Method for monitoring richness and morbidity of litchi pock spot disease infection source

Abstract

The invention relates to a method for monitoring the richness and morbidity of litchi pocking spot disease infection sources, and provides a simple and accurate litchi pocking spot disease prediction method for monitoring and early warning of litchi pocking spot disease latent infection sources in litchi producing areas of different areas. According to the method, the separation frequency of pathogenic bacteria of the asymptomatic fruit pocking spot disease and the severity of the field pocking spot disease are collected and detected regularly (one week) in the fruiting period, and the method can accurately monitor the richness of latent infection sources of the pocking spot disease. On the basis, the occurrence condition of the litchi pocking spot disease in the region in the current year can be predicted by combining weather forecast (rainfall days) of the local litchi fruit bearing period.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of comprehensive prevention and control of crop epidemic diseases, in particular to a method for monitoring the richness of infection sources and the occurrence of litchi pitting disease. BACKGROUND

[0002] Litchi pitting disease, also known as "duck head green", "black spot disease" or "green chicken head", is a symptom type of anthracnose disease and is a common disease in litchi planting, especially in Guiwei litchi. The main pathogen is Colletotrichum siamense, which belongs to the genus of Colletotrichum fungi. Colletotrichum siamense

[0003] The main symptoms are brown to black sesame dot-shaped small spots occurring on the surface of the leaf blade and the surface of the pericarp from the fruit stalk to the fruit shoulder. The disease is an important disease in litchi production in China and occurs in all litchi production areas in China, seriously affecting the appearance quality of fruits and continuing to harm during the postharvest storage and transportation period, causing significant economic losses.

[0004] Litchi pitting disease has typical latent infection characteristics, which is one of the important reasons for its difficulty in prevention and control. From late March to mid-July, it is the flowering and fruiting period of litchi, and the average daily temperature in the main litchi producing areas in China is between 14-32℃, which is the suitable temperature for the production of conidia of litchi anthracnose fungus (12-36℃, optimum 28-32℃), conidia germination (8-38℃, optimum 28-32℃) and mycelial growth (8-38℃, optimum 28℃) (Liu A, Chen W, Li X. Study on the biological characteristics of Colletotrichum gloeosporioides from litchi [J]. Plant Disease Report, 2003, 33(4): 313-316.). Once it rains, the humidity also reaches the humidity for conidia germination, and after germination, it can invade the pericarp and rapidly expand in the pericarp tissue. After the pathogen invades the pericarp tissue, it colonizes in the pericarp tissue but does not show any symptoms. When it encounters rainy or high-humidity weather and sufficient re-infection sources, the pathogen continues to invade and expand and shows symptoms, leading to the prevalence and disaster of litchi pitting disease. Therefore, climate and the richness of infection sources are important factors affecting the occurrence of litchi pitting disease.

[0005] Monitoring and early warning is an important content of guiding the prevention and control of crop epidemic diseases. By publishing prediction and forecast information in advance, judging the occurrence trend of the disease, and identifying key prevention and control areas, scientific prevention and control can be guided in a timely manner. At present, there is no report on the monitoring and early warning or prediction and forecast of litchi pitting disease. In actual production, people only know that litchi pitting disease will occur and be serious when it rains a lot, but there is no clear index for what degree of rain is considered a lot.

[0006] ​For litchi pockmark disease, the existing monitoring means still lacks efficient, non-destructive and scalable identification technology for latent infection. Although PCR detection technology has high sensitivity, it is costly and cannot distinguish non-viable pathogens. Currently, there is no monitoring and early warning research using this method for the disease; rapid detection technologies such as near-infrared spectroscopy and electronic nose are still in the model verification stage and have not been applied in orchard scenarios. The high concealment of latent infection and the sudden disaster coexist, which is the core bottleneck of litchi pockmark disease in Guangdong and Guangxi production areas. Latent infection has become a blind area for the prevention and control of litchi pockmark disease, and fruit farmers can only passively apply pesticides after the symptoms appear, missing the best prevention and control window. SUMMARY

[0007] The purpose of the present application is to overcome the shortcomings of the prior art and provide a method for monitoring the richness of litchi pockmark disease infection sources and the occurrence of the disease.

[0008] The first object of the present application is to provide a method for monitoring the richness of litchi pockmark disease infection sources.

[0009] The second object of the present application is to provide a method for predicting the occurrence and / or disease index of litchi pockmark disease.

[0010] The third object of the present application is to provide a method for preventing and controlling litchi pockmark disease.

[0011] In order to achieve the above-mentioned objects, the present application is realized by the following technical solutions: The present method establishes a standardized investigation and discrimination method by monitoring uniform elements. By regularly collecting and detecting the frequency of litchi pockmark disease pathogen isolation from symptomless fruits and the severity of litchi pockmark disease in the field during the fruiting period, the number of litchi pockmark disease pathogens in the latent infection state under natural environmental conditions is monitored to determine the richness of latent infection sources. If almost no litchi pockmark disease pathogens can be isolated under natural conditions in the orchard, it can be inferred that few fruits have been infected in the field, indicating that the previous climatic and environmental conditions were not suitable for litchi pockmark disease infection, and the pathogen spread was slow and not easy to show symptoms, so only preventive measures can be taken. On the contrary, if the frequency of litchi pockmark disease pathogen isolation from healthy fruits is high, it indicates that the previous climatic and environmental conditions were suitable for litchi pockmark disease infection, and the suitable conditions will lead to further expansion of the pathogen and show symptoms, so prevention and control need to be strengthened. Through years of experimental investigation at multiple sites, the relationship between the frequency of litchi pockmark disease pathogen isolation from symptomless fruits and the severity of litchi pockmark disease occurrence is established, and a unified standard monitoring, investigation and discrimination method is established.

[0012] The present application provides a method for monitoring the richness of litchi pockmark disease infection sources. During the fruiting period of litchi, the litchi fruit pockmark disease index in the orchard is investigated on the investigation day, and symptomless fruits are collected on the investigation day. The frequency of litchi pockmark disease pathogen isolation from symptomless fruit peel tissue is obtained using symptomless fruits; The isolation frequency of the pathogen of the fruit skin tissue of the symptomless fruit of the litchi fruit spot disease is 0, the disease index of the litchi fruit spot disease in the orchard is 0, and the latent infection source is none; The isolation frequency of the pathogen of the fruit skin tissue of the symptomless fruit of the litchi fruit spot disease is greater than 0 and less than 35.00%, the disease index of the litchi fruit spot disease in the orchard is greater than 0 and less than 5.00, and the latent infection source is scarce; The isolation frequency of the pathogen of the fruit skin tissue of the symptomless fruit of the litchi fruit spot disease is greater than or equal to 35.00%, the disease index of the litchi fruit spot disease in the orchard is greater than 0 and less than 5.00, the latent infection source is rich, and the source of the pathogen is sufficient; The isolation frequency of the pathogen of the fruit skin tissue of the symptomless fruit of the litchi fruit spot disease is greater than or equal to 35.00%, the disease index of the litchi fruit spot disease in the orchard is greater than or equal to 5.00, the latent infection source is extremely rich, and the source of the pathogen is extremely sufficient.

[0013] The present application determines the richness of the latent infection source of the litchi fruit spot disease in the evaluated litchi orchard based on the isolation frequency of the pathogen of the litchi fruit spot disease and the disease index, and further gives the monitoring and early warning / prediction and prevention and control suggestions of the occurrence of the litchi fruit spot disease in combination with the weather forecast (rainy days).

[0014] Preferably, the investigation day is 3-4 days before spraying.

[0015] The symptomless fruit refers to the fruit that does not show the symptom of the litchi fruit spot disease, which may be the fruit that is not infected with the pathogen of the litchi fruit spot disease or the fruit that is infected with the pathogen of the litchi fruit spot disease and is in the latent infection period.

[0016] Preferably, a part of the litchi trees in the litchi orchard is extracted as a sample for analysis and evaluation by using a random sampling method, the disease index of the litchi fruit spot disease in the orchard is investigated, and the occurrence of the litchi fruit spot disease on the fruit of the tree is evaluated according to the Guidelines for Field Efficacy Trials (2) Part 100: Fungicide for Controlling Litchi Downy Mildew.

[0017] Preferably, no less than 150 fruits per tree are investigated.

[0018] Preferably, no less than 30 symptomless fruits are collected.

[0019] Preferably, sampling is performed at five points of east, south, west, north and center of each tree, no less than 30 fruits per point are investigated, the total number of fruits and the number of fruits at each level are recorded, and the disease index is calculated.

[0020] The fruit classification standard of the litchi fruit spot disease is as follows: 0 level: no disease; 1 level: the diseased area accounts for less than 10% of the fruit surface area; 3 level: the diseased area accounts for 11%-25% of the fruit surface area; 5 level: the diseased area accounts for 26%-50% of the fruit surface area; Grade 7: the lesion occupies more than 50% of the fruit surface, Disease index formula: Disease index = × 100.

[0021] Preferably, the method for obtaining the frequency of the fruit skin tissue of symptomless fruit of the fruit spot pathogen is: Take the fruit skin crack piece tissue away from the ground side, alcohol and sodium hypochlorite surface disinfection, sterile water washing, and place the disinfected and washed tissue block on a potato dextrose agar (PDA) plate; After 3-4 days of constant temperature culture, observe the colonies of the isolated strains, record the number of fruit skin tissue blocks with fruit spot pathogen colony growth, and calculate the isolation frequency of the fruit spot pathogen: isolation frequency = number of fruit skin tissue blocks with fruit spot pathogen growth / total number of tissue blocks × 100%.

[0022] Preferably, the number of fruit skin crack pieces taken from the side away from the ground is not less than 35.

[0023] That is, at least one crack piece is taken from each fruit.

[0024] Preferably, 70% alcohol surface disinfection for 30-60 seconds, 2% sodium hypochlorite surface disinfection for 1.5-2 minutes, and sterile water washing for 3 times.

[0025] The present application also claims a method for predicting the occurrence of litchi fruit spot disease and / or disease index, according to which the abundance of litchi fruit spot disease infection sources is monitored, combined with the predicted number of rainy days 7-10 days after the investigation, and subsequent prevention and control suggestions are given: If the latent infection source is absent or scarce, and the predicted number of rainy days is 0-3 days, no prevention and control is needed or protective fungicides can be selected; If the latent infection source is absent or scarce, and the predicted number of rainy days is ≥4 days, fungicides with protective and therapeutic effects are selected for prevention and control; If the latent infection source is abundant, and the source is sufficient, fungicides with protective and therapeutic effects are selected for prevention and control; If the latent infection source is extremely abundant, and the source is extremely sufficient, fungicides with protective and therapeutic effects are selected for prevention and control.

[0026] Preferably, the rainfall is daily rainfall ≥0.1 mm.

[0027] The present application also claims a method for preventing and controlling litchi fruit spot disease, according to which the abundance of litchi fruit spot disease infection sources is monitored, combined with the predicted number of rainy days 7-10 days after the investigation, and subsequent prevention and control suggestions are given: If the latent infection source is absent or scarce, and the predicted number of rainy days is 0-3 days, no prevention and control is needed or protective fungicides can be selected; When the latent source of infection is scarce, and the predicted number of rainy days is more than 4, the fungicide with both protective and therapeutic effects can be selected. When the latent source of infection is abundant, and the source of fungus is sufficient, the fungicide with both protective and therapeutic effects can be selected. When the latent source of infection is extremely abundant, and the source of fungus is extremely sufficient, the fungicide with both protective and therapeutic effects can be selected.

[0028] Preferably, the investigation day is 3-4 days before the pesticide spraying, and the prevention and control suggestions for the pesticide spraying are given based on the abundance of the litchi scabby disease infection source obtained on the investigation day and the predicted number of rainy days after the investigation day.

[0029] Preferably, the effective component of the protective fungicide is mancozeb, metam, copper oxychloride or quinone copper.

[0030] Preferably, the effective component of the fungicide with both protective and therapeutic effects is pyraclostrobin, chlorothalonil, carbendazim, prochloraz or kresoxim-methyl.

[0031] More preferably, the effective component of the fungicide with both protective and therapeutic effects is pyraclostrobin, and chlorothalonil is further compounded.

[0032] More preferably, the effective component of the fungicide with both protective and therapeutic effects is pyraclostrobin, and metam is further compounded.

[0033] More preferably, the effective component of the fungicide with both protective and therapeutic effects is carbendazim, and mancozeb is further compounded.

[0034] Compared with the prior art, the present application has the following beneficial effects: The present application provides a simple and accurate litchi scabby disease prediction method for the monitoring and early warning of the litchi scabby disease latent source in different litchi production areas. For the orchard that has shown the risk of litchi scabby disease, the frequency of litchi scabby disease pathogen isolation and the field litchi scabby disease severity are collected and detected regularly (once a week) during the fruit setting period. This method can accurately monitor the abundance of the litchi scabby disease latent source. On this basis, combined with the weather forecast (the number of rainy days) during the litchi fruit setting period in the local area, the occurrence of litchi scabby disease in the region can be predicted. The detection of the abundance of the litchi scabby disease infection source 3-4 days before the preset pesticide spraying day can accurately give the guidance of the prevention and control of the pesticide spraying. DETAILED DESCRIPTION

[0035] For the purpose, technical scheme and advantages of the present application to be more clearly understood, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present application and not to limit the present application. The test methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used are commercially available reagents and materials unless otherwise specified.

[0036] Example 1 A method for monitoring the richness of latent infection source of litchi pit spot disease During the fruiting period (April to July), the disease severity (disease index) of litchi fruit pit spot disease in the field was investigated and calculated every week (the day was the investigation day), and at the same time, asymptomatic fruits were collected on the same day and taken back to the laboratory for tissue isolation to investigate the isolation of asymptomatic fruit pit spot disease pathogens. The richness of the latent infection source of litchi pit spot disease was evaluated by the disease index combined with the isolation of asymptomatic fruit pit spot disease pathogens.

[0037] 1. Time: Every year from April to July, during the litchi fruiting period, the occurrence of litchi fruit pit spot disease on the tree was investigated and asymptomatic fruits were collected once every 7 days.

[0038] 2. Investigation of litchi fruit pit spot disease index in orchard: Refer to GB / T 17980.100-2004 Field Efficacy Test Guidelines (II) Part 100: Fungicides for Controlling Litchi Pythium Blight to evaluate the occurrence of litchi fruit pit spot disease on the tree, sample 5 points of each tree, east, south, west, north and center, investigate not less than 30 fruits per point (investigate not less than 150 fruits per tree), record the total number of fruits and the number of fruits at each level, and calculate the disease index.

[0039] The fruit pit spot disease grading standard is: 0: no disease; 1: disease spot accounts for less than 10% of the fruit surface area; 3: disease spot accounts for 11-25% of the fruit surface area; 5: disease spot accounts for 26-50% of the fruit surface area; 7: disease spot accounts for more than 50% of the fruit surface area, Disease index calculation formula: .

[0040] 3. Investigation of asymptomatic fruit pit spot disease pathogen isolation: (1) Collect asymptomatic fruits on the tree, put them in a sealed bag and take them back to the laboratory for tissue isolation on the same day. Samples that cannot be processed in time are stored in a 4°C refrigerator and isolated the next day. Each time, not less than 30 fruits are collected.

[0041] (2) Separation of pericarp tissue and culture: take the pericarp crack piece tissue (one crack piece is one tissue piece) of the fruit far from the ground side, not less than 35 tissue pieces, surface sterilize with 70% alcohol for 30-60 seconds, surface sterilize with 2% sodium hypochlorite for 1.5-2 minutes, wash with sterile water for 3 times, place the sterilized and washed tissue pieces on potato dextrose agar (PDA) plates, and finally place in a 25°C incubator for constant temperature culture.

[0042] (3) Investigation of the frequency of separation of the pimple disease pathogen of pericarp tissue of symptomless fruit: after constant temperature culture at 25°C for 3-4 days, observe the colonies of the separated strains using a microscope, record the number of pericarp tissue pieces with growth of the pimple disease pathogen, and recheck and investigate again after constant temperature culture for 5 days.

[0043] Calculate the separation frequency of the pimple disease pathogen: separation frequency = number of pericarp tissue pieces with growth of the pimple disease pathogen / total number of tissue pieces x 100%.

[0044] 4. Discrimination of the richness of latent infection source: According to the disease index of the pimple disease of litchi fruit in the orchard and the separation frequency of the pimple disease pathogen of pericarp tissue of symptomless fruit on the tree, determine the situation of the latent infection source of the pimple disease of litchi in the orchard: The classification standards for the disease index of the pimple disease of litchi fruit in the orchard and the separation frequency of the pimple disease pathogen of pericarp tissue of symptomless fruit on the tree are: The separation frequency of the pimple disease pathogen of pericarp tissue of symptomless fruit is 0, the disease index of the pimple disease of litchi fruit in the orchard is 0, and there is no latent infection source; The separation frequency of the pimple disease pathogen of pericarp tissue of symptomless fruit is >0 and <35.00%, and the disease index of the pimple disease of litchi fruit in the orchard is >0 and <5.00, and the latent infection source is scarce; The separation frequency of the pimple disease pathogen of pericarp tissue of symptomless fruit is ≥35.00%, and the disease index of the pimple disease of litchi fruit in the orchard is >0 and <5.00, and the latent infection source is rich and the source of the pathogen is sufficient; The separation frequency of the pimple disease pathogen of pericarp tissue of symptomless fruit is ≥35.00%, and the disease index of the pimple disease of litchi fruit in the orchard is ≥5.00, and the latent infection source is extremely rich and the source of the pathogen is extremely sufficient.

[0045] Example 2 Prediction of the occurrence of the pimple disease and giving of prevention and control suggestions according to the richness of the latent infection source of the pimple disease of litchi After prediction of the richness of the latent infection source of the pimple disease of litchi according to the method of Example 1, the occurrence of the pimple disease is predicted according to Table 1 below, and prevention and control suggestions are given, wherein the relationship between the occurrence of the pimple disease of litchi and the disease index is: No occurrence: the disease index is 0; Litchi mild spot disease: 0 < disease index < 5.00; Litchi moderate spot disease: 5.00 ≤ disease index < 10.00; Litchi severe spot disease: disease index is ≥ 10.00.

[0046] Table 1:

[0047] Among them, the effective component of the protective fungicide is mancozeb, metiram, copper oxychloride or quinlo copper, the effective component of the fungicide with protective and therapeutic effects is pyraclostrobin, chlorothalonil, carbendazim, prochloraz or kresoxim-methyl. Among them, the effective component of the fungicide with protective and therapeutic effects is pyraclostrobin, which can also be compounded with chlorothalonil; the effective component of the fungicide with protective and therapeutic effects is pyraclostrobin, which can also be compounded with metiram; the effective component of the fungicide with protective and therapeutic effects is carbendazim, which can also be compounded with mancozeb.

[0048] The next spraying cycle is 7-10 days after predicting the richness of the latent infection source of litchi spot disease; the number of rainy days is the number of days with daily rainfall ≥0.1mm.

[0049] Example 3: Monitoring the richness of the latent infection source of litchi spot disease and predicting the incidence in a litchi garden in Dongguan City On May 7, May 22 and June 5, 2020, the richness of the latent infection source of litchi spot disease in a litchi garden in Dongguan City was monitored and the incidence was predicted according to the methods of Example 1 and Example 2, and the specific conditions are shown in Table 2: Table 2:

[0050] The above results show that by monitoring the richness of the infection source of litchi spot disease, combined with the rainfall in the future one spraying cycle, the predicted occurrence degree of litchi spot disease is consistent with the actual occurrence degree of spot disease in the orchard.

[0051] Example 4: Monitoring the richness of the latent infection source of litchi spot disease and predicting the incidence in a litchi garden in Huizhou City On May 15, May 29 and June 12, 2024, the richness of the latent infection source of litchi spot disease in a litchi garden in Huizhou City was monitored and the incidence was predicted according to the methods of Example 1 and Example 2, and the specific conditions are shown in Table 3: Table 3:

[0052] Because the weather forecast predicted only 2 rainy days in the next spraying cycle when the survey was conducted on May 15, it was predicted that the litchi mildew would occur in a mild manner; however, the actual rainfall reached 6 days, and if the 6-day rainfall was counted, the prediction of the litchi mildew occurring in a moderate manner was consistent with the actual occurrence.

[0053] The above results show that by monitoring the richness of the litchi mildew infection source and combining the rainfall in the next spraying cycle, the prediction of the occurrence of litchi mildew is consistent with the actual occurrence of litchi mildew in the orchard.

[0054] Experiments show that from 2020 to 2024, by monitoring the frequency of isolating the litchi mildew pathogen from symptomless fruit peels and the severity of litchi mildew, evaluating the richness of litchi mildew latent infection sources, and predicting the occurrence of litchi mildew, the results are consistent with the actual occurrence of litchi mildew in the region.

Claims

1. A method for monitoring the abundance of infection sources for litchi spot disease, characterized in that, During the litchi fruiting period, the disease index of litchi fruit spot disease in the survey area was investigated on the survey day, and asymptomatic fruits were collected on the survey day. The isolation frequency of the pathogen of spot disease in the peel tissue of asymptomatic fruits was obtained by using the asymptomatic fruits. The isolation frequency of pathogens causing freckle disease in the peel tissue of asymptomatic fruits was 0, the disease index of freckle disease in litchi fruits in the orchard was 0, and there was no latent source of infection. The isolation frequency of pathogens causing freckles in the peel tissue of asymptomatic fruits was >0 and <35.00%, and the disease index of freckles in litchi fruits in the orchard was >0 and <5.00, indicating a lack of latent sources of infection. The isolation frequency of pathogens causing freckle disease in the peel tissue of asymptomatic fruits was ≥35.00%, the disease index of freckle disease in litchi fruits in the orchard was >0 and <5.00, indicating abundant latent infection sources and sufficient inoculum. The frequency of isolation of pathogens causing freckle disease in the peel tissue of asymptomatic fruits was ≥35.00%, and the disease index of freckle disease in litchi fruits in the orchard was ≥5.00, indicating an extremely rich latent source of infection and an abundant source of pathogens.

2. The method according to claim 1, characterized in that, The incidence of litchi fruit spot disease in the orchard was assessed by referring to the "GB / T 17980.100-2004 Field Efficacy Trial Guidelines (II) Part 100: Control of downy mildew of litchi with fungicides".

3. The method according to claim 2, characterized in that, Each tree should have at least 150 fruits examined.

4. The method according to claim 1, characterized in that, Collect no fewer than 30 asymptomatic fruits.

5. The method according to claim 4, characterized in that, The method for obtaining the isolation frequency of the pathogen causing spotted disease in the pericarp tissue of asymptomatic fruits is as follows: Take a piece of the peel crack from the side of the fruit away from the ground, disinfect it with alcohol and sodium hypochlorite, wash it with sterile water, and place the disinfected and washed tissue block on a potato dextrose agar plate. After incubation at a constant temperature for 3-4 days, observe the colonies of the isolated strains, record the number of pieces of fruit peel tissue with colonies of the scab pathogen, and calculate the isolation frequency of the scab pathogen: Isolation frequency = Number of fruit peel tissue pieces with scab pathogen growth / Total number of tissue pieces × 100%.

6. The method according to claim 5, characterized in that, Take at least 35 pieces of the pericarp tissue from the side of the fruit away from the ground.

7. The method according to claim 5, characterized in that, Disinfect the surface with 70% alcohol for 30-60 seconds, disinfect the surface with 2% sodium hypochlorite for 1.5-2 minutes, and rinse with sterile water 3 times.

8. A method for predicting the occurrence and / or disease index of litchi freckle disease, characterized in that, The method described in claim 1 is used to monitor the abundance of sources of infection for litchi spot disease and to obtain the predicted number of rainfall days 7–10 days after the survey date, so as to predict the occurrence of litchi spot disease 7–10 days after the survey date. The latent source of infection is absent or scarce, and it is predicted that litchi spot disease will not occur or will occur mildly, with the disease index expected to be 0 to 5.00; The latent sources of infection are abundant, the inoculum is plentiful, and the number of rainy days is predicted to be 0 to 3 days, so a mild occurrence of litchi spot disease is predicted, with a disease index of 0 to 5.

00. With abundant latent sources of infection and sufficient inoculum, and with a predicted number of rainy days ≥ 4 days, moderate occurrence of litchi spot disease is predicted, with an expected disease index of 5.00–10.

00. The latent sources of infection are extremely abundant, and the inoculum is plentiful. It is predicted that moderate or severe litchi spot disease will occur, with an expected disease index of ≥5.

00.

9. The method according to claim 8, characterized in that, The rainfall is defined as daily rainfall ≥ 0.1 mm.

10. A method for controlling litchi freckle disease, characterized in that, Based on the method described in any one of claims 1 to 7, monitor the abundance of infection sources for litchi spot disease, and combine this with the predicted number of rainfall days 7 to 10 days after the survey date to provide subsequent prevention and control recommendations: If there are no or few latent sources of infection and the number of rainy days is predicted to be 0 to 3, then no prevention and control measures are needed or protective fungicides can be used. If there are no or few latent sources of infection and the number of days with predicted rainfall is ≥4, then a fungicide with both protective and curative effects should be used for prevention and control. If there are abundant latent sources of infection and sufficient bacterial sources, then fungicides with both protective and curative effects should be selected for prevention and control. If the latent sources of infection are abundant and the bacterial source is plentiful, then a fungicide with both protective and curative effects should be selected for prevention and control.

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