inhibitory effect on the growth of zucchini.

[0057] 6. Results of indirect ELISA method

[0058] Results of indirect ELISA detection method are as follows Figure 6 As shown, the treatment with *Alternanthera philoxeroides* significantly inhibited CMV, with an inhibition rate of 76.20%. *Bidens pilosa*, *Bidens trifoliata*, *Houttuynia cordata*, and peppermint also showed some inhibitory effects on CMV (10.06–53.72%). The ELISA results were consistent with the symptom manifestations of zucchini after the above treatments, indicating that *Alternanthera philoxeroides*, *Bidens pilosa*, *Bidens trifoliata*, *Houttuynia cordata*, and peppermint all had some inhibitory effects on CMV, with *Alternanthera philoxeroides* showing the most significant inhibitory effect.

[0059] Example 2: Preparation of Hollow Lotus Seed Extract

[0060] Weigh 5g of fresh *Nelumbo nucifera* (hollow lotus seed), grind it, add 20mL of deionized water, and extract intermittently twice using an ultrasonic extractor, 20min each time. After the above treatment, centrifuge the solution at 4000r / min for 30min, add 3 volumes of anhydrous ethanol to the supernatant, and precipitate overnight at 4℃. Subsequently, centrifuge at 4000r / min for 15min, dry the precipitate in a 65℃ oven, and dissolve the dried extract in deionized water for later use.

[0061] Example 3: Inhibitory effect of Hollow Lotus Seed Extract on CMV

[0062] To clarify the effect of the Hollow Lotus extract solution on CMV-inoculated zucchini, referring to step 2 of Example 1, the extract and CMV-infected leaves were ground in a certain proportion and then inoculated with healthy zucchini leaves that were growing uniformly.

[0063] The results are as follows Figure 7 As shown, after inoculating zucchini with Alternanthera philoxeroides extract, the zucchini leaves did not show mosaic symptoms, but the leaf edges showed slight yellowing. Figure 7 b); while the CMV control leaves showed chlorosis and more severe mosaic patterns, with curled leaf edges and more severe symptoms. Figure 7 c); The blank control group had good leaf condition. Figure 7a). The results of this experiment are consistent with the results of the above-mentioned experiment on the crude juice of Alternanthera philoxeroides, indicating that the extract of Alternanthera philoxeroides is the component in its crude juice that inhibits CMV.

[0064] The above results indicate that *Alternanthera philoxeroides*, *Bidens pilosa*, *Bidens trifoliata*, *Houttuynia cordata*, and peppermint all have certain inhibitory effects on CMV. *Alternanthera philoxeroides*, compared with *Bidens trifoliata*, *Bidens pilosa*, *Houttuynia cordata*, and peppermint, showed the most significant inhibitory effect on CMV. Furthermore, the extract of *Alternanthera philoxeroides* was the only CMV-inhibiting substance in the crude extract, exhibiting a significant inhibitory effect. Therefore, *Alternanthera philoxeroides*, *Bidens pilosa*, *Bidens trifoliata*, *Houttuynia cordata*, and peppermint can serve as new plant sources for the control of cucumber mosaic virus disease, providing more options for CMV prevention and control.

Claims

1. The application of any one or more of Alternanthera philoxeroides, Bidens trifoliata, or Dieffenbachia in the treatment of cucumber mosaic virus or in the preparation of a biocontrol agent against cucumber mosaic virus, characterized in that, The hollow lotus grass, three-leaf beggar-ticks, or red clover are crude juices obtained by grinding their fresh plants.

2. The application of any one or more of Alternanthera philoxeroides, Bidens trifoliata, or Dieffenbachia in the prevention and control of cucumber mosaic virus disease caused by cucumber mosaic virus, or in the preparation of biological control agents for the prevention and control of cucumber mosaic virus disease caused by cucumber mosaic virus, characterized in that, The hollow lotus grass, three-leaf beggar-ticks, or red clover are crude juices obtained by grinding their fresh plants.

3. The application of Alternanthera philoxeroides in the control of cucumber mosaic virus or in the preparation of biocontrol agents against cucumber mosaic virus, characterized in that, The hollow lotus herb is its water-extracted and alcohol-precipitated extract.

4. The application of *Alternanthera philoxeroides* in the control of cucumber mosaic virus disease caused by cucumber mosaic virus, or in the preparation of biological control agents for the control of cucumber mosaic virus disease caused by cucumber mosaic virus, characterized in that... The hollow lotus herb is its water-extracted and alcohol-precipitated extract.

5. The application of a plant-derived biocontrol agent in the control of cucumber mosaic virus or in the prevention and treatment of cucumber mosaic virus disease caused by cucumber mosaic virus, characterized in that, The plant-derived biological control agent contains one or more of Alternanthera philoxeroides, Bidens trifoliata, or Rhododendron molle as active ingredients; Alternanthera philoxeroides, Bidens trifoliata, or Rhododendron molle are crude juices obtained by grinding fresh plants.

6. The application of a plant-derived biocontrol agent in the control of cucumber mosaic virus or in the prevention and treatment of cucumber mosaic virus disease caused by cucumber mosaic virus, characterized in that, The plant-derived biocontrol agent contains Alternanthera philoxeroides as an active ingredient, which is its water-extracted and alcohol-precipitated extract.

7. The application according to claim 5 or 6, characterized in that, The plant-derived biocontrol agent also includes excipients acceptable for biocontrol agents.

8. The application according to claim 6, characterized in that, The preparation method of the aqueous extract and ethanol precipitation extract of Hollow Lotus is as follows: fresh Hollow Lotus is ground and added to deionized water at a material-to-liquid ratio of 1:4-5 g / mL. The extract is extracted intermittently by ultrasound 2-3 times, each time for 15-25 min. The solution is then centrifuged, and 2-4 times the volume of anhydrous ethanol is added to the supernatant. The ethanol is precipitated at 2-6 °C, centrifuged, and the precipitate is dried to obtain the final product.

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