JP7791572B2 - Method for preserving eggs of nematodes parasitic on rice planthoppers, method for controlling rice planthoppers, method for producing pesticides, and biological pesticides - Google Patents

Description

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.

Rice 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 trays, but also some insecticides sprayed on rice fields has decreased. While there are some insecticides that are highly effective, including new insecticides, these insecticides are also used overseas, which is the source of the insects' arrival, raising concerns about a decline in sensitivity. Therefore, there is a need for stable rice planthopper management techniques that do not rely on insecticides as much as possible.

In order to combat chemical-resistant pests, development is underway in vegetable cultivation to utilize natural enemies for pest control. 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 rice cultivation. This is due to the lack of technology for breeding promising native natural enemies, and the fact that rice paddies 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.

The insect-parasitic nematode, the aphid, has been known to exist since before the war as a native natural enemy of planthoppers. In rice paddies where the aphids live in high densities, their parasitism suppresses the proliferation of planthoppers and reduces the damage they cause. Furthermore, aphids have low mobility and dispersal abilities, but a high ability to settle.

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.

Non-patent document 1 describes that when egg samples of the Japanese hen bug 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.

Non-patent document 2 describes how eggs of the nematode species Filipjevimermis leipsandra are developed to the multicellular stage at room temperature and then maintained 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 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 when the eggs are collected, the period during which they can be used to control planthoppers is limited. With the technology described in Non-Patent Document 2, the storage period for stored eggs and the hatching rate after storage are unknown.

One aspect of the present invention has been made to solve the above-mentioned problems, and its purpose is to preserve eggs of nematodes that parasitize rice planthoppers for long periods of time while suppressing a decrease in hatchability.

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 for preserving the eggs after embryogenesis while maintaining the embryonic state.

A method for controlling rice planthoppers according to one embodiment of the present invention includes a step of using eggs preserved by a method for preserving eggs of nematodes that parasitize rice planthoppers according to one embodiment of the present invention.

A method for producing a pesticide according to one embodiment 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 embodiment of the present invention.

One aspect of the present invention is a biological pesticide that contains multiple packaged eggs of nematodes that parasitize embryonic rice planthoppers.

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

This is a diagram showing female adults and eggs of the planthopper. This is a photograph showing the eggs of the planthopper 15 days after collection. This is a photograph of the eggs of the planthopper on the day of egg collection (within one day of laying). This is a photograph of the eggs of the planthopper 6 days after collection (6th to 7th day after laying). This is a photograph of the eggs of the planthopper worm 9 days after egg collection (9th to 10th day after laying).

[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 the preservation method) includes a storage step of preserving the eggs that have already developed while maintaining their embryonic state. The preservation method may involve obtaining eggs that have already developed 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. That is, the preservation method may further include an embryogenesis step of allowing eggs of a nematode that parasitizes rice planthoppers to develop into embryos.

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, and nematodes of the genus Mermis. Examples of nematodes of the genus Agamermis include the rice planthopper (Agamermis unka) and Agamermis changshaensis.

(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.

The eggs used to develop embryos in the embryo development process 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 anywhere from a few eggs to several hundred eggs every day for several months, totaling several thousand eggs, so eggs are collected every day throughout the egg-laying period.

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 represents 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.

During the embryo development process, it is preferable to prevent the eggs of nematodes that parasitize rice planthoppers from drying out. For example, the eggs are kept in water. Alternatively, the eggs may be kept in a high humidity environment.

In the embryo development process, the eggs of the nematode that parasitizes rice planthoppers may be kept at a temperature of 13°C or higher and 30°C or lower. This allows the eggs of the nematode that parasitizes rice planthoppers to develop into embryos. In the embryo development process, it is more preferable to keep the eggs of the nematode that parasitizes rice planthoppers at 28°C.

In the embryo development process, the eggs of nematodes that parasitize rice planthoppers are held until they develop into embryos. In the embryo development process, for example, the eggs of nematodes that parasitize rice planthoppers are held for at least 1 day and not more than 20 days. In the embryo development process, the eggs of nematodes that parasitize rice planthoppers are preferably held for 15 days.

When eggs of nematodes that parasitize rice planthoppers are kept at low temperatures within the above 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 high temperatures within the above 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. As an example of the embryonic development process, eggs of nematodes that parasitize rice planthoppers are kept at 28°C for 15 days.

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

Whether or not an egg has developed into an embryo can be determined by examining the state of the egg under a microscope, etc. Here, we will explain the difference between an embryonic egg 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.

In Figure 2, the egg indicated by the white arrow is an egg that has completed embryonic development and has not yet hatched, with the planthopper morphologically formed within the egg. In Figure 2, the egg indicated by the black arrow is an undeveloped egg. As shown in Figure 2, whether an egg has undergone embryonic development can be determined by checking the condition of the egg.

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 a planthopper hen fly egg on the day of egg collection (within one day of laying). Figure 4 shows a planthopper hen fly egg 6 days after egg collection (6 to 7 days after laying). Figure 5 shows a planthopper hen fly egg 9 days after egg collection (9 to 10 days after laying). The white lines in Figures 3 to 5 represent a scale of 0.1 mm.

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 can be seen with worm-like larvae forming inside them. As shown in Figure 5, some of the eggs of the planthopper hen fly that are nine to ten days old can be seen with more slender planthopper larvae forming inside them. For example, hatching of planthopper eggs begins around the 17th to 18th day after laying.

In addition, eggs of nematodes that parasitize rice planthoppers may be determined to have developed when they are kept at a temperature between 13°C and 30°C for a specified 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 embryonic development. Therefore, eggs kept at a temperature between 13°C and 30°C for a specified period of time can be determined to have developed without checking the condition of the eggs.

(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.

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

During the storage process, embryonated eggs may be stored at a temperature between 2°C and 11°C. This allows the embryonated eggs to be stored while maintaining their embryonic state. However, if the eggs are stored for a long period of time, such as 180 days or more, hatching may occur at a temperature of several percent or more at 11°C. For this reason, if the storage process is to be carried out over a long period of time, it is preferable to store the embryonated eggs at a temperature between 3°C and 8°C, and more preferably between 4°C and 8°C.

In the storage process, the eggs are stored until they hatch and become nematodes that parasitize rice planthoppers, and are ready for use. To more reliably prevent egg hatching and preserve 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 process, embryonated eggs are stored for 30 days or more. In the storage process, embryonated eggs are preferably stored for 60 days or more, 90 days or more, 180 days or more, or 300 days or more.

According to one aspect of the present invention, by storing embryonic eggs of nematodes that parasitize rice planthoppers, it is possible to store the eggs for long periods of time while suppressing a decrease in hatching rate. According to 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 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 stored while maintaining a high hatching rate, making the method effective for controlling rice planthoppers.

[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.

As an example of a control method, eggs preserved using the above-mentioned preservation method are scattered over rice paddies infested with rice planthoppers. The mechanism of rice planthopper control using rice planthopper eggs is outlined below. 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 rice planthoppers' bodies, 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 planthopper. In this way, rice planthoppers can be controlled by using rice planthopper eggs.

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 the steps of hatching eggs preserved by the above-mentioned preservation method and spraying the hatched larvae over paddy fields inhabited by rice planthoppers. This allows the hatched nematodes to invade the bodies of rice planthoppers, inhibiting their egg-laying and ultimately killing them, thereby controlling rice planthoppers.

The control method may use a pesticide produced by the pesticide production method according to one embodiment of the present invention described below.

The control method according to one embodiment of the present invention uses eggs preserved by a preservation method according to one embodiment of the present invention, so even eggs preserved for a long period of time have a high hatch rate, enabling effective control of rice planthoppers.

[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.

In the method for producing a pesticide, a pesticide containing, as a main ingredient, eggs of a nematode that parasitizes rice planthoppers and that has been preserved by the preservation method described above is produced. In the method for producing a pesticide, the eggs of a nematode that parasitizes rice planthoppers and that has been preserved by the preservation method described above may also be hatched, and the resulting nematodes may be included in the pesticide. Furthermore, in the method for producing a pesticide, water may also be included in the pesticide, along with the eggs of a nematode that parasitizes rice planthoppers, to prevent the eggs from drying out.

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, resulting in a high hatchability rate even for eggs preserved for a long period of time, and a high effect in controlling rice planthoppers.

[Biopesticides]
A biological pesticide according to one embodiment of the present invention comprises a plurality of packaged eggs of a nematode that parasitizes rice planthoppers during embryonic development. The biological pesticide is obtained by collecting a predetermined number of eggs of a nematode that parasitizes rice planthoppers during 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.

The biopesticide preferably comprises packaged eggs of nematodes that parasitize rice planthoppers, for example, at least 500,000, at least 1 million, at least 5 million, at least 10 million, at least 50 million, at least 100 million, or at least 1 billion embryonic eggs of nematodes that parasitize rice planthoppers. The biopesticide may also be packaged with water to prevent the eggs from drying out, along with the eggs of nematodes that parasitize rice planthoppers.

The biological pesticide according to one embodiment of the present invention contains eggs of nematodes that parasitize rice planthoppers in embryonic stages, and therefore has a high hatching rate even when stored for long periods of time, resulting in a high rice planthopper control effect. Furthermore, the biological pesticide according to one embodiment of the present invention can store eggs for a sufficiently long period of time without a decline 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 biological pesticide according to one embodiment of the present invention has a long shelf life.

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.

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

Plantworms collected from paddy field soil in May were stored (at 20°C) in the soil where they were collected, with males and females mixed, for approximately two months. Female individuals were removed and placed one per well of a 12-well plate containing approximately 3-4 ml of tap water. The 12-well plate was left standing at 28°C, and oviposition and development of the laid eggs were confirmed under a stereomicroscope. Fertilized eggs usually had divided into two or more by the next day.

After confirming that they 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 eggs were collected in groups. Five days after egg laying was confirmed, 17 females were transferred to the plastic container, and three more females were added on the sixth day, one on the seventh day, and two on the eighth day. Eggs obtained between the sixth and eleventh days were used for storage tests.

Lines were drawn radially on the back of the plastic container, dividing it into 16 sections, and the number of eggs laid was counted. Since this test required a minimum of 1,700 eggs to be collected per day, the following process was carried out from the day when more than 2,000 eggs were collected.

In addition, a previous survey of another individual from the same collection site showed that the maximum egg production was around 80 eggs per day. Therefore, in order to obtain a larger number of eggs, additional female individuals that laid fertilized eggs were added even after egg collection for the storage test had begun.

The number of eggs used in the storage test was as follows:
Day 1 (6th day since egg laying was confirmed): 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.

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 six-well plate. The well plate was placed in a nylon bag, sealed, and placed in a 28°C incubator under completely dark conditions. 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. Another 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 six-well plate, and the same procedure was repeated. On the third day, approximately 100-200 eggs were transferred to well 3 of the same six-well plate, and the same procedure was repeated. This procedure was repeated for six days, for a total of six replicates (one well plate).

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). Because hatched larvae are very active swimmers, an 8x8 grid was created by attaching an insect specimen needle (No. 00 or fine needle) to the tip of a disposable chopstick or similar item. The nematodes were lifted up with the needle and transferred to another container, and the number of hatched individuals was counted. The hatching process for each well was observed for 85 days. After dispensing the eggs into the wells, an 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 8x8 grid had been drawn on the back of the six-well plate in advance for counting purposes.

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

For the containers stored at 4°C (Comparative Example 2) and 8°C (Comparative Example 1), 100-200 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 a 28°C incubator. This procedure was repeated for 6 days for each storage period, resulting in 6 replicates (one well plate) for each storage period.

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.

The samples included one well plate for the untreated group (Comparative Example 3), six sealed containers for each of the 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 the hatching test after each treatment.

Corning Incorporated Costar cell culture-treated multiwell plates were used as well plates. 12-well plates were used to confirm individual egg laying, and 6-well plates were used for hatching tests. Sample Tech Model 60 Maru-1 (85 ml, diameter 60 x 34 mm) (made of polystyrene) was used as the container for egg collection. Deltalab Model 2840 (20 ml, diameter 34 x 43 ml) (made of 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.

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.

As shown in Table 1, in Examples 1 and 2, a high hatching rate of over 80% 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 dropped significantly after 30 days of storage. In Comparative Example 4, the hatching rate was high after 30 days of storage, but then dropped, and was significantly lower by 180 days after egg collection. In Comparative Example 3, eggs hatched at a rate roughly equivalent to that of Examples 1 and 2, but many eggs did not hatch. This suggests that low-temperature storage after embryo development may improve the hatching rate.

It has been shown that by storing embryonic planthopper eggs, it is possible to store them for long periods of time without reducing the decline in hatchability.

(2) Development and hatching of Henkel eggs stored at 13°C In order to ensure the long-term storage of Henkel eggs, we investigated the development and hatching of eggs stored at 13°C. Eggs were used that were obtained in an egg collection test conducted to investigate the egg-laying potential of Henkel eggs from winter to early spring and the period until hatching begins at 25°C. For this test, Henkel eggs collected from paddy field soil in December were used.

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 left to stand at 25°C. Every day, the presence or absence of eggs was checked under a stereomicroscope, and individuals that had laid eggs were transferred to new wells. Egg collection continued daily until mid-March.

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, and then 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.

No hatching was observed in any of the wells until June 20th (storage period: 93 to 107 days), but hatched individuals began to be observed from the next inspection date, June 30th. Furthermore, the cumulative hatching rate up to the inspection date, September 12th, rose from 30% to 70%. This demonstrates that egg development can occur even at 13°C. Furthermore, it has been shown that when eggs are stored for 180 days or more, hatching can occur even at 13°C.

(3) Storage of Henkel eggs at 11°C In order to store Henkel eggs for a longer period of time more reliably, we investigated the hatching of Henkel eggs stored at 11°C. We used eggs obtained in an egg collection test conducted to investigate the egg-laying potential of Henkel eggs from winter to early spring. For this test, we used Henkel eggs collected from paddy field soil in February.

Ten collected adult females were placed in each well of a 12-well plate, one per well, along with 3-4 ml of tap water, and left to stand 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.

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 days 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.

In each well, the hatch rate was below 6% until August 18th (storage period: 141 to 146 days), but there were cases where the cumulative hatch rate exceeded 30% by September 12th. As such, it is possible that storage at 11°C may not be sufficient when storing eggs for 180 days or more. This indicates that storage at 8°C or below is preferable to more reliably guarantee the number of eggs stored over 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 hatch rates of 15-79% (average 53%) were observed after 151 to 158 days of storage.

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

Claims (8)

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. The method of claim 1, wherein the embryonated eggs are stored at a temperature of 4°C or higher and 8°C or lower during the storage step. The method of claim 1 or 2, wherein the embryonated eggs are preserved for 30 days or more in the storage step. The method of any one of claims 1 to 3, further comprising an embryogenesis step of causing the egg to develop into an embryo. The method of 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. A method for controlling rice planthoppers, comprising a step of using eggs preserved by the method of any one of claims 1 to 5. A method for producing a pesticide, comprising a step of using eggs preserved by the method of any one of claims 1 to 5. The product is a package of eggs of a nematode parasitic on rice planthoppers, which have been stored at a temperature of 2°C or higher and 11°C or lower and have developed into a state in which larvae have been formed within the eggs.
Biological pesticides.