Artificial breeding method of cotesia cunea gather and application of method in prevention and control of fall webworms

Abstract

The invention discloses a method for artificially breeding white moth gathering cotesia sinensis and applying the white moth gathering cotesia sinensis to biological control of fall webworm. According to the method, the key factors such as the optimal age, the optimal bee inoculation proportion and the optimal temperature of the hyphantria cunea larvae which are hosts for artificially breeding the cotesia cunea are determined, the parasitism rate and the offspring number of the cotesia cunea are effectively increased, the breeding period is shortened, and the bee breeding efficiency is improved. Meanwhile, an optimal scheme for prolonging the shelf life of the cotesia sinensis gather through low-temperature storage of the cocoons or newly-emerged adults is also defined. The new natural enemy product breeding application technology provided by the invention is specially applied to biological prevention and control of the fall webworms in the larval stage, not only enriches the types of existing fall webworm natural enemy products, but also provides a more comprehensive solution for biological prevention and control of the fall webworms, can reduce the excessive use of chemical pesticides, and is beneficial to environmental protection. And a powerful technical guarantee is provided for balance and health of an ecological system.

Description

Technical Field

[0001] The present invention relates to the technical field of biological control of pests, and particularly relates to an artificial breeding method of the natural enemy insect Cotesia congregata, and its application in controlling Hyphantria cunea. Background Art

[0002] Hyphantria cunea Hyphantria cunea belongs to the family Erebidae of the order Lepidoptera, and is a major forestry quarantine pest in China. This insect is native to North America and invaded Dandong, Liaoning in 1979. Now it has occurred and caused damage in 596 county-level administrative regions of 13 provinces in China. As an important part of the integrated pest management, the utilization of natural enemy insects is the most important link in biological control. According to statistics, there are 128 predatory natural enemies and 76 parasitic natural enemies of Hyphantria cunea in its native North America. The rich and diverse natural enemy groups are the important reasons why Hyphantria cunea has not caused major disasters in its native area. Since the end of the 20th century, a detailed investigation and research on the natural enemy groups of Hyphantria cunea in China have been carried out, and a large number of natural enemy resources that can parasitize different instars of Hyphantria cunea have been discovered, and the dominant natural enemy of the pupal stage of Hyphantria cunea, Chouioia cunea, has been successfully developed. Chouioia cunea This provides strong technical support for the green prevention and control of Hyphantria cunea. However, at the same time, the natural enemy insects that can be used for the biological control of Hyphantria cunea have always been only Chouioia cunea, and the natural enemy products targeting other instars of Hyphantria cunea have always been lacking. The larvae of Hyphantria cunea need to feed on a large amount of plant leaves, which is the main period of causing damage and also the critical period of prevention and control. Due to the lack of natural enemy products for controlling larvae, the control of the larval stage of Hyphantria cunea still largely depends on chemical pesticides, resulting in environmental pollution. Developing a natural enemy product targeting the larvae of Hyphantria cunea is of great significance for constructing a green prevention and control technology system for the whole growth period of Hyphantria cunea, improving the comprehensive control effect and maintaining ecological security.

[0003] Cotesia congregata Cotesia gregalis is a parasitic wasp that parasitizes the larvae of Hyphantria cunea. In recent years, in the research on investigating the richness of the natural enemy groups of Hyphantria cunea, it has been found that this parasitic wasp is the species with the highest dominance in the natural enemy complex of the larval stage of Hyphantria cunea, and has a strong control effect on the population of Hyphantria cunea. It is distributed in many places in North China and Northeast China, showing strong adaptability. At present, there are only relevant literatures on the description of new species regarding Cotesia congregata, and it is unknown how to achieve artificial breeding and how to apply it to the biological control of Hyphantria cunea. As a natural enemy insect with good utilization potential, solving its artificial breeding technology and clarifying the key links in the application are the basis for commercializing it and applying it to forestry production. Based on this, we have innovated the breeding method of Cotesia congregata and its application in controlling Hyphantria cunea. Summary of the Invention

[0004] The object of the present invention is to provide a method for artificially breeding Cotesia congregata, as well as a method for applying the artificially bred natural enemies in the forest to control Hyphantria cunea.

[0005] Therefore, the present invention provides a method for artificially breeding Cotesia congregata, which comprises the following steps: (1) Using 4th to 7th instar larvae of Hyphantria cunea as hosts and raising them in a culture dish; (2) Introducing mated female Cotesia congregata into the culture dish with hosts and culturing them in an artificial climate chamber, wherein the quantity ratio of Cotesia congregata to host Hyphantria cunea is 1:5 to 5:1; (3) After the Cotesia congregata completes the parasitism behavior, continue to raise the Hyphantria cunea larvae in the same artificial climate chamber and regularly add feed. Wait until the young wasps develop into maturity, escape from the host body and spin cocoons or wait until they emerge; (4) Collecting the cocoons or emerged adult wasps of Cotesia congregata and storing them in an artificial climate chamber for forest application.

[0006] In a specific embodiment, in the step (1), the most suitable age of the Hyphantria cunea larvae for breeding wasps is 4th or 5th instar.

[0007] In a specific embodiment, in the step (1), for facilitating large-scale inoculation and breeding, the specification of the culture dish is 90 mm×15 mm, and the density of Hyphantria cunea larvae is 25 heads / dish.

[0008] In a specific embodiment, in the step (2), the quantity ratio of Cotesia congregata to host Hyphantria cunea is 3:5 to 1:1, preferably 3:5.

[0009] In a specific embodiment, in the step (2), the conditions of the artificial climate chamber are 20 - 30°C, RH = 60%, photoperiod L:D = 16:8 h, and the temperature is preferably 25°C.

[0010] In a specific embodiment, in the step (4), when storing the parasitoid cocoons, the cocoon age is 1 - 5 days old, preferably 3 days old; the conditions of the artificial climate chamber are temperature 4 - 12°C, relative humidity RH = 70%, photoperiod L:D = 16:8 h, the temperature is preferably 10°C, and the storage time does not exceed 30 days.

[0011] In a specific embodiment, in the step (4), for storing the adult wasps, it is necessary to collect the newly emerged individuals; the conditions of the artificial climate chamber are temperature 5 - 25°C, relative humidity RH = 70%, photoperiod L:D = 16:8 h, the temperature is preferably 15°C, and the storage time does not exceed 25 days.

[0012] The present invention also provides an application method of Cotesia congregata in controlling Hyphantria cunea in the forest, which is obtained by breeding according to the above method. The method includes the following steps: (1) After detecting the web curtains of Hyphantria cunea in the forest, investigate the number of web curtains of Hyphantria cunea, and estimate the number of larvae in the web curtains according to the size of the web curtains to obtain the population density of Hyphantria cunea in the forest; (2) According to the population density obtained from the investigation, release the adult Cotesia congregata or cocoons in the forest, and investigate the parasitism of Hyphantria cunea larvae by Cotesia congregata 7 to 10 days later to evaluate the biological control effect.

[0013] In a specific embodiment, in step (1), the random sampling method is adopted to investigate the number of web curtains of Hyphantria cunea and the population density in the web curtains in the forest.

[0014] In a specific embodiment, in step (2), Cotesia congregata needs to be released at the initial stage when the larvae of Hyphantria cunea break through the web curtains; when releasing adult females, the release ratio is 3:1 to 1:3 of wasps to insects, preferably 1:1; when releasing cocoons, the release ratio is 4:1 to 1:4 of wasps to insects, preferably 2:1.

[0015] The present invention determines the parasitic preference of Cotesia congregata for larvae of different instars of Hyphantria cunea, clarifies the most suitable instar of the host for mass rearing of the wasps and the optimal control period for releasing the parasitoids, improves the efficiency of artificial mass rearing of the wasps, and enhances the control effect in field applications. By studying the optimal wasp-host ratio, it is found that the parasitism rate when the wasp-larva ratio is 3:5 is not significantly different from that when the wasp-larva ratio is 4:5 or 5:5, but is significantly higher than that when the wasp-larva ratio is 2:5 or 1:5; while when the wasp-larva ratio is 4:5 or 5:5, no more offspring parasitoids are obtained compared to the treatment with a wasp-larva ratio of 3:5, indicating that excessive investment in female wasps does not significantly improve the breeding efficiency of natural enemies. The above findings can ensure a high parasitism rate and the number of offspring while minimizing the input quantity of female wasps. At the same time, the present invention also determines the optimal rearing conditions. Under the conditions of 25 °C, RH = 60%, and a photoperiod of L:D = 16:8 h, Cotesia congregata only needs 15 days to complete one generation, significantly shortening the mass rearing cycle and improving the mass rearing efficiency. More importantly, according to the storage method of Cotesia congregata proposed by the present invention, the shelf life of natural enemies is significantly extended, which is beneficial to achieving inundative release of natural enemies at one time during control. The present invention also clarifies the optimal release period and the optimal release ratio of Cotesia congregata in field applications for controlling Hyphantria cunea, which not only most effectively reduces the damage loss of Hyphantria cunea but also maximally saves the usage amount of natural enemies, thereby reducing the cost of biological control. A new technology for breeding and applying natural enemy products provided by the present invention is specifically applied to the biological control of the larval stage of Hyphantria cunea, which not only enriches the existing types of natural enemy products for Hyphantria cunea but also provides a more comprehensive solution for the biological control of the entire growth period of Hyphantria cunea, can reduce the overuse of chemical pesticides, and provides a strong technical guarantee for the balance and health of the ecosystem. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Raise the larvae of Hyphantria cunea in a petri dish.

[0017] Figure 2 Mate the male and female adult Cotesia congregata.

[0018] Figure 3 After Cotesia congregata escapes from the body surface of the larvae of Hyphantria cunea, it spins a cocoon. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings:

[0020] Example 1:

[0021] (1)Parallel control setting: American white moth larvae of different instars were selected as hosts for bee propagation, including Treatment 1: 3rd instar; Treatment 2: 4th instar; Treatment 3: 5th instar; Treatment 4: 6th instar; Treatment 5: 7th instar. Five American white moth larvae of the same instar were placed in a petri dish (90 mm × 15 mm). As an example, Figure 1 shows the method of rearing American white moth larvae in a petri dish.

[0022] (2)One mated female adult wasp without parasitic experience was introduced into each petri dish and cultured in an artificial climate chamber at 25°C, photoperiod L:D = 16:8 h, and RH = 60%, which was recorded as one replication. Each instar treatment was replicated 30 times. As an example, Figure 2 shows the mating of male and female adult Apanteles glomeratus of the American white moth.

[0023] (3)The female wasp was removed 24 hours after introducing the wasp, and the artificial diet of the American white moth was replaced regularly. Wait for the parasitoid to develop until it escapes from the host body and spins a cocoon to pupate.

[0024] (4)After the offspring wasps escaped from the host body and spun cocoons, the parasitism rate of Apanteles glomeratus on hosts of different instars was counted. Successful parasitism was recorded when a parasitoid escaped from the host body. As an example, Figure 3 shows the parasitoid escaping from the host body and then spinning a cocoon to pupate.

[0025] (5)Count the parasitism rate of female wasps on hosts of different instars, the number of offspring of the parasitoid, and the developmental duration. The results are shown in Table 1: Table 1 Parasitism rate, developmental duration and number of offspring of Apanteles glomeratus when parasitizing larvae of different instars

[0026] It can be seen from the results in Table 1 that there are significant differences in the parasitism rate of Apanteles glomeratus on American white moth larvae of different instars, showing that as the host instar increases, the parasitism rate first increases and then decreases (F 4, 145 = 45.254, P < 0.001). When Apanteles glomeratus parasitizes 4th or 5th instar larvae, the average parasitism rate can reach more than 70%, but the average parasitism rate on 3rd instar larvae is only 15.33%. The reason for this phenomenon may be the difference in the size of the insect body. The 3rd instar larvae of the American white moth are smaller in size, and the ovipositor of the parasitoid cannot accurately pierce the insect body; however, the host body of the 6th - 7th instars is too large, and its ability to resist the attack of the parasitoid is stronger, resulting in a decrease in the parasitism rate because the female wasp cannot fully subdue the host. At the same time, the host instar also significantly affects the number of offspring of the parasitoid (F 4, 123= 13.930, P<0.001). Using the 4th or 5th instar larvae of Hyphantria cunea as the host for wasp propagation, more than 60 offspring wasps can be obtained by introducing a single mated female wasp, which is the optimal scheme among all treatments. In addition, the host instar also has a certain impact on the developmental duration of the parasitoid wasp. After parasitizing the 3rd or 4th instar host, the egg-larval stage of the parasitoid wasp is significantly prolonged (F 4, 123 = 201.078, P<0.001), and after parasitizing the 3rd instar host, the cocoon stage of the parasitoid wasp is also significantly prolonged (F 4, 123 = 11.658, P<0.001). The above results indicate that when using the 4th and 5th instar larvae of Hyphantria cunea as hosts, female wasps can exert the strongest parasitism and breed more offspring wasps; when the host is the 5th instar larva, the offspring wasps develop faster, indicating a shorter propagation cycle, suggesting that the 5th instar larvae of Hyphantria cunea are most suitable for breeding Cotesia congregata.

[0027] Example 2: (1) Place 5 5th instar larvae of Hyphantria cunea in a culture dish (90 mm × 15 mm) and provide artificial feed.

[0028] (2) Parallel test settings: Introduce 1 mated female Cotesia congregata wasp into each culture dish and culture it in an artificial climate chamber under the following temperature conditions, including Treatment 1: 15°C; Treatment 2: 20°C; Treatment 3: 25°C; Treatment 4: 30°C; Treatment 5: 35°C. Photoperiod L:D = 16:8 h, relative humidity RH = 60%. Each culture dish is regarded as one replicate, and each temperature treatment is replicated 30 times.

[0029] (3) Remove the female wasp 24 hours after introducing the wasp, regularly replace the artificial feed of Hyphantria cunea, and wait for the parasitoid wasp to develop until it escapes from the host body and spins a cocoon to pupate.

[0030] (4) After the offspring wasps escape from the host body and spin cocoons, count the parasitism rate of Cotesia congregata on hosts of different instars. Successful parasitism is recorded when a parasitoid wasp escapes from the host body.

[0031] (5) Count the parasitism rate, the number of offspring wasps, the developmental duration, and the emergence rate of female wasps at different temperatures. The results are shown in Table 2: Table 2 Parasitism rate, developmental duration, number of offspring wasps, and emergence rate of Cotesia congregata at different temperatures

[0032] As can be seen from the results in Table 2, there are significant differences in the parasitism rate of Cotesia congregata at different temperatures. As the temperature increases, the parasitism rate first increases and then decreases (F 4, 145= 33.210, P<0.001). Under Treatments 2 and 3, namely at 20°C and 25°C, the parasitism rate was significantly higher than that of other groups; while under Treatment 1, the activity of the parasitoid wasps was low and the parasitism behavior was weak; under Treatments 4 and 5, continuous high temperature easily caused female wasps to die due to heat stress, resulting in a decrease in the parasitism rate. At the same time, under low-temperature and high-temperature stresses, the growth and development of the offspring parasitoid wasps were inhibited. At the temperatures of Treatments 2 and 3, the eggs and larvae of the parasitoid wasps could grow and develop well in the host body, resulting in a significantly higher number of offspring of the parasitoid wasps developed under this condition than other treatments (F 4, 129 = 32.354, P<0.001). In addition, there were also significant differences in the developmental duration of the parasitoid wasps at different temperatures. Specifically, with the increase in temperature, both the egg-larval stage and the cocoon stage were significantly shortened (egg-larval stage: F 4, 129 = 1373.399, P<0.001; pupal stage: F 3, 104 = 2651.558, P<0.001). When the temperature was between 15 and 20°C, the developmental rate of the parasitoid wasps slowed down significantly, resulting in a significant extension of the reproductive cycle of Cotesia congregata. At 35°C, Cotesia congregata failed to emerge due to long-term high-temperature stress, while the emergence rate of the parasitoid wasps at 20 - 30°C was significantly higher than that at 15°C (F 3, 96 = 355.524, P<0.001). In summary, when the temperature was 25°C, Cotesia congregata had a high parasitism rate, a large number of offspring, and a short reproductive cycle, and could rapidly reproduce a large number of parasitoid wasps in a short period, which was the most suitable temperature for wasp propagation.

[0033] Example 3: (1) 25 fifth-instar larvae of Hyphantria cunea were introduced into a culture dish (90 mm × 15 mm), and artificial feed was provided.

[0034] (2) Parallel test settings: The mated female Cotesia congregata wasps were introduced into each culture dish according to the following wasp-to-host ratio (number of female wasps: number of hosts), including Treatment 1 with a ratio of 1:5; Treatment 2 with a ratio of 2:5; Treatment 3 with a ratio of 3:5; Treatment 4 with a ratio of 4:5; Treatment 5 with a ratio of 5:5. After introducing the wasps, they were placed in an artificial climate chamber at 25°C, L:D = 16:8 h, RH = 60% for cultivation. Each culture dish was recorded as one replicate, and each inoculation ratio treatment was repeated 10 times.

[0035] (3) The female wasps were removed 24 h after introducing the wasps, and the hosts continued to be reared in the artificial climate chamber with artificial feed until the parasitoid wasps developed to emerge from the host body and form cocoons and pupate.

[0036] After the offspring wasps emerged from the host larvae and spun cocoons, the parasitism rates of Cotesia congregata on hosts of different instars were counted, and successful parasitism was recorded when a parasitoid emerged from the host larva.

[0037] (5)The parasitism rates, the number of offspring and the sex ratio of female wasps were counted under different inoculation ratios. The results are shown in Table 3: Table 3 Parasitism rates, the number of offspring and the proportion of females of Cotesia congregata under different inoculation ratios

[0038] As can be seen from Table 3, there were significant differences in the parasitism rates of Cotesia congregata under different inoculation ratios. Specifically, as the number of female wasps increased, the average parasitism rate gradually increased (F 4, 45 = 75.066, P<0.001). Under the conditions of Treatment 2, Treatment 2, and Treatment 3, that is, when the inoculation ratio was 1:5 - 3:5, as the wasp-to-host ratio increased, the growth rate of the parasitism rate of the parasitoid was obvious. However, under the conditions of the inoculation ratio of 3:5 - 5:5, the growth rate gradually slowed down. This result indicates that when there are too many female wasps in a limited space, it may cause competition among female wasps for hosts, which is instead not conducive to fully exerting the parasitism ability of female wasps. At the same time, there were also significant differences in the number of offspring of the parasitoid under different inoculation ratio treatments. The number of offspring in Treatment 3 and Treatment 4 was significantly higher than that of other treatments (F 4, 45 = 283.148, P<0.001), and it showed that as the number of inoculated female wasps increased, the number of offspring first increased and then decreased. Among them, when the inoculation ratio was 5:5, although the parasitism rate of the parasitoid was relatively high, the number of offspring was significantly lower than that when the inoculation ratio was 3:5 - 4:5, indicating that the parasitoid did not exert the optimal reproductive efficiency at high density. In addition, different wasp inoculation densities also had a significant impact on the proportion of female offspring of the parasitoid. As the number of female wasps increased, the female ratio of the offspring gradually decreased (F 4, 45 = 63.427, P<0.001). Under the conditions of the inoculation ratio of 4:5 - 5:5, the female ratio of the offspring was significantly lower than that of other treatments. Generally speaking, when the wasp-to-host ratio was 3:5, its parasitism rate and the number of offspring were relatively high, and there was no significant difference from Treatment 4 and Treatment 5 (the wasp-to-host ratio was 4:5 or 5:5), but the proportion of female offspring of the parasitoid was significantly higher than that of the latter. The above results indicate that when artificially rearing wasps, an inoculation ratio of 3:5 can save the input of inoculated female wasps and at the same time obtain more female offspring, which is the best inoculation ratio for artificial wasp rearing.

[0039] Example 4: (1)Fifteen 5th instar larvae of Hyphantria cunea were introduced into a culture dish (90 mm × 15 mm), and artificial feed was provided.

[0040] (2) Introduce 9 mated female Cotesia congregata parasitoids that have parasitized Hyphantria cunea larvae, and culture them in an artificial climate chamber at 25 °C, with a light:dark cycle of L:D = 16:8 h and a relative humidity (RH) of 60%. Wait until the parasitoids develop and emerge from the host larvae to form cocoons and pupate.

[0041] (3) Parallel experiment setup: Collect 3-day-old cocoons in petri dishes (90 mm × 15 mm) and place them in the following artificial climate chambers: Treatment 1: 4 °C; Treatment 2: 6 °C; Treatment 3: 8 °C; Treatment 4: 10 °C; Treatment 5: 12 °C. The photoperiod and relative humidity for each temperature treatment are both L:D = 16:8 h and RH = 70%. Each treatment contains 30 cocoons, which is recorded as one replicate, and 10 replicates are set for each treatment.

[0042] (4) After 30 days of low-temperature storage, transfer each treatment to an artificial climate chamber at 25 °C, with a light:dark cycle of L:D = 16:8 h and a relative humidity of 60%, and count the emergence success rate of the cocoons stored at different temperatures. The results are shown in Table 4: Table 4 Adult emergence rate of cocoons after storage at different temperatures

[0043] As can be seen from Table 4, there are significant differences in the emergence rates of Cotesia congregata cocoons stored under different low-temperature conditions (F 4, 45 = 86.720, P < 0.001). The emergence rates of the parasitoids stored under Treatment 4 and Treatment 5 conditions are significantly higher than those of other treatments, being 81.43% and 86.21% respectively. This result indicates that storing parasitoid cocoons in an environment of 10 - 12 °C is beneficial for extending the shelf life of Cotesia congregata.

[0044] Example 5: (1) Introduce 15 fifth-instar larvae of Hyphantria cunea into a petri dish (90 mm × 15 mm) and provide artificial feed.

[0045] (2) Introduce 9 mated female Cotesia congregata parasitoids that have parasitized Hyphantria cunea larvae, and culture them in an artificial climate chamber at 25 °C, with a light:dark cycle of L:D = 16:8 h and a relative humidity of 60%, until the parasitoids develop and emerge.

[0046] (3) Parallel experiment setup: Collect newly emerged female parasitoids in plastic jars (diameter 8.5 cm, height 8.5 cm) and place them in the following artificial climate chambers: Treatment 1: 5 °C; Treatment 2: 10 °C; Treatment 3: 15 °C; Treatment 4: 20 °C; Treatment 5: 25 °C. The photoperiod and relative humidity for each temperature treatment are both L:D = 16:8 h and RH = 70%. Each treatment contains 100 female parasitoids. Record the survival status of the female parasitoids daily until all female parasitoids die. Count the average lifespan of the female parasitoids under different storage conditions with each parasitoid recorded as one replicate. The results are shown in Table 5: Table 5 Longevity of female wasps under different storage temperature conditions

[0047] As can be seen from Table 5, when the storage conditions are 15°C, L:D = 16:8 h, and RH = 70%, the average lifespan of Cotesia congregata is significantly higher than that of other treatments (F 4, 495 = 964.242, P<0.001). When the temperature is 5°C, the average lifespan of female wasps is significantly lower than that of other temperatures, indicating that too low temperature will affect the lifespan of female wasps. This may be related to the decrease in the metabolic rate of parasitoids and the slowdown of physiological activities caused by too low temperature. The above results show that when the storage temperature is 15°C, the adult lifespan of Cotesia congregata is the longest, which is the optimal condition for preserving female adult Cotesia congregata. Storing female wasps at this temperature is beneficial to preserving the wasp species and extending the shelf life of natural enemies.

[0048] Example 6: (1) Cotesia congregata was reproduced according to the breeding methods and conditions determined in the previous experiments.

[0049] (2) During the occurrence period of the 4th instar larvae of Hyphantria cunea, 5 independent forestlands with relatively consistent damage levels of Hyphantria cunea were selected. The number of webbing and larval density of Hyphantria cunea in the forest were investigated by the method of walking inspection.

[0050] (3) Parallel test settings: According to the number of Hyphantria cunea larvae in each plot, female Cotesia congregata were released at the following wasp-larva ratios, including Treatment 1: wasp-larva ratio = 3:1; Treatment 2: wasp-larva ratio = 2:1; Treatment 3: wasp-larva ratio = 1:1; Treatment 4: wasp-larva ratio = 1:2; Treatment 5: wasp-larva ratio = 1:3.

[0051] (4) Seven days after releasing the wasps, 5 damaged trees were randomly selected from each plot, and 250 Hyphantria cunea larvae were collected from each tree and brought back indoors. The larvae were fed with artificial feed in petri dishes (150 mm × 15 mm), and the feeding density was 50 larvae / dish. They were cultured in an artificial climate chamber at 25°C, L:D = 16:8 h, and RH = 60% until the parasitoids developed and emerged from the host larvae to form cocoons and pupate. Taking each tree as a replicate, the parasitism rate and the number of Cotesia congregata that could be reared from the parasitized Hyphantria cunea under different wasp release ratios were counted. The results are shown in Table 6: Table 6 Control effects of female Cotesia congregata at different release ratios

[0052] As can be seen from Table 6, there are significant differences in the parasitic effects of Cotesia congregata on the larvae of Hyphantria cunea under different bee - insect ratios. Specifically, the parasitism rate and the number of offspring under Treatment 1, Treatment 2, and Treatment 3 are significantly higher than those of other treatments (F 4, 20 = 24.868, P<0.001; F 4, 20 = 93.698, P<0.001). When the bee - insect ratio is 3:1 to 1:1, there is no significant difference in the average parasitism rate and the number of offspring; when the bee - insect ratio is 1:2, the average parasitism rate and the number of offspring show an obvious downward trend; when the bee - insect ratio is 1:3, the average parasitism rate drops to 18.48%, and the number of offspring obtained at this time is nearly 2 times less than that when the bee - insect ratio is 3:1. In summary, under Treatment 3, that is, when releasing parasitoid wasps at a bee - insect ratio of 1:1, while maintaining a relatively high parasitism rate and the number of offspring of parasitoid wasps, the input quantity of female wasps can be saved. On the premise of meeting the prevention and control effect and the sustainable prevention and control strategy, the control cost can be minimized. Therefore, when releasing female Cotesia congregata to control Hyphantria cunea in the forest, the release ratio of bee - insect ratio = 1:1 can be preferentially selected.

[0053] Example 7: (1) According to the breeding methods and conditions determined in the previous experiments, Cotesia congregata was reproduced, and the unhatched cocoons were used as the objects for release in the forest.

[0054] (2) During the occurrence period of the 4th - instar larvae of Hyphantria cunea, 7 independent forest lands with relatively consistent damage levels of Hyphantria cunea were selected. The line - transect survey method was used to investigate the number of webbing nests and the larval density of Hyphantria cunea in the forest.

[0055] (3) Parallel experiment settings: According to the number of Hyphantria cunea larvae in each plot, cocoons of Cotesia congregata were released at the following bee - insect ratios, including Treatment 1: bee - insect ratio = 4:1; Treatment 2: bee - insect ratio = 3:1; Treatment 3: bee - insect ratio = 2:1; Treatment 4: bee - insect ratio = 1:1; Treatment 5: bee - insect ratio = 1:2; Treatment 6: bee - insect ratio = 1:3; Treatment 7: bee - insect ratio = 1:4.

[0056] (4) Ten days after releasing the wasps, 5 damaged trees were randomly selected in each plot, and 250 larvae of Hyphantria cunea were collected from each tree and brought back indoors. Artificial feed was provided in petri dishes (150 mm×15 mm) for indoor feeding, and the feeding density was 50 larvae / dish. They were cultured in an artificial climate chamber at 25°C, L:D = 16:8 h, RH = 60% until the parasitoid wasps developed to emerge from the host larvae and spin cocoons to pupate. Taking each tree as a replicate, the parasitism rate under different release ratios and the number of Cotesia congregata that could be reared from the parasitized Hyphantria cunea were counted. The results are shown in Table 7: Table 7 Control effects of Cotesia congregata cocoons under different release ratios

[0057] As can be seen from Table 7, the parasitism rate and the number of offspring wasps in Treatments 1, 2, and 3 with higher wasp-to-insect ratios were significantly higher than those in other treatments (parasitism rate: F 6, 28 = 143.636, P<0.001; number of offspring wasps: F 6, 28 = 399.494, P<0.001). When the wasp-to-insect ratio was 2:1 to 4:1, there was no significant difference in the average parasitism rate and the number of offspring natural enemies; when the wasp-to-insect ratio was 1:1 to 1:4, the average parasitism rate and the number of offspring wasps showed an obvious downward trend. When the wasp-to-insect ratio was 1:4, the parasitism rate decreased to 9.36%, and the number of offspring natural enemies was also nearly 5 times less than that in Treatment 1. To sum up, when using the cocoons of Cotesia congregata to release natural enemies, releasing natural enemies in the forest at a wasp-to-insect ratio of 2:1 can achieve a higher control effect while incurring less cost, which is the optimal release ratio for controlling Hyphantria cunea by releasing the cocoons of Cotesia congregata in the wild.

Claims

1. A method for artificial breeding of Coleoptera cuneae, characterized in that: The following steps are involved: (1) Using 4th to 7th instar larvae of the American white moth as hosts, raising them in a petri dish (e.g., in a 90 mm × 15 mm petri dish at a density of 15 to 25 per dish); (2) The mated female wasps of the gypsophila were placed in a culture dish with a host and cultured in an artificial climate chamber, wherein the ratio of the number of the gypsophila to the host, the gypsy moth, was 1:5 to 5:1; (3) After the parasitism of the gypsy moth wasp was completed, the gypsy moth larvae in the culture dish were kept in the same artificial climate chamber and fed regularly until the larvae matured, escaped from the host and formed a cocoon, or emerged from the nest; (4) Collect the cocoons or emerged adult bees of the white moth aggregation disk cocoon wasp and store them in an artificial climate chamber for future use in the forest.

2. The breeding method according to claim 1, characterized in that: In step (1), the most suitable age of the gypsy moth larvae used for bee breeding is 4 or 5 instar.

3. The breeding method according to claim 1, characterized in that: In the step (2), the ratio of the number of the coleopteran wasp to the host American white moth is 3:5 to 1:1, preferably 3:

5.

4. The breeding method according to claim 1, characterized in that In step (2), the conditions of the artificial climate box are temperature 20-30°C, RH=60%, photoperiod L:D=16:8 h, and the temperature is preferably 25°C.

5. The breeding method according to claim 1, characterized in that: In the step (4), the age of the parasitic wasp cocoons during storage is 1 to 5 days, preferably 3 days; the conditions of the artificial climate box are a temperature of 4 to 12°C, a relative humidity RH = 70%, a photoperiod L:D = 16:8 h, a temperature of preferably 10°C, and the storage time does not exceed 30 days.

6. The breeding method according to claim 1, characterized in that: In the step (4), the storage of adult bees requires the collection of individuals that have just emerged; the conditions of the artificial climate box are a temperature of 5 to 25°C, a relative humidity RH = 70%, a photoperiod L:D = 16:8 h, a temperature of preferably 15°C, and a storage time of no more than 25 days.

7. Use of the Cotesia cunea obtained by the breeding method according to any one of claims 1 to 6 in controlling the gypsy moth.

8. The use according to claim 7, characterized in that The following steps are involved: (1) After the gypsy moth webs are found in the forest, the number of gypsy moth webs is investigated and the number of larvae inside the webs is estimated based on the size of the webs to obtain the population density of the gypsy moth in the forest; (2) Based on the insect population density obtained from the survey, adult bees or cocoons of the gypsy moth were released into the forest. After 7 to 10 days, the parasitism of the gypsy moth larvae by the gypsy moth was investigated to evaluate the biological control effect.

9. The use according to claim 8, characterized in that: In the step (1), a random sampling method is used to investigate the number of screens of the gypsy moth in the forest and the insect population density in the screens.

10. The use according to claim 8, characterized in that: In the step (2), the white moth aggregation disk cocoon wasp needs to be released at the early stage of the American white moth larvae breaking through the web; when releasing the female adult bees, the release ratio is 3:1~1:3, preferably 1:1; when releasing the cocoons, the release ratio is 4:1~1:4, preferably 2:1.

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