Application of high-stress-resistance and high-pathogenicity Steinernemararporapse XJ-39 nematode in prevention and treatment of Chinese chive maggots in arid and semi-arid regions

Abstract

The invention discloses an application of high-stress-resistance and high-pathogenicity Steinernemacarporapse XJ-39 nematode in prevention and treatment of Chinese chive maggots in arid and semi-arid regions, and provides a nematode strain S.carporapse XJ-39 which is high in pathogenicity to Chinese chive maggot pests, high in reproductive capacity and good in environmental adaptability at the same time. The corrected death rate of the Chinese chive maggots under the concentration of 150 IJs / larva reaches 75.55%; the number of live propagation nematodes of greater wax moths is 5.24 * 10 < 4 > IJs / larva and 2.10 * 10 < 4 > IJs / g; the death rate is 74.86% after treatment is conducted for 5 h at the temperature of 38 DEG C, and the death rate is only 23.64% after treatment is conducted for 4 h at the NaCl concentration of 10%; after being irradiated by 19W ultraviolet light for 4 hours, the death rate is 43.58%. The S.carpocapsae XJ-39 has good drought stress resistance, has relatively strong survivability under the humidity of a saturated solution of KCl and NaCl, and shows good compatibility with thiamethoxam. In the potting control effect, the control effect of mixed use of nematodes and thiamethoxam reaches 80% or above; after the pesticide is applied in the field, the correction control effect on Chinese chive maggots is 70.25%-60.24%, and the pesticide has fast-acting property and persistent effect. According to the technical scheme provided by the invention, healthy planting, sustainable and high-quality development of the Chinese chives in the arid and semi-arid regions can be further assisted.

Description

Technical Field

[0001] The invention belongs to the technical field of biotechnology, and in particular relates to the technical field of agricultural pest control in arid and semi-arid areas. Background Art

[0002] With the widespread cultivation of chives, the damage caused by leek maggots has become increasingly severe year by year. EPNs can actively locate leek maggots based on their odor. As natural enemies, they release highly effective parasitic pathogenic nematode symbionts during the infestation phase, effectively controlling the maggots. However, entomopathogenic nematodes are highly selective in their location and dominant host, making it crucial to trap and isolate the dominant nematode species or strains found in Xinjiang.

[0003] Entomopathogenic nematodes (EPNs) are divided into two major categories: Steinernematidae and Heterorhabditidae. They establish an obligate symbiotic relationship with specific symbiotic bacteria (Xenorhabdus and Photorhabdus). They act together on the insect host and cause the death of the host. Grewal et al. reported that S.feltiae has a good control effect on mushroom gnats; Yang Xiufen et al. screened out S.feltiae PS4, which has a control effect of more than 80% on the leek bradya larvae, and the control effect in field plot tests reached 55.8%; Wu Haibin et al. determined that S.feltiaeSF-SN has the highest pathogenicity to the third instar larvae of leek maggots, LD 50 The content of nematode pathogenic nematodes is 60.0IJs / head; Mahar et al. conducted indoor and potted experiments on leek maggots using different species of entomopathogenic nematodes; Liu and Glaze, Liu et al. studied the desiccation resistance and physiological and biochemical mechanisms of Heterorhabditis bacteriophora; Chung et al. reported that its pathogenicity and fecundity were affected by infection temperature and dose.

[0004] EPNs have good control effects on soil-dwelling and borer pests and are a good biological insecticide. Abiotic factors (such as temperature, salt concentration, and ultraviolet light) affect the survival, reproduction, and pathogenicity of EPNs. EPNs have certain host specificity, so different species and strains will have different control effects on the same host insect, and the same species or strain will have different control effects on different host insects. Due to the special climatic and geographical factors in Xinjiang, the soil temperature is high, the salinity is high, and the ultraviolet radiation is strong. Therefore, screening nematode species or strains that are better tolerant to abiotic stresses has become the key to native biological pest control in Xinjiang.

[0005] We screened out Xinjiang native insect pathogenic nematodes with high pathogenicity and good adaptability to leek maggot pests and initially applied them in the biological control of leek maggots, solving the technical difficulties of biological control in Xinjiang where leek maggots cause serious damage and the existing prevention and control methods are single and ineffective. Through the research and application of new biocontrol factors, we further reduced the food safety risks caused by excessive use of pesticides and excessive pesticide residues in leek. At the same time, through the application and research of new biocontrol factors for leek maggots, we further assisted the healthy cultivation, sustainable and high-quality development of Xinjiang leek. Summary of the Invention

[0006] In view of the technical problem that the existing nematode biological control technology cannot meet the needs of adapting to the environment of arid and semi-arid areas with high soil temperature, high salinity and strong ultraviolet radiation and achieving good biological control effects, screening nematode species or strains with better tolerance to abiotic stress and providing good application technology solutions have become the key to biological control of pests in the prevention and control of highly pathogenic leek maggots in arid and semi-arid areas. The present application aims to provide a nematode strain S.carpocapsae XJ-39 that has high pathogenicity and high fecundity to leek maggot pests and good adaptability to the environment. And provide the best-suited application technology solution for the prevention and control of leek maggots in arid and semi-arid areas, which can achieve good correction and prevention effects on leek maggots and has both fast-acting and long-lasting effects. The technical solution provided in this application can further contribute to the healthy cultivation, sustainable and high-quality development of leeks in arid and semi-arid areas.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] The present application provides an application of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode for the prevention and control of leek maggots in arid and semi-arid areas.

[0009] The Steinernemacarpocapsae XJ-39 nematode is screened using the following method: different species of nematodes are selected at a nematode concentration of 1000 IJs / mL; 2 mL of the suspension from each treatment is added individually to a 24-well plate, ensuring that only one strain of nematode suspension is contained in each well; the 24-well plate is wrapped and sealed with plastic wrap and placed in an incubator at 35°C, 38°C, and 40°C for heat stress treatment; 0.2 mL of the nematode suspension is removed from each well after 1, 2, 3, 4, 5, and 6 hours, 0.8 mL of distilled water is added to dilute the nematode concentration, and the diluted nematode suspensions are transferred to a 25°C incubator for further incubation for 24 hours; after 24 hours, the survival of the nematodes is examined and counted using a dissecting microscope to screen for heat-resistant Steinernemacarpocapsae XJ-39 nematodes.

[0010] The screening method for Steinernemacarpocapsae XJ-39 nematodes also includes: selecting a vigorous nematode suspension with a concentration of 1000 IJs / mL, and then dispensing the suspension into 1 mL to 2 mL centrifuge tubes; placing the suspension in 5%, 10%, and 15% NaCl solutions, respectively, to determine the salt tolerance of the nematodes under different NaCl concentrations; placing the treated suspension at room temperature of 25°C for 1, 2, 3, and 4 hours, respectively; performing the treatment experiment six times at each time point; and after a set time, observing the death of the nematodes, counting and analyzing the mortality rate, and screening for salt-tolerant Steinernemacarpocapsae XJ-39 nematodes.

[0011] The screening method for Steinernemacarpocapsae XJ-39 nematodes also includes: exposing a suspension with a concentration of 1000 IJs / mL to 19W and 30W UV-B radiation simulators at a distance of 20 cm from the radiation source for 1, 2, 3, and 4 hours, respectively; each irradiation treatment is considered an experimental group, and a nematode suspension that has not been exposed to ultraviolet light is set up as a control group; the experiment is repeated three times for each treatment condition; after reaching the predetermined irradiation time, 0.2 mL of the nematode suspension is removed from each treatment group and diluted with 0.8 mL of distilled water; then, the diluted nematode suspension is placed in an incubator at 25°C for incubation to promote the recovery of the nematodes; after the 24-hour recovery and incubation process, the number of live nematodes in each treatment group is counted, and the average survival rate of the nematodes is calculated based on the count; to ensure the accuracy of the data, each experimental treatment is repeated six times; and radiation-resistant Steinernemacarpocapsae XJ-39 nematodes are screened.

[0012] The screening method for Steinernema carpocapsae XJ-39 nematodes also includes: transferring approximately 2,000 IJs onto filter paper (55 mm, Whatman No. 1) in a 60 mm petri dish; removing excess water from a desiccator (23 cm diameter, 24 cm height) by vacuum filtration; and then placing the filter paper containing the nematodes in a desiccator where saturated solutions of KCl, NaCl, MgCl2, and KI are prepared. After being placed at 25°C for 24 and 48 hours, the filter paper was removed and placed in 5 mL of sterile water for 24 hours. The survival percentage was determined by probing the nematodes with a dissecting needle. Different strains of nematodes were repeated three times, and at least 50 IJs were counted in each sample. To ensure the accuracy of the data, each experimental treatment was repeated 6 times. The control humidity of saturated solutions of KCl, NaCl, MgCl2, and KI at 25°C was 84.24±0.36%, 75.29±0.13%, 32.78±0.16%, and 68.86±0.24%, respectively. The drought-stress-resistant SteinernemacarpocapsaeXJ-39 nematodes were screened.

[0013] Preferably, the high temperature resistance screening process is carried out at 40° C. for 1 hour.

[0014] Preferably, in the salt-alkali tolerance selection process, a NaCl concentration of 15% is selected for treatment for 3 hours.

[0015] Preferably, UV-B-30W treatment for 3 hours is selected during the high temperature resistance screening process.

[0016] Preferably, during the screening process for drought stress tolerance, a saturated solution of NaCl or KCl is used for treatment for 48 hours.

[0017] Furthermore, the application requires the use of Steinernemacarpocapsae XJ-39 nematodes in combination with chemical pesticides such as any one or more of thiamethoxam, clothianidin, phoxim and imidacloprid.

[0018] Preferably, any one or more of 95% thiamethoxam technical, 70% thiamethoxam water dispersible granules, 98% clothianidin technical, 95% imidacloprid, and 85% phoxim technical are used in the application.

[0019] More preferably, 70% thiamethoxam water dispersible granules are used in the application.

[0020] Furthermore, the amount of Steinernemacarpocapsae XJ-39 nematodes used is 1-2×10 8 IJs / mu.

[0021] Preferably, the amount of Steinernemacarpocapsae XJ-39 nematodes used is 1.5×10 8 IJs / mu.

[0022] Through the above technical solutions, this application achieves the following technical effects:

[0023] The technical solution provided in this application provides a nematode strain, S. carpocapsae XJ-39, that is highly pathogenic and fertile against leek maggot pests and has good environmental adaptability. It also provides an optimally adapted technical solution for the control of highly pathogenic leek maggots in arid and semi-arid regions. The corrected mortality rate against leek maggots at a concentration of 150 IJs / larva was 75.55%; the number of nematodes propagated by live propagation of greater wax moths was 5.24×10 4 IJs / larva and 2.10×10 4 IJs / g; at 38°C, the mortality rate was 74.86% after 5 hours of treatment, while at 10% NaCl concentration, the mortality rate was only 23.64% after 4 hours of treatment; and under 19W UV irradiation, the mortality rate was 43.58% after 4 hours of treatment. In a saturated KCl solution, the mortality rate of S. carpocapsae XJ-39 was 0.79% and 1.64% after 24 and 48 hours, respectively; in a saturated NaCl solution, the mortality rate was also only 0.79% and 11.39% after 24 and 48 hours. Thiamethoxam had the lowest mortality rate against S. carpocapsae XJ-39, with a mortality rate of only 2.11% at a concentration of 3FD, demonstrating good compatibility. In potted plants, the control efficacy of a combination of nematodes and thiamethoxam reached over 80%. Field trials further demonstrated that the combined nematode and thiamethoxam treatment achieved corrected efficacy against leek maggots of 70.25%, 60.24%, and 60.74% at 10, 20, and 30 days after application, respectively, demonstrating both rapid and sustained efficacy. The technical solution provided in this application can further facilitate the healthy, sustainable, and high-quality development of leek cultivation in arid and semi-arid regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Shown is the corrected mortality rate of seven EPNs against the third instar larvae of leek maggots.

[0025] Lowercase letters in the figure indicate the significant difference in the adjusted mortality rate between different nematode strains at the same concentration, and uppercase letters indicate the significant difference in the adjusted mortality rate between different treatment concentrations of the same nematode strain (Tukey, P < 0.05).

[0026] Figure 2 Shown is the resistance graph of seven EPNs at different temperatures.

[0027] Figure A shows the tolerance at 35°C, Figure B shows the tolerance at 38°C, and Figure C shows the tolerance at 40°C.

[0028] Lowercase letters in the figure indicate the significant difference in the adjusted mortality rate between different treatment times for the same nematode strain, and uppercase letters indicate the significant difference in the adjusted mortality rate between different nematode strains at the same treatment time (Tukey, P < 0.05).

[0029] Figure 3 Shown is the tolerance of seven EPNs nematodes to NaCl solutions of different concentrations.

[0030] Figure A shows the tolerance in 5% NaCl solution; Figure B shows the tolerance in 10% NaCl solution; and Figure C shows the tolerance in 15% NaCl solution.

[0031] Lowercase letters in the figure indicate the significant difference in the adjusted mortality rate between different treatment times for the same nematode strain, and uppercase letters indicate the significant difference in the adjusted mortality rate between different nematode strains at the same treatment time (Tukey, P<0.05).

[0032] Figure 4 Shown is a graph showing the resistance of seven EPNs under different UV-B conditions.

[0033] Figure A shows the resistance graph under UV-B-19W; Figure B shows the resistance graph under UV-B-30W.

[0034] In the figure, lowercase letters indicate the significant difference in the adjusted mortality rate between different treatment times for the same nematode strain, and uppercase letters indicate the significant difference in the adjusted mortality rate between different nematode strains at the same treatment time (Tukey, P<0.05).

[0035] Figure 5 Shown is the tolerance graph of seven EPNs under different saturated solution control humidity.

[0036] Figure A shows the tolerance graph under the control humidity of KCl saturated solution; Figure B shows the tolerance graph under the control humidity of NaCl saturated solution; Figure C shows the tolerance graph under the control humidity of KI saturated solution; Figure D shows the tolerance graph under the control humidity of MgCl2 saturated solution;

[0037] The lowercase letters in the figure indicate the significant difference in the adjusted mortality rate among different nematode strains at the same treatment time (Tukey, P<0.05).

[0038] Figure 6 Shown is a graph showing the effects of four pesticides on the survival rate of S. carpocapsae XJ-39.

[0039] Figure A shows thiamethoxam; Figure B shows clothianidin; Figure C shows phoxim; and Figure D shows imidacloprid.

[0040] The lowercase letters in the figure represent the difference in the corrected mortality of S. carpocapsae XJ-39 at the same concentration (Tukey, P < 0.05).

[0041] Figure 7 Shown are the potted control effects of S.carpocapsae XJ-39 on leek maggots at 3 and 7 days.

[0042] In the figure, lowercase letters indicate the significant difference in the adjusted mortality rate between different treatment concentrations at the same treatment time, and uppercase letters indicate the significant difference in the adjusted mortality rate between different treatment times at the same treatment concentration (Tukey, P<0.05). DETAILED DESCRIPTION

[0043] The technical solutions of the present invention are described clearly and completely below with reference to the embodiments. It is obvious that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0044] The reagents used in the present invention are: identification medium (NBTA): NaCl 5g, peptone 10g, beef extract 5g, agar powder 15g, bromothymol blue 0.025g, erythrosine 0.04g, distilled water 1000mL, pH 7±0.2. NA solid and NB liquid medium were purchased from Beijing Aoboxing Biotechnology Co., Ltd. 95% thiamethoxam technical, 98% clothianidin technical, and 95% imidacloprid technical were produced by Shanghai Yuanye Biotechnology Co., Ltd.; 85% phoxim technical was purchased from Shandong Essen Chemical Co., Ltd.; and 70% thiamethoxam water dispersible granules were produced by Shandong United Pesticide Industry Co., Ltd.

[0045] The fifth instar larvae of the greater wax moth (Galleria mellonella) used in this application were raised by the Crop Beneficial Microorganisms Team of the Institute of Microbiology, Xinjiang Academy of Agricultural Sciences.

[0046] The leek maggots used in this application were collected from the leek fields of Xinghuo Village, Urumqi City, Xinjiang (87°26'59.244" E, 44°1'48.563" N), and improved upon the artificial breeding method of Mu Wei et al. After one generation of rearing, third-instar larvae were selected for indoor virulence testing. The entire cultivation process was carried out in a light incubator with environmental conditions set at a temperature of 22°C ± 1°C, a relative humidity of 75% ± 2%, and a continuous dark-light cycle (DD).

[0047] The experimental data in this application were processed, integrated, and calculated using Microsoft Excel 2019, data analysis was performed using DPS Data Processing System 9.5, and graphs were drawn using Graphpad Prism 9.5. In this study, one-way analysis of variance with the Tukey test was used for analysis, and the significance level (P < 0.05) was used for analysis.

[0048] Unless otherwise specified in the following embodiments, the technical means used are conventional means well known to those skilled in the art.

[0049] Example 1: Application of a highly pathogenic nematode, Steinernemacarpocapsae XJ-39, in the control of leek maggots in arid and semi-arid areas

[0050] The present application provides an application of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode for the prevention and control of leek maggots in arid and semi-arid areas.

[0051] The Steinernemacarpocapsae XJ-39 nematode is screened using the following method: different species of nematodes are selected at a nematode concentration of 1000 IJs / mL; 2 mL of the suspension from each treatment is added individually to a 24-well plate, ensuring that only one strain of nematode suspension is contained in each well; the 24-well plate is wrapped and sealed with plastic wrap and placed in an incubator at 35°C, 38°C, and 40°C for heat stress treatment; 0.2 mL of the nematode suspension is removed from each well after 1, 2, 3, 4, 5, and 6 hours, 0.8 mL of distilled water is added to dilute the nematode concentration, and the diluted nematode suspensions are transferred to a 25°C incubator for further incubation for 24 hours; after 24 hours, the survival of the nematodes is examined and counted using a dissecting microscope to screen for heat-resistant Steinernemacarpocapsae XJ-39 nematodes.

[0052] The screening method for Steinernemacarpocapsae XJ-39 nematodes also includes: selecting a vigorous nematode suspension with a concentration of 1000 IJs / mL, and then dispensing the suspension into 1 mL to 2 mL centrifuge tubes; placing the suspension in 5%, 10%, and 15% NaCl solutions, respectively, to determine the salt tolerance of the nematodes under different NaCl concentrations; placing the treated suspension at room temperature of 25°C for 1, 2, 3, and 4 hours, respectively; performing the treatment experiment six times at each time point; and after a set time, observing the death of the nematodes, counting and analyzing the mortality rate, and screening for salt-tolerant Steinernemacarpocapsae XJ-39 nematodes.

[0053] The screening method for Steinernemacarpocapsae XJ-39 nematodes also includes exposing a suspension with a concentration of 1000 IJs / mL to 19W and 30W UV-B radiation simulators at a distance of 20 cm from the radiation source for 1, 2, 3, and 4 hours, respectively. Each irradiation treatment is considered an experimental group, and a nematode suspension that has not been exposed to UV radiation is set up as a control group. The experiment is repeated three times for each treatment condition. After the predetermined irradiation time, 0.2 mL of the nematode suspension is removed from each treatment group and diluted with 0.8 mL of distilled water. The diluted nematode suspension is then incubated in an incubator at 25°C to promote nematode recovery. After the 24-hour recovery and incubation period, the number of live nematodes in each treatment group is counted, and the average survival rate of the nematodes is calculated based on the number of live nematodes. To ensure data accuracy, each experimental treatment is repeated six times. The radiation-resistant Steinernemacarpocapsae XJ-39 nematodes are screened.

[0054] The screening method for Steinernemacarpocapsae XJ-39 nematodes also includes the following steps: approximately 2,000 IJs are transferred to a 55 mm Whatman No. 1 filter paper in a 60 mm Petri dish. Excess water is removed by vacuum filtration in a desiccator (23 cm diameter, 24 cm height). The filter paper containing the nematodes is then placed in a desiccator where saturated solutions of KCl, NaCl, MgCl2, and KI are prepared. After 24 and 48 hours at 25°C, the filter paper is removed and incubated in 5 mL of sterile water for 24 hours. The survival percentage is determined by probing the nematodes with a dissecting needle. Three replicates are performed for each nematode strain, and at least 50 IJs are counted in each sample. To ensure data accuracy, six replicates are performed for each experimental treatment. At 25℃, the control humidity of KCl, NaCl, MgCl2 and KI were made into saturated solutions of 84.24±0.36%, 75.29±0.13%, 32.78±0.16% and 68.86±0.24%, respectively, and the drought-resistant SteinernemacarpocapsaeXJ-39 nematode was screened.

[0055] Furthermore, the application requires the use of Steinernemacarpocapsae XJ-39 nematodes in combination with chemical pesticides such as any one or more of thiamethoxam, clothianidin, phoxim and imidacloprid.

[0056] More preferably, 70% thiamethoxam water dispersible granules are used in the application.

[0057] Furthermore, the amount of Steinernemacarpocapsae XJ-39 nematodes used is 1-2×10 8 IJs / mu.

[0058] Example 2: Screening of highly pathogenic entomopathogenic nematodes of leek maggots

[0059] Seven EPN species from different regions were used as experimental subjects. Four concentrations of nematode suspension were prepared: 30, 50, 100, and 150 IJs / larva. Each concentration served as an independent treatment, replicated three times. Two milliliters of the nematode suspension were evenly added to 9-cm glass Petri dishes lined with double-layer filter paper, while the same volume of sterile water was added to the control. Thirty third-instar larvae were placed in each dish and then placed in an artificial climate chamber set at a temperature of (22 ± 1)°C, a relative humidity of (75 ± 2)%, and a continuous dark photoperiod (DD). After 72 hours, larval mortality was examined and recorded.

[0060] The adjusted mortality rates of seven EPNs (XJ-39, HB-NLK, B5, XJ-88, Y29, YC, and HR-SF) at four concentrations (30, 50, 100, and 150 IJs / larva) are shown in the Appendix. Figure 1 The results showed that the corrected mortality of leek maggots increased with increasing nematode concentration. From 30 to 50 IJs / larva, there was no significant difference in the corrected mortality of nematodes against leek maggots, except for the XJ-39 strain. From 100 to 150 IJs / larva, there was no significant difference in the corrected mortality of nematodes across all strains, including the XJ-39 strain. The 150 IJs / larva treatment had the highest overall mortality, indicating that high nematode concentrations have a stronger pathogenicity against leek maggots. At the same concentration, different strains exhibited significant heterogeneity. At 30, 50, and 100 IJs / larva, the XJ-39, HB-NLK, and B5 treatments had significantly higher corrected mortality rates for leek maggots than the other treatments. At 150 IJs / larva, the XJ-39, HB-NLK, B5, and HR-SF treatments had the highest corrected mortality rates, at 73.33%, 70.00%, 73.33%, and 68.89%, respectively, with no significant differences among the four treatments. At all four concentrations, the YC treatment had the weakest pathogenicity against leek maggots and the lowest corrected mortality rate. At 150 IJs / larva, the corrected mortality rate was only 47.48%. Nematode strains XJ-39, HB-NLK, and B5 demonstrated good control efficacy against leek maggots at both low and high concentrations.

[0061] Example 3: Determination of reproductive capacity of entomopathogenic nematodes

[0062] Using a modified White trap method, mature larvae of the greater wax moth were infested with 100 IJs / larva of nematodes. The infected larvae were weighed, and each experiment was repeated three times. The larvae were then incubated at 25°C. When the infective nematodes emerged from the dead larvae and entered the water, the water containing the nematodes was transferred to a beaker. The nematodes were collected by continuously changing the water and allowing the water to settle. After collection, the total number of nematodes was counted using the dilution method. The number of infective nematodes produced per larva (IJs / larva) and per gram of larvae (IJs / g) was calculated.

[0063] The nematode yields of the seven EPNs propagated by G. mellonella are shown in Table 1. The nematode yields of the XJ-39 treatment group were significantly higher than those of the other six treatment groups, with significant differences. The nematode yields were 5.24×10 4 IJs / larva and 2.10×10 4IJs / g; there was no significant difference among the four treatment groups HB-NLK, B5, Y29 and HR-SF; the nematode yield in the YC treatment group was the lowest, with a yield of only 8.27×10 3 IJs / larva and 3.31×10 3 IJs / g. Thus, it can be seen that among the seven nematode strains, XJ-39 has the strongest reproductive capacity.

[0064] Table 1: In vivo reproductive capacity of seven different nematode species

[0065] Nematode number IJs / g IJs / larva XJ-39 <![CDATA[5.24×10 4a ]]> <![CDATA[2.10×10 4a ]]> HB-NLK <![CDATA[4.87×10 4b ]]> <![CDATA[1.95×10 4b ]]> B5 <![CDATA[3.20×10 4c ]]> <![CDATA[1.28×10 4c ]]> Y29 <![CDATA[4.67×10 4b ]]> <![CDATA[1.87×10 4b <!-- 6 -->]]> YC <![CDATA[8.27×10 3d ]]> <![CDATA[3.31×10 3d ]]> HR-SF <![CDATA[4.61×10 4b ]]> <![CDATA[1.84×10 4b ]]>

[0066] Note: Lowercase letters indicate significant differences in reproductive capacity among different nematode strains (Tukey, P<0.05).

[0067] Example 4: Study on heat stress of entomopathogenic nematodes

[0068] Different types of nematodes were selected, and the nematode concentration was 1000 IJs / mL. 2 mL of the suspension for each treatment was added to a 24-well plate one by one, making sure that there was only one strain of nematode suspension in each well. Wrap the 24-well plate with plastic wrap and seal it, and place it in an incubator at 35°C, 38°C, and 40°C for heat stress treatment. After 1, 2, 3, 4, 5, and 6 hours, 0.2 mL of nematode suspension was taken out from each well, and then 0.8 mL of distilled water was added to dilute the nematode concentration. These diluted nematode suspensions were transferred to a 25°C incubator and continued to be cultured for 24 hours. After 24 hours, the survival of the nematodes was examined and counted using a dissecting microscope to evaluate the lethal effect of high temperature on different strains of nematodes. Six replicates were set up for each treatment.

[0069] The heat resistance study of 7 EPNs using the water bath heating method showed that the mortality rate of nematodes increased with the increase of temperature and time. Figure 2 As shown in the figure. At 35℃, the mortality rates of the seven nematode strains were low at 1 hour and 2 hours. At 3 hours, the mortality rates of the three nematode strains, B5, XJ-88, and HR-SF, exceeded 10%. At 4 hours, the mortality rate of the XJ-88 strain was significantly different from that of the other six strains, reaching 33.10%. At 6 hours, the Y29 strain had the highest mortality rate, at 44.50%. Figure 2As shown in A. At 38°C, the mortality rates of the two strains of XJ-39 were low at 1 hour and 2 hours, both around 5%. The mortality rate of the HR-SF strain was as high as 46.00% at 1 hour. At 3 hours, the mortality rates of the seven strains were significantly higher than those at 1 and 2 hours. All the nematodes of the B5 and YC strains died at 3 hours, all the nematodes of the HR-SF strain died at 4 hours, all the nematodes of the XJ-88 and Y29 strains died at 5 hours, and some nematodes of the XJ-39 strain still survived at 6 hours (see attached). Figure 2 As shown in B. Under 40℃ conditions, after 1 hour of treatment, the mortality rates of B5, XJ-88, YC and HR-SF strains reached 100%, the mortality rates of HB-NLK and Y29 strains were 46.44% and 23.70%, and the mortality rate of XJ-39 strain was only 10.52%. After 2 hours, the mortality rate of XJ-39 strain was also the lowest, at 13.67%. The mortality rate of HB-NLK strain increased rapidly after 2 hours, increasing by 43.22% compared with 1 hour. The Y29 strain still had nematodes surviving after 4 hours as shown in the attached figure. Figure 2 As shown in C. Compared with the other six strains, the XJ-39 strain had stronger heat resistance under the three treatment temperatures.

[0070] Example 5: Study on NaCl stress of entomopathogenic nematodes

[0071] Select a vigorous nematode suspension with a concentration of 1000 IJs / mL and then distribute it into 1mL to 2mL centrifuge tubes. These suspensions were placed in 5%, 10% and 15% NaCl solutions to determine the salt tolerance of nematodes under different NaCl concentrations. The treated suspensions were placed at room temperature of 25°C and treated for 1, 2, 3, and 4 hours respectively. The treatment at each time point was repeated 6 times. After the set time, the death of nematodes was observed, and the mortality rate was counted and analyzed to evaluate the salt tolerance of nematodes under different NaCl concentrations.

[0072] The NaCl resistance of 7 EPNs was compared using the diluted salt concentration method. The results are shown in the attached Figure 3 As shown. The overall trend is that with the increase of NaCl concentration and time, the mortality rate of nematodes is getting higher and higher. When the NaCl concentration is 5%, after 1 hour of treatment, the mortality rate of the other 6 strains except Y29 is low, and the mortality rate is less than 5%; after 2 hours, the mortality rate of HB-NLK strain increased significantly, reaching 19.33%; after 3 hours, the mortality rate of nematodes in YC strain was significantly different from that of the other 6 strains; after 4 hours, the mortality rate of YC strain was 92.22%, and the mortality rate of other strains did not exceed 45%. Among them, the mortality rate of XJ-39 strain was the lowest, with a mortality rate of only 2.03%. See the attached Figure 3A. When the NaCl concentration was 10%, the mortality rate of the XJ-39 strain was relatively low at 1.77% and 2.59% at 1 hour and 2 hours, respectively. However, the mortality rates of the XJ-88 and Y29 strains reached 48.08% and 48.07% at 1 hour, respectively, showing a significant difference. At 3 hours, the mortality rate of the XJ-39 strain increased rapidly, reaching 20.16%. At 4 hours, all YC strains died. (See Appendix) Figure 3 As shown in Figure B. When the NaCl concentration was 15%, the mortality rate increased dramatically in 1 hour compared with the 5% and 10% NaCl concentrations. The mortality rate of the XJ-39 strain reached 18.54%, the mortality rate of the HB-NLK strain reached 57.21%, and the mortality rate of the HR-SF strain reached 45.25%. The XJ-88 and YC strains all died. At 2 hours, except for the XJ-39 and B5 strains, which still had some survival, the other strains all died. At 3 hours, the XJ-39 and B5 strains also all died. See the attached figure. Figure 3 As shown in C.

[0073] Example 6: Study on UV stress of entomopathogenic nematodes

[0074] The EPNs suspension (concentration of 1000 IJs / mL) was exposed to 19W and 30W UV-B radiation simulators at a distance of 20 cm from the radiation source for 1, 2, 3, and 4 hours of irradiation experiments, respectively. Each irradiation treatment was considered an experimental group, and a nematode suspension that was not exposed to UV radiation was set up as a control group. The experiment was repeated three times for each treatment condition. After reaching the predetermined irradiation time, 0.2mL of nematode suspension was taken from each treatment group and diluted with 0.8mL of distilled water. Subsequently, the diluted nematode suspension was placed in an incubator at 25°C to promote the recovery of the nematodes. After the 24-hour recovery culture process, the number of live nematodes in each treatment group was counted, and the average survival rate of the nematodes was calculated based on this. To ensure the accuracy of the data, each experimental treatment was repeated 6 times.

[0075] The UV tolerance of seven EPNs was studied using two wattages (19W and 30W) of UV-B light. The results are shown in the attached Figure 4As shown. With the increase of ultraviolet intensity and the growth of time, the mortality rate of nematodes is getting higher and higher. Ultraviolet light has a significant effect on nematodes. Under UV-B-19W, when the treatment time is 1 hour, except for the HR-SF strain, the mortality rate reached 23.03%. The mortality rate of the other 6 strains did not exceed 10%; when the treatment time was 2 hours, the mortality rate of the 7 strains increased significantly compared with that of 1 hour, among which the Y29 strain was as high as 99.25%, and the HR-SF strain was as high as 88.42%; the Y29 strain died within 3 hours; when the treatment time was 5 hours, except for the XJ-39 and B5 strains, the other strains all died; when the treatment time was 6 hours, all the nematodes of the strains died, see the attached Figure 4 A. When UV-B is at 30W, at 1 hour, the mortality rates of ALL and XJ-39 strains were relatively low, at 2.32% and 8.27%, respectively. The mortality rates of HB-NLK, B5, Y29, and HR-SF strains were around 40%. At 2 hours, all Y29 and HR-SF strains died. At 3 hours, all strains except XJ-39 died. At 5 hours, all nematodes of XJ-39 strain died. See attached. Figure 4 As shown in Figure B, the XJ-39 strain showed significantly better tolerance to UV light than the other six strains. While the nematodes could withstand short bursts of UV light, prolonged exposure to high-intensity UV light resulted in their death.

[0076] Example 7: Study on Desiccation Stress of Entomopathogenic Nematodes

[0077] Approximately 2,000 IJs were transferred to filter paper (55 mm, Whatman No. 1) in a 60 mm Petri dish. Excess water was removed by vacuum filtration in a desiccator (23 cm diameter, 24 cm height). The filter paper containing the nematodes was then placed in a desiccator where saturated solutions of KCl, NaCl, MgCl₂, and KI were prepared. After 24 and 48 h at 25°C, the filter paper was removed and incubated in 5 mL of sterile water for 24 h. Percent survival was determined by probing the nematodes with a dissecting needle. Three replicates were performed for each nematode strain, and at least 50 IJs were counted in each sample. Six replicates were performed for each treatment to ensure data accuracy. The control humidity of the saturated solutions of KCl, NaCl, MgCl₂, and KI at 25°C was 84.24 ± 0.36%, 75.29 ± 0.13%, 32.78 ± 0.16%, and 68.86 ± 0.24%, respectively.

[0078] The study on the tolerance of 7 EPNs to different humidity conditions showed that the mortality rate of nematodes increased with the decrease of humidity and the increase of time. In the saturated solution of KI and MgCl2, all 7 nematodes died within 24 hours. Figure 5 C. See attached Figure 5As shown in D; in KCl saturated solution, the mortality rate of HR-SF nematode strain exceeded 60% at 24 hours and all died at 48 hours. The B5 and XJ-88 nematode strains also all died at 48 hours. XJ-39 had the lowest mortality rate, with mortality rates of 0.79% and 1.64% at 24 hours and 48 hours, respectively, which was significantly lower than that of other nematode strains. Figure 5 As shown in A; in NaCl saturated solution, except for the XJ-39 strain, the mortality of the other six nematode strains was higher than 70% at 24 hours, while the mortality of the XJ-39 strain was only 0.79%. The mortality of the XJ-39 strain at 48 hours was also only 11.39%, which was significantly lower than that of other nematode strains. Figure 5 As shown in B.

[0079] Example 8: Effect of Chemical Pesticides on the Survival Rate of S.carpocapsae XJ-39

[0080] Following the method of diluting pesticides (Wu Haibin et al.), the concentrations of four pesticides were set according to the recommended field dose (FD). 19 mL of each pesticide was added to a Petri dish and mixed with 1 mL of the nematode suspension. A nematode suspension prepared with sterile distilled water served as the control group. Three replicates were performed for each treatment. The mixed Petri dishes were placed at (25 ± 1)°C. After 72 hours, 1 mL of the mixed suspension was randomly sampled and observed under a stereomicroscope. The number of surviving nematodes was recorded. The count was repeated six times to calculate the nematode survival rate.

[0081] The following criteria were used to determine the response of entomopathogenic nematodes to pesticides: (1) Death: The body is stiff or curled up, inactive, and unresponsive to needle pricks; (2) Sublethal: The body is curled up, and there are spastic or convulsive activities due to the paralyzing effect of the pesticide, and the nematodes have no response or very slow response to needle pricks; (3) Unaffected by the pesticide: The body is stretched or motionless, similar to the control nematodes, and the motionless nematodes react quickly after being touched by the probe.

[0082] The effects of four chemical pesticides (thiamethoxam, clothianidin, phoxim and imidacloprid) on S. carpocapsae XJ-39 were determined. None of the four chemical pesticides were sublethal to S. carpocapsae XJ-39. The results are shown in the attached Figure 6 Under FD (field use concentration), except for clothianidin (S. carpocapsae XJ-39 mortality rate 6.87%), the effects of the other three pesticides on S. carpocapsae XJ-39 were small (less than 0.5%), see Appendix Figure 6 As shown in A; at 1.5FD, the mortality rates of clothianidin and phoxim to S. carpocapsae XJ-39 exceeded 50%, which were 59.61% and 53.13% respectively. Figure 6B. See attached Figure 6 C; at 1.5FD, the mortality rates of clothianidin and phoxim to S.carpocapsaeXJ-39 exceeded 75%, which were 77.82% and 86.9% respectively. Figure 6 B. See attached Figure 6 C; Under 2FD, the mortality rates of thiamethoxam and imidacloprid against S.carpocapsaeXJ-39 were very low, 0.16% and 0.41% respectively. Figure 6 A. See attached Figure 6 D; Under 3FD, the mortality rate of thiamethoxam to S.carpocapsaeXJ-39 is only 2.11%, see Appendix Figure 6 As shown in A; Under 5FD, the lethality of imidacloprid to S.carpocapsaeXJ-39 increased significantly to 42.85%, see Appendix Figure 6 D. In summary, thiamethoxam had the least effect on S. carpocapsae XJ-39. Thiamethoxam was selected for combination with S. carpocapsae XJ-39 for potted and field control experiments.

[0083] Example 9: Effectiveness of S.carpocapsae XJ-39 in combination with pesticides against leek maggots in indoor potted plants

[0084] Leek seedlings were transplanted into pots (20 cm × 20 cm × 15 cm). When the leeks reached a height of 15 cm, weaker seedlings were removed, retaining 15 seedlings. One hundred third-instar leek maggot larvae of equal activity were placed in the topsoil, close to the leek pseudostems. One day later, six different root irrigation treatments were applied. Treatments included 100 million, 150 million, 200 million, and 150 million maggots / mu, along with a 0.5 field concentration of thiamethoxam. 70% thiamethoxam water-dispersible granules served as a positive control, and a water treatment served as a control. Four replicates were set up for each treatment to assess mortality within each group.

[0085] The control effect of S.carpocapsaeXJ-39 and thiamethoxam on leek maggots in potted plants is shown in the attached Figure 7 As shown in the data, at 3 days, in the combination treatment group, although the control effect was different compared with that of thiamethoxam alone, the mortality rate of leek maggots was as high as 74.00% and 88.07% at 3 days and 7 days, and it had a good control effect compared with the group treated with nematodes alone; in the treatment of S.carpocapsaeXJ-39 alone, the mortality rate of leek maggots increased with the increase of S.carpocapsaeXJ-39 concentration; at 7 days, there was also a similar trend, and the mortality rate of leek maggots increased with the passage of time.

[0086] Example 10: Field control effect of S.carpocapsae XJ-39 and pesticides in combination on leek maggots

[0087] The chive field in Xinghuo Village, Liushihu, Xinshi District, Urumqi was used as the field control effect experimental site (87°27'6.116" east longitude, 44°1'37.981" north latitude). The experimental site was completely randomly divided into 24 plots, each with an area of 40m 2 . Before applying the drug, the native nematodes in the plot were first investigated by the trapping method to check whether the native EPNs were present in the plot, and the number of leek maggots in each plot was investigated. The survey method was based on the methods of Zhang et al. and Ma et al. and slightly modified. In each plot, the number of leek maggots was counted by a five-point sampling method, and the area of each sampling point was 20 cm × 20 cm. Under the premise of ensuring that the plants were not damaged, the soil was gently turned to a depth of 15 cm using a shovel, and then the number of larvae around the roots and bulbs of the leek was recorded in detail. Six different treatment groups were set up in the experiment, including 100 million, 150 million, 200 million IJs / mu, 150 million IJs / mu and 0.5 times the field concentration of thiamethoxam, as well as drug control and clear water control. Each treatment had 4 replicates. In addition, in order to prevent geographical location and environmental factors from interfering with the experimental results, a 1-meter-wide isolation zone was set between each plot. According to the calculation formula of the pesticide field efficacy test guideline GB / T17980.67-2004.

[0088] Pest population reduction rate (%) = ((number of live insects before control - number of live insects after control) / number of live insects before control) × 100

[0089] Corrected control effect (%) = ((pest population reduction rate in the control area - pest population reduction rate in the control area) /

[0090] (100-insective population reduction rate in control area) × 100

[0091] As can be seen from Table 2, in the combined treatment group, the corrected control efficacy against leek maggots at 10d, 20d and 30d was 70.25%, 60.24% and 60.74%, respectively. Compared with the group treated with nematodes alone, it had a good control effect. At the same time, compared with the group treated with thiamethoxam alone, the corrected control efficacy at 20d and 30d was significantly different. On the 10th day after application, S.carpocapsaeXJ-392 billion IJs / mu and thiamethoxam had a good control effect on leek maggots, with corrected control efficacy of 60.09% and 74.06%, respectively. The corrected control efficacy of S.carpocapsaeXJ-39100 million IJs / mu was the lowest at 38.64%, indicating a poor effect. On the 20th day after application, the corrected efficacy of S. carpocapsae XJ-39 against leek maggots reached 41.67%, 56.85%, 60.87%, and 45.75% for treatments with 100 million IJs / mu, 150 million IJs / mu, and 200 million IJs / mu, respectively, and thiamethoxam. The efficacy of thiamethoxam decreased by approximately 30% compared to the corrected efficacy at 10 days. On the 30th day after application, the corrected efficacy of thiamethoxam was only 26.84%, while the corrected efficacy of S. carpocapsae XJ-39 at 100 million IJs / mu, 150 million IJs / mu, and 200 million IJs / mu was 49.48%, 63.77%, and 63.02%, respectively. The efficacy was stable and long-lasting.

[0092] Table 2: Field control efficacy of different concentrations of S. carpocapsae XJ-39

[0093]

[0094] Note: Lowercase letters indicate significant differences in the insect population reduction rate and corrected control efficacy between different treatment concentrations at the same treatment time; uppercase letters indicate significant differences in the insect population reduction rate and corrected control efficacy between different treatment times at the same treatment concentration (Tukey, P<0.05).

[0095] The technical solution provided in this application has screened out a Xinjiang native entomopathogenic nematode strain, S. carpocapsae XJ-39, which has high pathogenicity against leek maggot pests, high fecundity, and good environmental adaptability. At a concentration of 150 IJs / larva, the corrected mortality rate against leek maggots reached 75.55%; the number of nematodes propagated by live propagation of greater wax moths was 5.24×10 4 IJs / larva and 2.10×10 4IJs / g; at 38°C, the mortality rate was 74.86% after 5 hours of treatment, while at 10% NaCl concentration, the mortality rate was only 23.64% after 4 hours of treatment; and under 19W UV irradiation, the mortality rate was 43.58% after 4 hours of treatment. In a saturated KCl solution, the mortality rate of S. carpocapsae XJ-39 was 0.79% and 1.64% after 24 hours and 48 hours, respectively; in a saturated NaCl solution, the mortality rate was also only 0.79% and 11.39% after 24 hours and 48 hours, respectively. Thiamethoxam had the lowest mortality rate against S. carpocapsae XJ-39, with a mortality rate of only 2.11% at 3FD concentration, demonstrating good compatibility. In potted plants, the control efficacy of the combined nematode and thiamethoxam treatment reached over 80%. Field trials further showed that the corrected control efficacy of the mixed nematode and thiamethoxam treatment group against leek maggots was 70.25%, 60.24% and 60.74% at 10, 20 and 30 days after application, respectively, showing both rapid and long-lasting effects.

[0096] The above embodiments are only for illustrating the technical concept and features of the present invention in a specific scenario. Its purpose is to enable people who need this technology to understand the content of the present invention and implement it. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of a highly pathogenic leek maggot Steinernemacarpocapsae XJ-39 nematode in the prevention and control of highly pathogenic leek maggots in arid and semi-arid areas.

2. The application of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode in the prevention and treatment of leek maggots in arid and semi-arid areas as claimed in claim 1, characterized in that The Steinernemacarpocapsae XJ-39 nematode is screened using the following method: different species of nematodes are selected at a nematode concentration of 1000 IJs / mL; 2 mL of the suspension from each treatment is added individually to a 24-well plate, ensuring that only one strain of nematode suspension is contained in each well; the 24-well plate is wrapped and sealed with plastic wrap and placed in an incubator at 35°C, 38°C, and 40°C for heat stress treatment; 0.2 mL of the nematode suspension is removed from each well after 1, 2, 3, 4, 5, and 6 hours, 0.8 mL of distilled water is added to dilute the nematode concentration, and the diluted nematode suspensions are transferred to a 25°C incubator for further incubation for 24 hours; after 24 hours, the survival of the nematodes is examined and counted using a dissecting microscope to screen for heat-resistant Steinernemacarpocapsae XJ-39 nematodes.

3. The application of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode in the prevention and treatment of leek maggots in arid and semi-arid areas as claimed in claim 2, characterized in that The screening method for Steinernemacarpocapsae XJ-39 nematodes also includes: selecting a vigorous nematode suspension with a concentration of 1000 IJs / mL, and then dispensing it into 1mL to 2mL centrifuge tubes; placing the suspension in 5%, 10% and 15% NaCl solutions, respectively, to measure the salt tolerance of the nematodes under different NaCl concentrations; placing the treated suspension at room temperature of 25°C for 1, 2, 3 and 4 hours, respectively; performing the treatment experiment at each time point six times; and after a set time, observing the death of the nematodes, counting and analyzing the mortality rate, and screening for salt-tolerant Steinernemacarpocapsae XJ-39 nematodes.

4. The application of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode in the prevention and treatment of leek maggots in arid and semi-arid areas as claimed in claim 2, characterized in that The screening method for Steinernemacarpocapsae XJ-39 nematodes also includes: exposing a suspension with a concentration of 1000 IJs / mL to 19W and 30W UV-B radiation simulators at a distance of 20 cm from the radiation source for 1, 2, 3, and 4 hours, respectively; each irradiation treatment is considered an experimental group, and a nematode suspension that has not been exposed to ultraviolet light is set up as a control group; the experiment is repeated three times for each treatment condition; after reaching the predetermined irradiation time, 0.2 mL of the nematode suspension is removed from each treatment group and diluted with 0.8 mL of distilled water; then, the diluted nematode suspension is placed in an incubator at 25°C for incubation to promote the recovery of the nematodes; after the 24-hour recovery and incubation process, the number of live nematodes in each treatment group is counted, and the average survival rate of the nematodes is calculated based on the count; to ensure the accuracy of the data, each experimental treatment is repeated six times; and radiation-resistant Steinernemacarpocapsae XJ-39 nematodes are screened.

5. The use of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode of leek maggots in the prevention and treatment of leek maggots in arid and semi-arid areas as claimed in claim 2, characterized in that: The screening method for Steinernemacarpocapsae XJ-39 nematodes further comprises: in a 60 mm petri dish, approximately 2,000 IJs are transferred onto filter paper (55 mm, Whatman 1); excess water was removed from a desiccator (23 cm in diameter and 24 cm in height) by vacuum filtration, and the filter paper containing the nematodes was then placed in the desiccator. Saturated solutions of KCl, NaCl, MgCl2, and KI were prepared in the desiccator, respectively; after being placed at 25°C for 24 and 48 h, the filter paper was removed and incubated in 5 mL of sterile water for 24 h. The survival percentage of the nematodes was determined by probing the nematodes with a dissecting needle. Three replicates were performed for each strain of nematodes, and at least 50 IJs were counted in each sample. To ensure data accuracy, the counting was repeated six times for each experimental treatment; the control humidity of saturated solutions of KCl, NaCl, MgCl2, and KI at 25°C was 84.24±0.36%, 75.29±0.13%, 32.78±0.16%, and 68.86±0.24%, respectively, to obtain the desiccation-resistant Steinernemacarpocapsae XJ-39 nematodes.

6. The use of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode of leek maggots in the prevention and treatment of leek maggots in arid and semi-arid areas as claimed in claim 2, characterized in that: During the high temperature resistance screening process, the treatment was performed at 40°C for 1 hour; during the salt resistance screening process, the treatment was performed at a NaCl concentration of 15% for 3 hours; during the high temperature resistance screening process, the treatment was performed at UV-B-30W for 3 hours; during the drought stress resistance screening process, the treatment was performed at 25°C with a saturated solution of KCl or NaCl for 48 hours.

7. The use of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode of leek maggots in arid and semi-arid areas as claimed in claim 1, characterized in that: The application requires the use of Steinernemacarpocapsae XJ-39 nematodes in combination with chemical pesticides such as any one or more of thiamethoxam, clothianidin, phoxim and imidacloprid.

8. The use of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode of leek maggots in the prevention and treatment of leek maggots in arid and semi-arid areas as claimed in claim 7, characterized in that: The application uses 70% thiamethoxam water dispersible granules.

9. The use of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode of any one of claims 1 to 8 in the control of leek maggots in arid and semi-arid areas, characterized in that: The amount of Steinernemacarpocapsae XJ-39 nematodes used is 1-2×10 8 IJs / mu.

10. Use of the highly pathogenic Steinernemacarpocapsae XJ-39 nematode of any one of claims 1 to 8 for controlling leek maggots in arid and semi-arid areas, characterized in that: The amount of Steinernemacarpocapsae XJ-39 nematodes used is 1.5×10 8 IJs / mu.

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