JP2022132073A - Method for storing egg of nematode to parasitize rice planthopper, method for controlling rice planthopper, method for producing agrochemical, and biological pesticide - Google Patents

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 The present invention relates to a method for preserving eggs of nematodes parasitic on rice planthoppers, a method for controlling rice planthoppers, a method for producing an agricultural chemical, and a biopesticide.

Brown planthoppers, which have acquired insecticide resistance, flew to Japan from China, causing great damage in various places. Not only the conventional pesticides for nursery boxes, but also some of the pesticides sprayed by Honda have decreased effectiveness. Although there are some insecticides that are highly effective, including new insecticides, there are concerns about a decrease in susceptibility because these insecticides are also used overseas, where they are the source of the virus. Therefore, there is a demand for highly stable brown planthopper management techniques that do not depend on insecticides as much as possible.

As a countermeasure against drug-resistant insect pests, the development of control technology using natural enemies in vegetable cultivation is underway. Especially in protected cultivation, techniques for releasing introduced natural enemies and techniques for enhancing the action of indigenous natural enemies have been developed. However, in paddy rice cultivation, technology for free-range use of natural enemies has not progressed. The reasons for this include the lack of a promising technique for propagating indigenous natural enemies in paddy rice cultivation, and the fact that paddy fields are open systems, so even if natural enemies are released, they have poor colonization. Therefore, there is a demand for the development of techniques for artificially proliferating and introducing indigenous natural enemies with low migration and dispersal ability.

The insect-parasitic nematode, the leafhopper worm, has been known since before World War II as an indigenous natural enemy of planthoppers. In paddy fields inhabited with high density of planthoppers, the parasitism suppresses the proliferation of planthoppers, thereby deterring their damage. In addition, it has a low ability to disperse movement and a high ability to settle.

However, when planthoppers, especially brown planthoppers, are scarce, the density of planthoppers in the soil of paddy fields is extremely low. From June to September, the planthopper lays several to a hundred and several dozen eggs every day, totaling several thousand eggs. The expected control period is around August to September. Therefore, in order to effectively control planthoppers, a technique is required to store the eggs of the leafhoppers until the appropriate period for planthopper control.

In Non-Patent Document 1, when the eggs of the leaf-crested nematode were stored at 5°C immediately after egg collection, the hatching rates after 30 days, 90 days and 180 days from the start of storage were 80%, 66% and 17%, respectively. It is stated that

Non-Patent Document 2 describes developing eggs of the nematode species Filipjevimermis leipsandra at room temperature to the multicellular stage and then keeping them at 5°C.

Choo et al., Biocontrol Science and Technology, 5:209-223, 1995 Creighton & Fassuliotis, Journal of Economic Entomology, vol.75, no.4, p.701-703, 1982

In order to achieve effective control of planthoppers, it would be advantageous to be able to store the eggs of the planthopper for long periods of time without reducing hatchability. In the technique described in Non-Patent Document 1, the hatching rate drops significantly after 3 months from the start of storage, and the period when it can be used for controlling planthoppers is limited depending on the time of egg collection. In the technique described in Non-Patent Document 2, the storage period of stored eggs and the hatchability after storage are unknown.

One aspect of the present invention has been made to solve the above-described problems, and an object thereof is to store eggs of nematodes parasitic on rice planthoppers for a long period of time while suppressing a decrease in hatchability. aim.

In order to solve the above problems, a method for preserving eggs of nematodes parasitic on rice planthoppers according to one aspect of the present invention includes a storage step of preserving the eggs that have undergone embryogenesis while maintaining the state of embryogenesis. contain.

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

A method for producing an agricultural chemical according to one aspect of the present invention includes a step of using eggs preserved by a method for preserving eggs of nematodes parasitic on rice planthoppers according to one aspect of the present invention.

A biopesticide according to one aspect of the present invention is obtained by packaging a plurality of nematode eggs parasitic on embryonic rice planthoppers.

According to one aspect of the present invention, eggs of nematodes parasitic on rice planthoppers can be stored for a long period of time while suppressing a decrease in hatchability.

Fig. 2 shows adult females and eggs of the leaf-crested nematode. FIG. 15 shows eggs of the leaf-crested nematode 15 days after egg retrieval. Fig. 10 shows eggs of the leaf-hopper flounder on the day of egg collection (within 1 day after laying). Fig. 10 shows eggs of the leaf-crested nematode 6 days after egg collection (6 to 7 days after laying). Fig. 10 shows eggs of the plant-flying fern 9 days after egg collection (9th to 10th day after laying).

[Method for preserving eggs of nematodes parasitic on rice planthoppers]
A method for preserving eggs of nematodes parasitic on rice planthoppers according to one aspect of the present invention (hereinafter sometimes referred to as a preservation method) is a storage method in which the eggs that have undergone embryogenesis are preserved while maintaining the state of embryogenesis. including steps. As a storage method, eggs that have already developed into embryos may be obtained and stored in the storage step, or eggs may be collected from nematodes parasitic on rice planthoppers, embryos may be developed, and stored in the storage step. That is, the preservation method may further include an embryonic development step of embryonic development of eggs of nematodes parasitic on rice planthoppers.

The preservation method is a method for preserving eggs of nematodes parasitic on rice planthoppers. Nematodes that parasitize rice planthoppers are natural enemies of rice planthoppers such as brown planthopper, brown planthopper, and brown planthopper, and are nematodes that parasitize rice planthoppers to suppress their growth and kill them. Nematodes parasitic on rice planthoppers are nematodes of the family Mermithidae, and examples thereof include nematodes of the genus Agamermis, nematodes of the genus Amphimermis, nematodes of the genus Hexamermis, and nematodes of the genus Mermis. . Examples of nematodes belonging to the genus Agamermis include Agamerimis unka and Agamermis changshaensis.

(embryonic development process)
The embryogenesis step is a step of embryonic development of eggs of nematodes parasitic on rice planthoppers. The embryogenesis step is a step of making eggs of nematodes parasitic on rice planthoppers into any state of embryogenesis from cell division to morphogenesis. In the embryogenesis step, as an example, the embryonic development of eggs of nematodes parasitic on rice planthoppers is completed. Here, the completion of embryogenesis is intended to be the state before larvae are formed within the egg and hatched.

Eggs for embryogenesis in the embryonic development process are eggs collected from nematodes parasitic on rice planthoppers. One aspect of the present invention may further include a step of collecting eggs from nematodes parasitic on rice planthoppers. As an example, the leaf-spotted flycatcher lays several eggs to a hundred and several dozen eggs every day for several months, for a total of several thousand eggs, so the eggs are collected every day during the spawning period.

Fig. 1 shows adult females and eggs of the leaf-crested nematode. In FIG. 1, the laid eggs are indicated by arrows. The white line shown at the bottom of FIG. 1 represents a scale of 10 mm. When exposed to light for egg collection, the plant tangles and clumps, as shown in Fig. 1.

In the embryonic development process, it is preferable to prevent drying of eggs of nematodes parasitic on rice planthoppers, and as an example, the eggs are kept in water. Alternatively, the eggs may be held while maintaining high humidity.

In the embryonic development step, eggs of nematodes parasitic on rice planthoppers may be held at 13°C or higher and 30°C or lower. As a result, eggs of nematodes parasitic on rice planthoppers can be embryonized. In the embryogenesis step, it is more preferable to keep the eggs of the nematodes parasitic on rice planthoppers at 28°C.

In the embryogenesis step, the egg of the nematode parasitic on rice planthoppers is retained until the egg undergoes embryogenesis. In the embryonic development step, for example, eggs of nematodes parasitic on rice planthoppers are held for 1 day or more and 20 days or less. In the embryonic development step, eggs of nematodes parasitic on rice planthoppers are preferably retained for 15 days.

When eggs of nematodes parasitic on rice planthoppers are kept at a low temperature within the above temperature range, it is preferable to keep the eggs for a long period of time to promote embryo development. On the other hand, when eggs of nematodes parasitic on rice planthoppers are held at a high temperature within the above temperature range, the embryonic development progresses rapidly, so the holding period may be short. The holding temperature and holding period may be appropriately set according to the progress of embryogenesis. In the embryonic development step, for example, eggs of nematodes parasitic on rice planthoppers are kept at 28° C. for 15 days.

In the embryonic development step, it may be determined whether or not eggs of nematodes parasitic on rice planthoppers have undergone embryogenesis, and the eggs may be retained until it is determined that they have undergone embryogenesis. That is, one aspect of the present invention may further include a determination step of determining whether or not eggs of nematodes parasitic on rice planthoppers have undergone embryogenesis.

Whether or not the egg has undergone embryogenesis can be determined by confirming the state of the egg with a microscope or the like. An embryonic egg and an undeveloped egg will now be described with reference to FIG. FIG. 2 is a diagram showing the eggs of the plant-flying nematode kept at 28° C. for 15 days after egg retrieval. The black line shown at the bottom of FIG. 2 represents a scale of 1 mm.

In FIG. 2 , the egg indicated by the white arrow is the egg before hatching in which the embryonic development is completed and the leaf-hopper fern is morphologically formed inside the egg. In FIG. 2, eggs indicated by black arrows are undeveloped eggs. As shown in FIG. 2, whether or not an egg has undergone embryonic development can be determined by confirming the state of the egg.

Furthermore, the process of embryonic development will be described with reference to FIGS. 3 to 5. FIG. FIGS. 3 to 5 are diagrams for explaining the process of embryonic development of the leaf-hopper nematode. FIG. 3 shows an egg of the leaf-hopper nematode on the day of oviposition (within one day after laying). FIG. 4 shows the eggs of the plant-flying finch 6 days after egg collection (6 to 7 days after laying). FIG. 5 shows the eggs of the plant-flying finch 9 days after egg collection (9 to 10 days after laying). The white lines shown in FIGS. 3-5 represent a scale of 0.1 mm.

As shown in FIG. 3, the eggs of the leaf-crested nematode within one day of laying have not yet started cell division or have just started cell division. As shown in FIG. 4, worm-like larvae are sometimes found in the eggs of 6 to 7 days after laying. As shown in FIG. 5, some 9- to 10-day-old eggs of the leaf-hopper nematode have more elongated leaf-hopper larvae formed inside the egg. As an example, the hatching of the eggs of the leaf-crested nematode begins around the 17th to 18th day after birth.

Further, when eggs of nematodes parasitic on rice planthoppers are held at 13° C. or higher and 30° C. or lower for a predetermined period of time, it may be determined that the eggs have undergone embryogenesis. As an example, eggs of nematodes parasitic on rice planthoppers are determined to have undergone embryogenesis when held at 28° C. for 15 days. As shown in FIG. 2, the embryonic development of the eggs kept at 28° C. for 15 days after collection is almost complete. Therefore, eggs that have been kept at 13° C. or higher and 30° C. or lower for a predetermined period of time can be determined to have undergone embryonic development without confirming the state of the eggs.

(Storage process)
The storage step is a step of preserving the eggs that have undergone embryogenesis while maintaining the state of embryogenesis. In the storage step, the eggs that have undergone embryogenesis in the above-described embryogenesis step may be stored, or eggs that have already undergone embryogenesis may be obtained and stored without being limited to the above-described embryogenesis step. The storage step preserves the embryonated eggs in their embryonic state without hatching. In the storage step, as an example, eggs in which larvae are formed are stored in a state prior to hatching.

In the storage step, it is preferable to prevent desiccation of the embryonated eggs, for example by keeping the eggs in water.

In the storage step, embryonated eggs may be stored at 2° C. or higher and 11° C. or lower. As a result, eggs that have undergone embryogenesis can be preserved while maintaining the state of embryogenesis. In the case of long-term storage such as 180 days or more, hatching of several percent or more may occur at 11°C. For this reason, when the storage step is for a long period of time, it is preferable to store embryonated eggs at 3° C. or higher and 8° C. or lower, more preferably 4° C. or higher and 8° C. or lower.

In the storage step, eggs are hatched and stored until nematodes parasitic on rice planthoppers are used. Stored below. In the storage step, embryonated eggs are stored for 30 days or longer. In the storage step, the embryonated egg is preferably stored for 60 days or longer, 90 days or longer, 180 days or longer, or 300 days or longer.

According to the storage method according to one aspect of the present invention, by storing eggs of nematode parasites that have developed embryos, eggs can be stored for a long period of time while suppressing a decrease in hatchability. According to the storage method according to one aspect of the present invention, a high hatching rate is maintained even when the eggs of nematodes parasitic on rice planthoppers are stored for 30 days or more. According to the storage method according to one aspect of the present invention, even when eggs of nematodes parasitic on rice planthoppers are stored for 300 days or longer, a decrease in hatchability is suppressed. Therefore, even if there is a long period of time from the collection of eggs of nematodes that parasitize rice planthoppers to the emergence of rice planthoppers, the eggs can be preserved while maintaining a high hatching rate. It can be effectively used for control.

[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.

In the control method, as an example, the eggs preserved by the preservation method described above are sprayed on paddy fields inhabited by rice planthoppers. The outline of the control mechanism of rice planthoppers by using eggs of planthoppers is explained. Eggs scattered in the paddy field hatch in the water or on the soil surface of the paddy field. Then, the hatched planthopper larvae invade the body of the rice planthopper larvae present at the source of the rice stock or on the surface of the rice paddy. As a result, planthoppers grow in the bodies of the rice planthoppers, sterilizing the rice planthoppers and suppressing spawning. Ultimately, the planthopper breaks through the epidermis of the planthopper and escapes from its body, killing and injuring the planthopper. Thus, rice planthoppers can be controlled by using the eggs of the planthopper.

In the control method, larvae of nematodes parasitic on rice planthoppers obtained by hatching eggs preserved by the above preservation method may be used. That is, the control method may include a step of hatching the eggs preserved by the above-described preservation method, and a step of spraying the larvae obtained by hatching to paddy fields inhabited by rice planthoppers. As a result, the hatched nematodes invade the bodies of the rice planthoppers, the spawning of the rice planthoppers is suppressed, and finally the rice planthoppers are killed or injured, so that the rice planthoppers can be controlled.

As for the control method, an agricultural chemical manufactured by a method for manufacturing an agricultural chemical according to one embodiment of the present invention, which will be described later, may be used.

In the control method according to one embodiment of the present invention, since eggs preserved by the preservation method according to one embodiment of the present invention are used, the hatching rate is high even with eggs preserved for a long period of time, and rice planthoppers are effectively controlled. can do.

[Method for producing pesticide]
A method for producing an agricultural chemical 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 pesticide production method is a biological pesticide for controlling rice planthoppers.

In the method for producing an agricultural chemical, an agricultural chemical containing, as a main component, eggs of nematodes parasitic on rice planthoppers preserved by the above-described preservation method is produced. In addition, in the method for producing an agricultural chemical, eggs of nematodes parasitic on rice planthoppers preserved by the above-described preservation method may be hatched, and the obtained nematodes may be included in the agricultural chemical. Furthermore, in the method for producing an agricultural chemical, the agricultural chemical may contain eggs of nematodes parasitic on rice planthoppers and water that prevents the eggs from drying out.

In the method for producing an agricultural chemical according to one embodiment of the present invention, since eggs preserved by the preservation method according to one embodiment of the present invention are used, the hatching rate is high even with eggs preserved for a long period of time, and the effect of controlling rice planthoppers. is high.

[Biological pesticide]
A biopesticide according to one embodiment of the present invention is obtained by packaging a plurality of nematode eggs parasitic on embryonic rice planthoppers. The biopesticide is obtained by collecting a predetermined number of nematode eggs parasitic on embryonic rice planthoppers and housing (packaged) them in one container. The biopesticide may be produced by the method for producing an agrochemical according to one aspect of the present invention described above.

The biopesticide parasitizes, 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 embryonic rice planthoppers. It is preferable that the nematode eggs are packaged. In addition, the biopesticide may be packaged with eggs of nematodes parasitic on rice planthoppers and water to prevent the eggs from drying out.

Since the biopesticide according to one embodiment of the present invention contains eggs of nematodes parasitic on embryonated rice planthoppers, the eggs have a high hatching rate even when stored for a long period of time, and are highly effective in controlling rice planthoppers. In addition, the biopesticide according to one aspect of the present invention can store eggs while preventing a decrease in hatchability for a sufficiently long period of time, considering storage of inventory after production and storage until spraying at the farm where it was purchased. . That is, the biopesticide according to one aspect of the present invention has a long effective period.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

(1) Comparison of Preservation Methods for Eggs of Leaf-crested Hedgehog A comparison was made of the hatchability of eggs of the leaf-crested nematode between the preservation method according to one embodiment of the present invention and the conventional method.

The leaf-crested worms collected from the paddy field soil in May were stored (at 20°C) for about two months in the collected soil in a mixed sex. A female individual was taken out and placed in each well of a 12-well plate containing about 3 to 4 ml of tap water. The 12-well plate was allowed to stand at 28° C., and oviposition and development of laid eggs were confirmed under a stereoscopic microscope. In the case of a fertilized egg, it was usually divided into two or more by the next day.

After confirming the laying of fertilized eggs for several days, the female individuals that laid fertilized eggs were transferred to a plastic container with an inner diameter of about 60 mm, and eggs were collected in groups. On the 5th day after confirming spawning, 17 females were transferred to a plastic container, 3 females were added on the 6th day, 1 female was added on the 7th day, and 2 females were added on the 8th day. Eggs obtained from the 6th day to the 11th day were subjected to a storage test.

A line dividing the back surface of the plastic container into 16 radial lines was drawn in advance, and the number of laid eggs was counted. Since at least 1,700 eggs per day were required for this test, the following steps were carried out from the day when 2,000 eggs or more began to be obtained.

In addition, the number of eggs laid by a separate specimen derived from the same collection site was about 80 eggs/day at most. Therefore, in order to obtain a larger number of eggs, females that laid fertilized eggs even after starting egg collection for the storage test were added.

The number of eggs subjected to the storage test was as follows:
Day 1 (sixth day after confirming spawning) 2,254 eggs;
Day 2 2,616 eggs;
Day 3 2,438 eggs;
Day 4 3,558 eggs;
Day 5 3,280 eggs;
6th day (11th day after confirming spawning) 3,488 eggs.

After egg collection for the storage test was started, females were transferred to another plastic container every 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 placed in a nylon bag, sealed, and placed in a 28° C. incubator under all-dark conditions. 1/4 of the leftover egg was placed in a sealable plastic container and left at 8°C and 1/4 at 4°C. Further, each 1/4 portion was placed in two similar plastic containers and allowed to stand in a thermostat at 28°C. The next day, approximately 100-200 eggs were transferred to well 2 of the same 6-well plate, and so on. Additionally, on day 3, approximately 100-200 eggs were transferred to well 3 of the same 6-well plate, and so on. This operation was repeated for 6 days, making a total of 6 repetitions (1 well plate).

The 6-well plate containing the eggs was observed under a stereoscopic microscope every day, and hatched individuals were counted (Comparative Example 3: untreated group). Since the hatched larvae swim very actively, a needle for insect specimens (No. 00 or fine needle) is attached to the tip of a disposable chopstick to create a needle with a handle, lift the nematode with the needle, and transfer it to another container. The number of hatched individuals was counted by Each well was observed for 85 days of hatching progress. After the eggs were dispensed into the wells, the approximate number was counted and if less, the volume was increased accordingly. Unhatched eggs were counted on the last day of each repetition and combined with the number of hatched eggs to calculate hatchability. The back of the 6-well plate was pre-drawn with an 8x8 grid for counting.

After 15 days of storage at 28°C, the two containers placed at 28°C were transferred to incubators at 4°C (Example 1) and 8°C (Example 2), respectively.

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 days, 90 days, 180 days, and 300 days after the start of low-temperature storage. It was placed in a thermostat at °C. This operation was repeated for 6 days for each storage period, making 6 repetitions (1 well plate) for each storage period.

Eggs that had been refrigerated after collection were counted for 55 days, and eggs that had been left to stand at 28° C. for 15 days after collection and then refrigerated for 40 days were counted according to the procedure described above.

In addition, untreated group (Comparative Example 3) 1 well plate, stored at 4°C (Comparative Example 2), stored at 8°C (Comparative Example 1), stored at +4°C for 15 days at 28°C (Example 1), stored at 28°C for 15 days There were 6 sealed containers for each treatment stored at +8°C (Example 2) and 4 well plates for hatching test after each treatment.

The well plates used were Costar cell culture treated multi-well plates from Corning Incorporated. A 12-well plate was used for individual oviposition confirmation and a 6-well plate for hatching tests. Model 60maru-1 (85 ml, diameter 60×34 mm) (made of polystyrene) manufactured by Sun Platec Co., Ltd. was used as a container for collecting eggs. A Deltalab model 2840 (20 ml, 34 x 43 ml diameter) (polypropylene) security clean container was used as a closed container for egg storage. Since eggs may adhere to well plates and plastic containers, the eggs were suspended by pipetting firmly when dispensing the eggs.

Table 1 shows the results. The results of Examples 1 and 2 and Comparative Examples 1 to 3 in Table 1 are average values of n=6. As Comparative Example 4, the data (n=6) of Non-Patent Document 1 was cited.

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 a decrease in hatching rate was suppressed even after 300 days of storage. was On the other hand, in Comparative Examples 1 and 2, the hatchability decreased significantly after 30 days of storage. In Comparative Example 4, the hatching rate was high after 30 days of storage, but decreased thereafter, and decreased significantly 180 days after egg collection. In Comparative Example 3, almost the same number of eggs as in Examples 1 and 2 were generated, but many eggs that did not hatch were observed. It was suggested that cryopreservation after embryonic development may improve the hatchability.

It was shown that eggs of the leaf-hopper nematode that had developed embryos could be stored for a long period of time without decreasing the hatchability.

(2) About the development and hatching of the eggs of the leaf-crested nematode during storage at 13°C In order to ensure the long-term storage of the eggs of the leaf-crested nematode, investigate the development and hatching of the eggs during storage at 13°C. did. Eggs obtained in an egg collection test conducted to investigate the egg-laying potential from winter to early spring and the period from the start of hatching at 25° C. were used. In addition, in this test, we used the leaf-crested nematodes collected from the soil of the paddy field in December.

Ten female imagoes that had been stored in soil at 18°C after collection were placed in each well of a 12-well plate with 3 to 4 ml of tap water at the end of January, and allowed to stand at 25°C. Every day, the presence or absence of egg laying was confirmed under a stereomicroscope, and the egg-laying individuals were transferred to new wells, and the daily egg collection was continued until mid-March.

Ten wells containing laid eggs were selected from March 3 to March 18, and the number of eggs that had begun to develop on the day following egg collection was counted and then stored at 13°C. The number of hatched individuals was counted every several days to 10 days after the start of preservation until August 18th. After that, the number of hatched individuals was counted on September 12th. Table 2 shows the results.

In each well, hatching was not observed until June 20 (storage period: 93 days to 107 days), but hatched individuals were observed from the next survey date, June 30. In addition, the cumulative hatching rate up to September 12, the date of the survey, increased from 30% to 70%. Thus, it was shown that egg development may proceed even at 13°C. It was also shown that when eggs are stored for 180 days or more, hatching may proceed even when stored at 13°C.

(3) Preservation of the eggs of the plant-flying nematode at 11°C In order to more reliably store the eggs of the plant-flying nematode for a long period of time, the hatching of the eggs of the plant-flying nematode under storage at 11°C was investigated. . We used the eggs obtained in the egg collection test conducted to investigate the egg-laying potential of the brood-crested mantis from winter to early spring. In addition, in this test, we used the leaf-crested nematodes collected from the paddy field soil in February.

10 collected female imagoes were placed in each well of a 12-well plate together with 3 to 4 ml of tap water and allowed to stand at 28°C. Every day, the presence or absence of egg laying was confirmed under a stereoscopic microscope, and the egg-laying individuals were transferred to new wells, and the daily egg collection was continued until the end of March.

Of the wells containing laid eggs, select wells from March 10 to 15, count the number of eggs in which nematodes were formed after 15 days at 28 ° C. after egg collection, and then store in a refrigerator at 11 ° C. did. The number of hatched individuals was counted every several days to 10 days after the start of preservation until August 18th. After that, the number of hatched individuals was counted on September 12th. Table 3 shows the results.

In each well, the hatching rate was 6% or less until August 18 (storage period: 141 days to 146 days), but some cases where the cumulative hatching rate exceeded 30% on September 12 were observed. Thus, if eggs are to be stored for 180 days or longer, storage at 11°C may not be sufficient. It was shown that storage at 8° C. or less is desirable in order to more reliably guarantee the number of stored eggs for a long period of time. A 13° C. storage test was also conducted on the eggs obtained in the same manner as in this test, and a hatching rate of 15 to 79% (average 53%) was observed after storage for 151 to 158 days.

INDUSTRIAL APPLICABILITY The present invention can be used in fields such as agriculture and agricultural chemicals.

Claims (8)

A method for preserving eggs of nematodes parasitic on rice planthoppers, comprising:
A method comprising a storage step of preserving said embryonated egg while maintaining its embryogenic state. 2. The method according to claim 1, wherein in the storage step, the embryonated eggs are stored at 4[deg.]C or higher and 8[deg.]C or lower. 3. The method according to claim 1 or 2, wherein in the storing step, the embryonated eggs are stored for 30 days or more. 4. The method of any one of claims 1-3, further comprising an embryogenesis step of embryogenerating the egg. 5. The method of claim 4, wherein the egg is maintained at 13[deg.]C or higher and 30[deg.]C or lower in the embryonic development step. 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. A method for producing an agricultural chemical, comprising a step of using eggs preserved by the method according to any one of claims 1 to 5. A biological pesticide that is made by packaging multiple nematode eggs that parasitize embryonic rice planthoppers.

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