JP5307450B2 - Method for producing encapsulated fumigant - Google Patents

Description

The present invention relates to a method for producing an encapsulated fumigant suitable for controlling pests and pathogens that invade roots of crops such as root-knot nematodes.

  In the production of agricultural crops, if continuous cropping or soil-biased soil management continues for many years, pests such as root-knot nematodes that invade crop roots in the soil, pathogens, viruses, etc. will breed and increase the production activity. It becomes difficult. For this reason, it is necessary to regularly control pests on farmland, and one of the control methods is a control method using a soil fumigant.

  Conventionally, methyl bromide has been widely used as an effective fumigant for soil. This methyl bromide has been widely used because it has little phytotoxicity to crops, is effective against many types of pests, and has high volatility, so it has a stable effect even in winter when the temperature is low. Since the ozone layer was found to be destroyed by a force 58 times that of chlorine, its use except for essential uses was abolished in 2005.

Therefore, in recent years, as a fumigant for soil, chloropicrin, which has a high bactericidal and insecticidal effect and is highly volatile, has been frequently used, although it is less effective than methyl bromide (Patent Documents 1 to 3). 3).
Japanese Patent Application Laid-Open No. 07-112905 JP 2000-336003 A JP 2002-29902 A

 However, although chlorpicrin is highly volatile and does not remain in the soil, it is a harmful liquid equivalent to a deleterious substance with a strong irritating odor and tearing properties, so it is not easy to handle as a fumigant and control There are problems in terms of work safety, and there are concerns about environmental pollution due to gas emission around the controlled farmland. On the other hand, consumer needs for agricultural products that refrain from using chemical fertilizers and pesticides due to organic farming methods are increasing, and the promotion of farming methods that reduce chemical fertilizers and pesticides is an important agricultural policy internationally. Has been.

  Under such circumstances, there is an urgent need to develop and disseminate a fumigant for soil that has high bactericidal and insecticidal performance, has little adverse effects on the human body and the environment, and is easy to handle.

  In view of the above circumstances, the present inventors are a compound that has been approved as a food additive in the process of intensive studies to develop a high-performance fumigant that can replace conventional methyl bromide and chloropicrin. We focused on allyl isothiocyanate. This allyl isothiocyanate is a compound with excellent sterilizing and insecticidal ability and a unique strong irritating odor, but has no harm to the human body and the environment as used in food additives, and was used as a fumigant. In this case, the safety of the control work can be ensured, and the adverse effect on the surrounding environment is not caused.

  However, since allyl isothiocyanate is a highly volatile substance, it is necessary to take measures to bring about moderate sustained release in the soil in order to fully exhibit the fumigation effect. Therefore, as a result of further earnest studies on means for obtaining this sustained release property, it was found that moderate sustained release property can be imparted to allyl isothiocyanate by microencapsulation, and the present invention has been made.

That is, the method for producing an encapsulated fumigant according to the invention of claim 1 comprises an organic phase containing an isocyanate compound containing all or one isocyanate group and allyl isothiocyanate, and an aqueous phase containing a dispersion stabilizer. It is characterized by stirring and mixing in a non-oxidizing atmosphere, generating matrix-type polyurea microcapsules having allyl isothiocyanate as a core material by an oil-water interface reaction, and freeze-drying the microcapsules obtained by filtration.

According to a second aspect of the present invention, in the method for producing an encapsulated fumigant according to the first aspect , the isocyanate compound in the organic phase includes tolylene diisocyanate and phenyl isocyanate.

According to a third aspect of the present invention, in the method for producing an encapsulated fumigant according to the second aspect, the molar ratio of tolylene diisocyanate / phenyl isocyanate is set to 3.5 / 1 to 5/1.

According to a fourth aspect of the present invention, in the method for producing an encapsulated fumigant according to the first or second aspect , the organic phase includes a dispersion stabilizer and the aqueous phase includes a gelatin as a dispersion stabilizer.

According to the manufacturing method of encapsulating fumigant according to the invention of claim 1, the oil-water interfacial reaction with O / W emulsion was excellent and disinfection insecticidal performance and vaporizable is harmless to the human body and the environment, allyl A matrix-type polyurea microcapsule containing isothiocyanate can be reliably produced.

According to the second aspect of the present invention, in the above method for producing an encapsulated fumigant, high-quality matrix-type polyurea microcapsules can be obtained because tolylene diisocyanate and phenyl isocyanate are used as the isocyanate compound in the organic phase.

According to the invention of claim 3, in the method for producing an encapsulated fumigant, since the molar ratio of tolylene diisocyanate and phenyl isocyanate forming the wall material of the microcapsule is set within a specific range, a high microcapsule yield is obtained. Rate and allyl isothiocyanate content are obtained.

According to the invention of claim 4, in the method for producing the encapsulated fumigant, since the organic phase contains a dispersion stabilizer and gelatin as the aqueous phase dispersion stabilizer, allyl isothiocyanate excellent as the fumigant. The matrix-type polyurea microcapsules can be produced more reliably.

In the encapsulated fumigant of the present invention, allyl isothiocyanate (CH ₂ ═CHCH ₂ —N═C═S) used as a volatile active ingredient is a highly volatile insecticidal insecticidal ability as described above. It is a compound and has a unique strong irritating odor but is recognized as a food additive. In the present invention, in order to sufficiently exhibit the bactericidal and insecticidal ability of this highly volatile allyl isothiocyanate to soil or the like, it is microencapsulated to give sustained release properties. In addition, the microencapsulation improves the handling of the fumigant and significantly reduces the irritating odor peculiar to allyl isothiocyanate.

  As means for obtaining the microcapsules, there are many production methods ranging from chemical production methods to physicochemical production methods and mechanical production methods, and the most suitable means is an interfacial polymerization method belonging to the chemical production method. In this interfacial polymerization method, a monomer component is polymerized at the interface between the content (core substance) and the dispersion solvent like an O / W emulsion to produce a polymer film of the wall material. Polyurea is recommended as this wall material polymer. Is done.

  That is, in a microcapsule using a polyurea film as a wall material, the permeability can be controlled by the degree of porosity and thickness of the wall material, and thus the sustained release behavior of allyl isothiocyanate as a core material can be adjusted appropriately, and the allyl isothiocyanate can be adjusted. Can be completely transpired over time, and inhibition of germination of plant seeds due to the residue can be prevented. In addition, such polyurea microcapsules are advantageous in that the environmental impact is small in terms of material and the manufacturing cost can be reduced because they are relatively easy to manufacture.

  In order to produce such an allyl isothiocyanate-encapsulated polyurea microcapsule, an organic phase containing an allyl isothiocyanate as a core material and an isocyanate compound containing one or more isocyanate groups as a wall material monomer, dispersion stability The aqueous phase containing the agent is stirred and mixed in a non-oxidizing atmosphere to form an O / W emulsion, and stirring and mixing is continued in the same atmosphere for a certain period of time, so that allyl isothiocyanate can be obtained by wall reaction at the oil-water interface. A matrix type polyurea microcapsule having a core material as a core material may be produced, and the microcapsule obtained by filtration and washing with water may be freeze-dried.

The polyurea skeleton of the microcapsule is generated by the reaction of the following formulas [I] and [II], but micropores are formed by degassing of carbon dioxide gas (CO ₂ ) generated in the formula [I], so that the matrix type It becomes a polyurea microcapsule having a porous structure.

H O
｜ ‖
_{-NCO + H 2 O → -N-} C-OH → -NH 2 + CO 2 ↑ ... [I]

H O H
｜ ｜ ｜
_{-NCO + -NH 2 → -N-C} -N- ... (II)

  Here, as an isocyanate compound of the wall material monomer, a monoisocyanate compound such as tolylene isocyanate (phenyl isocyanate), 2,4-tolylene diisocyanate (tolylene diisocyanate), phenylene diisocyanate, dinaphthalene diisocyanate, hexamethylene diisocyanate, Diisocyanate compounds such as diphenylmethane diisocyanate, isophorone diisocyanate, xylylene diisocyanate, methylene bis (cyclohexyl isocyanate), bis (isocyanate methyl) cyclohexane, 1,5-naphthalene diisocyanate, ethylene diisocyanate, methylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, 1・ 6 ・ 11-Undecantry Cyanate, triisocyanate compounds such as triphenylmethane diisocyanate, these compounds a polyvalent isocyanate compound obtained by reacting a polyvalent alcohol compound and a polyvalent amine compound, an isocyanurate modified product thereof and the like compounds.

  Among these isocyanate compounds, aromatic isocyanate compounds are suitable for obtaining microcapsules having a particularly large particle size. Among these aromatic isocyanate compounds, preferred are tolylene diisocyanate and phenyl isocyanate, and both are used in the range where the former / the latter molar ratio is 0.5 / 1 to 5/1. It is recommended. Furthermore, in order to obtain a high microcapsule yield and allyl isothiocyanate content, it is particularly preferable to set the molar ratio in the range of 3.5 / 1 to 5/1.

  It is recommended that the organic phase contain a dispersion stabilizer for stabilizing the O / W emulsion together with the allyl isothiocyanate as the core material and the isocyanate compound as the wall material monomer. Such a dispersion stabilizer is a component corresponding to a surfactant, but an oil-soluble one is used when added to the organic phase. On the other hand, the dispersion stabilizer in the aqueous phase is also a component corresponding to a surfactant, but becomes water-soluble when added to the aqueous phase.

  Preferred examples of the dispersion stabilizer include tri- or distyryl phenyl ether added with polyoxyethylene, alcohol ether added with polyoxyethylene, and tween surface activity such as sorbitan oleate added with polyoxyethylene. Agents, spanning surfactants such as sorbitan oleate, sodium alkyl naphthalene sulfonate, sodium lauryl sulfate, sodium dodecyl sulfate, sodium lignin sulfonate, formaldehyde condensate of sodium alkyl naphthalene sulfonate, formaldehyde condensate of sodium phenol sulfonate , Isobutylene-maleic anhydride copolymer, sodium polycarboxylate, sodium alkylbenzenesulfonate, polyglycenol condensed ricinoleate, monolaur Phosphate decaglycerol, gelatin, gum arabic, casein, dextrin, pectin, sodium alginate methylcellulose, ethylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone, tribasic calcium phosphate, L- glutamic acid dioleyl ribitol and the like. Of these dispersion stabilizers, those that are oil-soluble can be used for the organic phase, and those that are water-soluble can be used for the aqueous phase. Many of these dispersion stabilizers are both oil-soluble and water-soluble depending on the molecular weight, the kind and ratio of the additional component, etc. Thus, gelatin is most preferred as the aqueous phase dispersion stabilizer.

In the wall material reaction, an amine (—NH ₂ ) produced by liberation of carbon dioxide from carbamic acid (—NHCOOH) produced by the reaction of an isocyanate group (—NCO) of the formula [I] with water; An isocyanate group reacts as shown in the formula [II] to form a polyurea skeleton, but an amine organic compound may be separately added to the reaction system so as to substitute a part of the amine. Further, it has been found that the separate addition of such an amine organic compound increases the microcapsule yield and the allyl isothiocyanate content in the microcapsules. In addition, the time of addition of the amine organic compound added separately is recommended for 10 to 30 minutes after the start of the reaction in terms of microcapsule yield.

  Such an amine organic compound is not particularly limited, but is a primary amine-modified acrylic polymer, 3 · 3′-iminobis (propylamine), 3- (methylamino) propylamine, N-methyl-3 · 3 ′. -Iminobis (propylamine), ethylenediamine, hexamethylenediamine, orthophenylmethylenediamine, metaphenylmethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, carbohydrazide, guanidine, guanylthiourea, 1.4- Diaminobutane, diaminopropane, diaminomaleonitrile, dicyandiamide, 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxaspiro [5,5] undecane, thiocarbohydrazide Thiosemicarbazide, thiourea, dodecanedioic acid dihydrazide, hexamethylenediamine, formamidine, m-xylylenediamine, dianisidine, 4,4'-diaminostilbene-2,2'-disulfonic acid, 1,4-diminoanthraquinone, 4,4'-diamino-3,3'-diethyldiphenylmethane, 4,4'-diaminobenzanilide, diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, tolidine base, m-toluylenediamine , Phenylenediamine, amidol, paramine, acetoguanamine, 1- (2-aminoethyl) piperazine, 2,4-diamino-6- (2-methyl-1-imidazolyl) -ethyl-1,3,5-triazine, 1 3-bis (hydrazinocarboethyl) -5-iso Lopyrhydantoin, piperazine, benzoguanamine, melamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminobiphenyl, aminopolyacrylamide, polyallylamine, bisbenchamine N- (2-aminoethyl) ethanolamine, N-methylethanolamine, 12-aminododecanoic acid, 3-amino-1-propanol, monoisopropanolamine, diisopropanolamine, monoethanolamine, diethanolamine, N-carboxy- 4.4'-methylenebiscyclohexylamine, cysteamine, 2-hydroxyethylaminopropylamine, formamide oxime, p-aminobenzoic acid, 2-amino-4-chlorophenol, 2-aminothiophenol, Aminophenol, anthranilic acid, 2-amino-5-naphthol-7-sulfonic acid, p-hydroxyphenylacetamide, leuco-1,4-diaminoanthraquinone, p-hydroxyphenylglycine, 2-amino-4-chlorobenzoic acid, Examples include isoleucine, threonine, tryptophan, valine, histidine, phenylalanine, methionine, lysine, aspartame, alanine, glycine, and theanine. Of these amine organic compounds, ethylenediamine is most preferred.

  Thus, the temperature of the reaction system for wall material reaction is preferably in the range of 30 to 70 ° C, particularly in the range of 40 to 60 ° C. Moreover, the setting which makes a reaction system into non-oxidizing atmosphere is good to set it as nitrogen atmosphere from a cost surface. On the other hand, lyophilization is preferably performed for about 10 to 120 minutes because allyl isothiocyanate contained in the lyophilized solution volatilizes and causes a decrease in content.

  The encapsulated fumigant thus obtained consists of nearly spherical particles of uniform particle size compared to the comparative hand, and demonstrates excellent bactericidal and insecticidal performance with the encapsulated volatile active ingredient allyl isothiocyanate. Therefore, the safety of the control work can be ensured, the adverse effect on the surrounding environment can be prevented, and the moderate fumigation effect can be obtained, so that a good fumigation effect can be obtained. In addition, this fumigant has the advantage that it is easy to handle due to microencapsulation, and there is little irritating odor peculiar to allyl isothiocyanate.

  The particle size of such encapsulated fumigant can be adjusted in the range of about 5 μm to 3 mm as an average particle size depending on the wall material monomer composition and reaction conditions. Therefore, when the average particle size is set in the range of 0.05 to 1 mm in particular, there is an advantage that the miscibility with soil is improved, the scattering is difficult, and the handleability is further improved.

  When this encapsulated fumigant is used as a soil fumigant, the mixing amount with respect to the soil is about 5 to 30 liters in apparent volume per 10 ares, and may be increased or decreased within this range depending on the type of pest and the degree of contamination. . In soil fumigation, encapsulated fumigant is mixed into treated soil, and the soil surface is covered with a film or the like and left to fumigate for about a week to 10 days. Instead of leaving for about one week to about 10 days, degassing and then sowing the required plants.

  In addition, although there is no restriction | limiting in the pest of the soil made into control object, it is very effective especially in the control of root-knot nematodes. Moreover, this encapsulated fumigant is suitable for removing pests other than soil, and is also very effective for exterminating corn borers distributed around the world as pests of cereals, for example.

Hereinafter, the encapsulated fumigant of the present invention will be specifically described with reference to examples. In addition, each component used for manufacture of the following encapsulated fumigants is as follows.
Allyl isothiocyanate: Reagent manufactured by Takasago International Corporation Tolylene diisocyanate: Reagent manufactured by Wako Pure Chemical Industries Phenyl isocyanate: Special grade reagent manufactured by Wako Pure Chemical Industries Gelatin: Reagent manufactured by Sigma (Type A: From Porcin Skin)
Sorbitan monooleate: trade name Span 80 manufactured by Wako Pure Chemical Industries
Ethylenediamine: Special grade reagent manufactured by Wako Pure Chemical Industries

[Encapsulated fumigant 1-6]
Each component of allyl isothiocyanate, tolylene diisocyanate, phenyl isocyanate, sorbitan monooleate is mixed in the mixing ratio shown in Table 1 of the latter stage to prepare an organic phase, and gelatin is dissolved in distilled water at the mixing ratio in the same table. To prepare an aqueous phase. Then, at room temperature (18 ° C.), the organic phase was added to this aqueous phase while stirring with a magnetic stirrer, and stirring was continued for 10 minutes to prepare an O / W emulsion, and then the emulsion was heated to 50 ° C. Then, the wall material reaction was carried out at 150 rpm for the time indicated in the same table using a double-blade stirrer (EYELA, NTT-20s) having a diameter of 5 cm, the produced microcapsules were filtered and washed, and the obtained microcapsules were frozen for 30 minutes. It dried and manufactured encapsulated fumigant 1-6. Note that the blending amount of sorbitan monooleate corresponds to 1% by weight of the organic phase.

[Encapsulated fumigant 7]
Using the organic phase and the aqueous phase prepared at the blending ratios described in Table 1 of the late stage, and adding ethylenediamine in the amount described in the table 15 minutes after the start of the wall material reaction, the same as in the encapsulated fumigants 1-6 Encapsulated fumigant 7 was produced.

  In the production of the encapsulated fumigants 1-7, the mass of the organic phase charged, the addition amount of allyl isothiocyanate (abbreviated as AITC), the microcapsule yield, the AITC inclusion amount, the organic phase recovery rate, the AITC inclusion efficiency, the AITC content, Table 2 shows the encapsulation state. The ethylenediamine used in the encapsulated fumigant 7 was included in the organic phase to calculate each item. And the quantification of allyl isothiocyanate encapsulated in the encapsulated fumigant was determined by gas chromatography (Clarus500GC manufactured by Perkin Elmer) using acetone as a solvent and 1-pentanol as an internal standard substance, with a sample vaporization chamber temperature of 150 ° C., Measurement was performed under the condition of a detector temperature of 160 ° C. In addition, the encapsulation state was evaluated as good for ◯, slightly good for Δ, and poor for ×.

  From the results shown in Table 2, the microcapsules are excellent even when the molar ratio of tolylene diisocyanate to phenyl isocyanate is 1: 1, 2: 1, 3: 1, 4: 1 in the organic phase. It can be seen that The organic phase recovery rate, AITC encapsulation efficiency, and AITC content increase as the molar ratio increases (the ratio of tolylene diisocyanate increases), and the encapsulated fumigant 4 having a molar ratio of 4: 1 is the highest. It became. However, when the molar ratio is 4: 1, that is, tolylene diisocyanate alone is used as the wall material monomer without using phenyl isocyanate, the wall material reaction does not encapsulate well in 2 hours (encapsulated fumigant 5). Although the reaction was extended to 3 hours (encapsulated fumigant 6), the organic phase recovery rate, AITC encapsulation efficiency, and AITC content were all decreased in a slightly moist state. Accordingly, it has been found that the presence of phenyl isocyanate is effective even in a small amount.

  On the other hand, when ethylenediamine is added to the reaction system at a molar ratio of 4: 1 (encapsulated fumigant 7), the organic phase recovery rate is slightly reduced, but both AITC encapsulation efficiency and AITC content are improved and better. It has been found that an encapsulated fumigant can be obtained.

  In addition, about the encapsulated fumigant 4 whose said molar ratio is 4: 1, the electron micrograph is shown to Fig.1 (a) (b). From FIG. 1, it can be seen that the encapsulated fumigant of the present invention is composed of spherical particles with uniform particle sizes.

  FIG. 2 shows the transpiration behavior of the encapsulated fumigant 4 and AITC (allyl isothiocyanate) alone. As shown in the figure, it can be seen that the encapsulated fumigant of the present invention evaporates almost all of the allyl isothiocyanate encapsulated in about 2 weeks. In addition, when the transpiration behavior of the encapsulated fumigant 7 obtained by adding ethylenediamine to the reaction system was examined, the results were almost the same as those of the encapsulated fumigant 4, and the addition of ethylenediamine had no effect on the transpiration behavior. There was found.

[Reference example]
In a solution of 1.52 g of poly-ε-caprolactone (molecular weight 70,000 to 100,000) dissolved in 30.1 g of dichloromethane, allyl isothiocyanate (AITC) impregnated spherical activated carbon (average particle size of about 1.2 mm, AITC content of about 16 wt. %) 5.09 g was added and stirred for 10 minutes to prepare an activated carbon dispersion. Then, the activated carbon dispersion is added to an aqueous solution in which 100 g of tricalcium phosphate (TCP-10U manufactured by Ohira Chemical Co., Ltd.) and 6 g of gelatin are dissolved in 200 g of water, and at a liquid temperature of 25 ° C. while stirring at a stirring speed of 300 rpm. After maintaining for 5 minutes and then drying in liquid at 900 hPa and 30 ° C. for 1 hour, and further drying in liquid at 700 hPa and 35 ° C. for 2 hours, followed by filtration and washing with hydrochloric acid, poly-ε -AITC impregnated spherical activated carbon coated with caprolactone membrane was obtained.

  The transpiration behavior of the AITC-impregnated spherical activated carbon of the above reference example is shown in FIG. As shown in the figure, this AITC-impregnated spherical activated carbon has a transpiration rate of 40% even in 10 days (240 hours), so that when used as a soil fumigant, allyl isothiocyanate remains in the soil for a long time. Therefore, there is a concern about the phytotoxicity to plants due to the residue, and it is necessary to set a long safe period until sowing, which hinders cultivation of crops.

[Fumigant Field Test 1]
The soil contained in 1 / 5000a (a = Earl) Wagner pot is added with sweet potato nematode larvae and fumigant at a density of 102.2 / 20g (soil), and each Wagner pot is covered with vinyl for 7 days. After fumigation, the soil was mixed, degassed for 7 days, cucumber seeds germinated for 2 days were sown at a rate of 5 seeds per pot, and after a certain number of days, nematode density and catfish (root nodules) parasitic status The cucumber growth situation was investigated. The encapsulated fumigant was the product of the present invention manufactured at the molar ratio of 4: 1 and used with an AITC content of 15.1%.

  Table 3 shows the test conditions, Table 4 shows the nematode density and the parasitic state of the root, Table 5 shows the root index, and Table 6 shows the cucumber growth state. In addition, the nematode density of Table 4 was investigated by the Bellman method (a method in which the collected soil was immersed in water and the nematode was swallowed to separate it), and the parasitic state of the cat root was examined by observation with acidic fuchsin staining.

The ranks of cats shown in Table 5 are (0) no cats, (1) a few cats are recognized, but the damage is not noticeable, (2) cats are recognized at first glance, but those that are large or connected There are few, (3) many large and small cats are recognized, but less than 50% of the whole root area, (4) many roots are full of cat roots, more than 50% of the whole root area, and in appearance The state is as shown in FIG. Then, the Nekob index is calculated by the following formula using numerical values of ranks 0 to 4, where n is the number of shares. In this case, the degree index is 4.
Nekob index = (0n + 1n + 2n + 3n + 4n) / number of strains surveyed / about index × 100

  As is clear from the results of Tables 4 and 5, when the encapsulated fumigant of the present invention is used, the treatment amount is 1/10, which is very low compared to the treatment sections D and E using the AITC stock solution and the commercial preparation. However, the treatment area C is slightly inferior to the nematode prevention effect, but the treatment area A with a treatment amount of 2/5 and the treatment area B with a treatment amount of 1/5 have almost the same excellent nematode prevention effect. As a result, according to the encapsulated fumigant of the present invention, AITC (allyl isothiocyanate), which is a volatile active ingredient, is not harmful to the human body and the environment, and exhibits a high pest control effect with a small amount of use. I understand.

  From the results of Table 6, in the treatment with the encapsulated fumigant of the present invention, no effect on germination and growth up to 40 days after sowing was observed. It was confirmed that the number of leaves and the area of the main leaves were much better, and no phytotoxicity was caused. The root weight of the untreated section was the heaviest due to nematode parasitism.

[Fumigant Field Test 2]
In the same Wagner pot as in Field Test 1, 250 g of cultured soil with a fumigant added was stored, and after 7 days of fumigation and 7 days of degassing as in Field Test 1, Chingensai Seed 100 Grains were sown and the germination rate and growth rate were examined. Table 7 shows the test conditions, Table 8 shows the germination rate, and Table 9 shows the growth rate.

  From the results of Tables 8 and 9, in the treatment with the encapsulated fumigant of the present invention, the effect on germination was almost eliminated (90% or more) by sowing 7 days after the degassing treatment, and also on the growth after germination. The effect was also almost disappeared after seeding after 3 days, and was almost equivalent to the treatment with the AITC stock solution. Therefore, it can be said that this encapsulated fumigant has good handling properties because the safety days for germination (degassing period) are 14 days after fumigation treatment and the safety days for growth are the same 10 days.

The electron micrograph of the encapsulated fumigant of this invention is shown, (a) is a low magnification, (b) is a high magnification photograph. It is a characteristic view which shows the transpiration | evaporation behavior of the encapsulated fumigant and allyl isothiocyanate simple substance. It is a characteristic view which shows the transpiration | evaporation behavior of the allyl isothiocyanate impregnation spherical activated carbon of a reference example. It is a figure which shows the rank of the parasitic condition of a root-knot nematode.

Claims (4)

  An organic phase containing an isocyanate compound containing one or more isocyanate groups and allyl isothiocyanate and an aqueous phase containing a dispersion stabilizer are stirred and mixed in a non-oxidizing atmosphere, and allyl isothiocyanate is obtained by an oil-water interface reaction. A method for producing an encapsulated fumigant, comprising producing a matrix-type polyurea microcapsule as a core substance and freeze-drying the microcapsule obtained by filtration. The method for producing an encapsulated fumigant according to claim 1 , comprising tolylene diisocyanate and phenyl isocyanate as the isocyanate compound in the organic phase. The method for producing an encapsulated fumigant according to claim 2 , wherein the molar ratio of tolylene diisocyanate / phenyl isocyanate is set to 3.5 / 1 to 5/1. The method for producing an encapsulated fumigant according to claim 1 or 2 , wherein the organic phase contains a dispersion stabilizer and gelatin is contained as a dispersion stabilizer in the aqueous phase.

Images