A method for field sustained release of trichogramma

Abstract

The present application relates to the technical field of biological control of forestry pests, in particular to a long-acting release method of trichogramma in the field, which solves the problems of short duration, low survival rate and frequent replenishment of the existing trichogramma release. The method uses chitosan and carrageenan as the base material, which is modified by silane coupling agent to form porous slow-release microspheres. The trichogramma eggs are mixed with bamboo flavone-based compound preservative and then loaded on the microspheres. The microspheres are loaded into a temperature and humidity responsive degradable release device. In the field, 60-75 release points per hectare are arranged in a chessboard pattern, and the dynamic replenishment by unmanned aerial vehicle is implemented in combination with sex pheromone monitoring. The present application realizes the long-acting release of trichogramma for 30-40 days, the survival rate is increased to more than 90%, the parasitic rate of pest eggs is stably maintained at more than 85%, the replenishment frequency is greatly reduced, the release is uniform and there is no dead angle, the carrier and device can be naturally degraded without residue, the operation is simple, and the present application is suitable for large-scale green control of forestry pests.

Description

Technical Field

[0001] This invention relates to the field of biological control technology for agricultural and forestry pests, specifically a method for slow-release and long-lasting release of Trichogramma wasps in the field. Background Technology

[0002] Trichogramma wasps are oviparous parasitic insects belonging to the genus Trichogramma in the family Trichogramidae of the order Hymenoptera. They can parasitize the eggs of various lepidopteran pests such as corn borers, sugarcane stem borers, cotton bollworms, and cutworms. By laying eggs and developing within the host eggs, they feed on the yolk and pupate, ultimately causing the host eggs to die. They are natural enemies of insects with great application value in the green control of agricultural and forestry pests. They have the advantages of being pollution-free, harmless to humans and animals, and not damaging to the ecological environment. They have been widely used in the control of pests in various crops such as rice, corn, sugarcane, and cotton.

[0003] Currently, the main methods for releasing Trichogramma wasps in the field include wasp card release, dart release, spherical release, and drone release. Among these, wasp card release and drone release are the two most widely used methods. According to the People's Republic of China Agricultural Industry Standard NY / T3542.2—2025 "Technical Specification for Releasing Trichogramma Wasps to Control Pests Part 2: Sugarcane Fields", wasp card release requires 75,000 Trichogramma wasps per hectare per release, 5 times; drone-launched dart release requires 90,000 Trichogramma wasps per hectare per release, 4 times. The release cycle is short, requiring frequent manual replenishment, which not only increases labor costs and intensity but also easily leads to gaps in control due to untimely replenishment, affecting the control effect.

[0004] The core problems with existing Trichogramma release techniques lie in their poor release timeliness and short duration of effectiveness, making long-term pest control difficult. On one hand, existing release carriers are mostly ordinary bee cards or simple release devices, lacking slow-release capabilities. Trichogramma eggs emerge in a concentrated manner, and the large number of emerging wasps cannot find host eggs in a short time, resulting in a low survival rate of only 60-70%. Furthermore, the emerged wasps are susceptible to environmental factors such as wind, rain, high temperatures, and low temperatures in the field, causing a rapid decline in activity and preventing them from sustaining their parasitic effect. The effective period is generally only 7-10 days, requiring multiple releases to cover the entire egg stage of the pest. On the other hand, existing release methods lack targeted survival measures. During field storage and emergence, Trichogramma eggs are prone to nutritional deficiencies and environmental stress, leading to an increased rate of deformed wasps and further reducing control effectiveness. Simultaneously, release devices are mostly fixed structures, unable to adjust the release speed according to field temperature, humidity, and other environmental conditions. When environmental conditions are unsuitable for Trichogramma activity, a large number of emerging wasps cannot effectively parasitize, resulting in resource waste.

[0005] Furthermore, while drone-based releases solve the problem of low efficiency associated with manual releases, the downwash winds can easily cause mechanical damage to Trichogramma wasp eggs, leading to a deformity rate of 5%-8%. Moreover, current release rates are mostly static indicators, lacking dynamic correction mechanisms based on changes in field pest populations, temperature, and humidity, thus hindering precise release. Additionally, existing release carriers are mostly non-degradable or simply biodegradable materials, which, when left in the soil, can easily disrupt the soil's microecological environment, contradicting the principles of green agriculture.

[0006] Existing technologies include some improved release methods for Trichogramma wasps, such as publicly available Trichogramma nutrient solutions, which improve the survival rate of Trichogramma wasps by adding fermented soybean meal and bamboo flavonoids. However, this method only focuses on nutritional supplementation for Trichogramma wasps and does not address the issues of slow-release and long-lasting effects. Other methods use microcapsules to encapsulate Trichogramma wasp eggs, but these often use single materials to prepare the microcapsules, resulting in poor slow-release effects and failing to incorporate field environmental response mechanisms, thus failing to achieve on-demand release. Therefore, developing a release method that can achieve slow-release and long-lasting effects, improve survival rates, reduce the frequency of re-release, and adapt to complex field environments has become a pressing technical challenge in the field of Trichogramma biological control. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies, such as short-lasting effect of Trichogramma wasp release in the field, uneven release, low survival rate of Trichogramma wasp, need for multiple artificial re-releases, high control costs, and unstable effects. This invention provides a slow-release, long-lasting release method for Trichogramma wasp in the field. By integrating modified slow-release carriers, composite survival agents, temperature and humidity responsive release devices, stratified deployment, and dynamic re-release techniques, this method achieves slow, uniform, and long-lasting release of Trichogramma wasp, improving survival and parasitism rates, reducing the number of re-releases, lowering control costs, and ensuring stable and lasting control effects.

[0008] The technical solution adopted by this invention to solve its technical problem is: a method for sustained-release and long-lasting release of Trichogramma wasps in the field, comprising the following steps: (1) Preparation of sustained-release carrier: Chitosan and carrageenan are used as substrates, and silane coupling agents are added for modification to prepare porous sustained-release microspheres. The pore size of the sustained-release microspheres is 0.3-0.5 mm and the porosity is 40-50%. (2) Loading and preservation treatment of Trichogramma bee eggs: After mixing Trichogramma bee eggs with a compound preservation agent evenly, the mixture is drawn into the pores of the slow-release microspheres. The compound preservation agent is made by mixing bamboo flavonoids, trehalose, and traditional Chinese medicine honey in a weight ratio of 2:3:5. The loading amount is 800-1000 Trichogramma bee eggs per gram of slow-release microspheres. (3) Assembly of release device: Load the slow-release microspheres loaded with Trichogramma eggs into a temperature and humidity responsive release device. The device includes a shell, a vent, a temperature and humidity sensor and a controllable release valve. The diameter of the vent is 0.2-0.4 mm. When the field temperature is 25-30℃ and the humidity is 60-80%, the controllable release valve will open automatically. (4) Layered deployment in the field: Distribute the release devices evenly in the crop field at 60-75 release points per hectare. Each release point is set up with three layers of release units: upper, middle and lower. The spacing between each layer is 30-50cm. The upper layer corresponds to the crop canopy, the middle layer corresponds to the middle part of the crop, and the lower layer corresponds to the area near the crop roots. (5) Dynamic release: Monitor the dynamics of adult pests in the field using sex pheromone traps. When the emergence rate of pests reaches 20% or the parasitism rate of stem borer eggs is less than 70%, release once, with the amount of release being 30-40% of the initial release amount.

[0009] Specifically, the modification process described in step (1) is as follows: chitosan and carrageenan are mixed at a weight ratio of 1:1, deionized water is added to prepare a mixed solution with a concentration of 3-5%, 0.5-1% of silane coupling agent is added to the total mass of the mixed solution, and the mixture is stirred at 60-70℃ for 30-40 minutes. After cooling to room temperature, porous slow-release microspheres are prepared by freeze drying at a temperature of -20 to -15℃ for 12-16 hours.

[0010] Specifically, the Trichogramma eggs mentioned in step (2) are mid-to-late stage pupal eggs of Trichogramma maculatum or Trichogramma cornii, with an egg parasitism rate ≥70%, an emergence rate ≥85%, and a deformed bee rate ≤5%.

[0011] Specifically, the housing of the release device in step (3) is made of biodegradable polylactic acid material, and the surface of the housing is evenly distributed with vent holes. The controllable release valve is electrically connected to the temperature and humidity sensor. The valve opening angle is 30-60°, the opening frequency is once every 2-4 hours, and the opening time is 10-15 minutes each time.

[0012] Specifically, the release points in step (4) are arranged in a checkerboard pattern. For crops planted in contiguous areas, the distance between adjacent release points is 12-15m. For crops planted in scattered areas, a release point is set up for every 50-60 crops.

[0013] Specifically, in step (4), the upper release unit is 10-20cm away from the crop canopy, the middle release unit is located on the back of the upper and middle leaves of the crop, and the lower release unit is 10-15cm away from the ground.

[0014] Specifically, in step (5), 40-50 sex pheromone traps are deployed per hectare, and the number of adult pests and the parasitism of stem borer eggs are monitored once a week. When re-releasing, drones are used to precisely deploy the re-release device.

[0015] Specifically, the compound activator also contains 0.1-0.2% of a compound vitamin, which includes vitamin C, B vitamins and vitamin E in a weight ratio of 1:2:1.

[0016] Specifically, in step (2), the mixing ratio of Trichogramma eggs and compound survivability agent is 0.5-1g of compound survivability agent per 1000 Trichogramma eggs, the mixing time is 10-15min, and the mixing temperature is controlled at 20-25℃.

[0017] Specifically, the slow-release carrier degrades naturally in the field in 45-60 days, leaving no soil residue after degradation and not affecting crop growth or the soil micro-ecological environment.

[0018] The beneficial effects of this invention are: 1. Achieving sustained-release and reducing the number of re-releases: This invention uses chitosan-carrageenan modified porous sustained-release microspheres as a carrier, combined with a temperature and humidity responsive release device, to achieve slow release of Trichogramma bee eggs after eclosion. At the same time, the release units are arranged in layers, and the eclosion speed of different layers of carriers varies, further extending the release cycle. The effective period can reach 30-40 days, which is significantly longer than the 7-10 days of the existing technology. The number of re-releases is reduced from 4-5 times to 1-2 times, greatly reducing labor costs and labor intensity.

[0019] 2. Improve the survival rate and parasitism rate of Trichogramma wasps: The addition of compound survival agents provides sufficient nutrition for the emergence of Trichogramma wasp eggs, enhances the resistance of Trichogramma wasps, reduces the damage caused by environmental stress, and increases the survival rate of Trichogramma wasps to over 90%; the temperature and humidity responsive release device can release Trichogramma wasps as needed according to field environmental conditions, ensuring that Trichogramma wasps are active and parasitizing in the most suitable environment, and the parasitism rate of field pest eggs is stable at over 85%, with a control effect significantly better than existing technologies.

[0020] 3. Uniform release with no blind spots: The checkerboard-style layered deployment method, combined with precise release by drones, ensures that the Trichogramma wasps are evenly distributed in the field, covering pest eggs at different heights of crops. This solves the problems of uneven distribution and many blind spots in existing release methods, and is suitable for a variety of crops planted in contiguous or scattered areas.

[0021] 4. Green and environmentally friendly, with no environmental residue: The slow-release carrier and release device are made of biodegradable materials. After natural degradation in the field, there is no soil residue, which does not affect crop growth and soil micro-ecological environment. This is in line with the development concept of green agriculture and ecological control. At the same time, it reduces the use of chemical pesticides and reduces the harm of pesticide residues to the environment and human body.

[0022] 5. Simple operation and suitable for large-scale pest control: The entire method has clear steps, the slow-release carrier and release device can be prepared in batches in advance, and field deployment and supplementary release can be completed by drones, which has high operational efficiency and is suitable for pest control of large-scale agricultural and forestry crops. It solves the problems of low efficiency of manual release and difficulty in adapting to large-scale planting in the existing technology. Attached Figure Description

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

[0024] Figure 1 The flowchart of a field-based slow-release and long-acting release method for Trichogramma wasps provided by 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 As shown, the present invention provides a method for sustained-release and long-lasting release of Trichogramma wasps in the field, comprising the following steps: (1) Preparation of sustained-release carrier: Chitosan and carrageenan were used as substrates and modified with silane coupling agents to prepare porous sustained-release microspheres. Chitosan and carrageenan are both natural biodegradable materials with good biocompatibility and porous structure, which are suitable as loading carriers for Trichogramma wasp eggs. The addition of silane coupling agents can improve the pore structure of the substrate, improve the stability and sustained-release performance of the carrier, and avoid the rapid degradation of the carrier in the field, which would lead to premature emergence and release of Trichogramma wasp eggs. The specific modification process is as follows: Chitosan and carrageenan are mixed at a weight ratio of 1:1, and deionized water is added to prepare a mixed solution with a concentration of 3-5%. 0.5-1% of the total mass of the mixed solution is added as a silane coupling agent. The mixture is stirred at 60-70℃ for 30-40 minutes to allow the silane coupling agent to fully react with the substrate. After cooling to room temperature, porous slow-release microspheres are prepared by freeze-drying at a temperature of -20 to -15℃ for 12-16 hours to ensure that the microspheres form a uniform porous structure with a pore size controlled at 0.3-0.5 mm and a porosity of 40-50%. This ensures that the microspheres can support a sufficient number of Trichogramma wasp eggs and achieve slow release after the Trichogramma wasps emerge.

[0027] (2) Trichogramma egg loading and survival treatment: Select mid-to-late stage pupal eggs of Trichogramma maculatum or Trichogramma corn borer, requiring an egg parasitism rate ≥70%, an emergence rate ≥85%, and a deformed bee rate ≤5%. These eggs have a relatively concentrated emergence time and a high survival rate. After mixing the Trichogramma eggs with the compound survival agent evenly, the mixture is drawn into the pores of the slow-release microspheres. The compound survival agent is made by mixing bamboo flavonoids, trehalose, and traditional Chinese medicine honey in a weight ratio of 2:3:5. 0.1-0.2% of compound vitamins (vitamin C, B vitamins, and vitamin E in a weight ratio of 1:2:1) can also be added. Bamboo flavonoids have antibacterial and antiviral effects, which can enhance the stress resistance of Trichogramma eggs. Trehalose can protect the cell membrane of Trichogramma eggs and reduce damage caused by environmental stress. Traditional Chinese medicine honey and compound vitamins can supplement the nutrients required for Trichogramma egg emergence, thereby improving the emergence rate and survival rate. The mixing ratio of Trichogramma bee eggs and compound survivability agent is 0.5-1g of compound survivability agent per 1000 Trichogramma bee eggs, with a mixing time of 10-15 minutes and a mixing temperature of 20-25℃ to avoid high or low temperatures affecting the activity of Trichogramma bee eggs. The loading is controlled at 800-1000 Trichogramma bee eggs per gram of slow-release microspheres to ensure a reasonable carrier loading that does not crowd and affect emergence, while also ensuring the number of bees required for control.

[0028] (3) Assembly of release device: Load the slow-release microspheres loaded with Trichogramma eggs into a temperature and humidity responsive release device, which includes a shell, vent holes, temperature and humidity sensors and controllable release valve. The shell is made of biodegradable polylactic acid material, which can naturally degrade in the field in 45-60 days, leaving no soil residue and not affecting the soil micro-ecological environment. The shell surface has evenly distributed air pores with a diameter of 0.2-0.4 mm, ensuring internal air permeability to provide sufficient oxygen for Trichogramma wasp egg emergence while preventing predators such as ants from entering and damaging the eggs. A temperature and humidity sensor monitors field temperature and humidity in real time. A controllable release valve is electrically connected to the sensor. When the field temperature is 25-30℃ and the humidity is 60-80%, the environmental conditions are most suitable for Trichogramma wasp activity and parasitism. The controllable release valve automatically opens at an angle of 30-60°, every 2-4 hours, for 10-15 minutes each time, allowing for slow, on-demand release of Trichogramma wasps after emergence, avoiding resource waste caused by mass emergence of Trichogramma wasps when the environment is unsuitable.

[0029] (4) Layered deployment in the field: The release devices are evenly deployed in the crop field at 60-75 release points per hectare. The deployment method adopts a checkerboard pattern for uniform distribution. For crops planted in contiguous areas, the distance between adjacent release points is 12-15m. For crops planted in scattered areas, one release point is set for every 50-60 crops to ensure uniform release and no blind spots in control. Each release point is set with three layers of release units: upper, middle and lower. The distance between each layer is 30-50cm. The upper release unit is 10-20cm away from the crop canopy and corresponds to the pest eggs near the crop canopy. The middle release unit is located on the back of the upper and middle leaves of the crop and corresponds to the pest eggs in the middle of the crop. The lower release unit is 10-15cm away from the ground and corresponds to the pest eggs near the crop roots. Through layered deployment, comprehensive control of pest eggs at different heights can be achieved. At the same time, the eclosion speed of the slow-release microspheres in different layers is slightly different, which can further extend the release cycle and achieve long-term control.

[0030] (5) Dynamic supplementary release: The dynamics of adult pests in the field are monitored by using sex pheromone traps. 40-50 sex pheromone traps are set up per hectare. The number of adult pests and the parasitism of stem borer eggs are monitored once a week. When the emergence rate of pests reaches 20% or the parasitism rate of stem borer eggs is less than 70%, it indicates that the current number of Trichogramma wasps is insufficient and effective control cannot be achieved. At this time, a supplementary release is carried out. The supplementary release amount is 30-40% of the initial release amount. During the supplementary release, drones are used to accurately deliver the supplementary release device to ensure uniform release and avoid the problems of low efficiency and uneven distribution of manual supplementary release, so as to further ensure the stability of the control effect. Example 1

[0031] This embodiment provides a slow-release, long-lasting release method for Trichogramma wasps in the field, applied to the control of corn borers in corn fields. The specific steps are as follows: (1) Preparation of sustained-release carrier: Chitosan and carrageenan were selected as substrates and mixed at a weight ratio of 1:1. Deionized water was added and stirred to dissolve the mixture, resulting in a 4% concentration mixed solution. 0.8% of the total mass of the mixed solution was added to the mixed solution as silane coupling agent (KH-550). The mixed solution was placed in a constant temperature water bath at 65°C and stirred for 35 minutes to allow the silane coupling agent to fully react with chitosan and carrageenan to form a stable mixed system. The mixed solution after reaction was poured into a mold, cooled to room temperature, and then placed in a freeze dryer. It was freeze-dried at -18°C for 14 hours to prepare porous sustained-release microspheres. The test results showed that the pore size of the sustained-release microspheres was 0.4 mm, the porosity was 45%, the texture was uniform, and it had good air permeability and sustained-release performance. It could remain stable in cornfield soil for more than 35 days and the degradation time was about 50 days.

[0032] (2) Trichogramma egg loading and survival treatment: The mid-to-late stage pupal eggs of Trichogramma corn borer were selected. The parasitism rate of the Trichogramma eggs was 75%, the emergence rate was 88%, and the rate of deformed eggs was 3%, which met the requirements for use. A compound survival agent was prepared by weighing bamboo flavonoids, trehalose, Chinese herbal honey (honeysuckle and coptis chinensis as the nectar source) and compound vitamins (vitamin C, vitamin B complex, and vitamin E in a weight ratio of 1:2:1) in a weight ratio of 2:3:5:0.15, mixing them evenly and grinding them into powder. The Trichogramma eggs and the compound survival agent were mixed at a ratio of 1000 eggs per 1000 eggs. Mix Trichogramma eggs with 0.8g of composite preservative and gently stir for 12 minutes at 22°C to ensure that the composite preservative is evenly attached to the surface of the Trichogramma eggs. The mixture of Trichogramma eggs and composite preservative is then aspirated into the pores of the slow-release microspheres prepared in step (1) by vacuum aspiration. The loading is controlled to be 900 Trichogramma eggs per gram of slow-release microspheres. After loading, the slow-release microspheres are placed in an environment of 25°C and 75% humidity for 2 hours to ensure that the Trichogramma eggs and the carrier are fully combined and that the activity of the Trichogramma eggs is not affected.

[0033] (3) Assembly of the release device: Select biodegradable polylactic acid material to make the housing of the release device. The housing is cylindrical with a diameter of 5cm and a height of 8cm. The surface of the housing is evenly distributed with vent holes. The diameter of the vent holes is 0.3mm and the spacing between the vent holes is 0.5cm to ensure good air permeability inside the housing. Install a temperature and humidity sensor (model: DHT11) and a controllable release valve (model: SLA-0420) inside the housing. The temperature and humidity sensor and the controllable release valve are electrically connected by wires. Set the temperature and humidity trigger threshold as follows: temperature 25-30℃, humidity 60-80%. When the field temperature and humidity reach the threshold, the controllable release valve will automatically open with an opening angle of 45° and an opening frequency of once every 3 hours. Each opening time is 12min. Load the slow-release microspheres loaded with Trichogramma eggs in step (2) into the housing of the release device. Each release device is loaded with 5g of slow-release microspheres. Then seal the housing, leaving only the vent holes and valve outlet to complete the assembly of the release device.

[0034] (4) Layered deployment in the field: The experimental cornfield area was 1 hectare. The release devices were evenly deployed in a checkerboard pattern, with a total of 70 release points and a spacing of 13m between adjacent release points. Each release point was set up with three layers of release units: upper, middle and lower. The release devices were fixed with bamboo poles. The upper release unit was 15cm away from the corn canopy, the middle release unit was fixed on the back of the upper and middle leaves of the corn, and the lower release unit was 12cm away from the ground. The spacing between each layer was 40cm. The deployment time was selected when the overwintering adult corn borer first appeared. It was carried out after 16:00 on a sunny day to avoid the release effect being affected by high temperature and strong wind. During the deployment process, it was ensured that the release devices were firmly fixed, the ventilation holes were unobstructed, and the valve outlet faced the direction of the corn plant.

[0035] (5) Dynamic replenishment: 45 pheromone traps (with corn borer sex pheromone as the lure core) were evenly deployed per hectare in the experimental cornfield. The number of adult corn borers in the traps was monitored once every Monday morning. At the same time, a 5-point sampling method was used, with 20 corn plants continuously investigated at each sampling point. Corn borer egg masses were collected and brought back to the laboratory for microscopic examination, and the parasitism rate of the eggs was calculated. On the 15th day after the initial deployment, the corn borer emergence rate was monitored to be 20%, and the corn borer egg parasitism rate was 68%, which was lower than 70%. At this time, a replenishment was carried out, with the replenishment amount being 35% of the initial release amount. The replenishment device was accurately deployed using a plant protection drone (model: DJI T60). The replenishment release point coincided with the initial release point to ensure uniform replenishment. Monitoring continued after the replenishment until the end of the corn borer egg stage. If the parasitism rate was no longer lower than 70%, no further replenishment was required.

[0036] Experimental results: The release method in this embodiment has an effective period of 35 days, a Trichogramma wasp survival rate of 92%, an average corn borer egg parasitism rate of 88%, and a corn heart failure rate of 2.1%. Compared with the existing bee card release method, the effective period is extended by 25 days, the Trichogramma wasp survival rate is increased by 22%, the corn borer egg parasitism rate is increased by 18%, the corn heart failure rate is reduced by 6.8%, and the number of re-releases is reduced from 5 to 1, which significantly reduces labor costs. Example 2

[0037] This embodiment provides a slow-release, long-lasting release method for Trichogramma wasps in the field, applied to the control of sugarcane borers in sugarcane fields. The specific steps are as follows: (1) Preparation of sustained-release carrier: Chitosan and carrageenan were selected as substrates and mixed at a weight ratio of 1:1. Deionized water was added and stirred to dissolve the mixture, resulting in a 3% concentration mixed solution. 0.5% of the total mass of the mixed solution was added to the mixed solution as silane coupling agent (KH-560). The mixed solution was placed in a constant temperature water bath at 60℃ and stirred for 30 min to allow the silane coupling agent to fully react with the substrate. The mixed solution after reaction was poured into a mold, cooled to room temperature, and then placed in a freeze dryer. It was freeze-dried at -20℃ for 12 h to prepare porous sustained-release microspheres. The test results showed that the pore size of the sustained-release microspheres was 0.3 mm and the porosity was 40%. The microspheres could remain stable in sugarcane field soil for more than 32 days and the degradation time was about 45 days, with no soil residue.

[0038] (2) Trichogramma egg loading and survival treatment: The mid-to-late stage pupal eggs of Trichogramma pygmygdalis were selected. After testing, the parasitism rate of the Trichogramma eggs was 72%, the emergence rate was 86%, and the rate of deformed eggs was 4%, which met the requirements for use. A compound survival agent was prepared by weighing bamboo flavonoids, trehalose, Chinese herbal honey (the nectar source is gallnut and forsythia) and compound vitamins (vitamin C, vitamin B complex, and vitamin E in a weight ratio of 1:2:1) in a weight ratio of 2:3:5:0.1, mixing them evenly and grinding them into powder. The Trichogramma eggs and the compound survival agent were then mixed at a ratio of 1:2:1. 1000 Trichogramma eggs were mixed with 0.5g of composite activator and gently stirred for 10 minutes at 20°C to ensure that the composite activator was evenly attached to the surface of the Trichogramma eggs. The mixture of Trichogramma eggs and composite activator was then aspirated into the pores of the slow-release microspheres prepared in step (1) by vacuum aspiration. The loading was controlled to be 800 Trichogramma eggs per gram of slow-release microspheres. After loading, the slow-release microspheres were placed in an environment of 24°C and 70% humidity for 1.5 hours to ensure that the activity of the Trichogramma eggs was not affected.

[0039] (3) Assembly of the release device: The release device shell is made of biodegradable polylactic acid material. The shell is cylindrical with a diameter of 4.5 cm and a height of 7 cm. The surface of the shell is evenly distributed with vent holes. The diameter of the vent holes is 0.2 mm and the spacing between the vent holes is 0.4 cm. A temperature and humidity sensor (model: DHT22) and a controllable release valve (model: SLA-0310) are installed inside the shell. The temperature and humidity sensor is electrically connected to the controllable release valve. The temperature and humidity trigger thresholds are set as follows: temperature 25-30℃, humidity 60-80%. The opening angle of the controllable release valve is 30°, the opening frequency is once every 2 hours, and the opening time is 10 min each time. The slow-release microspheres loaded with Trichogramma eggs are loaded into the release device shell. Each release device is loaded with 4 g of slow-release microspheres. After sealing the shell, ensure that the vent holes and valve outlet are unobstructed to complete the assembly.

[0040] (4) Layered deployment in the field: The experimental sugarcane field area was 1 hectare. The release devices were evenly deployed in a checkerboard pattern, with a total of 60 release points and a spacing of 15m between adjacent release points. Each release point was set up with three layers of release units: upper, middle and lower. The release units were fixed with bamboo poles. The upper release unit was 10cm away from the sugarcane canopy, the middle release unit was fixed on the back of the sugarcane leaves in the upper middle part of the sugarcane, and the lower release unit was 10cm away from the ground. The spacing between each layer was 30cm. The deployment time was selected when the overwintering generation of sugarcane borers first appeared. It was carried out on a sunny day after 17:00 to avoid heavy rain and strong winds. After deployment, the release devices were checked to ensure they were secure and to prevent them from being blown over by the wind or soaked by rainwater.

[0041] (5) Dynamic supplementary release: 40 sex pheromone traps (with sugarcane borer sex pheromone as the lure core) were evenly deployed per hectare in the experimental sugarcane field. The number of adult sugarcane borers was monitored once every Tuesday morning. At the same time, a 5-point sampling method was used, and 20 sugarcane plants were continuously investigated at each sampling point. Egg masses of borers were collected and examined under a microscope, and the parasitism rate of borer eggs was calculated. On the 12th day after the initial deployment, the sugarcane borer emergence rate reached 20% and the parasitism rate of borer eggs was 67%. A supplementary release was carried out, with the amount of supplementary release being 30% of the initial release amount. The supplementary release device was precisely deployed using a plant protection drone, and the supplementary release point coincided with the initial release point. On the 18th day after the supplementary release, the monitoring was carried out again, and the parasitism rate of borer eggs was 87%. No further supplementary release was required until the end of the sugarcane borer egg stage.

[0042] Experimental results: The release method in this embodiment has an effective period of 32 days, a Trichogramma wasp survival rate of 90%, an average sugarcane borer egg parasitism rate of 86%, and a sugarcane dead heart rate of 1.9%. Compared with the existing drone dart release method, the effective period is extended by 22 days, the Trichogramma wasp survival rate is increased by 20%, the sugarcane borer egg parasitism rate is increased by 16%, the sugarcane dead heart rate is reduced by 7.1%, and the number of re-releases is reduced from 4 to 1, significantly reducing the cost and labor intensity of prevention and control. Example 3

[0043] This embodiment provides a slow-release, long-lasting release method for Trichogramma wasps in the field, applied to the control of bollworms in cotton fields. The specific steps are as follows: (1) Preparation of sustained-release carrier: Chitosan and carrageenan were selected as substrates and mixed at a weight ratio of 1:1. Deionized water was added and stirred to dissolve the mixture, resulting in a 5% concentration mixed solution. 1% of the total mass of the mixed solution was added to the mixed solution as silane coupling agent (KH-570). The mixed solution was placed in a constant temperature water bath at 70℃ and stirred for 40 minutes to allow the silane coupling agent to fully react with the substrate. The mixed solution after reaction was poured into a mold, cooled to room temperature, and then placed in a freeze dryer. It was freeze-dried at -15℃ for 16 hours to prepare porous sustained-release microspheres. The test results showed that the pore size of the sustained-release microspheres was 0.5 mm and the porosity was 50%. The microspheres could remain stable in cotton field soil for more than 38 days and the degradation time was about 60 days. The degradation did not affect cotton growth or soil microecology.

[0044] (2) Trichogramma egg loading and survival treatment: The mid-to-late stage pupal eggs of Trichogramma corn borer were selected. After testing, the parasitism rate of the Trichogramma eggs was 78%, the emergence rate was 90%, and the deformed bee rate was 2%, which met the requirements for use. A compound survival agent was prepared by weighing bamboo flavonoids, trehalose, Chinese herbal honey (honeysuckle and forsythia as nectar sources) and compound vitamins (vitamin C, vitamin B complex, and vitamin E in a weight ratio of 1:2:1) in a weight ratio of 2:3:5:0.2, mixing them evenly and grinding them into powder. The Trichogramma eggs and the compound survival agent were mixed at a ratio of 10 Mix 00 Trichogramma eggs with 1g of composite preservative and gently stir for 15 minutes at 25°C to ensure that the composite preservative is evenly attached to the surface of the Trichogramma eggs. The mixture of Trichogramma eggs and composite preservative is then aspirated into the pores of the slow-release microspheres prepared in step (1) by vacuum aspiration. The loading is controlled to be 1000 Trichogramma eggs per gram of slow-release microspheres. After loading, the slow-release microspheres are placed in an environment of 26°C and 80% humidity for 2.5 hours to ensure that the Trichogramma eggs and the carrier are fully combined and maintain their activity.

[0045] (3) Assembly of the release device: The release device shell is made of biodegradable polylactic acid material. The shell is cylindrical with a diameter of 5.5 cm and a height of 9 cm. The surface of the shell is evenly distributed with vent holes. The diameter of the vent holes is 0.4 mm and the spacing between the vent holes is 0.6 cm. A temperature and humidity sensor (model: DHT11) and a controllable release valve (model: SLA-0520) are installed inside the shell. The temperature and humidity sensor is electrically connected to the controllable release valve. The temperature and humidity trigger thresholds are set as follows: temperature 25-30℃, humidity 60-80%. The opening angle of the controllable release valve is 60°, the opening frequency is once every 4 hours, and the opening time is 15 min each time. The slow-release microspheres loaded with Trichogramma eggs are loaded into the release device shell. Each release device is loaded with 6 g of slow-release microspheres. After sealing the shell, check whether the vent holes and valve outlet are unobstructed to complete the assembly.

[0046] (4) Layered deployment in the field: The experimental cotton field area was 1 hectare. The release devices were evenly deployed in a checkerboard pattern, with a total of 75 release points. The distance between adjacent release points was 12m. Each release point was set up with three layers of release units: upper, middle and lower. The release units were fixed with bamboo poles. The upper release unit was 20cm away from the cotton canopy, the middle release unit was fixed on the back of the upper and middle leaves of the cotton, and the lower release unit was 15cm away from the ground. The distance between each layer was 50cm. The deployment time was selected when the overwintering generation of cotton bollworm adults first appeared. It was carried out on a sunny day after 16:30 to avoid high temperature and strong wind. After deployment, the release devices were ensured to be firmly fixed to prevent them from being washed away by rain or blown away by the wind.

[0047] (5) Dynamic supplementary release: 50 sex pheromone traps (with bollworm sex pheromone as the lure core) were evenly deployed per hectare in the experimental cotton field. The number of adult bollworms was monitored once every Wednesday morning. At the same time, a 5-point sampling method was used, with 20 cotton plants continuously investigated at each sampling point. Bollworm egg masses were collected and examined under a microscope to calculate the parasitism rate of the moth eggs. On the 18th day after the initial deployment, the bollworm emergence rate was monitored to be 20% and the moth egg parasitism rate was 69%. A supplementary release was carried out, with the supplementary release amount being 40% of the initial release amount. The supplementary release device was precisely deployed using a plant protection drone, with the supplementary release point coinciding with the initial release point. On the 20th day after the supplementary release, the moth egg parasitism rate was monitored again to be 89%. No further supplementary release was required until the end of the bollworm egg stage.

[0048] Experimental results: The release method in this embodiment has an effective period of 38 days, a Trichogramma wasp survival rate of 93%, an average bollworm egg parasitism rate of 89%, and a cotton damage rate of 1.7%. Compared with the existing wasp release method, the effective period is extended by 28 days, the Trichogramma wasp survival rate is increased by 23%, the bollworm egg parasitism rate is increased by 19%, the cotton damage rate is reduced by 7.3%, the number of re-releases is reduced from 5 to 1, the control effect is stable, and it is suitable for large-scale control in cotton fields.

[0049] Compare with Example 1 (existing bee card release method) This comparative example uses the existing conventional bee card release method, applied to the same cornfield as Example 1 for corn borer control. The specific steps are as follows: Trichogramma corn borer eggs, identical to those in Example 1, were selected and made into adhesive anti-ant wasp cards. Each card contained ≥1000 Trichogramma wasps, with an egg parasitism rate of 75%, an emergence rate of 88%, and a deformed wasp rate of 3%. The cards were evenly distributed in cornfields at 75 release points per hectare, with one card affixed to each point. The cards were attached to the underside of the upper and middle leaves of the corn plants, with the front side facing down. The release timing was the same as in Example 1: the first release occurred when the overwintering adults of the corn borer first appeared; the second release occurred 5 days later; the third release occurred 5 days after the second release; the fourth release occurred when the emergence rate of the second generation of corn borers reached 20%; and the fifth release occurred when the emergence rate reached 50%. Each release contained 75,000 Trichogramma wasps per hectare. During the release process, the corn borer egg parasitism rate and the survival rate of Trichogramma wasps were monitored weekly, and the duration of effectiveness and the rate of dead heart in the corn plants were recorded.

[0050] Experimental results: The release method of this control case had an effective period of 10 days, a Trichogramma wasp survival rate of 70%, an average corn borer egg parasitism rate of 70%, a corn heart deadness rate of 8.9%, and required 5 re-releases. The labor cost was high, and the control effect was unstable, with a high risk of control gaps in the later stages.

[0051] Compare with Example 2 (release method without modified carrier) This comparative example uses unmodified chitosan-carrageenan microspheres as a carrier. The remaining steps are completely consistent with those in Example 1. It is applied to the control of corn borer in corn fields. The specific difference is that: in step (1), no silane coupling agent is added for modification treatment. Chitosan and carrageenan are directly mixed to form microspheres. The microspheres have a pore size of 0.2 mm and a porosity of 30%. They can only exist stably in the field for about 15 days.

[0052] Experimental results: The release method of this control example had an effective period of 18 days, the survival rate of Trichogramma wasps was 78%, the average parasitism rate of corn borer eggs was 76%, the corn heart deadness rate was 5.3%, and the number of re-releases was 3. Due to the lack of modification of the carrier, the slow release effect was not good, the Trichogramma wasps emerged in a concentrated manner, and it was not possible to continuously provide enough Trichogramma wasps in the later stage, so the control effect was not as good as that of Example 1.

[0053] Compare with Example 3 (Release method without temperature and humidity response device) This comparative example uses a common release device (without temperature and humidity sensors and controllable release valves). The remaining steps are completely consistent with those in Example 1. It is applied to the control of corn borers in corn fields. The specific difference is that in step (3), the release device is only a biodegradable shell with ventilated holes, without temperature and humidity response function. The valve is always in the open state, and the Trichogramma wasps are released directly after they emerge.

[0054] Experimental results: The release method of this control example had an effective period of 22 days, a survival rate of 82% for Trichogramma wasps, an average parasitism rate of 79% for corn borer eggs, and a corn heart deadness rate of 4.5%. The number of re-releases was 2. Due to the lack of temperature and humidity response function, some Trichogramma wasps emerged when the environment was unsuitable and could not effectively parasitize, resulting in a decrease in survival rate and parasitism rate. The control effect was not as good as in Example 1.

[0055] Comparative Example 4 (release method without compound activator) This comparative example does not add a compound surviving agent, and the remaining steps are completely consistent with those in Example 1. It is applied to the control of corn borer in corn fields. The specific difference is that in step (2), the Trichogramma eggs are directly loaded into the slow-release microspheres and are not mixed with the compound surviving agent.

[0056] Experimental results: The release method of this control example had an effective period of 30 days, the survival rate of Trichogramma wasps was 75%, the average parasitism rate of corn borer eggs was 75%, the corn heart deadness rate was 6.2%, and the number of re-releases was 2. Due to the absence of compound survival agent, the Trichogramma wasps eggs were malnourished during the emergence process, had poor resistance, and the survival rate and parasitism rate decreased, resulting in a control effect that was not as good as that of Example 1.

[0057] The comparison between the above embodiments and control examples shows that the field slow-release method for Trichogramma wasps of the present invention, through the synergistic effect of modified slow-release carrier, compound survival agent, temperature and humidity responsive release device, layered deployment and dynamic re-release, significantly prolongs the effective period, improves the survival rate of Trichogramma wasps and the parasitism rate of pest eggs, reduces the number of re-releases, lowers the control cost, and provides stable 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 method for sustained-release and long-lasting release of Trichogramma wasps in the field, characterized in that, Includes the following steps: (1) Preparation of sustained-release carrier: Chitosan and carrageenan are used as substrates, and silane coupling agents are added for modification to prepare porous sustained-release microspheres. The pore size of the sustained-release microspheres is 0.3-0.5 mm and the porosity is 40-50%. (2) Loading and preservation treatment of Trichogramma bee eggs: After mixing Trichogramma bee eggs with a compound preservation agent evenly, the mixture is drawn into the pores of the slow-release microspheres. The compound preservation agent is made by mixing bamboo flavonoids, trehalose, and traditional Chinese medicine honey in a weight ratio of 2:3:

5. The loading amount is 800-1000 Trichogramma bee eggs per gram of slow-release microspheres. (3) Assembly of release device: Load the slow-release microspheres loaded with Trichogramma eggs into a temperature and humidity responsive release device. The device includes a shell, a vent, a temperature and humidity sensor and a controllable release valve. The diameter of the vent is 0.2-0.4 mm. When the field temperature is 25-30℃ and the humidity is 60-80%, the controllable release valve will open automatically. (4) Layered deployment in the field: Distribute the release devices evenly in the crop field at 60-75 release points per hectare. Each release point is set up with three layers of release units: upper, middle and lower. The spacing between each layer is 30-50cm. The upper layer corresponds to the crop canopy, the middle layer corresponds to the middle part of the crop, and the lower layer corresponds to the area near the crop roots. (5) Dynamic release: Monitor the dynamics of adult pests in the field using sex pheromone traps. When the emergence rate of pests reaches 20% or the parasitism rate of stem borer eggs is less than 70%, release once, with the amount of release being 30-40% of the initial release amount.

2. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: The specific process of the modification treatment in step (1) is as follows: chitosan and carrageenan are mixed at a weight ratio of 1:1, deionized water is added to prepare a mixed solution with a concentration of 3-5%, 0.5-1% of silane coupling agent is added to the total mass of the mixed solution, and the mixture is stirred at 60-70℃ for 30-40 min. After cooling to room temperature, porous slow-release microspheres are prepared by freeze drying at a temperature of -20 to -15℃ for 12-16 h.

3. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: The Trichogramma eggs mentioned in step (2) are mid-to-late stage pupal eggs of Trichogramma maculatum or Trichogramma corn borer, with an egg parasitism rate ≥70%, an emergence rate ≥85%, and a deformed bee rate ≤5%.

4. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: The housing of the release device in step (3) is made of biodegradable polylactic acid material. The surface of the housing has evenly distributed vent holes. The controllable release valve is electrically connected to the temperature and humidity sensor. The valve opening angle is 30-60°, the opening frequency is once every 2-4 hours, and the opening time is 10-15 minutes each time.

5. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: The release points in step (4) are arranged in a checkerboard pattern. For crops planted in contiguous areas, the distance between adjacent release points is 12-15m. For crops planted in scattered areas, a release point is set up for every 50-60 crops.

6. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: In step (4), the upper release unit is 10-20cm away from the crop canopy, the middle release unit is located on the back of the upper and middle leaves of the crop, and the lower release unit is 10-15cm away from the ground.

7. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: The sex pheromone traps described in step (5) are deployed at a rate of 40-50 per hectare. The number of adult pests and the parasitism of stem borer eggs are monitored once a week. During re-release, drones are used to precisely deploy the re-release device.

8. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: The compound activator also contains 0.1-0.2% of a compound vitamin, which includes vitamin C, B vitamins and vitamin E in a weight ratio of 1:2:

1.

9. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: In step (2), the mixing ratio of Trichogramma eggs and compound survivability agent is 0.5-1g of compound survivability agent per 1000 Trichogramma eggs, the mixing time is 10-15min, and the mixing temperature is controlled at 20-25℃.

10. The method for sustained-release and long-lasting release of Trichogramma wasps in the field according to claim 1, characterized in that: The slow-release carrier degrades naturally in the field in 45-60 days, leaving no soil residue after degradation and not affecting crop growth or the soil micro-ecological environment.

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