Method for preserving eggs of nematodes parasitic on rice planthoppers, method for controlling rice planthoppers, method for producing pesticides, and biological pesticides

Abstract

To store an egg of a nematode to parasitize a rice planthopper for a long time while preventing a decrease in the hatching rate.SOLUTION: A method for storing an egg of a nematode to parasitize a rice planthopper method, includes a storage step for storing the egg in which embryonic development has already started, while keeping the embryonic state.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for preserving eggs of nematodes that parasitize rice planthoppers, a method for controlling rice planthoppers, a method for producing pesticides, and biological pesticides. [Background technology]

[0002] Brown planthoppers that have acquired insecticide resistance have flown from China to Japan, causing significant damage in various areas. The effectiveness of not only conventional insecticides applied to seedling boxes, but also some insecticides sprayed on rice fields has decreased. There are insecticides that are highly effective, including new insecticides, but these insecticides are also used overseas, which are the source of the insects' arrival, so there are concerns about a decrease in sensitivity. For this reason, there is a need for stable brown planthopper management techniques that do not rely on insecticides as much as possible.

[0003] As a measure against chemical-resistant pests, development of control techniques using natural enemies is progressing in vegetable cultivation. In particular, in greenhouse cultivation, techniques for releasing introduced natural enemies and techniques for enhancing the effectiveness of native natural enemies have been developed. However, techniques for releasing natural enemies have not progressed in paddy rice cultivation. This is due to the lack of technology for breeding promising native natural enemies in paddy rice cultivation, and the fact that paddy fields are open systems, which means that even if natural enemies are released, they do not settle well. Therefore, there is a need to develop techniques for artificially breeding and introducing native natural enemies that have low mobility and dispersal capabilities.

[0004] The insect-parasitic nematode, the planthopper, has been known to exist since before the war as a natural enemy of planthoppers. In rice paddies where the planthopper inhabits in high density, the parasitism suppresses the proliferation of planthoppers and reduces the damage they cause. Furthermore, the planthopper has low mobility and dispersal ability, but a high ability to settle.

[0005] However, when there is little infestation of planthoppers, especially brown planthoppers, the density of planthopper worms in paddy field soil drops drastically. Planthopper worms lay anywhere from a few eggs to over a hundred eggs every day from June to September, totaling several thousand eggs, but planthopper emergence occurs from June or July to October, and the expected control period for planthopper emergence is around August to September. Therefore, in order to effectively control planthoppers, a technique is needed to store planthopper worm eggs until the optimum time for planthopper control.

[0006] Non-patent document 1 describes that when eggs of the Japanese rhinoceros beetle were stored at 5°C immediately after collection, the hatching rates after 30, 90, and 180 days of storage were 80%, 66%, and 17%, respectively.

[0007] Non-Patent Document 2 describes that eggs of the nematode species Filipjevimermis leipsandra are developed to the multicellular stage at room temperature and then kept at 5°C. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Choo et al., Biocontrol Science and Technology, 5:209-223, 1995 [Non-patent document 2] Creighton & Fassuliotis, Journal of Economic Entomology, vol. 75, no. 4, p.701-703,1982 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to effectively control planthoppers, it would be advantageous to be able to store planthopper eggs for long periods of time without reducing the hatching rate. With the technology described in Non-Patent Document 1, the hatching rate drops significantly after three months of storage, and depending on the time of egg collection, the period during which the eggs can be used to control planthoppers is limited. With the technology described in Non-Patent Document 2, the storage period of the stored eggs and the hatching rate after storage are unknown.

[0010] One aspect of the present invention has been made to solve the above-mentioned problems, and its object is to preserve eggs of nematodes that parasitize rice planthoppers for a long period of time while suppressing a decrease in hatching rate. [Means for solving the problem]

[0011] In order to solve the above problems, one embodiment of the present invention provides a method for preserving eggs of nematodes that parasitize rice planthoppers, which includes a storage step of preserving the eggs that have developed into embryos while maintaining the embryonic state.

[0012] A method for controlling rice planthoppers according to one embodiment of the present invention includes a step of using eggs preserved by the method for preserving eggs of nematodes parasitic on rice planthoppers according to one embodiment of the present invention.

[0013] A method for producing a pesticide according to one embodiment of the present invention includes a step of using eggs preserved by the method for preserving eggs of nematodes parasitic on rice planthoppers according to one embodiment of the present invention.

[0014] A biological pesticide according to one embodiment of the present invention comprises a plurality of packaged eggs of a nematode that parasitizes embryonic rice planthoppers. [Effects of the Invention]

[0015] According to one aspect of the present invention, eggs of nematodes that parasitize rice planthoppers can be stored for a long period of time while suppressing a decrease in hatching rate. [Brief explanation of the drawings]

[0016] [Figure 1]This is a diagram showing female adults and eggs of the planthopper. [Figure 2] This is a photograph of the eggs of the planthopper 15 days after collection. [Figure 3] This is a photograph of the eggs of the planthopper on the day of egg collection (within one day of laying). [Figure 4] This is a photograph of the eggs of the planthopper 6 days after collection (6 to 7 days after laying). [Figure 5] This is a photograph of the eggs of the planthopper worm 9 days after collection (9th to 10th day after laying). DETAILED DESCRIPTION OF THE INVENTION

[0017] [Method for preserving eggs of nematodes that parasitize rice planthoppers] A method for preserving eggs of a nematode that parasitizes rice planthoppers according to one embodiment of the present invention (hereinafter sometimes referred to as a preservation method) includes a storage step of preserving the eggs that have already developed into embryos while maintaining the embryonic state. The preservation method may involve obtaining eggs that have already developed into embryos and preserving them in the storage step, or collecting eggs from a nematode that parasitizes rice planthoppers, allowing them to develop into embryos, and preserving them in the storage step. In other words, the preservation method may further include an embryogenesis step of allowing eggs of a nematode that parasitizes rice planthoppers to develop into embryos.

[0018] The preservation method is a method for preserving eggs of nematodes that parasitize rice planthoppers. Nematodes that parasitize rice planthoppers are natural enemies of rice planthoppers such as the brown planthopper, the white-backed planthopper, and the striate brown planthopper, and are nematodes that parasitize rice planthoppers, inhibiting their proliferation and killing them. Nematodes that parasitize rice planthoppers are nematodes of the family Mermithidae, and examples include nematodes of the genus Agamermis, nematodes of the genus Amphimermis, nematodes of the genus Hexamermis, nematodes of the genus Mermis, etc. Examples of nematodes of the genus Agamermis include the rice planthopper (Agamerimis unka) and Agamermis changshaensis, etc.

[0019] (Embryonic development process) The embryonic development process is a process of causing embryonic development in eggs of nematodes that parasitize rice planthoppers. The embryonic development process is a process of bringing eggs of nematodes that parasitize rice planthoppers into any stage of the embryonic development process from cell division to morphogenesis. In one example of the embryonic development process, the embryonic development of eggs of nematodes that parasitize rice planthoppers is completed. Here, completion of embryonic development refers to a state before larvae are formed in the eggs and hatch.

[0020] The eggs to be developed in the embryogenesis step are eggs collected from nematodes that parasitize rice planthoppers. One aspect of the present invention may further include a step of collecting eggs from nematodes that parasitize rice planthoppers. As an example, rice planthopper worms lay several to several hundred eggs every day for several months, totaling several thousand eggs, so eggs are collected every day throughout the egg-laying period.

[0021] Figure 1 shows a female adult planthopper and eggs. Arrows are attached to the eggs that have been laid in Figure 1. The white line at the bottom of Figure 1 indicates a 10 mm scale. When light is shone on them to collect the eggs, the planthopper worms become tangled and form a mass, as shown in Figure 1.

[0022] In the embryo development step, it is preferable to prevent the eggs of the nematodes that parasitize rice planthoppers from drying out, and for example, the eggs are kept in water. Alternatively, the eggs may be kept in a high humidity environment.

[0023] In the embryonic development step, the eggs of the nematode parasitic on rice planthoppers may be kept at a temperature of 13°C or higher and 30°C or lower, thereby allowing the eggs of the nematode parasitic on rice planthoppers to develop into embryos. In the embryonic development step, the eggs of the nematode parasitic on rice planthoppers are more preferably kept at 28°C.

[0024] In the embryonic development step, the eggs of the nematode parasitic on rice planthoppers are held until they develop into embryos. In the embryonic development step, the eggs of the nematode parasitic on rice planthoppers are held, for example, for 1 day or more and 20 days or less. In the embryonic development step, the eggs of the nematode parasitic on rice planthoppers are held preferably for 15 days.

[0025] When eggs of nematodes that parasitize rice planthoppers are kept at a low temperature within the above-mentioned temperature range, it is preferable to keep them for a long period of time to allow embryonic development to proceed. On the other hand, when eggs of nematodes that parasitize rice planthoppers are kept at a high temperature within the above-mentioned temperature range, embryonic development proceeds quickly, so the keeping period can be short. The keeping temperature and keeping period can be set appropriately depending on the progress of embryonic development. In one example of the embryonic development process, eggs of nematodes that parasitize rice planthoppers are kept at 28°C for 15 days.

[0026] In the embryonic development step, it may be determined whether or not the eggs of the nematode parasitic on rice planthoppers have developed into embryos, and the eggs may be held until it is determined that embryos have developed. That is, one aspect of the present invention may further include a determination step of determining whether or not the eggs of the nematode parasitic on rice planthoppers have developed into embryos.

[0027] Whether or not an egg has undergone embryonic development can be determined by examining the state of the egg using a microscope or the like. Here, we will explain the difference between an egg in an embryonic state and an undeveloped egg with reference to Figure 2. Figure 2 shows eggs of the planthopper that have been kept at 28°C for 15 days after collection. The black line at the bottom of Figure 2 represents a scale of 1 mm.

[0028] In Figure 2, the egg indicated by the white arrow is an egg that has completed embryonic development and has not yet hatched, and in which the planthopper has formed. The egg indicated by the black arrow is an undeveloped egg. Whether an egg has undergone embryonic development can be determined by checking the condition of the egg, as shown in Figure 2.

[0029] Furthermore, the embryonic development process will be explained with reference to Figures 3 to 5. Figures 3 to 5 are diagrams explaining the embryonic development process of the planthopper hen fly. Figure 3 shows planthopper hen fly eggs on the day of egg collection (within one day of laying). Figure 4 shows planthopper hen fly eggs six days after egg collection (six to seven days after laying). Figure 5 shows planthopper hen fly eggs 9 days after egg collection (ninth to tenth day after laying). The white lines in Figures 3 to 5 represent a scale of 0.1 mm.

[0030] As shown in Figure 3, within one day of laying, the eggs of the planthopper hen fly have not yet begun cell division, or have only just begun cell division. As shown in Figure 4, some of the eggs of the planthopper hen fly that are six to seven days old have worm-like larvae formed inside them. As shown in Figure 5, some of the eggs of the planthopper hen fly that are nine to ten days old have more slender planthopper larvae formed inside them. For example, hatching of planthopper eggs begins around the 17th to 18th day after laying.

[0031] Alternatively, eggs of nematodes that parasitize rice planthoppers may be determined to have developed when they are kept at a temperature of 13°C or higher and 30°C or lower for a predetermined period of time. As an example, eggs of nematodes that parasitize rice planthoppers are determined to have developed when they are kept at 28°C for 15 days. As shown in Figure 2, eggs kept at 28°C for 15 days after collection have largely completed their development. Therefore, eggs kept at a temperature of 13°C or higher and 30°C or lower for a predetermined period of time can be determined to have developed without checking the state of the eggs.

[0032] (Storage process) The storage step is a step of storing embryonated eggs while maintaining the embryonic state. The storage step may store eggs that have been embryonated by the above-described embryonic development step, or may store eggs that have already been embryonated, without being limited to the above-described embryonic development step. The storage step stores embryonated eggs in the embryonic state without hatching them. In one example of the storage step, eggs in which larvae have formed are stored in the state before hatching.

[0033] During the storage process, it is preferable to prevent the embryonated eggs from drying out, and for example, the eggs are kept in water.

[0034] In the storage step, embryonated eggs may be stored at a temperature of 2°C or higher and 11°C or lower. This allows the embryonated eggs to be stored while maintaining their embryonic state. However, when storing for a long period of time, such as 180 days or longer, at 11°C, several percent or more of eggs may hatch. Therefore, when the storage step is carried out over a long period of time, it is preferable to store the embryonated eggs at a temperature of 3°C or higher and 8°C or lower, and more preferably at a temperature of 4°C or higher and 8°C or lower.

[0035] In the storage step, the eggs are stored until they hatch and the nematodes that parasitize rice planthoppers are used. To more reliably prevent egg hatching and store the eggs for a long period of time, the eggs are stored at a temperature of 4°C or higher and 8°C or lower. In the storage step, embryonated eggs are stored for 30 days or more. In the storage step, embryonated eggs are preferably stored for 60 days or more, 90 days or more, 180 days or more, or 300 days or more.

[0036] According to a preservation method of one aspect of the present invention, by storing embryonic eggs of nematodes that parasitize rice planthoppers, the eggs can be preserved for a long period of time while suppressing a decrease in hatching rate. According to a preservation method of one aspect of the present invention, a high hatching rate is maintained even when eggs of nematodes that parasitize rice planthoppers are stored for 30 days or more. According to a preservation method of one aspect of the present invention, a decrease in hatching rate is also suppressed even when eggs of nematodes that parasitize rice planthoppers are stored for 300 days or more. Therefore, even when there is a long period of time between the collection of eggs of nematodes that parasitize rice planthoppers and the emergence of rice planthoppers, the eggs can be preserved while maintaining a high hatching rate, and the method can be effectively used to control rice planthoppers.

[0037] [Method for controlling rice planthoppers] A method for controlling rice planthoppers according to one embodiment of the present invention includes a step of using eggs preserved by the preservation method according to one embodiment of the present invention.

[0038] In one example of a control method, eggs preserved by the above-described preservation method are scattered over rice paddies inhabited by rice planthoppers. The mechanism of rice planthopper control using rice planthopper eggs is outlined below. The eggs scattered over rice paddies hatch in the water or on the soil surface of the paddy field. The hatched rice planthopper larvae then invade the bodies of rice planthopper larvae at the base of rice plants or above the water. As a result, the rice planthopper larvae grow inside the bodies of the rice planthoppers, rendering them sterile and suppressing egg laying. Ultimately, the rice planthopper larvae break through the rice planthopper's cuticle and escape from its body, killing or injuring the rice planthoppers. Thus, rice planthoppers can be controlled by using rice planthopper eggs.

[0039] The control method may use nematode larvae that parasitize rice planthoppers and are obtained by hatching eggs preserved by the above-mentioned preservation method. That is, the control method may include a step of hatching the eggs preserved by the above-mentioned preservation method and a step of spraying the hatched larvae over paddy fields inhabited by rice planthoppers. As a result, the hatched nematodes invade the bodies of rice planthoppers, suppressing egg laying by the rice planthoppers and ultimately killing and injuring them, thereby controlling rice planthoppers.

[0040] In the control method, a pesticide produced by the pesticide production method according to one embodiment of the present invention described below may be used.

[0041] In the control method according to one embodiment of the present invention, eggs preserved by the preservation method according to one embodiment of the present invention are used, so that even eggs preserved for a long period of time have a high hatching rate, and rice planthoppers can be effectively controlled.

[0042] [Pesticide manufacturing method] A method for producing a pesticide according to one embodiment of the present invention includes a step of using eggs preserved by the preservation method according to one embodiment of the present invention. The pesticide produced by the method for producing a pesticide is a biological pesticide for controlling rice planthoppers.

[0043] In the method for producing a pesticide, a pesticide containing, as a main ingredient, eggs of a nematode parasitic on rice planthoppers preserved by the above-mentioned preservation method is produced. In the method for producing a pesticide, the eggs of a nematode parasitic on rice planthoppers preserved by the above-mentioned preservation method may be hatched, and the resulting nematodes may be contained in the pesticide. Furthermore, in the method for producing a pesticide, water may be contained in the pesticide together with the eggs of a nematode parasitic on rice planthoppers to prevent the eggs from drying out.

[0044] In the method for producing a pesticide according to one embodiment of the present invention, eggs preserved by the preservation method according to one embodiment of the present invention are used, and therefore, even eggs preserved for a long period of time have a high hatching rate and are highly effective in controlling rice planthoppers.

[0045] [Biopesticides] A biological pesticide according to one embodiment of the present invention comprises a plurality of packaged eggs of nematodes that parasitize rice planthoppers in embryonic development. The biological pesticide is obtained by collecting a predetermined number of eggs of nematodes that parasitize rice planthoppers in embryonic development and storing (packaging) them in a single container. The biological pesticide may be produced by the method for producing a pesticide according to one embodiment of the present invention described above.

[0046] The biopesticide preferably comprises, for example, 500,000 or more, 1 million or more, 5 million or more, 10 million or more, 50 million or more, 100 million or more, or 1 billion or more embryonated eggs of a nematode that parasitizes rice planthoppers. The biopesticide may also be packaged with water to prevent the eggs from drying out together with the eggs of a nematode that parasitizes rice planthoppers.

[0047] The biopesticide according to one embodiment of the present invention contains eggs of nematodes that parasitize rice planthoppers at embryonic stage, and therefore has a high hatching rate even when the eggs are stored for a long period of time, resulting in a high rice planthopper control effect. Furthermore, the biopesticide according to one embodiment of the present invention can store eggs for a sufficiently long period of time while preventing a decrease in hatching rate, taking into account the storage of inventory after production and storage until spraying at farms where the eggs are purchased. In other words, the biopesticide according to one embodiment of the present invention has a long shelf life.

[0048] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0049] (1) Comparison of methods for preserving egg of the Japanese hen bug The hatching rate of eggs of the planthopper was compared between the preservation method according to one embodiment of the present invention and a conventional method.

[0050] Planthopper worms collected from paddy field soil in May were stored in the soil for approximately two months at 20°C, with both males and females mixed. Female individuals were removed and placed in each well of a 12-well plate containing approximately 3-4 ml of tap water. The 12-well plate was left at 28°C, and oviposition and development of the laid eggs were observed under a stereomicroscope. Fertilized eggs usually had divided into two or more by the next day.

[0051] After confirming that females were laying fertilized eggs for several days, the females that had laid fertilized eggs were transferred to a plastic container with an inner diameter of approximately 60 mm and the eggs were collected in groups. On the fifth day after confirming egg laying, 17 females were transferred to the plastic container, and on the sixth day, three more females were added, on the seventh day, one more female, and on the eighth day, two more females were added. The eggs obtained from the sixth to eleventh days were used for storage tests.

[0052] The number of eggs laid was counted by drawing 16 radial lines on the back of the plastic container. Since the test required a minimum of 1,700 eggs to be collected per day, the following procedure was carried out from the day when more than 2,000 eggs were collected.

[0053] Furthermore, a previous survey of another individual from the same collection site showed that the maximum egg production was about 80 eggs per day. Therefore, in order to obtain a larger number of eggs, we added a female individual that laid fertilized eggs even after we began collecting eggs for the storage test.

[0054] The number of eggs used in the storage test was as follows: Day 1 (6th day since egg production began): 2,254 eggs; Day 2: 2,616 eggs; Day 3 2,438 eggs; Day 4 3,558 eggs; Day 5 3,280 eggs; Day 6 (11th day since egg laying began): 3,488 eggs.

[0055] After egg collection for the storage test began, females were transferred to a separate plastic container each day. The eggs in the container were counted, and approximately 100–200 eggs were transferred to well 1 of a 6-well plate. The well plate was sealed in a nylon bag and placed in a 28°C incubator under total darkness. One-quarter of the remaining eggs were placed in a sealable plastic container and placed at 8°C, and the other quarter was similarly placed at 4°C. Further, one-quarter of each was placed in two similar plastic containers and placed in a 28°C incubator. The next day, approximately 100–200 eggs were transferred to well 2 of the same 6-well plate, and the same procedure was repeated. Furthermore, on the third day, approximately 100–200 eggs were transferred to well 3 of the same 6-well plate, and the same procedure was repeated. This procedure was repeated for 6 days, resulting in a total of 6 replicates (1 well plate).

[0056] The six-well plates containing the eggs were observed under a stereomicroscope every day, and the number of hatched individuals was counted (Comparative Example 3: Untreated group). Since the hatched larvae swim very actively, an insect specimen needle (No. 00 or fine needle) was attached to the tip of a disposable chopstick or the like to create a needle with a handle. The nematodes were lifted with the needle and transferred to another container to count the number of hatched individuals. The hatching process for each well was observed for 85 days. After dispensing the eggs into the wells, the approximate number was counted, and if the number was low, the amount was increased as appropriate. On the final day of each replication, the number of unhatched eggs was counted, and the hatching rate was calculated based on the number of hatched eggs. An 8 x 8 grid was previously drawn on the back of the six-well plate for counting purposes.

[0057] The two containers kept at 28°C were transferred to incubators at 4°C (Example 1) and 8°C (Example 2), respectively, on the 15th day of storage at 28°C.

[0058] For the containers stored at 4°C (Comparative Example 2) and 8°C (Comparative Example 1), 100 to 200 eggs were transferred to a 6-well plate 30, 90, 180, and 300 days after the start of low-temperature storage, and then placed in an incubator at 28°C. This procedure was repeated for 6 days for each storage period, resulting in 6 replicates (one well plate) for each storage period.

[0059] The number of hatched individuals was counted using the procedure described above for 55 days for eggs stored in a refrigerator after collection, and for 40 days for eggs stored in a refrigerator after being left at 28°C for 15 days after collection.

[0060] The samples included one well plate for the untreated group (Comparative Example 3), six sealed containers for each of the following treatments: storage at 4°C (Comparative Example 2), storage at 8°C (Comparative Example 1), storage at 28°C for 15 days + 4°C (Example 1), and storage at 28°C for 15 days + 8°C (Example 2), and four well plates for hatching tests after each treatment.

[0061] Corning Incorporated's Costar cell culture-treated multiwell plates were used as well plates. 12-well plates were used for individual egg-laying confirmation, and 6-well plates were used for hatching tests. Sample Tech's Model 60 Maru-1 (85 ml, diameter 60 × 34 mm) (polystyrene) was used as the container for egg collection. Deltalab's Model 2840 (20 ml, diameter 34 × 43 ml) (polypropylene) security clean container was used as the airtight container for egg storage. Because eggs may adhere to well plates and plastic containers, the eggs were pipetted firmly when dispensed to suspend them.

[0062] The results are shown in Table 1. The results of Examples 1 and 2 and Comparative Examples 1 to 3 in Table 1 are average values ​​of n=6. For Comparative Example 4, data (n=6) from Non-Patent Document 1 was cited. [Table 1]

[0063] As shown in Table 1, in Examples 1 and 2, a high hatching rate of 80% or more was maintained even after 180 days of storage, and the decline in hatching rate was suppressed even after 300 days of storage. On the other hand, in Comparative Examples 1 and 2, the hatching rate significantly decreased after 30 days of storage. In Comparative Example 4, the hatching rate was high after 30 days of storage, but then decreased, and was significantly lower by 180 days after egg collection. In Comparative Example 3, eggs were hatched at a rate roughly equivalent to that in Examples 1 and 2, but many eggs did not hatch. This suggests that low-temperature storage after embryo development may improve the hatching rate.

[0064] It was shown that by storing embryonic planthopper eggs, it is possible to store them for long periods of time without reducing the hatching rate.

[0065] (2) Development and hatching of egg of the Japanese plague worm stored at 13℃ In order to ensure the long-term storage of Heteroptera pentagonalum eggs, we investigated the development and hatching of eggs stored at 13°C. We used eggs obtained in an egg collection test conducted to investigate the egg-laying potential of Heteroptera pentagonalum from winter to early spring and the period until hatching begins at 25°C. For this test, we used Heteroptera pentagonalum collected from paddy field soil in December.

[0066] Ten adult females, which had been stored in soil at 18°C ​​after collection, were placed in each well of a 12-well plate in late January, along with 3-4 ml of tap water, and allowed to stand at 25°C. Every day, the presence or absence of eggs was checked under a stereomicroscope, and those that had laid eggs were transferred to new wells. Egg collection continued daily until mid-March.

[0067] Of the wells containing laid eggs, 10 wells from March 3rd to 18th were selected, and the number of eggs that had begun to develop was counted the day after egg collection, after which they were stored at 13°C. From the start of storage until August 18th, the number of hatched individuals was counted every few to 10 days. Thereafter, the number of hatched individuals was counted again on September 12th. The results are shown in Table 2. [Table 2]

[0068] In each well, no hatching was observed until June 20th (storage period: 93 to 107 days), but hatched individuals began to be observed from the next survey date, June 30th. Furthermore, the cumulative hatching rate up to the survey date, September 12th, was 30% to 70%. This indicates that egg development can proceed even at 13°C. Furthermore, it was shown that if eggs are stored for 180 days or more, hatching can proceed even when stored at 13°C.

[0069] (3) Preservation of the eggs of the planthopper at 11℃ In order to more reliably preserve the eggs of the planthopper for a long period of time, we investigated the hatching of eggs stored at 11°C. We used eggs obtained in an egg collection test conducted to investigate the egg-laying potential of the planthopper from winter to early spring. For this test, we used planthopper worms collected from paddy field soil in February.

[0070] Ten collected adult females were placed in each well of a 12-well plate with 3-4 ml of tap water and left at 28°C. Every day, the presence or absence of egg laying was checked under a stereomicroscope, and individuals that had laid eggs were transferred to new wells. Egg collection continued daily until late March.

[0071] Wells containing laid eggs were selected from March 10th to 15th, and the number of eggs containing nematodes was counted 15 days after collection at 28°C. The wells were then refrigerated at 11°C. The number of hatched individuals was counted every few to 10 days from the start of storage until August 18th. The number of hatched individuals was then counted again on September 12th. The results are shown in Table 3. [Table 3]

[0072] In each well, the hatchability rate was below 6% until August 18 (storage period: 141 to 146 days), but there were cases where the cumulative hatchability rate exceeded 30% by September 12. As such, storage at 11°C may not be sufficient when storing eggs for 180 days or more. It was shown that storage at 8°C or below is preferable to more reliably guarantee the number of eggs stored for a long period of time. Eggs obtained in the same manner as in this test were also subjected to a 13°C storage test, and hatchability rates of 15 to 79% (average 53%) were observed after 151 to 158 days of storage. [Industrial Applicability]

[0073] The present invention can be used in the fields of agriculture, pesticides, etc.

Claims

1. A method for preserving eggs of nematodes parasitic on rice planthoppers, comprising the steps of: The method includes a storage step of storing the eggs that have developed into embryos with larvae formed within the eggs at a temperature of 2°C or higher and 11°C or lower, while maintaining the embryonic development state.

2. 2. The method according to claim 1, wherein the embryonated eggs are stored at a temperature of 4°C or higher and 8°C or lower in the storage step.

3. 3. The method according to claim 1 or 2, wherein the embryonated eggs are preserved for 30 days or more in the storage step.

4. The method according to any one of claims 1 to 3, further comprising an embryogenesis step of causing the egg to develop into an embryo.

5. The method according to claim 4, wherein the eggs are maintained at a temperature of 13°C or higher and 30°C or lower during the embryo development step.

6. A method for controlling rice planthoppers, comprising a step of using eggs preserved by the method according to any one of claims 1 to 5.

7. A method for producing a pesticide, comprising a step of using eggs preserved by the method according to any one of claims 1 to 5.

8. A package of multiple eggs of a nematode parasitic on rice planthoppers, which have been stored at a temperature between 2°C and 11°C and have developed into embryos with larvae formed within the eggs. Biological pesticides.

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