Trichogramma gradient release method giving consideration to diffusion and retention

Abstract

The invention relates to the technical field of agricultural and forestry biological prevention and control, in particular to a trichogramma gradient release method giving consideration to diffusion and retention, and solves the problems of uneven release, short retention time, low parasitic efficiency and the like of existing trichogramma. The method comprises the following steps: preparing three degradable gradient slow-release carriers with different slow-release speeds, dividing a control area into a center area, a transition area and a peripheral area, configuring a composite auxiliary retention system containing pest sex pheromones and a micro-humidity regulation and control module, accurately matching the carriers with the areas, releasing the carriers in 2-3 stages in the egg stage of pests according to the release amount of 5: 3: 2, and adopting an unmanned aerial vehicle to assist in releasing, the humidity and the attractant are continuously regulated and controlled after release. According to the method, ordered gradient diffusion of the trichogramma is achieved, the residence time of the trichogramma in a target area is prolonged to 5-7 days, the worm egg parasitism rate is greatly increased, and the carrier is degradable, free of residues, easy and convenient to operate, wide in applicability and suitable for green prevention and control of lepidoptera pests of various crops.

Description

Technical Field

[0001] This invention relates to the field of biological control technology in agriculture and forestry, specifically a gradient release method for Trichogramma wasps that combines diffusion and retention. Background Technology

[0002] Trichogramma wasps are parasitic natural enemy insects that specifically parasitize the eggs of lepidopteran pests. By blocking egg hatching, they inhibit the growth of pest populations at the source. They have advantages such as being pollution-free, residue-free, safe for natural enemies, and having significant control effects, and have been widely used in green pest control in agriculture and forestry. With the promotion of green agriculture concepts, the application scope of Trichogramma wasp biological control technology is constantly expanding. However, existing Trichogramma wasp release methods still have many shortcomings, leading to unstable control effects and room for improvement in parasitism efficiency, making it difficult to meet the needs of large-scale, precise control.

[0003] Currently, existing methods for releasing Trichogramma wasps mainly include manual scattering, drone-based flooding release, and egg card suspension release. Manual scattering is labor-intensive, inefficient, and uneven, easily resulting in localized areas of excessively high or insufficient concentrations, failing to achieve a reasonable spatial distribution. While drone-based flooding release is more efficient, it is a uniform release method that does not consider the distribution differences of pests in the field, leading to insufficient wasps in high-density areas and excessive waste in low-density areas. Furthermore, the released wasps lack effective retention mechanisms and are easily affected by wind, humidity, and other factors, rapidly dispersing and being lost, failing to sustain their parasitic effect in the target area and significantly reducing the control effect.

[0004] Existing technologies have seen some improvements in the release carriers for Trichogramma wasps, such as using cardboard folds to create wasp cards or combining water hyacinths as support carriers. However, these carriers are mostly single-structured and lack gradient slow-release capabilities. The Trichogramma wasps are still released in a single emergence, failing to achieve phased, gradient diffusion and making it difficult to balance diffusion range and residence time. Furthermore, existing release methods rely on relatively simple auxiliary retention mechanisms, often limited to simple carrier shielding without incorporating biological attraction and environmental control techniques. This results in short residence times for the wasps, typically spreading out of the target control area in large numbers within 1-2 days after emergence. This mismatch between the peak hatching period of pest eggs and the peak parasitism period of the wasps further reduces parasitism efficiency.

[0005] Furthermore, current methods for releasing Trichogramma wasps are mostly fixed-time, one-time releases, without phased control based on the dynamic changes in the pest's life cycle. Since the insect egg stage typically lasts several days, some released wasps, after emergence, will be unable to find a parasitic target before a large number of eggs have hatched, resulting in wasp resource waste. Others will emerge after the peak hatching period of the insect eggs, failing to exert their parasitic effect in time, thus affecting control efficacy. Simultaneously, current release methods do not regulate post-release environmental conditions. The emergence and survival rates of Trichogramma wasps are significantly affected by environmental humidity; when the humidity is too low, the emergence rate drops significantly, further impacting control effectiveness.

[0006] Therefore, developing a method for releasing Trichogramma wasps that can achieve gradient diffusion, extend the residence time in the target area, accurately match the occurrence period of pests, and improve parasitism efficiency, and solve the problems of uneven diffusion, short residence time, and unstable control effect in existing technologies, has become an urgent technical challenge in the field of Trichogramma wasp biological control technology. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing Trichogramma release methods, such as uneven diffusion, short residence time in the target area, low parasitism efficiency, unstable control effect, and waste of Trichogramma resources. This invention provides a gradient release method for Trichogramma that balances diffusion and residence. Through the synergistic effect of gradient slow-release carriers, gradient region division, composite auxiliary residence system, and phased release regulation, it achieves orderly gradient diffusion and continuous stable residence of Trichogramma in the target control area, accurately matching the insect egg stage, improving parasitism efficiency and control effect, reducing release costs, and meeting the needs of large-scale, precise, and green pest control in agriculture and forestry.

[0008] The technical solution adopted by this invention to solve its technical problem is: a gradient release method for Trichogramma wasps that takes into account both diffusion and retention, comprising the following steps: (1) Prepare a gradient sustained-release carrier, wherein the gradient sustained-release carrier includes at least three biodegradable carriers with different sustained-release rates, wherein the biodegradable carrier has a cavity for accommodating Trichogramma eggs or pupae, and the carrier surface has pores. The porosity of the pores is adjusted according to the sustained-release rate, wherein the porosity of the high sustained-release rate carrier is lower than that of the medium sustained-release rate carrier, and the porosity of the medium sustained-release rate carrier is lower than that of the low sustained-release rate carrier. (2) Set up a gradient release area and divide the target control area into a central area, a transition area and an outer area. The central area is the high-density occurrence area of ​​pests, the transition area is the medium-density occurrence area of ​​pests, and the outer area is the low-density occurrence area or potential occurrence area of ​​pests. (3) Configure a composite auxiliary retention system, add insect sex pheromone attractant into the containment cavity of the gradient slow-release carrier, and set a micro-humidity control module on the outside of the carrier. The micro-humidity control module is used to stably control the humidity of the environment around the carrier at 55-75%. (4) Determine the timing and amount of gradient release. Based on the prediction of the occurrence of the target pest, release gradient slow-release carriers in 2-3 stages from the early to the middle stage of the pest's egg stage. The release amount in the central area is greater than that in the transition area, and the release amount in the transition area is greater than that in the outer area. The carrier with high slow-release rate corresponds to the central area, the carrier with medium slow-release rate corresponds to the transition area, and the carrier with low slow-release rate corresponds to the outer area. (5) Post-release regulation: Regularly check the working status of the micro-humidity regulation module, replenish the attractant in time, and ensure that the humidity around the carrier is stable until all Trichogramma bees emerge and spread to all parts of the target area.

[0009] Specifically, the material of the biodegradable carrier is selected from one or more of polylactic acid, starch-based biodegradable materials, and cellulose-based biodegradable materials.

[0010] Specifically, the sustained-release period of the high-speed carrier is 7-10 days, the sustained-release period of the medium-speed carrier is 4-6 days, and the sustained-release period of the low-speed carrier is 1-3 days.

[0011] Specifically, the insect sex pheromone attractant is selected from one or more of the following: beet armyworm sex pheromone, sugar beet armyworm sex pheromone, and corn borer sex pheromone, and the amount added is 0.1-0.5 mg per gram of carrier.

[0012] Specifically, the micro-humidity control module includes a moisturizing cotton and a slow-release hydrating capsule. The moisturizing cotton is wrapped around the outside of the carrier, and the slow-release hydrating capsule is embedded inside the moisturizing cotton for continuous moisture release.

[0013] Specifically, the area ratio of the central area, transition area, and outer area is 1:2-3:3-4, and the release ratio is 5:3:2.

[0014] Specifically, the release timing is as follows: the first stage is the early stage of the insect's egg stage, with 40-50% of the total release volume; the second stage is the middle stage of the egg stage, with 30-35% of the total release volume; and the third stage is the middle and late stages of the egg stage, with 15-20% of the total release volume.

[0015] Specifically, the containment cavity of the gradient sustained-release carrier also contains a Trichogramma eclosion promoter, which is a mixture of B vitamins and glucose, and the amount added is 0.2-0.8 mg per gram of carrier.

[0016] Specifically, drones are used for delivery. The drones fly 5-15 meters above the top of the target crop, and the flight speed is adjusted according to the area, with the central area flying slower than the transition and outer areas.

[0017] Specifically, after release, check the micro-humidity control module once a day. When the humidity is below 55%, replenish the slow-release hydration capsules to ensure stable humidity.

[0018] The beneficial effects of this invention are: 1. Achieving gradient diffusion of Trichogramma wasps solves the problem of uneven release in existing technologies: By preparing gradient slow-release carriers with different slow-release rates and combining them with the division of gradient release areas, Trichogramma wasps diffuse in an orderly manner from the central area to the transition and peripheral areas. The concentration of Trichogramma wasps in the central area is high and the residence time is long, while the Trichogramma wasps in the peripheral area can diffuse rapidly, achieving full coverage of the target area and avoiding the problem of excessively high or insufficient local concentrations, thus improving the rationality of the spatial distribution of Trichogramma wasps.

[0019] 2. Extending the residence time of Trichogramma wasps in the target area and improving parasitism efficiency: Through the configuration of the composite auxiliary residence system, the insect sex pheromone attractant can attract Trichogramma wasps to be active near the target area, and the micro-humidity control module can provide a suitable living environment for Trichogramma wasps, improving the survival rate and parasitism. The two work together to extend the residence time of Trichogramma wasps in the target area to 5-7 days, which is significantly improved compared to 1-2 days in the existing technology, ensuring that the peak period of Trichogramma wasp emergence and the peak period of insect egg hatching are accurately matched.

[0020] 3. Phased release regulation to reduce Trichogramma wasp resource waste: By combining the dynamic changes in the insect egg stage, carriers with different slow release rates are released in stages, so that the emergence process of Trichogramma wasps is synchronized with the hatching process of insect eggs, avoiding the waste of Trichogramma wasp resources caused by a one-time release and improving the utilization rate of Trichogramma wasps.

[0021] 4. Environmentally friendly and pollution-free, with wide applicability: The gradient slow-release carrier is made of biodegradable materials, capable of natural degradation and causing no environmental pollution; the composite auxiliary retention system uses biological attractants and physical moisturizing methods, leaving no chemical residues and conforming to the concept of green agriculture. Furthermore, this method can be adjusted according to different pest species, crop types, and planting scales, making it suitable for the control of lepidopteran pests on various crops such as corn, rice, cotton, and vegetables, demonstrating broad applicability.

[0022] 5. Simple operation and low cost: The use of drones for delivery reduces labor intensity and improves release efficiency; the preparation process of the gradient sustained-release carrier is simple, the raw materials are readily available, and the cost is low; post-release regulation is simple, requiring no complex equipment or technology, making it easy to promote and apply on a large scale. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Figure 1A flowchart of the gradient release method for Trichogramma wasps that combines diffusion and retention provided by the present invention; Figure 2 This is a schematic diagram of the gradient release region division in this invention; Figure 3 This is a schematic diagram of the composite auxiliary retention system of the present invention. Detailed Implementation

[0025] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0026] like Figure 1-3 As shown, the gradient release method for Trichogramma wasps that balances diffusion and retention, as described in this invention, includes the following steps: S1. Preparation of Gradient Slow-Release Carriers: At least three biodegradable carriers with different slow-release rates were prepared: a high-speed slow-release carrier, a medium-speed slow-release carrier, and a low-speed slow-release carrier. The biodegradable carriers were made of polylactic acid, starch-based biodegradable materials, or cellulose-based biodegradable materials, exhibiting good biocompatibility and biodegradability, thus avoiding environmental pollution. The carriers contained cavities to accommodate Trichogramma wasp eggs or pupae. The size of the cavities was adjusted according to the number of Trichogramma wasps being raised, ensuring sufficient space for the wasps during emergence. The carrier surface had pores with porosity adjusted according to the slow-release rate. The high-speed slow-release carrier had lower porosity to slow down the emergence rate of the Trichogramma wasps, achieving continuous release; the medium-speed slow-release carrier had moderate porosity to achieve a medium-speed emergence and release; and the low-speed slow-release carrier had higher porosity to achieve rapid emergence and release, thus creating a gradient slow-release effect. During the preparation process, the sustained-release period of the three carriers can be precisely controlled by adjusting the mixing ratio of materials, molding pressure, and the number of pores. The sustained-release period of the high-slow-release carrier is 7-10 days, that of the medium-slow-release carrier is 4-6 days, and that of the low-slow-release carrier is 1-3 days. Simultaneously, a small amount of Trichogramma wasp emergence promoter, a mixture of B vitamins and glucose, is added to the containment cavity to promote the emergence of Trichogramma wasp eggs or pupae and increase the emergence rate.

[0027] S2. Setting of Gradient Release Zones: Conduct on-site investigations of the target control area and divide the target area into a central zone, a transition zone, and an outer zone based on the pest density and distribution range. The central zone is a high-density pest area with a large number of insect eggs and severe damage, requiring a greater number of Trichogramma wasps to remain there. The transition zone is a medium-density pest area, serving as a transition zone between the central and outer zones, requiring an appropriate amount of Trichogramma wasps to balance dispersal and retention. The outer zone is a low-density or potential pest area, primarily requiring rapid Trichogramma wasp dispersal for preventative purposes. The area ratio of the central, transition, and outer zones is controlled at 1:2-3:3-4 to ensure that the distribution of Trichogramma wasps in each area matches the pest density.

[0028] S3. Configuration of the composite auxiliary retention system: To prolong the residence time of Trichogramma wasps in the target area, a pest sex pheromone attractant is added to the containment cavity of the gradient slow-release carrier. The attractant is selected from one or more of the sex pheromones of the beet armyworm, the beet armyworm, and the corn borer. The appropriate attractant is selected according to the species of the target pest, and the addition amount is 0.1-0.5 mg per gram of carrier. Through the attraction of the pheromone, the Trichogramma wasps can move around near the target area after emergence, reducing dispersal and loss. At the same time, a micro-humidity control module is set on the outside of the carrier. The micro-humidity control module includes a moisturizing cotton and a slow-release water-replenishing capsule. The moisturizing cotton wraps around the outside of the carrier to play a moisturizing role, and the slow-release water-replenishing capsule is embedded in the moisturizing cotton to continuously release moisture, so as to stably control the humidity of the environment around the carrier at 55-75%. This humidity range is most suitable for the survival and activity of Trichogramma wasps, which can improve the survival rate and parasitic activity of Trichogramma wasps and further prolong the residence time.

[0029] S4. Determination of the timing and amount of gradient release: Based on the predicted occurrence of the target pest and the emergence cycle of Trichogramma wasps, gradient slow-release carriers are released in 2-3 stages from the early to mid-stage of the pest's egg stage. The first stage is the early egg stage, releasing 40-50% of the total amount, mainly high-speed slow-release carriers and some medium-speed slow-release carriers, concentrated in the central and transitional zones to ensure sufficient Trichogramma wasps for parasitism when the pest eggs begin to hatch. The second stage is the mid-egg stage, releasing 30-35% of the total amount, mainly medium-speed slow-release carriers and some low-speed slow-release carriers, placed in the transition and peripheral zones to achieve gradient diffusion of Trichogramma wasps. The third stage is the late mid-egg stage, releasing 15-20% of the total amount, mainly low-speed slow-release carriers, placed in the peripheral zones to further expand the diffusion range and prevent pest spread. The release ratio for each zone is central zone: transition zone: peripheral zone = 5:3:2, ensuring sufficient Trichogramma wasps remain in the central zone and sufficient Trichogramma wasps in the peripheral zones for diffusion prevention. During release, drones can be used to assist in the delivery. The drones should fly 5-15 meters above the top of the target crop, with a slower flight speed in the central area to ensure even delivery. The flight speed in the transition and outer areas can be appropriately increased to improve delivery efficiency.

[0030] S5. Post-release management: After release, check the working status of the micro-humidity control module daily. When the ambient humidity around the carrier is below 55%, replenish the slow-release hydration capsules promptly to ensure the humidity remains stable within a suitable range. Simultaneously, regularly check the carrier's emergence. If the attractant effect weakens, replenish the attractant promptly to ensure the Trichogramma wasps are continuously attracted and reduce dispersal loss. Continue this process until all Trichogramma wasps have emerged and dispersed to all parts of the target area, completing the entire release process. Example 1

[0031] This embodiment is applied to the control of corn borers in cornfields. The target control area is 100 mu (approximately 6.7 hectares). The corn borer is the main pest to be controlled. According to the field survey, the corn borer is unevenly distributed in the field. The central area (high density of pests) is 20 mu (approximately 1.3 hectares), the transition area (medium density of pests) is 30 mu (approximately 2 hectares), and the outer area (low density of pests) is 50 mu (approximately 3.3 hectares). The area ratio of the central area, the transition area, and the outer area is 1:1.5:2.5. This ratio was adjusted to 1:2:3 to meet the requirements (slightly adjusted to adapt to the actual field distribution).

[0032] 1. Preparation of Gradient-Release Carriers: Three biodegradable carriers with different release rates were prepared: a high-release carrier, a medium-release carrier, and a low-release carrier. The high-release carrier was made of polylactic acid (PLA). The preparation process was as follows: PLA particles were heated and melted, a small amount of starch was added as a pore conditioner, and after uniform mixing, the mixture was molded into a cylindrical carrier with a diameter of 2 cm and a height of 3 cm. An internal cavity with a diameter of 1 cm and a height of 2 cm was provided. The carrier surface had 5 pores with a diameter of 0.1 cm, a porosity of 10%, and a release period of 8 days. The medium-release carrier was made by mixing PLA and starch-based biodegradable materials in a 1:1 ratio. The molding process was the same as that for the high-release carrier. The carrier surface had 8 pores, a porosity of 20%, and a release period of 5 days. The low-release carrier is made of starch-based biodegradable material using the same molding process. The carrier surface has 12 permeable pores with a porosity of 30%, and a release period of 2 days. A Trichogramma wasp emergence promoter was added to the containment cavity of all three carriers at a dosage of 0.5 mg per gram of carrier. This emergence promoter was a mixture of vitamin B2 and glucose in a 1:2 ratio. Cultured Trichogramma wasp pupae (emergence rate ≥95%) were placed into the containment cavity, with each carrier holding 50 pupae. The carrier opening was then sealed with a biodegradable film to ensure normal emergence of the pupae and prevent moisture loss.

[0033] 2. Setting up gradient release zones: Based on the field distribution of corn borers, delineate a central zone, a transition zone, and an outer zone. The central zone, covering 20 mu (approximately 1.3 hectares), is the area with a corn borer egg density ≥ 50 eggs / 100 plants, mainly concentrated in the middle of the field; the transition zone, covering 30 mu (approximately 2 hectares), is the area with a corn borer egg density of 20-50 eggs / 100 plants, surrounding the central zone; the outer zone, covering 50 mu (approximately 3.3 hectares), is the area with a corn borer egg density < 20 eggs / 100 plants, located outside the transition zone, encompassing the edge of the entire target control area. Clearly marked boundaries for each zone facilitate precise drone deployment.

[0034] 3. Configuration of the composite assisted retention system: Corn borer pheromones were selected as the attractant, with an addition amount of 0.3 mg per gram of carrier. The attractant was evenly applied to the inner wall of the containment cavity to ensure that the Trichogramma wasps could smell the pheromone after emergence. The micro-humidity control module consists of 0.5 cm thick moisturizing cotton and slow-release hydration capsules. The moisturizing cotton wraps around the carrier, and the slow-release hydration capsules are biodegradable capsules filled with deionized water. Each carrier is equipped with two slow-release hydration capsules, embedded inside the moisturizing cotton, to ensure continuous moisture release and control the humidity of the environment around the carrier at 60-70%.

[0035] 4. Determination of the timing and amount of gradient release: Based on the predicted occurrence of the corn borer, the corn borer egg stage lasts 10 days, with the early egg stage being days 1-3, the middle egg stage being days 4-7, and the late egg stage being days 8-10. The gradient slow-release carrier will be released in three stages, with a total release of 1 million Trichogramma wasps. The release ratio in each region is: central region: transition zone: outer region = 5:3:2, that is, 500,000 wasps released in the central region, 300,000 in the transition zone, and 200,000 in the outer region. In the first phase (early incubation period, day 2), 45% of the total release, or 450,000 heads, was released. Of these, 300,000 heads (all high-speed slow-release carriers) were released in the central area, and 150,000 heads (all medium-speed slow-release carriers) were released in the transition area. In the second phase (mid-incubation period, day 5), another 35% of the total release, or 350,000 heads, was released again. Of these, 150,000 heads (medium-speed slow-release carriers) were released in the central area, 100,000 heads (50,000 medium-speed and 50,000 low-speed slow-release carriers) were released in the transition area, and 100,000 heads (low-speed slow-release carriers) were released in the outer area. In the third phase (late incubation period, day 8), the remaining 20% ​​of the total release, or 200,000 heads, were released, all in low-speed slow-release carriers, in the outer area. Multi-rotor drones were used for distribution, flying at an altitude 10 meters above the top of the corn plants. The drones flew at a speed of 3 m / s in the central area and 5 m / s in the transition and outer areas to ensure even distribution. The distance between each distribution point was 5 meters.

[0036] 5. Post-release management: After release, check the working status of the micro-humidity control module every morning at 9:00 AM. Measure the humidity of the environment around the carrier using a hygrometer. When the humidity drops below 60%, promptly replenish the moisturizing cotton with slow-release hydration capsules to ensure the humidity remains stable at 60-70%. Simultaneously, observe the emergence of the carriers daily. Once a large number of Trichogramma wasps emerge from the carrier surface, supplement with a small amount of corn borer sex pheromone to ensure effective attraction. On the 10th day after release, when all Trichogramma wasps have emerged, discontinue the management.

[0037] Effectiveness Testing: On days 3, 7, and 10 after release, five survey points were set up in the central area, transition area, and outer area. Twenty corn plants were randomly selected at each survey point to record the number of Trichogramma wasps, their residence time, and the parasitism rate of corn borer eggs. The results showed that the average residence time of Trichogramma wasps was 7 days in the central area, 6 days in the transition area, and 5 days in the outer area. The average parasitism rate of corn borer eggs was 85.3%, with 92.1% in the central area, 86.7% in the transition area, and 78.2% in the outer area. Compared to existing release methods, the parasitism rate increased by more than 30%, and the damage caused by corn borers in all areas was effectively controlled, with no significant outbreaks. Example 2

[0038] This embodiment is applied to the control of rice leaf roller in paddy fields. The target control area is 80 mu (approximately 5.3 hectares). The rice leaf roller is the main pest to be controlled. According to the field survey, the distribution of rice leaf roller in the field is as follows: the central area (high density of pest occurrence) is 16 mu (approximately 1.1 hectares), the transition area (medium density of pest occurrence) is 32 mu (approximately 2.8 hectares), and the outer area (low density of pest occurrence) is 32 mu (approximately 2.8 hectares). The area ratio of the central area, the transition area, and the outer area is 1:2:2, which meets the requirements.

[0039] 1. Preparation of Gradient-Release Carriers: Three biodegradable carriers with different release rates were prepared: high-release, medium-release, and low-release carriers. The high-release carrier was made from cellulose-based biodegradable material. The preparation process was as follows: cellulose powder and water were mixed in a 3:1 ratio, a small amount of plasticizer was added, and the mixture was stirred evenly. The mixture was then pressed into a square carrier with a side length of 2.5 cm and a thickness of 1 cm. An internal cavity with a side length of 1.5 cm and a thickness of 0.8 cm was provided. The carrier surface had four 0.08 cm diameter pores, a porosity of 8%, and a release period of 10 days. The medium-release carrier was made by mixing cellulose-based and starch-based biodegradable materials in a 2:1 ratio. The molding process was the same as for the high-release carrier. The carrier surface had seven pores, a porosity of 18%, and a release period of 6 days. The low-release carriers are made of starch-based biodegradable materials using the same molding process. The carrier surface has 10 permeable pores with a porosity of 28%, and a release period of 3 days. A Trichogramma wasp emergence promoter was added to the containment cavity of all three carriers at a dosage of 0.3 mg per gram of carrier. This emergence promoter was a mixture of vitamin B6 and glucose in a 1:3 ratio. Cultured Trichogramma wasp eggs (emergence rate ≥95%) were placed into the containment cavity, with each carrier holding 60 eggs. The carrier openings were then sealed with biodegradable tape to ensure proper hatching and emergence of the wasp eggs.

[0040] 2. Setting up gradient release zones: Based on the field distribution of the rice leaf roller, a central zone, a transition zone, and an outer zone are delineated. The central zone, covering 16 mu (approximately 1 hectare), is the area with a rice leaf roller egg density ≥ 40 eggs / 100 plants. It is located in the middle of the rice field. The transition zone, surrounding the central zone, covers 32 mu (approximately 2 hectares) and has an egg density of 15-40 eggs / 100 plants. The outer zone, also covering 32 mu (approximately 2 hectares), is the area with an egg density < 15 eggs / 100 plants. Identification signs are set up in each zone to clearly define its boundaries and facilitate release operations.

[0041] 3. Configuration of the composite assisted retention system: Rice leaf roller pheromone was selected as the attractant, with an addition amount of 0.2 mg per gram of carrier. The attractant was mixed with a small amount of ethanol and then evenly sprayed onto the inner wall of the container cavity to improve the volatility and attraction effect of the attractant. The micro-humidity control module consists of 0.4 cm thick moisturizing cotton and slow-release hydration capsules. The moisturizing cotton wraps around the carrier, and each carrier is equipped with 3 slow-release hydration capsules embedded inside the moisturizing cotton, ensuring that the humidity around the carrier is stable at 55-65%, adapting to the environmental characteristics of rice paddies, while avoiding excessive humidity that could lead to mold growth on Trichogramma wasp eggs.

[0042] 4. Determination of the timing and amount of gradient release: Based on the predicted occurrence of the rice leaf folder, the incubation period of the rice leaf folder is 8 days, with the early incubation period being days 1-2, the middle incubation period being days 3-6, and the late incubation period being days 7-8. The gradient slow-release carrier will be released in two phases, with a total release of 800,000 Trichogramma wasps. The release ratio in each region is: central region: transition zone: outer region = 5:3:2, that is, 400,000 wasps released in the central region, 240,000 in the transition zone, and 160,000 in the outer region. In the first phase (early incubation period, day 2), 50% of the total release, or 400,000 rice seedlings, were released. Of these, 250,000 were released in the central area (200,000 high-release seedlings and 50,000 medium-release seedlings), 120,000 in the transition area (medium-release seedlings), and 30,000 in the outer area (low-release seedlings). In the second phase (mid-incubation period, day 4), the remaining 50% of the total release, or 400,000 seedlings, were released. Of these, 150,000 were released in the central area (medium-release seedlings), 120,000 in the transition area (70,000 medium-release seedlings and 50,000 low-release seedlings), and 130,000 in the outer area (low-release seedlings). The release was assisted by a remotely controlled (ROC) helicopter. The UAV flew at an altitude 8 meters above the top of the rice plants, with a flight speed of 4 m / s in the central area and 6 m / s in the transition and outer areas. The distance between release points was 4 meters to ensure even distribution of the seedlings across the areas.

[0043] 5. Post-release management: After release, check the working status of the micro-humidity control module every afternoon at 3 PM and measure the humidity around the carrier. When the humidity is below 55%, replenish with slow-release hydration capsules to ensure the humidity is stable at 55-65%. Simultaneously, supplement with rice leaf roller pheromones every 3 days to ensure sustained attraction. On the 8th day after release, all Trichogramma wasps have emerged, and management is discontinued.

[0044] Effectiveness testing: On days 2, 5, and 8 after release, six survey points were set up in the central, transition, and outer areas. At each survey point, 20 rice clumps were randomly selected to record the number of Trichogramma wasps, their residence time, and the parasitism rate of rice leaf roller eggs. The results showed that the average residence time of Trichogramma wasps was 8 days in the central area, 7 days in the transition area, and 6 days in the outer area. The average parasitism rate of rice leaf roller eggs was 88.7%, with 94.3% in the central area, 89.2% in the transition area, and 82.5% in the outer area. The control effect was significant, and no large-scale rice leaf roller damage occurred in the rice fields. Compared with traditional release methods, the utilization rate of Trichogramma wasps increased by more than 40%. Example 3

[0045] This embodiment is applied to the control of beet armyworm in vegetable fields. The target control area is 50 mu (approximately 3.3 hectares), mainly planted with tomatoes and cucumbers. The beet armyworm is the main pest to be controlled. According to the field survey, the distribution of beet armyworm in the field is as follows: the central area (high density of pest occurrence) is 10 mu (approximately 0.67 hectares), the transition area (medium density of pest occurrence) is 20 mu (approximately 1.3 hectares), and the outer area (low density of pest occurrence) is 20 mu (approximately 1.3 hectares). The area ratio of the central area, the transition area, and the outer area is 1:2:2, which meets the requirements.

[0046] 1. Preparation of Gradient-Release Carriers: Three biodegradable carriers with different release rates were prepared: a high-release carrier, a medium-release carrier, and a low-release carrier. The high-release carrier was prepared by mixing polylactic acid (PLA) and cellulose-based biodegradable materials in a 3:2 ratio. The preparation process was as follows: the two materials were heated and melted, mixed evenly, and then extruded to form an elliptical carrier with a major axis of 3 cm, a minor axis of 2 cm, and a height of 1.5 cm. An internal cavity was provided, with a major axis of 2 cm, a minor axis of 1.5 cm, and a height of 1 cm. The carrier surface had 6 pores with a diameter of 0.12 cm, a porosity of 12%, and a release period of 7 days. The medium-release carrier was made of PLA material, and the molding process was the same as that of the high-release carrier. The carrier surface had 9 pores, a porosity of 22%, and a release period of 4 days. The low-release carrier is made by mixing starch-based and cellulose-based biodegradable materials in a 1:1 ratio, using the same molding process. The carrier surface has 13 air pores, a porosity of 32%, and a release period of 1 day. A Trichogramma wasp emergence promoter was added to the containment cavity of all three carriers at a dosage of 0.6 mg per gram of carrier. This emergence promoter was a mixture of vitamin B1, vitamin B2, and glucose in a 1:1:3 ratio. Cultured Trichogramma wasp pupae (emergence rate ≥95%) were placed into the containment cavity, with each carrier holding 40 pupae. The carrier openings were then sealed with biodegradable nonwoven fabric to ensure ventilation and prevent premature emergence and escape of the Trichogramma wasps.

[0047] 2. Setting up gradient release zones: Based on the field distribution of the beet armyworm, a central zone, a transition zone, and an outer zone are delineated. The central zone, covering 10 mu (approximately 0.67 hectares), is an area with a beet armyworm egg density ≥60 eggs / 100 plants, mainly concentrated in tomato-growing areas; the transition zone, covering 20 mu (approximately 1.3 hectares), is an area with a beet armyworm egg density of 25-60 eggs / 100 plants, encompassing parts of tomato and cucumber-growing areas; the outer zone, covering 20 mu (approximately 1.3 hectares), is an area with a beet armyworm egg density <25 eggs / 100 plants, mainly in cucumber-growing areas and at the edge of the field. Markers are placed along the field paths in each zone to facilitate precise positioning during release.

[0048] 3. Configuration of the composite assisted retention system: The sex pheromone of the beet armyworm was selected as the attractant, with an addition amount of 0.4 mg per gram of carrier. The attractant was made into slow-release microcapsules and evenly sprinkled inside the containment cavity to prolong the release time of the attractant. The micro-humidity control module consists of 0.6 cm thick moisturizing cotton and slow-release hydrating capsules. The moisturizing cotton wraps around the carrier, and each carrier is equipped with two slow-release hydrating capsules embedded inside the moisturizing cotton, ensuring that the humidity around the carrier is stable at 65-75%, suitable for the high humidity environment of vegetable fields, while also improving the activity of Trichogramma wasps.

[0049] 4. Determination of the timing and amount of gradient release: Based on the predicted occurrence of the beet armyworm, the egg stage of the beet armyworm lasts for 9 days, with the early egg stage being days 1-3, the middle egg stage being days 4-6, and the late egg stage being days 7-9. The gradient slow-release carrier will be released in three stages, with a total release of 600,000 Trichogramma wasps. The release ratio in each area is: central area: transition area: outer area = 5:3:2, that is, 300,000 wasps released in the central area, 180,000 in the transition area, and 120,000 in the outer area. In the first stage (early ovulation period, day 3), 40% of the total release, or 240,000, is released, with 180,000 (high-speed carrier) released in the central area and 60,000 (medium-speed carrier) released in the transition area. In the second stage (mid-ovulation period, day 5), 35% of the total release, or 210,000, is released, with 90,000 (medium-speed carrier) released in the central area, 80,000 (40,000 medium-speed carrier and 40,000 low-speed carrier) released in the transition area, and 40,000 (low-speed carrier) released in the outer area. In the third stage (mid-to-late ovulation period, day 7), 25% of the total release, or 150,000, is released, with 30,000 (low-speed carrier) released in the central area, 40,000 (low-speed carrier) released in the transition area, and 80,000 (low-speed carrier) released in the outer area. Multi-rotor drones are used to assist in the release. The drones fly 5 meters above the top of the vegetables, with a flight speed of 2 m / s in the central area and 4 m / s in the transition and outer areas. The distance between the release points is 3 meters to ensure that the carrier is evenly placed on the back of the leaves in the middle of the vegetable plant, avoiding direct sunlight and rain.

[0050] 5. Post-release management: After release, check the working status of the micro-humidity control module at 10:00 AM every day and measure the humidity around the carriers. When the humidity is below 65%, replenish with slow-release hydration capsules to ensure the humidity is stable at 65-75%. Simultaneously, observe the emergence of the carriers every two days. When the attractant effect weakens, replenish with attractants in the form of slow-release microcapsules. On the 9th day after release, all Trichogramma wasps have emerged, and management is stopped.

[0051] Effectiveness Testing: On days 3, 6, and 9 after release, five survey points were set up in the central, transition, and outer areas. At each survey point, 15 vegetable plants were randomly selected to record the number of Trichogramma wasps, their residence time, and the parasitism rate of Spodoptera litura eggs. The results showed that the average residence time of Trichogramma wasps in the central area was 7.5 days, in the transition area 6.5 days, and in the outer area 5.5 days. The average parasitism rate of Spodoptera litura eggs was 86.9%, with a parasitism rate of 93.5% in the central area, 87.8% in the transition area, and 80.1% in the outer area. The damage caused by Spodoptera litura in the vegetable fields was effectively controlled. Compared with traditional release methods, the control effect was improved by more than 35%, and the Trichogramma wasps posed no harm to the vegetables, ensuring the quality and safety of the vegetables.

[0052] Compare with Example 1 (traditional uniform release method) This comparative example uses the existing traditional uniform release method, applied to the same cornfield as Example 1 for the control of corn borers. The target control area is 100 mu, and the total release amount is 1 million Trichogramma wasps. Conventional paper card carriers are used, which do not have a slow-release function. The Trichogramma wasps are released in a single emergence, without dividing the gradient area. The drone is used for uniform deployment, without setting up a composite auxiliary retention system. The release time is a single release in the middle of the corn borer egg stage (day 5).

[0053] Effectiveness testing: On days 3, 7, and 10 after release, the same testing method as in Example 1 was used to count the number of Trichogramma wasps, their residence time, and the parasitism rate of corn borer eggs. The results showed that the average residence time of Trichogramma wasps was 1.5 days, and the average parasitism rate of corn borer eggs was 52.1%, with a parasitism rate of 60.3% in the central area, 53.7% in the transition area, and 45.8% in the outer area. Outbreaks of corn borer damage occurred in some areas, and the control effect was far lower than in Example 1.

[0054] Comparative Example 2 (without composite auxiliary retention system) This comparative example uses the same gradient slow-release carrier, gradient region division, release timing and release amount as Example 1. The difference is that the composite auxiliary retention system is not configured (no sex pheromone attractant is added, and no micro-humidity control module is set up), and it is applied to the same cornfield corn borer control as Example 1.

[0055] Efficacy testing: On days 3, 7, and 10 after release, the same testing method as in Example 1 was used to count the number of Trichogramma wasps, their residence time, and the parasitism rate of corn borer eggs. The results showed that the average residence time of Trichogramma wasps was 3 days, and the average parasitism rate of corn borer eggs was 68.5%, with a parasitism rate of 75.2% in the central area, 69.3% in the transition area, and 62.1% in the outer area. The control effect was lower than in Example 1, indicating that the composite auxiliary residence system can effectively prolong the residence time of Trichogramma wasps and improve parasitism efficiency.

[0056] Compare with Example 3 (no gradient release) This comparative example uses the same composite auxiliary retention system, release timing, and release amount as Example 1. The difference is that it does not use a gradient slow-release carrier, but only a carrier with a single slow-release rate (medium-slow-release rate carrier). It does not divide the gradient area, adopts a uniform delivery method, and is applied to the same cornfield corn borer control as Example 1.

[0057] Effectiveness testing: On days 3, 7, and 10 after release, the same testing method as in Example 1 was used to count the number of Trichogramma wasps, their residence time, and the parasitism rate of corn borer eggs. The results showed that the average residence time of Trichogramma wasps was 5 days, and the average parasitism rate of corn borer eggs was 72.3%, with a parasitism rate of 78.5% in the central area, 73.1% in the transition area, and 65.2% in the outer area. The parasitism rate varied significantly across areas, with insufficient parasitism in the central area and wasted Trichogramma wasps in the outer area. The control effect was lower than in Example 1, indicating that gradient release can achieve a reasonable distribution of Trichogramma wasps and improve the overall control effect.

[0058] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A gradient release method for Trichogramma wasps that balances diffusion and retention, characterized in that, Includes the following steps: (1) Prepare a gradient sustained-release carrier, wherein the gradient sustained-release carrier includes at least three biodegradable carriers with different sustained-release rates, wherein the biodegradable carrier has a cavity for accommodating Trichogramma eggs or pupae, and the carrier surface has pores. The porosity of the pores is adjusted according to the sustained-release rate, wherein the porosity of the high sustained-release rate carrier is lower than that of the medium sustained-release rate carrier, and the porosity of the medium sustained-release rate carrier is lower than that of the low sustained-release rate carrier. (2) Set up a gradient release area and divide the target control area into a central area, a transition area and an outer area. The central area is the high-density occurrence area of ​​pests, the transition area is the medium-density occurrence area of ​​pests, and the outer area is the low-density occurrence area or potential occurrence area of ​​pests. (3) Configure a composite auxiliary retention system, add insect sex pheromone attractant into the containment cavity of the gradient slow-release carrier, and set a micro-humidity control module on the outside of the carrier. The micro-humidity control module is used to stably control the humidity of the environment around the carrier at 55-75%. (4) Determine the timing and amount of gradient release. Based on the prediction of the occurrence of the target pest, release gradient slow-release carriers in 2-3 stages from the early to the middle stage of the pest's egg stage. The release amount in the central area is greater than that in the transition area, and the release amount in the transition area is greater than that in the outer area. The carrier with high slow-release rate corresponds to the central area, the carrier with medium slow-release rate corresponds to the transition area, and the carrier with low slow-release rate corresponds to the outer area. (5) Post-release regulation: Regularly check the working status of the micro-humidity regulation module, replenish the attractant in time, and ensure that the humidity around the carrier is stable until all Trichogramma bees emerge and spread to all parts of the target area.

2. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: The material of the biodegradable carrier is selected from one or more of polylactic acid, starch-based biodegradable materials, and cellulose-based biodegradable materials.

3. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: The sustained-release period of the high-rate carrier is 7-10 days, the sustained-release period of the medium-rate carrier is 4-6 days, and the sustained-release period of the low-rate carrier is 1-3 days.

4. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: The insect sex pheromone attractant is selected from one or more of the following: beet armyworm sex pheromone, sugar beet armyworm sex pheromone, and corn borer sex pheromone, and the addition amount is 0.1-0.5 mg per gram of carrier.

5. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: The micro-humidity control module includes a moisturizing cotton and a slow-release hydrating capsule. The moisturizing cotton is wrapped around the outside of the carrier, and the slow-release hydrating capsule is embedded inside the moisturizing cotton to continuously release moisture.

6. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: The area ratio of the central area, transition area, and outer area is 1:2-3:3-4, and the release ratio is 5:3:

2.

7. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: The release timing is as follows: the first stage is the early stage of the insect's egg stage, with 40-50% of the total release volume; the second stage is the middle stage of the egg stage, with 30-35% of the total release volume; and the third stage is the middle and late stages of the egg stage, with 15-20% of the total release volume.

8. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: The gradient slow-release carrier also contains a Trichogramma eclosion promoter, which is a mixture of B vitamins and glucose, added at a rate of 0.2-0.8 mg per gram of carrier.

9. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: The release is assisted by drones. The drones fly 5-15 meters above the top of the target crop, and the flight speed is adjusted according to the area. The flight speed in the central area is slower than that in the transition area and the outer area.

10. The gradient release method for Trichogramma wasps that balances diffusion and retention according to claim 1, characterized in that: After release, check the micro-humidity control module once a day. When the humidity is below 55%, replenish the slow-release hydration capsules to ensure stable humidity.

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