Method for removing sporadic citrus huanglongbing trees in a citrus orchard

Abstract

The present application belongs to the technical field of fruit tree disease prevention and control, and particularly relates to a method for removing sporadic citrus Huanglongbing trees in citrus orchards. According to the epidemiological characteristics of citrus Huanglongbing, the control strategy of 'completely removing diseased plants, strictly preventing and controlling citrus psyllids, and comprehensively preventing and controlling' is implemented at sporadic disease points in the diffusion front area. The sporadic disease point orchards are promptly cleaned of diseased trees, and the diffusion front area is comprehensively prevented and controlled to prevent the disease from occurring again. In this way, disease information and risk warnings can be promptly released, the removal of diseased trees and the strict prevention and control of citrus psyllids can be achieved, the invasion and reproduction of exogenous psyllids can be hindered, the risk of healthy seedlings getting sick can be reduced, and the spread of citrus Huanglongbing can be blocked. The present application provides technical support for delaying the further spread of citrus Huanglongbing and saves human and material resources.

Description

A method for removing scattered citrus trees infected with Huanglongbing (HLB) in citrus orchards Technical Field

[0001] This invention belongs to the field of fruit tree disease control technology, specifically relating to a method for eliminating scattered citrus Huanglongbing (HLB) trees in citrus orchards. Background Technology

[0002] Citrus Huanglongbing (HLB) is a systemic infectious disease of citrus caused by Gram-negative bacteria. Infected plants exhibit mottled yellowing of leaves, small and poor-quality fruit, and weakened tree vigor, generally leading to death within 5-8 years of infection, severely impacting the economic value of the plant. Typical symptoms of HLB include: ① Mottled yellowing of leaves: Irregularly shaped patches of chlorosis or yellowing appear from the base of the leaf, along the sides of the midrib, or at the leaf margins. This symptom is generally observed from late autumn / early winter to the following spring, mostly located in the lower and middle parts of the canopy or on shoots emerging from the inner trunk (see Figure 1); ② "Red-nosed fruit" symptoms: Abnormal fruit coloring, the opposite of normal fruit coloring, starting coloring from the stem end and ceasing after only completing coloring at the shoulder, or the entire fruit remaining green without coloring. The fruit is smaller than normal, skewed to one side along the central axis, has a thicker peel, and is lighter in weight (see Figure 2). There is currently no effective chemical treatment for this disease, and it is transmitted through insect vectors. If a single infected tree is not treated promptly, it can destroy an entire orchard; therefore, it is often referred to as "citrus cancer." In recent years, Huanglongbing (HLB) has caused serious damage to my country's citrus industry. Taking Ganzhou, Jiangxi Province as an example, since 2012, more than 45 million diseased trees have been cut down due to the disease, resulting in enormous economic losses.

[0003] Citrus psyllids are the primary vector insects for citrus Huanglongbing (HLB) in the field. Influenced by factors such as global warming, citrus psyllids are migrating northward, and this northward migration of vector insects is also driving the gradual northward spread of the disease. If the disease continues to spread northward, the resulting economic losses and the economic value required for disease control will be incalculable. The disease's frontal zone is a high-risk area for northward spread, where diseased trees have not yet appeared or are at a very low level of sporadic occurrence in individual orchards. In this situation, timely and thorough removal of diseased trees to prevent recurrence is crucial for delaying and stopping the continued spread of citrus HLB. However, currently, there are no relevant technologies in this field for the removal of sporadic HLB-infected citrus trees, especially for the frontal zone, where the application and implementation of such technologies is urgently needed to stop the spread of citrus HLB. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing scattered citrus Huanglongbing (HLB) trees in citrus orchards. This method can promptly release disease information and risk warnings, achieve the removal of diseased trees and strict control of citrus psyllids, hinder the invasion and reproduction of exogenous psyllids, reduce the risk of healthy seedlings being infected, and at the same time slow down the spread of HLB.

[0005] This invention provides a method for eliminating scattered citrus trees infected with Huanglongbing (HLB) in citrus orchards, comprising the following steps:

[0006] 1) Conduct a general survey and monitoring of citrus trees in the citrus orchard and conduct regular random inspections to detect trees infected with Huanglongbing (HLB);

[0007] 2) Carry out citrus psyllid control in citrus orchards containing the aforementioned citrus Huanglongbing (HLB) trees, and treat the HLB trees accordingly;

[0008] 3) Conduct a second inspection of the citrus orchards that have completed step 2), and treat the citrus trees infected with Huanglongbing (HLB) again as described in step 2); the second inspection includes: testing the citrus trees in the orchards for Huanglongbing pathogens;

[0009] 4) Implement integrated prevention and control of citrus Huanglongbing (HLB) in citrus orchards, including those containing HLB-infected trees.

[0010] Preferably, the survey and monitoring in step 1) includes: identifying citrus trees infected with Huanglongbing through Huanglongbing symptoms; the regular sampling includes: testing citrus trees for Huanglongbing pathogens; and the number of citrus trees sampled regularly is not less than 0.06% of the total number of citrus trees.

[0011] Preferably, the treatment in step 2) includes removing the entire diseased tree and / or removing the above-ground part of the diseased tree; when removing the above-ground part of the diseased tree, the treatment includes: leaving the remaining diseased stump at a height not exceeding 10cm, applying a decomposing agent to the cut surface of the diseased stump and covering it with a covering; the decomposing agent includes glyphosate, kerosene, asphalt or diesel.

[0012] Preferably, the areas to be investigated again include key areas and non-key areas. The key area is an area with a radius of 10 meters centered on the citrus Huanglongbing tree, and the non-key area is the area outside the key area. Citrus Huanglongbing fungus is tested on all citrus trees in the key area; citrus Huanglongbing fungus is tested on no less than 20% of the citrus trees in the non-key area.

[0013] Preferably, the re-investigation includes three investigations: the first investigation is conducted after the citrus Huanglongbing trees are treated, and the second and third investigations are conducted three months and six months after the first investigation, respectively.

[0014] Preferably, the detection of Huanglongbing pathogen in citrus is performed according to "GB / T28062 Real-time Fluorescent PCR Detection Method for Huanglongbing Pathogen in Citrus".

[0015] Preferably, the integrated prevention and control includes one or more of A to G:

[0016] A: When planting citrus trees, select disease-free seedlings and set up a net shed during the temporary planting and cultivation stage;

[0017] B. Remove Rutaceae plants, Zanthoxylum nitidum, and Evodia rutaecarpa from around the citrus orchard;

[0018] C. Set up insect-proof nets or protective forests around the citrus orchard;

[0019] D. Remove scattered summer shoots, late shoots, and winter shoots from citrus trees, and allow shoots to grow uniformly;

[0020] E. Chemical control of citrus psyllids at each shoot growth stage of citrus trees;

[0021] F. Fertilize citrus trees 2-3 times per year; implement chemical control measures in citrus orchards;

[0022] G: Test citrus Huanglongbing pathogens on seedlings and scions before they leave the nursery.

[0023] Preferably, the mesh count of the netting and the insect-proof netting is 60 mesh or more; the duration of the temporary planting and cultivation stage is 1.5 to 2 years; and the protective forest includes eucalyptus and / or fir trees.

[0024] Preferably, the chemical control includes the following two measures: I and / or II:

[0025] Ⅰ: During winter sanitation, spray the entire orchard with neonicotinoid insecticides and mineral oil;

[0026] II: During the peak period of citrus psyllids, spray with 1000 times dilution of D-limonene and 3500 times dilution of 20% thiamethoxam·lufenuron.

[0027] Preferably, the chemical control includes: spraying pesticides at each shoot stage when each new shoot grows to 0.1-1.0 cm, wherein the sprayed pesticides include spraying D-limonene at a dilution of 1000 times and 10% thiamethoxam wettable powder at a dilution of 1500 times.

[0028] Beneficial effects:

[0029] This invention provides a method for eliminating scattered citrus trees infected with Huanglongbing (HLB) in citrus orchards, comprising the following steps:

[0030] 1) Conduct a general survey and monitoring of citrus trees in the citrus orchard and conduct regular random inspections to detect trees infected with Huanglongbing (HLB);

[0031] 2) Carry out citrus psyllid control in citrus orchards containing the aforementioned citrus Huanglongbing (HLB) trees, and treat the HLB trees accordingly;

[0032] 3) Conduct a second investigation of key and non-key areas in the citrus orchards that have completed step 2), and treat the citrus trees infected with Huanglongbing (HLB) again as described in step 2); the second investigation includes: testing the citrus trees in the citrus orchard for Huanglongbing pathogens;

[0033] 4) Implement integrated prevention and control of citrus Huanglongbing (HLB) in citrus orchards, including those containing HLB-infected trees.

[0034] Based on the epidemiological characteristics of citrus Huanglongbing (HLB), this invention implements a control strategy of "thoroughly eliminating infected plants, strictly controlling citrus psyllids, and comprehensive prevention and control" in scattered disease sites at the front line of the spread. This involves timely removal of diseased trees from orchards with scattered disease sites and comprehensive prevention and control measures in planting areas with scattered disease sites (the front line of the spread) to prevent the recurrence of the disease. Furthermore, it enables timely dissemination of disease information and risk warnings, achieving the removal of diseased trees and strict control of citrus psyllids, hindering the invasion and reproduction of exogenous psyllids, reducing the risk of infection in healthy seedlings, and simultaneously slowing the spread of HLB. This provides technical support for delaying the further spread of HLB while saving human and material resources. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0036] Figure 1 shows the symptoms of citrus Huanglongbing (HLB) on diseased leaves as described in the background section of this invention;

[0037] Figure 2 shows the symptoms of citrus Huanglongbing disease on the fruit as described in the background section of this invention;

[0038] Figure 3 shows the leaf symptoms of the diseased citrus plant in Example 1 of the present invention;

[0039] Figure 4 shows the qPCR detection results of leaves of diseased citrus plants in Example 1 of the present invention;

[0040] Figure 5 shows the results of the investigation of Huanglongbing in citrus trees in key and non-key areas in Embodiment 1 of the present invention;

[0041] Figure 6 shows the results of the second and third investigations of Huanglongbing in citrus trees in key and non-key areas in Embodiment 1 of the present invention. Detailed Implementation

[0042] This invention provides a method for eliminating scattered citrus trees infected with Huanglongbing (HLB) in citrus orchards, comprising the following steps:

[0043] 1) Conduct a general survey and monitoring of citrus trees in the citrus orchard and conduct regular random inspections to detect trees infected with Huanglongbing (HLB);

[0044] 2) Carry out citrus psyllid control and treat the citrus Huanglongbing trees in the citrus orchards containing the aforementioned citrus Huanglongbing trees;

[0045] 3) Conduct a second inspection of the citrus orchards that have completed step 2), and treat the citrus trees infected with Huanglongbing (HLB) again as described in step 2); the second inspection includes: testing the citrus trees in the orchards for Huanglongbing pathogens;

[0046] 4) Implement integrated prevention and control of citrus Huanglongbing (HLB) in citrus orchards, including those containing HLB-infected trees.

[0047] This invention involves conducting a comprehensive survey and regular sampling of citrus trees in citrus orchards to detect trees infected with Huanglongbing (HLB). Preferably, the survey and detection methods described in this invention include identifying HLB-infected citrus trees based on HLB symptoms.

[0048] This invention does not specifically limit the characteristics of the Huanglongbing (HLB) symptoms. Any typical symptoms of HLB can assist those skilled in the art in identifying HLB-affected citrus trees. For example, the HLB symptoms described in this invention preferably include one or more of the following: mottled yellowing of leaves, "red-nosed fruit" symptoms of citrus fruits, and yellowing of spring shoots. The mottled yellowing of leaves specifically preferably includes: irregularly shaped patches of chlorosis or yellowing starting from the base of the leaf, the leaf tissue on both sides of the midrib, or the leaf edge. The symptoms are located in the lower part of the canopy or in the inner trunk of the tree. The "red-nosed fruit" symptoms specifically preferably include: abnormal fruit coloring, the opposite of normal fruit coloring, coloring starting from the stem end, coloring only at the shoulder of the fruit and then ceasing, or the entire fruit remaining green without coloring, smaller than normal fruit, skewed to one side along the central axis, thicker peel, and lighter weight. The yellowing of spring shoots preferably includes zinc deficiency mosaic symptoms on the leaves.

[0049] The periodic sampling inspection described in this invention preferably includes: detecting citrus Huanglongbing (HLB) on citrus trees, wherein the HLB detection is preferably performed according to "GB / T28062 Real-time Fluorescent PCR Detection Method for Citrus Huanglongbing"; the number of citrus trees sampled periodically is not less than 0.06% of the total number of citrus trees. The preferred time interval for the periodic sampling inspection is once a year, and the preferred season for the periodic sampling inspection is spring.

[0050] After obtaining the citrus Huanglongbing trees, the present invention carries out citrus psyllid control and treatment on the citrus orchards containing the citrus Huanglongbing trees.

[0051] In this invention, the preferred time for controlling citrus psyllids in citrus orchards containing trees infected with Huanglongbing (HLB) is within 24 hours of discovering the infected trees. The control of citrus psyllids in this invention preferably follows the "GB4285 Standard for Safe Use of Pesticides" and the "NY / T2920-2016 Technical Regulations for the Prevention and Control of Huanglongbing in Citrus," using contact pesticides for citrus psyllids; the contact pesticides preferably include highly effective deltamethrin, acetamiprid, imidacloprid, or dinotefuran.

[0052] The treatment described in this invention preferably includes removing the entire diseased tree and / or removing the above-ground parts of the diseased tree, more preferably removing the entire diseased tree or removing the above-ground parts of the diseased tree. When removing the above-ground parts of the diseased tree, the height of the remaining diseased stump is preferably no more than 10 cm; and preferably, a decomposition-promoting agent is applied to the cut surface of the diseased stump and covered with a covering to accelerate the rotting of the outer bark of the diseased stump, preventing the new shoots that sprout the following year from attracting citrus psyllids and spreading disease. The decomposition-promoting agent of this invention preferably includes glyphosate, kerosene, asphalt, or diesel. The decomposition-promoting agent is preferably applied evenly in one layer on the surface of the diseased stump, and preferably two layers are applied evenly on the top of the diseased stump. The covering is preferably a black film; the material of the black film is not particularly limited, as long as it achieves the technical effect of shading light, such as a black plastic bag. This invention preferably also includes the centralized destruction of the removed entire diseased tree and the above-ground parts of the diseased tree. The method of destruction is not particularly limited, and can be carried out according to the conventional methods for destroying diseased trees in the art.

[0053] After treating the citrus Huanglongbing trees, the present invention re-inspects the key areas and non-key areas in the treated citrus orchard, and treats the citrus Huanglongbing trees again in step 2); the key area is preferably an area with a radius of 10 meters centered on the citrus Huanglongbing tree, and the non-key area is the area outside the key area.

[0054] The areas to be re-inspected in this invention preferably include key areas and non-key areas; the key area is preferably an area with a radius of 10 meters centered on the citrus Huanglongbing tree, and the non-key area is preferably an area outside the key area. This invention preferably includes testing all citrus trees in the key area for Huanglongbing pathogens; and testing at least 20% of the citrus trees in the non-key areas for Huanglongbing pathogens. The method for testing Huanglongbing pathogens in this invention is preferably the same as the above technical solution and will not be repeated. The re-inspection in this invention preferably includes three inspections: a first inspection is preferably conducted after treating the citrus Huanglongbing trees, and a second and third inspection are preferably conducted three months and six months after the first inspection, respectively. The present invention preferably involves treating the citrus Huanglongbing trees identified in the re-inspection as described in the above technical solution, controlling citrus psyllids in the citrus orchard, and re-dividing the citrus Huanglongbing area into key and non-key areas based on the newly detected citrus Huanglongbing trees; when citrus Huanglongbing trees are found again after the re-inspection of the re-divided key and non-key areas, it indicates that the citrus Huanglongbing disease has spread in the corresponding orchard, and it is recommended that the entire orchard be cut down and rebuilt.

[0055] Following the subsequent investigation, this invention provides comprehensive prevention and control of citrus Huanglongbing (HLB) in citrus orchards containing HLB-infected trees.

[0056] The integrated prevention and control method described in this invention preferably includes one or more of A to G:

[0057] A: When planting citrus trees, select disease-free seedlings and set up a net shed during the temporary planting and cultivation stage;

[0058] B. Remove Rutaceae plants, Zanthoxylum nitidum, and Evodia rutaecarpa from around the citrus orchard;

[0059] C. Set up insect-proof nets or protective forests around the citrus orchard;

[0060] D. Remove scattered summer shoots, late shoots, and winter shoots from citrus trees, and allow shoots to grow uniformly;

[0061] E. Chemical control of citrus psyllids at each shoot growth stage of citrus trees;

[0062] F. Fertilize citrus trees 2-3 times per year; implement chemical control measures in citrus orchards;

[0063] G: Test citrus Huanglongbing pathogens on seedlings and scions before they leave the nursery.

[0064] In this invention, the mesh size of the netting is preferably 60 mesh or more; the duration of the temporary planting and cultivation stage is preferably 1.5 to 2 years; preferably, the citrus trees are replanted with soil after the temporary planting and cultivation, and the replanted citrus trees are in sync with the shoot growth of the original large trees in the orchard.

[0065] In this invention, the mesh size of the insect-proof net is preferably 60 mesh or more, more preferably 60 mesh; the insect-proof net can effectively block the invasion of exogenous citrus psyllids. The protective forest of this invention preferably includes eucalyptus and / or fir trees. Eucalyptus and fir trees have good growth characteristics, and after rapid maturation, they can play a certain role in blocking and isolating citrus psyllids from flying into the orchard.

[0066] In this invention, the preferred method for chemical control of citrus psyllids at various shoot stages of citrus trees includes spraying pesticides at each shoot stage when new shoots emerge to 0.1–1.0 cm. The pesticides used are preferably, but are not limited to, spraying a 1000-fold dilution of D-limonene and a 1500-fold dilution of 10% thiamethoxam wettable powder. The preferred frequency of spraying is twice per shoot stage, with a preferred interval of 7–10 days between sprays. This chemical control method can prevent adult oviposition and kill eggs and young nymphs. When spraying, mineral oil can be added to the pesticide to increase its permeability and extend its duration of action. The type and amount of mineral oil used are not particularly limited; conventional dosages in the art are acceptable, such as adding acetamiprid according to the product dosage instructions.

[0067] In this invention, the chemical control preferably includes the following two measures: I and / or II: I: During winter orchard sanitation, it is preferred to spray the entire orchard with neonicotinoid insecticides and mineral oil to reduce the number of overwintering citrus psyllids. II: During the peak period of citrus psyllids, it is preferred to spray, but not limited to, a 1000-fold dilution of D-limonene and a 3500-fold dilution of 20% thiamethoxam·lufenuron, the agents having both sustained and rapid effects. The spraying method in the chemical control of this invention preferably includes: spraying the tree canopy, advancing the spraying from the outside to the inside, ensuring no omissions in the undersides of the leaves and focusing on new shoots. When carrying out the chemical control of this invention, it is also preferred to combine fast-acting and systemic agents according to the technical knowledge of those skilled in the art, and to rotate the use of agents with different mechanisms of action to delay the development of pesticide resistance in citrus psyllids.

[0068] The method for detecting citrus Huanglongbing (HLB) in seedlings and scions of this invention is preferably the same as the above-described technical solution and will not be repeated here. Preferably, all scions are tested for HLB; the number of seedlings tested for HLB is preferably 0.06% of the total number of seedlings.

[0069] The present invention preferably also includes recording the occurrence time, disease incidence, severity, control measures and control effects of citrus Huanglongbing in citrus orchards to provide technical records and support for subsequent prevention and control of citrus Huanglongbing.

[0070] Based on the epidemiological characteristics of citrus Huanglongbing (HLB), this invention implements a control strategy of "thoroughly eliminating infected plants, strictly controlling citrus psyllids, and comprehensive prevention and control" in scattered disease sites at the forefront of the spread. This involves timely removal of diseased trees from orchards with scattered disease sites and comprehensive prevention and control measures in the spread-leading area to prevent disease recurrence. Furthermore, it enables timely dissemination of disease information and risk warnings, achieving the removal of diseased trees and strict control of citrus psyllids, hindering the invasion and reproduction of exogenous psyllids, reducing the risk of infection in healthy seedlings, and simultaneously slowing the spread of HLB. This provides technical support for delaying the further spread of HLB while saving human and material resources.

[0071] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0072] Example 1

[0073] A method for removing scattered citrus trees infected with Huanglongbing (HLB) in a citrus orchard, the steps of which are as follows:

[0074] Location of implementation: Aoshang, Tengqiao Town, Linchuan District, Fuzhou City (116.4986°E, 27.7515°N), with an orchard area of ​​approximately 30 mu.

[0075] (1) In March 2022, a plant suspected of being infected with citrus Huanglongbing was found in Aoshang Orchard, Tengqiao Town, Linchuan District, Fuzhou City. The lower part of the leaf crown on the shaded side of the plant showed typical mottled yellowing symptoms, and it was suspected to be a plant infected with citrus Huanglongbing.

[0076] Symptomatic leaves were collected (as shown in Figure 3) and brought back to the laboratory for testing according to the "GB / T28062 Real-time Fluorescent PCR Detection Method for Citrus Huanglongbing". The qPCR amplification Ct value was 24, as shown in Figure 4, thus confirming that the plant was a susceptible plant.

[0077] (2) Feedback the test results to the orchard owner and inform them to immediately spray pesticides, specifically a 100-fold dilution of mineral oil and a 1500-fold dilution of 10% thiamethoxam wettable powder, to kill psyllids. 24 hours after killing the psyllids, cut down the infected plants, leaving stumps no more than 10cm high, apply glyphosate to the stumps, and cover them with black film to prevent new shoots from sprouting.

[0078] (3) Plant screening in key areas: Within a 10-meter radius (approximately 314m) of the area where diseased plants were cut down. 2Leaves were collected from all plants (approximately 25 plants) within this area for laboratory testing. For each sample, leaves showing symptoms were collected whenever possible; otherwise, leaves were collected from four different locations. The collected leaves were brought back to the laboratory and tested according to the "GB / T28062 Real-time Fluorescent PCR Detection Method for Citrus Huanglongbing". The results are shown in Figure 5.

[0079] The qPCR test results in Figure 5 show that none of the samples had amplification curves, indicating that none of the samples in this area were infected.

[0080] Non-key areas were investigated. The orchard covers an area of ​​approximately 20 mu (about 3.3 hectares) and contains about 1,000 citrus seedlings. Following a 10% sampling rate for non-key areas, 100 samples were randomly collected from outside the key areas for testing. The testing method followed the "GB / T28062 Real-time Fluorescent PCR Detection Method for Citrus Huanglongbing". The results are shown in Figure 5; all samples showed no amplification curve, indicating that all samples in this area were free of disease.

[0081] (5) In June and September 2022, steps (3) and (4) were repeated to investigate the key and non-key areas of the orchard again. No diseased plants were found. The results are shown in Figure 6, where A is the result of the investigation in June and B is the result of the investigation in September.

[0082] As shown in Figure 4, there are no amplification curves in A and B of Figure 4, indicating that the sporadic disease sites in the orchard have been completely eradicated.

[0083] Currently, the orchard regularly monitors and screens citrus trees for Huanglongbing (HLB) symptoms, and no further cases have been found. The orchard's control measures include: removing scattered summer, late, and winter shoots from citrus trees and allowing them to grow uniformly; applying fertilizer to citrus trees 2-3 times per year; implementing chemical control measures in the citrus orchard; and eliminating Rutaceae psyllid host plants around the citrus orchard.

[0084] From the above embodiments, it can be concluded that the removal method described in this invention can achieve the purpose of removing scattered citrus Huanglongbing trees, inhibiting the further spread of Huanglongbing, and reducing the losses caused by citrus Huanglongbing to fruit farmers.

[0085] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for clearing scattered citrus Huanglongbing trees in a citrus orchard, comprising the following steps: 1) Conducting a general survey and monitoring of citrus trees in the citrus orchard and conducting regular random sampling to detect citrus Huanglongbing trees; The survey and monitoring includes: identifying citrus trees infected with Huanglongbing (HLB) through symptoms; the regular sampling includes: testing citrus trees for HLB pathogens; the number of citrus trees sampled regularly is no less than 0.06% of the total number of citrus trees; 2) spraying pesticides on citrus psyllids in citrus orchards containing HLB-infected trees, and treating the HLB-infected trees; the treatment includes removing the entire diseased tree and / or removing the above-ground parts of the diseased tree; when removing the above-ground parts of the diseased tree, the treatment includes: leaving a remaining stump no more than 10cm high, applying a decomposing agent to the cut surface of the stump and covering it with a covering; the decomposing agent includes glyphosate, kerosene, asphalt or diesel; 3) conducting a second survey of citrus orchards that have completed step 2), and treating the HLB-infected citrus trees again using the treatment described in step 2); the second survey... The investigation includes: 4) detecting Huanglongbing (HLB) on citrus trees in citrus orchards; 5) implementing comprehensive prevention and control measures for HLB in citrus orchards containing HLB-infected trees; the areas to be investigated again include key areas and non-key areas. The key area is a 10-meter radius area centered on the HLB-infected tree, and the non-key area is the area outside the key area; HLB detection is performed on all citrus trees in the key area and on at least 20% of the citrus trees in the non-key area; the investigation includes three investigations: the first investigation is conducted after treating the HLB-infected trees, and the second and third investigations are conducted three months and six months after the first investigation, respectively; the HLB detection is performed according to "GB / T28062 Real-time Fluorescent PCR Detection Method for Huanglongbing".

2. The cleaning method according to claim 1, characterized in that, The integrated pest management includes one or more of A to G: A: When planting citrus trees, select disease-free seedlings and set up net sheds during the temporary planting and cultivation stage; B: Remove Rutaceae plants, Zanthoxylum nitidum, and Evodia rutaecarpa from around the citrus orchard; C: Set up insect-proof nets or protective forests around the citrus orchard; D: Remove scattered summer shoots, late shoots, and winter shoots of citrus trees and allow them to grow uniformly; E: Conduct chemical control of citrus psyllids at each shoot growth stage of citrus trees; F. Fertilize citrus trees 2-3 times per year; carry out chemical control in citrus orchards; G. Test seedlings and scions for citrus Huanglongbing (HLB).

3. The cleaning method according to claim 2, characterized in that, The mesh count of the netting and insect-proof netting is 60 mesh or higher; the duration of the temporary planting and cultivation stage is 1.5 to 2 years; the protective forest includes eucalyptus and / or fir trees.

4. The cleaning method according to claim 2, characterized in that, The chemical control measures include the following two measures: I and / or II: I: During winter sanitation, spray the entire orchard with neonicotinoid insecticides and mineral oil; II: During the peak period of citrus psyllids, spray with 1000 times dilution of D-limonene and 3500 times dilution of 20% thiamethoxam·lufenuron.

5. The cleaning method according to claim 2, characterized in that, The chemical control measures include: spraying pesticides at each shoot stage when the new shoots grow to 0.1-1.0 cm. The pesticides sprayed include 1000 times dilution of D-limonene and 1500 times dilution of 10% thiamethoxam wettable powder.

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