Application of thymol in preventing and treating peronophythora litchii

Abstract

The invention provides a natural phenolic compound thymol for inhibiting peronophythora litchii, and further provides an application of the thymol in preventing and treating the peronophythora litchii. The natural phenolic compound thymol can be used for preventing and treating the peronophythora litchii. In-vitro bacteriostasis experiments and prevention and control experiments prove that thymol has remarkable inhibitory activity on peronophythora litchii and can effectively reduce the incidence rate of peronophythora litchii. The thymol is used as an active component for preparing the biopesticide or the plant source bacteriostatic agent for preventing and treating the litchi peronophythora blight for the first time, and the thymol has the characteristics of high efficiency, low toxicity and environment friendliness, can replace a traditional chemical bactericide and can reduce pesticide residues and pathogenic bacterium drug resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of modern agriculture, and particularly relates to application of thymol in preventing and controlling litchi downy mildew. Background Art

[0002] Lychees are renowned both domestically and internationally for their vibrant color, rich fragrance, and sweet flavor. Their fresh fruit and processed products have become a key pillar of the southern Chinese economy. However, litchi downy blight, the most significant disease in lychee production, infects both pre- and post-harvest lychees, causing rot and resulting in significant losses to the industry.

[0003] Litchi downy mildew is caused by the obligate parasitic oomycete - litchi downy mildew ( Peronophythora litchii ) is a systemic disease caused by litchi downy mildew. Litchi downy mildew can infect branches, ears and fruits in a latent state before harvest, or it can infect fruits after harvest through mechanical trauma and gradually grow as the fruits are stored. Litchi downy mildew can spread widely by continuously inoculating healthy litchi fruits, seriously threatening the litchi post-harvest industry. Litchi downy mildew ( P . litchii ) belongs to Chromista, Oomycota, Oomycetes, Peronosporales, Peronophythoraceae, and Genus Peronophythoraceae. Peronophythora ). This pathogenic oomycete is very different from fungi such as anthrax and Fusarium: its life history includes two stages: asexual and sexual. Its asexual reproduction produces sporangium stalks and sporangia. The sporangium stalks are significantly differentiated, with different lengths and a morphology similar to branches, showing a multi-level limited growth pattern; sexual reproduction forms oospores. Litchi downy mildew mainly overwinters in the form of oospores or mycelium on infected leaves and fruits, becoming the initial source of infection for the disease the following year. The fungus can produce sporangia, which are spread by wind and rain. After encountering water, they can directly germinate to form germ tubes, or release zoospores first and then develop germ tubes, and then infect leaves and fruits, causing disease. The infected leaves and fruits will produce sporangia again, triggering subsequent infection, thus completing its infection cycle. The systemic harm of this pathogen stems from its unique oomycete biological characteristics: it belongs to the phylum Oomycota taxonomically, and there is an evolutionary gap with the fungi kingdom. Its cell wall is composed of β-glucan and cellulose as the core skeleton (fungi rely on chitin), and the diploid chromosome set encodes unique infection effector factors; during development, it relies on biflagellate zoospores for waterborne transmission (fungi are airborne through aflagellate conidia), and sterol metabolism synthesizes stigmasterol (fungi synthesize ergosterol). Such multi-dimensional differences have led to the general ineffectiveness of control agents against fungal pathogens against litchi downy mildew.

[0004] Current chemical pest control methods pose risks of pesticide residues and resistance, necessitating the development of natural solutions. Thymol (2-isopropyl-5-methylphenol), also known as thymol, thymol, and thymol, is a naturally occurring monoterpene phenol found primarily in the essential oils of thyme, oregano, and orange peel. Thymol has been listed as a food additive by the U.S. Food and Drug Administration (FDA) as a Generally Recognized as Safe (GRAS) substance. Although the prior art shows that thymol has good broad-spectrum antifungal activity against a variety of plant pathogenic fungi such as Rhizopus creeping, Penicillium italicum, Colletotrichum gloeosporioides, Geotrichum candidum, Rhizoctonia solani, Rhizoctonia solani, Fusarium oxysporum, etc., Peronophythora litchii ) belongs to the pathogenic oomycetes, not fungi, and has significant particularity in its pathogenic characteristics, which makes its prevention and control face unique challenges, and also makes the effectiveness of thymol not obvious or simple to extrapolate. Thymol inhibits pathogens by destroying cell membranes, inducing lipid peroxidation and interfering with ergosterol synthesis, but the unique membrane lipid composition of litchi downy mildew (such as a high proportion of oleic acid and linoleic acid) makes it more sensitive to membrane damage effects. During the infection process, the fungus induces the host to produce a large amount of reactive oxygen species (ROS), and thymol can simultaneously inhibit the growth of pathogens and reduce host oxidative damage by scavenging reactive oxygen species and inhibiting membrane lipid peroxidation. This dual action mechanism has not yet been confirmed in other plant-pathogen interaction systems. The above means that thymol may have the potential to be developed as a new plant pesticide for the prevention and control of litchi downy mildew. Summary of the Invention

[0005] The first aspect of the present invention aims to provide a use of thymol in preparing a product for inhibiting the activity of Peronophytum litchii.

[0006] The second aspect of the present invention aims to provide the use of thymol in preparing products for preventing and treating litchi downy mildew.

[0007] The third aspect of the present invention aims to provide a method for preventing and controlling litchi downy mildew.

[0008] In order to achieve the above-mentioned purpose of the present invention, the technical solution adopted by the present invention is: The first aspect of the present invention provides the use of thymol in preparing a product for inhibiting the activity of litchi peronophyte, wherein the chemical formula of the thymol is C 10 H 14 O, the structural formula is shown in formula (I): Formula (I).

[0009] In some embodiments of the present invention, the activity of inhibiting litchi downy mildew comprises any one or more of the following: (1) Inhibit the mycelial growth of litchi downy mildew; (2) Inhibit the production of sporangia of litchi downy mildew; (3) Inhibit the release of zoospores of Lychee Downy Phytophthora; (4) Inhibit the production of oospores of litchi downy mildew; (5) Destroy the cell membrane structure of litchi downy mildew; (6) Induce the production and release of active oxygen by litchi downy mildew.

[0010] The second aspect of the present invention provides the use of thymol in preparing a product for preventing and controlling litchi downy mildew.

[0011] In some embodiments of the present invention, the litchi downy mildew disease is caused by infection with the fungus Peronophytum litchi, primarily affecting nearly mature and mature fruit, and sometimes also affecting young fruit, inflorescences, and leaves. White mold grows on the surfaces of affected leaves, flowers, and fruit, and the inflorescences and fruit turn brown and rot.

[0012] Regarding the first and second aspects of the present invention: In some embodiments of the present invention, the prevention and treatment include prophylaxis and treatment.

[0013] In some embodiments of the present invention, the thymol comprises thymol or a pharmaceutically acceptable salt form thereof.

[0014] In some embodiments of the present invention, the pharmaceutically acceptable salts include acid addition salts and base addition salts.

[0015] In some embodiments of the present invention, "pharmaceutically acceptable acid addition salts" refers to salts that retain the biological effectiveness and properties of the free bases, are not biologically or otherwise undesirable, and are formed with inorganic acids such as, but not limited to, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and the like, and organic acids such as, but not limited to, acetic acid, adipic acid, alginic acid, ascorbic acid, aspartic acid, benzenesulfonic acid, benzoic acid, camphoric acid, camphor-10sulfonic acid, capric acid, hexanoic acid, caprylic acid, carbonic acid, cinnamic acid, citric acid, cyclamic acid, dodecylsulfuric acid, ethane-1,2-disulfonic acid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, fumaric acid, galactaric acid, gentisic acid, gluconic acid, glucuronic acid, glutamic acid, glutaric acid, 2-hydroxy-1,2-disulfonic acid, ethanesulfonic ... Oxoglutaric acid, glycerophosphate, glycolic acid, hippuric acid, isobutyric acid, lactic acid, lactobionic acid, lauric acid, maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonic acid, etc.

[0016] In some embodiments of the present invention, "pharmaceutically acceptable base addition salts" refer to salts that retain the biological effectiveness and properties of the free acid and are not biologically or otherwise undesirable. These salts are prepared by the addition of inorganic or organic bases to the free acid. Salts derived from inorganic bases include, but are not limited to, sodium salts, potassium salts, lithium salts, ammonium salts, calcium salts, magnesium salts, iron salts, zinc salts, copper salts, manganese salts, aluminum salts, and the like. Preferred inorganic salts are ammonium salts, sodium salts, potassium salts, calcium salts, and magnesium salts. Salts derived from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines, substituted amines (including naturally occurring substituted amines), cyclic amines, and basic ion exchange resins, such as ammonia, isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, diethanolamine, ethanolamine, dicyclohexylamine, lysine, arginine, histidine, caffeine, ethylenediamine, glucamine, methylglucamine, theobromine, triethanolamine, tromethamine, purines, piperazine, piperidine, N-ethylpiperidine, polyamine resins, and the like. Particularly preferred organic bases are isopropylamine, diethylamine, ethanolamine, trimethylamine, dicyclohexylamine, choline, and caffeine.

[0017] In some embodiments of the invention, the product comprises a pesticide.

[0018] In some embodiments of the present invention, the pesticide includes a pharmaceutically acceptable excipient.

[0019] In some embodiments of the present invention, the pharmaceutically acceptable excipients include at least one of solvents, propellants, solubilizers, cosolvents, emulsifiers, colorants, adhesives, disintegrants, fillers, lubricants, wetting agents, osmotic pressure regulators, stabilizers, glidants, preservatives, suspending agents, fragrances, anti-adhesives, penetration enhancers, pH regulators, buffers, plasticizers, surfactants, foaming agents, defoaming agents, thickeners, inclusion agents, humectants, absorbents, diluents, flocculants and deflocculating agents, and filter aids.

[0020] In some embodiments of the present invention, the pharmaceutically acceptable excipients are generally recognized for this purpose and are used as inactive ingredients in pharmaceutical preparations. A compilation of pharmaceutically acceptable excipients can be found in reference books such as the Handbook of Pharmaceutical Excipients (2nd edition, edited by A. Wade and P.J. Weller; published by the American Pharmaceutical Association, Washington and The Pharmaceutical Gess, London, 1994); and the Pharmacopoeia of the People's Republic of China - List of Pharmaceutical Excipients.

[0021] In some embodiments of the present invention, the dosage form of the pesticide includes one of a solid preparation, a liquid preparation, and a volatile preparation.

[0022] In some embodiments of the present invention, the dosage form of the pesticide can be found in national standards such as "Pesticide Formulation Names and Codes GB / T19378-2017".

[0023] In some embodiments of the present invention, the thymol is used at a concentration of 1 to 500 μg / mL.

[0024] In some embodiments of the present invention, when used to inhibit the mycelial growth of Peronophytum litchii, the thymol is used at a concentration of 50-150 μg / mL.

[0025] In some embodiments of the present invention, when used to inhibit the production of sporangia of Peronophytum litchii, the concentration of thymol is 40-70 μg / mL.

[0026] In some embodiments of the present invention, when used to inhibit the release of zoospores of Peronophytum litchii, the concentration of thymol is 40-160 μg / mL.

[0027] In some embodiments of the present invention, when used to inhibit the production of oospores of Peronophytum litchii, the concentration of thymol is 2-15 μg / mL.

[0028] In some embodiments of the present invention, when used to destroy the cell membrane structure of Peronophytum litchii, the concentration of thymol is 40-150 μg / mL.

[0029] In some embodiments of the present invention, when used to induce the production and release of active oxygen by Peronophythora litchii, the concentration of thymol is 40-100 μg / mL.

[0030] A third aspect of the present invention provides a method for preventing and controlling litchi downy mildew, comprising the following steps: Treat lychees with thymol.

[0031] In some embodiments of the present invention, the prevention and treatment include prophylaxis and treatment.

[0032] In some embodiments of the present invention, the prevention and control includes prevention and control during the growth and after harvest of litchi.

[0033] In some embodiments of the present invention, the thymol is in the form of an aqueous solution and is used to soak the fruit for 1 to 10 minutes.

[0034] In some embodiments of the present invention, when used for prevention, the concentration of thymol in the aqueous solution is 100-500 mg / kg (100-500 mg / L).

[0035] In some embodiments of the present invention, when used for treatment, the concentration of thymol in aqueous solution is 200-500 mg / kg (200-500 mg / L).

[0036] The beneficial effects of the present invention are: The present invention provides a natural phenolic compound thymol in inhibiting litchi peronophytum ( Peronophythora litchii ) also provides the use of thymol in controlling litchi downy mildew. In vitro antibacterial and control experiments confirmed that thymol has significant inhibitory activity against litchi downy mildew and can effectively reduce the incidence of litchi downy mildew. This invention proposes for the first time the use of thymol as an active ingredient in the preparation of a biopesticide or botanical antibacterial agent for controlling litchi downy mildew. This biopesticide exhibits high efficacy, low toxicity, and environmental friendliness, and can replace traditional chemical fungicides, reducing pesticide residues and pathogen resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which: Figure 1 The inhibitory effects of different concentrations of thymol on the mycelial growth of litchi downy mildew, where A is the phenotypic result and B is the statistical result.

[0038] Figure 2 The inhibitory effect of different concentrations of thymol on the sporangium production of litchi downy mildew, where A is the phenotypic result and B is the statistical result.

[0039] Figure 3 The inhibitory effect of different concentrations of thymol on the zoospore release of litchi downy mildew, where A is the phenotypic result and B is the statistical result.

[0040] Figure 4 The results show the inhibitory effect of different concentrations of thymol on the oospore production of litchi downy mildew.

[0041] Figure 5 The changes in electrical conductivity of Phytophthora mycelium after thymol treatment.

[0042] Figure 6 SYTOX Green staining test of Downy Phytophthora hyphae after thymol treatment.

[0043] Figure 7 The effect of thymol treatment on the production of reactive oxygen species in Phytophthora parasitica hyphae.

[0044] Figure 8 The control effect of thymol on downy mildew of postharvest litchi fruit. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0046] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0047] Test pathogen: The litchi downy mildew fungus used in the present invention is the wild-type reference strain SHS3, which is the preserved strain in this experiment.

[0048] Main reagents: Thymol was purchased from Hainan Qingfeng Biotechnology Co., Ltd. with a purity of >98%. The pure compound thymol was dissolved in anhydrous ethanol to prepare 5×10 4 μg / mL stock solution for future use. 10% V8 medium is used to culture Peronophytum litchii. Note: 10% V8 medium consists of 100 mL V8 vegetable juice, 900 mL HO, and 20 g agar, with a pH of 7.2.

[0049] Example 1 Activity test of thymol on the growth of Peronophytum litchii mycelium Specific procedures: The inhibitory effect of different concentrations of thymol on the mycelial growth of the pathogen was determined using the mycelial growth rate method. After culturing P. litchiensis on V8 medium for 5 days, the bacterial cakes were punched with a 5 mm diameter cork hole and inoculated onto V8 plates containing thymol at final concentrations of 30, 40, 60, 90, and 130 μg / mL. An ethanol solvent control group was included in each experiment, and three parallel treatments were set up. After 5 days of incubation, the colony diameters of the thymol-treated colonies were measured using the cross-hatch method, and the inhibition rate was calculated. Each experiment was repeated three times. The virulence regression equation and the median inhibitory concentration (EC50) were then calculated using SPSS software.

[0050] See the results Figure 1Mycelial growth of P. litchii continued throughout the incubation period, but thymol effectively inhibited mycelial growth. After 5-day treatment with thymol at concentrations of 30, 40, 60, 90, and 130 μg / mL, the diameter of the Phytophthora colonies decreased by 10.2%, 21.26%, 55.51%, 92.79%, and 97.76%, respectively. The half-maximal effect concentration (EC50) of thymol on mycelial growth of P. litchii was 54.10 μg / mL.

[0051] Example 2 Activity test of thymol in inhibiting the production of sporangia of Peronophythora litchii Procedure: A 5 mm diameter cake of Peronophytum litchii was inoculated onto V8 medium plates containing thymol at final concentrations of 0, 40, 50, 60, and 70 μg / mL. A solvent control and a blank control were also set up, with three replicates. After 5 days of incubation, 5 mL of deionized water was added to the colony and filtered to obtain a total sporangium suspension. 10 μL of this suspension was then placed on a hemocytometer, which was then observed under a microscope and the number of sporangia was counted using a hemocytometer. Each sample was counted six times, with three replicates and three replicates per experiment. The toxicity regression equation and the median inhibitory concentration (EC50) were then calculated using SPSS software.

[0052] See the results Figure 2 The number of sporangia in the blank control group was 63.70×10 5 / mL, while the sporangium yields after treatment with 30, 40, 50, 60 and 70 μg / mL thymol were 47.78, 32.78, 21.85, 13.15, 6.11×10 5 / mL, indicating that thymol inhibited the production of sporangia of Peronophytum litchii. The half-maximal effect concentration (EC50) value of thymol on the production of sporangia of Peronophytum litchii was 40.77 μg / mL.

[0053] Example 3 Activity test of thymol in inhibiting zoospore release of Peronophythora litchii Specific procedures: After each test strain was cultured on V8 solid medium for 5 days, 3 mL of sterile water was added to the colony and gently pipetted. The sporangium suspension was aspirated into a 2 mL centrifuge tube and thymol was added to achieve final thymol concentrations of 30, 40, 60, 80, and 160 μg / mL. After cold treatment at 12°C for 0.5 h, the tubes were allowed to stand at room temperature for 10 min. Zoospores of each strain were observed and counted under a microscope, and the inhibition rate was calculated. The toxicity regression equation and the median inhibitory concentration (EC50) were then calculated using SPSS software.

[0054] See the results Figure 3Thymol showed a significantly higher inhibitory effect on zoospore release from P. litchie than the control group, with inhibition rates reaching 38.05%, 65.3%, 75.84%, 89.20%, and 96.79% at thymol concentrations of 30, 40, 60, 80, and 160 μg / mL, respectively. The half-maximal effect concentration (EC50) of thymol on zoospore release from P. litchie was 43.68 μg / mL.

[0055] Example 4 Activity test of thymol in inhibiting oospore production of Peronophytum litchii Specific procedures: A 5 mm diameter cake of Peronophytum litchii was inoculated onto V8 medium plates containing thymol at final concentrations of 2.5, 5, 7.5, 10, and 15 μg / mL. After incubation at 25°C in the dark for 10 days, hyphae and sporangia were scraped from the surface of the medium. A 5 mm diameter mycelial block was removed from the original inoculated mycelial block using a micropipette and pressed onto a disc. The number of oospores from each strain was counted. Three mycelial blocks were collected per plate, and 10 fields containing oospores were microscopically examined in each block. Each experiment was repeated three times, and the inhibition rate was calculated. The virulence regression equation and the median inhibitory concentration (EC50) were then calculated using SPSS software.

[0056] See the results Figure 4 Thymol showed strong inhibitory activity against the production of oospores of Phytophthora litchii. In contrast, the sensitivity of oospore production was significantly enhanced (EC 50 = 2.76 μg / mL).

[0057] Example 5 Effect of thymol on cell membrane permeability of Peronophytum litchii Membrane permeability of Peronophythora litchii was measured using the conductivity method. Mycelial plugs were incubated in V8 liquid medium on a rotary shaker (25°C, 120 rpm) for 48 h. The mycelia were then washed three times with sterile distilled water, drained using a Büchner funnel, and exposed to thymol solutions at varying concentrations (0, 30, 40, 60, 90, and 130 μg / mL). Sterile distilled water served as a control. Conductivity was measured using a conductivity meter at 0, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160, and 180 min. Finally, the mycelia were boiled for 20 min, and the final conductivity was measured to calculate relative conductivity. Each experiment was repeated three times.

[0058] See the results Figure 5 The relative conductivity of Phytophthora mycelia increased with increasing thymol treatment time, then plateaued in the later stages. The relative conductivity values increased with increasing thymol concentration, indicating that thymol disrupted the cell membranes of Phytophthora mycelia.

[0059] Example 6 Effect of thymol on the cell membrane integrity of Peronophytum litchii Specific operation: SYTOX Green staining was used to evaluate the membrane integrity of P. litchii. Sporangia suspension of P. litchii was collected from V8 (1×10 5 Sporangia / mL) were treated with 50 and 80 μg / mL thymol at 25°C for 6 h, and a blank control was set up. The sporangium suspension was then stained with 0.2 μM SYTOX Green at 25°C in the dark for 30 min, washed three times with phosphate-buffered saline (PBS), and observed under a fluorescence microscope.

[0060] See the results Figure 6 In the control, no fluorescence was observed in sporangia, whereas stronger fluorescence was observed in sporangia treated with 80 μg / mL thymol. This demonstrates disruption of membrane integrity. Furthermore, when sporangia were treated with a lower concentration of 50 μg / mL, weaker fluorescence was observed compared to those treated with 80 μg / mL. Therefore, these data also indicate that thymol-induced changes in the plasma membrane are concentration-dependent.

[0061] Example 7 - Effect of thymol on active oxygen production by Peronophythora litchii Specific procedures: The accumulation of intracellular reactive oxygen species (ROS) was evaluated by observing spores stained with 2′,7′-dichlorofluorescein diacetate (DCFH-DA). DCFH-DA was used as a ROS fluorescent probe because it emits green fluorescence in the presence of ROS. A sporangium suspension of Peronophythora litchii was adjusted to 1 × 10 4 Sporangium mL -1 , and treated with 50 μg / mL, 80 μg / mL, or sterile water (control) for 6 h. Then, all sporangia were collected, washed with phosphate-buffered saline (PBS), and then incubated in a 10 μmol L -1 DCFH-DA was incubated in PBS at 25°C for 20 min and observed under a fluorescence microscope.

[0062] See the results Figure 7 Quantitative determination showed that the fluorescence intensity of thymol-treated sporangia was 1.32 and 1.95 times that of the control, respectively. Thymol treatment induced the accumulation and release of intracellular ROS in a dose-dependent manner.

[0063] Example 8 Experiment on the efficacy of thymol in preventing downy mildew of postharvest litchi fruits Test Materials: Litchi cultivar "Fei Zi Xiao" was purchased from the market. Healthy lychees of uniform size, shape, and maturity were selected and sterilized in 75% alcohol for 30 seconds and then rinsed three times with sterile water.

[0064] Procedure: To determine its protective activity, litchi fruits were immersed in thymol solutions (100, 200, and 400 mg kg-1) for 5 min, air-dried, and incubated at 25°C in the dark. After 24 h, they were inoculated with mycelial plugs. The fruits were then incubated at 25°C under humid conditions for 72 h. To determine its therapeutic activity, the fruits were inoculated and incubated at 25°C for 24 h, then immersed in thymol solutions (100, 200, and 400 mg kg-1). -1 ) for 5 minutes, air-dried, and incubated for a further 48 hours. The inhibition rate was calculated according to the formula, and significance was analyzed using a t-test. Each experiment was repeated three times. Inhibition rate (%) = (lesion size of control fruit - lesion size of treated fruit) / lesion size of control fruit × 100.

[0065] See the results Figure 8 The experimental results showed that thymol showed excellent control effect on litchi downy mildew, and the protective effect of thymol was better than the therapeutic effect. 72 hours after infection, 100, 200 and 400 mg·kg -1 The protective efficacy of thymol at 100, 200 and 400 mg·kg -1 The therapeutic efficacy was 2.67%, 41.67% and 83.33% respectively.

[0066] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. Application of thymol in preparing products for inhibiting the activity of litchi downy mildew.

2. The use according to claim 1, characterized in that: The activity of inhibiting litchi downy mildew includes any one or more of the following: (1) Inhibit the mycelial growth of litchi downy mildew; (2) Inhibit the production of sporangia of litchi downy mildew; (3) Inhibit the release of zoospores of Lychee Downy Phytophthora; (4) Inhibit the production of oospores of litchi downy mildew; (5) Destroy the cell membrane structure of litchi downy mildew; (6) Induce the production and release of active oxygen by litchi downy mildew.

3. Application of thymol in the preparation of products for preventing and controlling litchi downy mildew.

4. The use according to claim 1 or 3, characterized in that: The thymol includes thymol or a pharmaceutically acceptable salt thereof.

5. The use according to claim 1 or 3, characterized in that: The products include pesticides.

6. The use according to claim 5, characterized in that: The pesticide includes pharmaceutically acceptable excipients.

7. The use according to claim 6, characterized in that: The pharmaceutically acceptable excipients include at least one of solvents, propellants, solubilizers, cosolvents, emulsifiers, colorants, adhesives, disintegrants, fillers, lubricants, wetting agents, osmotic pressure regulators, stabilizers, glidants, preservatives, suspending agents, fragrances, anti-adhesive agents, penetration enhancers, pH regulators, buffers, plasticizers, surfactants, foaming agents, defoaming agents, thickeners, inclusion agents, humectants, absorbents, diluents, flocculants and deflocculating agents, and filter aids.

8. The use according to claim 5, characterized in that: The dosage form of the pesticide includes one of a solid preparation, a liquid preparation and a volatile preparation.

9. The use according to claim 1 or 3, characterized in that: The thymol is used at a concentration of 1-500 μg / mL.

10. A method for preventing and controlling litchi downy mildew, comprising the following steps: Treat lychees with thymol.

Images