Solution, method, and apparatus for settling insect eggs on plants by spraying

Abstract

The present disclosure makes it possible to increase the likelihood of eggs settling on plants when the eggs are sprayed. The present disclosure is a solution for settling insect eggs on plants by spraying, wherein the solution comprises water and a substance that is viscous when mixed with water.

Description

Solution, method, and apparatus for establishing insect eggs by spreading them on plants

[0001] The present disclosure relates to an additive used for establishing insect eggs on leaves and the like of plants.

[0002] How to prevent damage to crops caused by pests is a critical issue in agriculture. In addition to conventional methods using chemical pesticides, methods for controlling pest damage by utilizing the relationships between living organisms have been tested. For example, methods for controlling pests using specific insects are known. Such specific insects are called natural enemies of pests, and those that have been registered as agricultural chemicals based on the Agricultural Chemicals Regulation Law are called biopesticides, natural enemy pesticides, or natural enemy preparations (see Article 2, Paragraph 2 of the Agricultural Chemicals Regulation Law).

[0003] For example, by attaching eggs of Ephestia kuehniella to the surface of plants, natural enemies that prey on these Ephestia kuehniella eggs, such as carnivorous stink bugs, ladybugs, and predatory mites, can be propagated, and by establishing the natural enemies in the field, they prey on pests, thereby making it possible to reduce damage caused by the target pests (Patent Document 1).

[0004] Japanese Patent Application Publication No. 2007-297293

[0005] When utilizing natural enemies in agriculture, it is necessary to establish the natural enemies in the field, but if there are few pests living in the field, establishment is difficult, and the pest control effect of the natural enemies has been limited. As a method for promoting the establishment of natural enemies in fields, the use of companion plants such as insectary plants and banker plants is known, but there have been problems such as the labor required to install and maintain these plants in fields, and the fact that the natural enemy species for which each companion plant can promote establishment in fields is limited.

[0006] The eggs of the striped rice moth (hereinafter referred to as striped rice eggs) are known as an alternative food source for a wide range of natural enemies, such as the Chinese flower bug, tobacco bug, large-eyed bug, Swirski mite, yellow mite, Limonica mite, Cucumeris mite, false largo mite, ladybug, small tortoise beetle, and Japanese lacewing. However, striped rice eggs have a very high market price, and methods such as scattering them on crops were not practical because the eggs were likely to fall off the crops due to rain, irrigation, or wind.

[0007] The eggs that serve as food for natural enemies are expensive, and there was a problem in that the number of times the eggs were scattered had to be increased in order to always have a certain number of eggs on the plants.

[0008] Therefore, the applicant considered increasing the probability of the eggs settling on plants by mixing a substance with a certain degree of viscosity into the water when scattering (spraying) the eggs.

[0009] This disclosure relates to a solution for fixing insect eggs on a plant by scattering the eggs, wherein the solution consists of water and a substance that becomes viscous when mixed with water. Another aspect of this disclosure is a solution in which the viscous substance is cellulose nanofiber or xanthan gum.

[0010] By using the configuration of this disclosure, it is possible to improve the rate at which eggs scattered on plants are established on the plants.

[0011] Figure 1 shows the results after scattering eggs onto plant leaves and irrigating them. Figure 1 is a magnified view of a section of Figure 1, showing the eggs of the predatory mite *Amblyseius spp.* and the predatory mites that feed on them. Figure representing a leaf disc. Figure showing the number of eggs attached to leaves in *Amblyseius spp.* egg suspension treatment using only pure water, CNF, or Xan (0.2%) aqueous solution. Figure showing the relationship between the concentration of CNF and Xan added to the *Amblyseius spp.* egg suspension and the number of eggs attached. Figure showing the changes in the number of *Swirski* individuals in each experimental group. Figure showing a nozzle suitable for this disclosure that can be attached to a PET bottle or the like.

[0012] <1. Materials and Methods> (1) Evaluation of natural enemy establishment promoters using staghorn fern eggs a) Searching for substances and concentrations that promote the attachment of staghorn fern eggs to plants Seven different solutions of different substances and concentrations were prepared using cellulose nanofibers (hereinafter also called CNF) and xanthan gum (hereinafter also called Xan) (Table 1).

[0013] Table 1 shows the types and concentrations of substances added to the natural enemy establishment promoter.

[0014] A suspension was prepared by uniformly mixing 0.5 g of string bean eggs with 100 mL of each solution. Although referred to as a suspension, a clear liquid may also be used. 0.5 g of string bean eggs corresponds to approximately 18,500 eggs. Using a spray bottle (for example, see the product name "Spray Bottle that can be used upside down" manufactured by Ryohin Keikaku Co., Ltd.), each prepared suspension was sprayed onto one primary leaf of a bean plant in two separate applications.

[0015] In this experiment, the amount of spray used per application was approximately 1 to 1.5 mL. In this case, primary leaves were used to ensure the reproducibility of the experiment, but the method itself can be applied not only to primary leaves but also to other leaves. Furthermore, parts of the plant other than leaves, such as stems and trunks, can also be used. After spraying, the sample was air-dried, and then the moth eggs were removed by irrigating from above with a watering can for 10 seconds. The number of moth eggs remaining on the leaves after the removal treatment was counted, and the adhesion effect of each solution was evaluated. Each experimental group consisted of 6 replicates. Figure 1 shows the appearance of the leaves after eggs were scattered on them and irrigated. Figure 2 is a magnified view of the area in Figure 1, showing moth eggs and the predatory mites that feed on them. In Figure 2, moth eggs are visible on the left side of the center of the photograph, and Swirski mites (hereinafter referred to as Swirski) that feed on these eggs can be seen on the right side of the center.

[0016] b) Evaluation of the effects of CNF and Xan addition on natural enemies and their establishment-promoting effects. Figure 3 shows the prepared leaf discs. Eggs of *Platypleura kaempferi* are placed on the leaves of the leaf discs. Leaf discs were prepared using primary bean leaves with the upper surface facing upwards. A suspension of *Platypleura kaempferi* eggs containing 0.2% CNF or Xan was sprayed once onto these discs and allowed to air dry for two days. As a control, leaf discs without spraying were also prepared. Here, a leaf disc refers to a substrate used for rearing insects and mites, or for phytotoxicity experiments, where leaves are placed on damp cotton wool. After drying, two adult female Swirski mites, natural enemies, were released onto each leaf disc. For 10 days from the start of release, the number of Swirski mites on each disc (total number of adults, larvae / nymphs, and eggs) was investigated every other day. Based on these counting results, the effects of CNF and Xan on Swirski mites and their establishment-promoting effects were evaluated. Each experimental group consisted of four replicates.

[0017] <2. Results and Discussion> a) Searching for substances and concentrations that promote the attachment of staghorn worm eggs to plants Figure 4 shows the number of eggs attached to leaves in staghorn worm egg suspension treatments using pure water only, and 0.2% aqueous solutions of CNF or Xan. There was no significant difference in hatching rates among the experimental groups with the same letter (multiple comparisons by Steel-Dwass method, p < 0.05). Solutions with 0.2% CNF or Xan added to pure water resulted in a significantly higher number of staghorn worm eggs attached to leaves compared to pure water alone (Figure 4). The concentrations described herein are mass percentage concentrations. For example, the concentrations of each additive shown represent the mass percentage concentration relative to 300 g of pure water + additive, with 0.5 g of staghorn worm eggs mixed in 300 g of aqueous solution.

[0018] The data shown in Figure 4 is as follows in Table 2. In Table 2, the concentration of each additive is 0.2%.

[0019] Figure 5 shows the relationship between the concentrations of CNF and Xan added to the stag beetle egg suspension and the number of attached eggs. Furthermore, when the relationship between the concentrations of CNF and Xan and the number of attached eggs was investigated and analyzed, it was suggested that with Xan addition, a nearly constant number of stag beetle egg attachments were observed regardless of the concentration, whereas with CNF addition, although the number of attached eggs was small at low concentrations, attachments increased significantly with increasing concentration (generalized linear mixed model (GLMM) assuming a Poisson distribution, p < 0.05) (Figure 5).

[0020] The data shown in Figure 5 is as presented in Table 3.

[0021] b) Evaluation of the effects of CNF and Xan addition on natural enemies and their establishment-promoting effects. Figure 6 shows the changes in the number of Swirski swamps in each experimental group. The number of Swirski swamps showed different trends in the CNF group, the Xan group, and the control group (pure water, no eggs) (Figure 6).

[0022] The data shown in Figure 6 is as presented in Table 4. This table shows the number of Swirski mite individuals and the number of days elapsed.

[0023] In the control group, the number of Swirski morphs decreased slightly over time, but this change was not statistically significant (generalized linear mixed model, significance level adjusted by Tukey method, p < 0.05).

[0024] On the other hand, the number of Swirski morphs increased significantly in the CNF and Xan groups compared to the control group. In particular, the increase was remarkable in the CNF group, with the number of morphs more than double that of the Xan group after 8 days. These results suggest that adding CNF or Xan to the natural enemy establishment promoter does not have a negative or minimal negative effect on natural enemies. Furthermore, since equal amounts of the staghorn fern egg suspension were sprayed into each test group in this study, the amount of staghorn fern eggs supplied to the leaf disc was approximately 60, which is considered to be equivalent. Therefore, the significant difference in the number of Swirski morphs at the end of the study between the CNF and Xan groups is presumed to be due to the properties of the two additives themselves. It is known that Xan aqueous solution exhibits high viscosity even at relatively low concentrations. This is described, for example, in Miyoshi, Emiko and Yoshimura, Miki (1998), Polysaccharide mixed gels. Journal of Food Science and Technology 45:73-82.

[0025] In this study, both substances showed a tendency for the number of attached *Cypripedium macranthos* eggs to increase with increasing concentration. However, under low concentration conditions, the number of attached *Cypripedium macranthos* eggs was significantly higher in the Xan group (Figure 5). This suggests that the increase in viscosity of the aqueous solution mainly contributes to the number of *Cypripedium macranthos* eggs attached to the leaves. Furthermore, a significant increase in the number of Swirski staghorn flies was observed in the CNF group (Figure 6). In this study, *Cypripedium macranthos* egg suspensions with concentrations of 0.2% CNF and Xan were used. However, since both of these substances are polysaccharides, it is considered unlikely that they have a direct chemical effect on the number of Swirski staghorn flies.

[0026] Therefore, the significant difference in population size between the CNF and Xan groups suggests that the physical properties of each substance, particularly the effect of inhibiting feeding, may be a contributing factor. Furthermore, the results in Figure 5 indicate that, at a concentration of 0.2% for each substance, the Xan group is predicted to have a higher number of leaf-borne *Platypleura sericea* eggs than the CNF group in the predictive model. This suggests that Xan exhibits higher viscosity at a concentration of 0.2%. In summary, these results suggest a trade-off between the leaf-borne attachment rate of *Platypleura sericea* eggs due to solution viscosity and the physical inhibitory effect on feeding by *Swirski* insects. In the future, it will be necessary to determine the optimal additives and concentrations to maximize the establishment and proliferation rates of natural enemies, including *Swirski* insects.

[0027] In this test, Xan and CNF were used, but other substances that can increase the viscosity of aqueous solutions, similar to Xan and CNF, are listed in Table 5.

[0028] Figure 7 shows a nozzle suitable for this disclosure that can be attached to a PET bottle or the like. Such a nozzle can be attached to the mouth of a commercially available PET bottle. The average size of the staghorn flea eggs to be scattered is an ellipsoid with a major axis of 0.57 mm and a minor axis of 0.30 mm. Therefore, when scattering staghorn flea eggs, the diameter of the opening (spray nozzle) at the tip of the nozzle should be at least 0.6 mm, preferably 1 mm or more. When scattering eggs other than staghorn flea eggs, the diameter of the opening (spray nozzle) must be larger than the major axis of the egg.

[0029] The embodiments of this disclosure are described below. <Appendix 1> A solution for fixing insect eggs by scattering them onto a plant, wherein the solution consists of water and a substance that becomes viscous when mixed with water. <Appendix 2> The solution according to Appendix 1, wherein the viscous substance is cellulose nanofiber or xanthan gum. <Appendix 3> The solution according to Appendix 2, wherein the concentration of cellulose nanofiber is 0.1% or more by mass percentage. <Appendix 4> The solution according to Appendix 2, wherein the concentration of xanthan gum is between 0.1% and 0.3% by mass percentage. <Appendix 5> The solution according to Appendix 1 or 2, wherein the eggs are the eggs of the striped rice leaf moth. <Appendix 6> A method for scattering insect eggs, wherein the insect eggs are mixed with a solution of water and cellulose nanofiber or xanthan gum, and the mixture is scattered onto the surface of a plant. <Note 7> A device for dispersing insect eggs, which mixes insect eggs with a solution of water and cellulose nanofiber or xanthan gum and then sprays the solution onto the surface of plants.

[0030] All disclosures in the specification, drawings, and abstract contained in the Japanese application No. 2025-042418, filed on 17 March 2025, are incorporated herein by reference.

[0031] This disclosure is applicable to solutions, methods, apparatus, etc.

Claims

1. A solution for fixing insect eggs by scattering them on a plant, wherein the solution consists of water and a substance that becomes viscous when mixed with water.

2. The solution according to claim 1, wherein the viscous substance is cellulose nanofiber or xanthan gum.

3. The solution according to claim 2, wherein the concentration of the cellulose nanofibers is 0.1% or more by mass.

4. The solution according to claim 2, wherein the concentration of xanthan gum is between 0.1% and 0.3% by mass.

5. The solution according to claim 2, wherein the eggs are eggs of the striped rice meal moth.

6. A method for scattering insect eggs, comprising mixing the insect eggs with a solution of water and cellulose nanofiber or xanthan gum, and then scattering the solution onto the surface of a plant.

7. A device for dispersing insect eggs, which mixes insect eggs with a solution of water and cellulose nanofiber or xanthan gum and disperses them onto the surface of plants.

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