JPH08277277A - Isothiazolecarboxylic acid derivative and rice neck rotcontrolling agent with the same as active ingredient - Google Patents

Abstract

PURPOSE: To obtain a new isothiazolecarboxylic acid derivative as a rice neck rot-controlling agent, long in the sustainability of its effect, and having stable effect. CONSTITUTION: This new compound is expressed by formula I (R is H or a 1-4C alkyl; X is H, a halogen, 1-4C alkyl, 1-4C alkoxyl or 1-4C alkylthio; (n) is 1-2) e.g. N-phenylsulfonyl-3-methylisothiazole-5-carboxylic: acrid amide. The compound of formula I is obtained by reaction of a benzenesulfonamide of formula II with a carboxylic acid halide of formula III (Y is Cl, Br or I) in a solvent (e.g. benzene), if needed in the presence of a base (e.g. sodium methoxide) at 0-150 deg.C. Rice neck rot is controlled by applying an agrochemical containing the compound of formula I as active ingredient to pathogenic fungi or their habitats.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to novel isothiazolecarboxylic acid derivatives and rice blast control agents containing these as active ingredients.

[0002]

BACKGROUND OF THE INVENTION Rice blast is a disease with the highest yield loss among various diseases. The cause is largely due to abnormal weather such as low temperature in summer and heavy rain. However, it is also due to unreasonable cultivation of varieties vulnerable to blast disease and poor control due to labor shortage. Japanese Patent Laid-Open No. 5-59024 discloses
The isothiazolecarboxylic acid derivative represented by the following formula (2) (chemical formula 4) is described as a rice blast control agent.

[0003]

[Chemical 4][Wherein, R¹ Is a hydrogen atom, a halogen atom, or 1 to 4 carbon atoms
Of alkyl groups or alkoxy groups having 1 to 4 carbon atoms
Then R² Represents a hydrogen atom, a halogen atom or a nitro group.
Z is morpholino group, piperidinyl group, OR³ {here
And R³ Is a hydrogen atom, an alkali metal atom, or a carbon atom of 1 to 4
Alkyl group or NHR^FiveR⁶R⁷ (R^Five , R ⁶ And R
⁷ Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
You )}, Or NHR^Four (Where R^Four Is a hydrogen atom,
Straight or branched alkyl group having 1 to 18 carbon atoms, shik
Low alkyl group, cycloalkenyl group, dimethylamino
Group, furfuryl group, alkoxy group, alkylthio group, furfuryl group
Phenyl group or a halogen-substituted phenyl group
Represents a rutile group] Infection by blast fungus is extreme from the leaf blast stage to the ear blast
It has been a long time,
When the compounds disclosed in the examples of the report are used in paddy fields,
The initial control effect is sufficiently high, but it will continue for a long time after the chemical treatment.
The effect gradually declines, and the drug's persistence is short
There was a problem.

[0004]

Therefore, an object of the present invention is to provide a drug which exhibits an excellent controlling effect against rice blast and has a long duration of effect and a stable effect.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted research on isothiazolecarboxylic acid derivatives in order to solve these problems, and as a result, the above-mentioned JP-A-5-59024.
It was found that a novel isothiazolecarboxylic acid derivative not disclosed in the publication is extremely excellent as a control agent for rice blast disease, has a long-lasting effect, and has excellent characteristics of showing a stable effect. The present invention has been completed. That is, the present invention is based on the formula (1)

[0006]

Embedded image (In the formula, R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or 1 to 4 carbon atoms. 4 represents an alkylthio group, and n represents an integer of 1 to 2), a rice blast control agent containing the isothiazolecarboxylic acid derivative as an active ingredient, and its application to pathogenic fungi or their habitat. The method for controlling rice blast disease is characterized by Specific examples of R in the isothiazolecarboxylic acid derivative represented by the formula (1) include hydrogen atom; methyl group, ethyl group, propyl group, isopropyl group, butyl group, s-butyl group, t-butyl group, and the like. Examples thereof include an alkyl group having 1 to 4 carbon atoms.

On the other hand, specific examples of X include hydrogen atom; halogen atom such as fluorine atom, chlorine atom, bromine atom or iodine atom; methyl group, ethyl group, propyl group, isopropyl group, t-butyl group and the like. Examples thereof include an alkyl group having 1 to 4 carbon atoms; an alkoxy group having 1 to 4 carbon atoms such as methoxy group, ethoxy group and propoxy group; and an alkylthio group having 1 to 4 carbon atoms such as methylthio group, ethylthio group and butylthio group.

The isothiazolecarboxylic acid derivative represented by the formula (1) of the present invention is a novel compound and can be produced, for example, by the following (method A) or (method B) (chemical formula 6).

[0009]

[Chemical 6] (In the formula, R, X and n have the above-mentioned meanings, and Y represents a chlorine atom, a bromine atom or an iodine atom.) That is, in (A method), various benzenes represented by the formula (3) It can be produced by reacting a sulfonamide with a carboxylic acid halide represented by the formula (4) in a molten state or in a solvent.

Examples of the solvent used in the reaction in the method (A) include aliphatic hydrocarbons such as hexane and petroleum ether, aromatics such as benzene, toluene, chlorobenzene and anisole, dioxane tetrahydrofuran,
Ethers such as diethyl ether, acetonitrile,
Nitriles such as propionitrile, esters such as ethyl acetate and butyl acetate, halogenated hydrocarbons such as dichloromethane, chloroform and 1,2-dichloroethane, dimethylformamide, dimethylsulfoxide,
Examples include aprotic solvents such as N, N-dimethylimidazolidinone, and mixed solvents thereof are also used.

This reaction may also be carried out in the presence of a base, and as the base, for example, hydroxides of alkali metals and alkaline earth metals such as sodium hydroxide, potassium hydroxide and calcium hydroxide; calcium oxide, oxidation Alkali metal and alkaline earth metal oxides such as magnesium; Alkali metal and alkaline earth metal hydrides such as sodium hydride and calcium hydride; Alkali metal amides such as lithium amide and sodium amide; Sodium carbonate, carbonic acid Alkali metal and alkaline earth metal carbonates such as potassium, calcium carbonate and magnesium carbonate; alkali metal and alkaline earth metal hydrogen carbonates such as sodium hydrogen carbonate and potassium hydrogen carbonate; methyllithium, butyllithium, phenyllithium, Methyl magnesium chloride Alkali metal alkyl and the like; sodium methoxide, sodium ethoxide, potassium -t- butoxide, alkoxides of alkali metals and alkaline earth metals such as dimethoxy magnesium; triethylamine, pyridine, N, N-dimethylaniline, N
Examples thereof include organic bases such as -methylpiperidine, lutidine, and 4- (N, N-dimethylamino) pyridine, and triethylamine and pyridine are particularly preferable. The amount of these bases used is not particularly limited, and in the case of the above various organic bases, they can be used as a solvent.

The various benzenesulfonamide represented by the above formula (3) are generally used in an equimolar amount with the isothiazolecarboxylic acid halide represented by the formula (4). May be used in excess of 1 mol% to 20 mol% with respect to the other. Reaction temperature is 0-150 ℃
And preferably 0 to 40 ° C. In the method (B), the formula (1) can be produced by reacting the compound represented by the formula (5) with various alkylating agents in the presence of a base. The solvent used in the reaction of the method (B) may be any solvent inert to the reaction, for example, aliphatic hydrocarbons such as hexane and petroleum ether, aromatics such as benzene, toluene, chlorobenzene and anisole, and dioxane. Tetrahydrofuran, ethers such as diethyl ether, dimethylformamide, dimethylsulfoxide,
Examples include aprotic solvents such as N, N-dimethylimidazolidinone, and mixed solvents thereof are also used.

As the base used in this reaction, for example, hydroxides of alkali metals and alkaline earth metals such as sodium hydroxide, potassium hydroxide and calcium hydroxide;
For example, oxides of alkali metals such as calcium oxide and magnesium oxide, alkaline earth metals; sodium hydride,
Alkali metal and alkaline earth metal hydrides such as calcium hydride; Alkali metal amides such as lithium amide and sodium amide; Alkali metal and alkaline earth metal carbonates such as sodium carbonate, potassium carbonate, calcium carbonate and magnesium carbonate Salts; sodium hydrogen carbonate, potassium hydrogen carbonate and other alkali metal and alkaline earth metal hydrogen carbonates; methyl lithium, butyl lithium, phenyl lithium, methyl magnesium chloride and other alkali metal alkyls; sodium methoxide, sodium ethoxide, potassium -Alkoxides of alkali metals and alkaline earth metals such as -t-butoxide and dimethoxymagnesium; triethylamine, pyridine,
N, N-dimethylaniline, N-methylpiperidine,
1,8-diazabicyclo [5.4.0] undecene-7
Examples thereof include organic bases such as (DBU) and 4- (N, N-dimethylamino) pyridine.

Specific examples of the alkylating agent used in this reaction include alkyl halides such as methyl iodide, ethyl bromide and butyl iodide; sulfuric acid esters such as dimethyl sulfate and diethyl sulfate; diazomethane and the like. Is used, but is not limited thereto. The drug thus obtained, which contains the compound of the present invention as an active ingredient, is excellent as a rice blast control agent in terms of its action characteristics, and the effect lasts for a long time after treatment.

The compounds of the present invention are isothiazole-5-
It differs from the compounds described in JP-A-5-59024 in that various benzenesulfonamide groups are introduced into the amino group portion of the carboxylic acid amide. In improving the performance as a blast control agent, the significance of the amino group part being a benzenesulfonamide group is significant, and when the compound of the present invention is applied to blast, as is clear from the test examples described below, It is extremely excellent as a blast control agent, has a long-lasting effect, and has excellent characteristics of exhibiting a stable effect. The agricultural and horticultural fungicides of the present invention are other fungicides, insecticides, and herbicides. Not only can it be used in combination with a pesticide such as a plant growth regulator, a soil conditioner or a fertilizer, but a mixed preparation with these is also possible.

The compounds of the invention may be used as such, but are preferably applied in the form of a composition in admixture with a carrier, which may include a solid or liquid diluent. As used herein, the term carrier means a synthetic or natural inorganic or organic substance formulated to help the active ingredient reach the site to be treated and to facilitate the storage, transport, and handling of the active ingredient compound. . Suitable solid carriers include montmorillonite,
Clay such as kaolinite and bentonite, diatomaceous earth,
Examples thereof include clay, talc, vermiculite, gypsum, calcium carbonate, silica gel, ammonium sulfate and other inorganic substances, soybean flour, sawdust, wheat flour and other plant organic substances, and urea.

Suitable liquid carriers include aromatic hydrocarbons such as toluene, xylene and cumene, paraffin hydrocarbons such as kerosene and mineral oil, halogenated hydrocarbons such as carbon tetrachloride, chloroform and dichloroethane, and acetone. , Ketones such as methyl ethyl ketone, ethers such as dioxane, tetrahydrofuran and diethylene glycol dimethyl ether, alcohols such as methanol, ethanol, propanol and ethylene glycol, dimethylformamide, dimethyl sulfoxide and water. Further, in order to enhance the efficacy of the compound of the present invention, the following auxiliary agents can be used alone or in combination according to the purpose in consideration of the dosage form of the preparation, the application scene and the like.

As an auxiliary agent, for the purpose of emulsification, dispersion, spreading, wetting, binding, stabilization, etc., lignin sulfonate, alkylbenzene sulfonate, alkyl sulfate ester salt, polyoxyalkylene alkyl sulfate salt, and poly Anionic surfactants such as oxyalkylene alkyl phosphate salts, polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl aryl ethers, polyoxyalkylene alkyl amines, polyoxyalkylene alkyl amides, polyoxyalkylene alkyl thioethers, polyoxyalkylene fatty acid esters , Glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyalkylene sorbitan fatty acid ester, and polyoxypropylene polyoxyethylene block polymer On surfactant, calcium stearate, lubricants such as wax, stabilizers such as isopropyl hydroperoxide diene phosphate, other cellulose, carboxymethyl cellulose, casein, gum arabic, and the like. However, these components are not limited to those described above.

The amount of the active ingredient of the compound of the present invention is usually 0.5 to 20% by weight for powders, 5 to 50% by weight for emulsions, 10 to 90% by weight for wettable powders, and 0.1 to 20 for granules. %, And 10-90% by weight for flowable formulations. On the other hand, the amount of the carrier in each dosage form is usually 60 to 99% by weight for powders and 10 to 90% by weight for wettable powders.
Granules are 80 to 99% by weight, emulsions are 40 to 95% by weight, flowable formulations are 10 to 90% by weight, and the amount of auxiliary agent is usually 0.1 to 20% by weight for powders and 1 to 20% for emulsions. 20% by weight, 0.1-20% by weight of wettable powder,
Granules are 0.1 to 20% by weight, and flowable formulations are 0.1 to 20% by weight.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to examples and test examples. Example 1 Synthesis of N-phenylsulfonyl-3-methylisothiazole-5-carboxylic acid amide (Compound No. 4) A solution of 8.0 g of benzenesulfonamide in 50 ml of pyridine was stirred at room temperature under stirring with 3-methylisothane. Thiazole-5-carboxylic acid chloride (8.0 g of 3-methylisothiazole-5-carboxylic acid and 10 g of thionyl chloride)
10 ml of a benzene solution (prepared from above) was added dropwise, the mixture was stirred for 2 hours, and then left overnight. Drain the reaction mixture into water,
Washed with ethyl acetate. The aqueous layer was adjusted to pH 3 with concentrated hydrochloric acid and extracted with ethyl acetate. The organic layer was washed with water and dried over sodium sulfate. The solvent was concentrated under reduced pressure and crystallized from ether / hexane to obtain 10.7 g of the desired product (yield 75
%).

Example 2 Synthesis of N-methyl-N-phenylsulfonyl-3-methylisothiazole-5-carboxylic acid amide (Compound No. 5) N-methylbenzenesulfone sulfonic acid amide 1.0 g
Is dissolved in 10 ml of methanol, and 1.1 g of sodium methoxide (28% methanol product) is added. 1 at room temperature
After stirring for an hour, the solvent was concentrated under reduced pressure. 1.7 g of 3-methylisothiazole-5-carboxylic acid chloride was added to a solution prepared by dissolving this in 1 ml of N, N-dimethylformamide. After stirring at room temperature for 1.5 hours, the reaction solution was discharged into ice water and extracted with ethyl acetate. The organic layer was washed successively with diluted hydrochloric acid and saturated sodium hydrogen carbonate, and dried over sodium sulfate. The solvent was concentrated under reduced pressure, suction filtered and washed with hexane to obtain 1.29 g of the desired product (yield 75%). Melting point: 48 to 52 ° C. Compounds synthesized in the same manner as above are shown in Table 1 (Table 1,
2).

[0022]

[Table 1]

[0023]

[Table 2] These compounds may be used as they are, but they are more effective when formulated. The formulation example is shown below,
These are some of them. In the following, "parts" means "parts by weight".

Formulation Example 1 Granules N- (4-chlorobenzenesulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 1)
5 parts, 22 parts of bentonite, 70 parts of talc, 3 parts of Solpol 5060 (surfactant: trade name of Toho Kagaku Co., Ltd.) and a small amount of an antifoaming agent were uniformly kneaded and granulated with a basket granulator. It was then dried to obtain 100 parts of granules.

Formulation Example 2 Granules N- (2-tolylsulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 2) 5 parts, bentonite 60 parts, talc 31 parts, sodium dodecylbenzene sulfonate 1 Parts, 1 part of polyoxyethylene alkyl allyl ether, and 2 parts of sodium lignin sulfonate are added, and then an appropriate amount of water is added and uniformly kneaded, and the mixture is granulated with a basket granulator and then dried to obtain granules 100 I got a part.

Formulation Example 3 Granules N- (4-tolylsulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 3) 5 parts, bentonite 35 parts, talc 57 parts, lignin sulfonate sodium 2 parts , And 1 part of sodium dodecylbenzenesulfonate were mixed, and then an appropriate amount of water was added to uniformly knead the mixture, which was granulated by a basket granulator and then dried to obtain 100 parts of granules.

Formulation Example 4 Granules N-benzenesulfonyl-3-methylisothiazole-
After mixing 5 parts of 5-carboxylic acid amide (Compound No. 4), 60 parts of bentonite, 32 parts of clay, and 3 parts of sodium alkylbenzene sulfonate, an appropriate amount of water was added and uniformly kneaded, and granulated with a basket granulator. After granulating, it was dried to obtain 100 parts of granules.

Formulation Example 5 Granules N-methyl-N-benzenesulfonyl-3-methylisothiazole-5-carboxylic acid amide (Compound No. 5) 3
Parts, 93.7 parts of clay, 0.2 parts of dialkyl sulfosuccinate, 0.1 part of alkyl sulfate ester soda, and 3.0 parts of sodium polycarboxylic acid were uniformly kneaded and granulated with a basket granulator. It was then dried to obtain granules.

Formulation Example 6 Granules N- (4-chlorobenzenesulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 1)
3 parts of clay, 93.5 parts of clay, 0.5 part of dialkyl sulfosuccinate, and 3 parts of carboxymethyl cellulose are mixed, and then an appropriate amount of water is added and kneaded, and granulated and dried by a usual method using a granulator. , 100 parts of granules were obtained.

Formulation Example 7 Wettable powder 50 parts of N- (2-tolylsulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 2),
40 parts of calcium carbonate, 5 parts of Solpol 5039 (mixture of anionic surfactant and white carbon: trade name of Toho Chemical Co., Ltd.) and 5 parts of white carbon were uniformly mixed and pulverized to obtain a wettable powder.

Formulation Example 8 Wetting agent 70 parts of N- (4-tolylsulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 3),
25 parts of kaolinite, 3 parts of Solpol 5039 (mixture of anionic surfactant and white carbon: trade name of Toho Chemical Co., Ltd.), and 2 parts of white carbon were uniformly mixed and pulverized to obtain a wettable powder.

Formulation Example 9 Wettable powder N-benzenesulfonyl-3-methylisothiazole-
50 parts of 5-carboxylic acid amide (Compound No. 4), 40 parts of calcium carbonate, 5 parts of Solpol 5039 (mixture of anionic surfactant and white carbon: Toho Chemical Co., Ltd. trade name), and 5 parts of white carbon are uniform. And pulverized to obtain a wettable powder.

Formulation Example 10 Wettable powder N-methyl-N-benzenesulfonyl-3-methylisothiazole-5-carboxylic acid amide (Compound No. 5) 7
0 parts, 25 parts of kaolinite, 3 parts of Sorpol 5039 (mixture of anionic surfactant and white carbon: trade name of Toho Chemical Co., Ltd.), and 2 parts of white carbon were uniformly mixed and pulverized to obtain a wettable powder. .

Formulation Example 11 Emulsion N- (4-chlorobenzenesulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 1)
20 copies, Solvesso 150 (Exxon Chemical Co., Ltd.) 75
And 5 parts of Solpol 2680 (surfactant) were uniformly mixed to obtain an emulsion.

Formulation Example 12 Flowable Agent 40 parts of N- (2-tolylsulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 2),
Sorpol 3353 (nonionic surfactant: trade name of Toho Kagaku Co., Ltd.) 5 parts, 1% aqueous solution of xanthan gum 5 parts,
In 40 parts of water and 10 parts of ethylene glycol, components other than the active ingredient are uniformly dissolved, and then the compound of the present invention is added.
After stirring well, wet pulverization was performed with a sand mill to obtain a flowable agent.

Formulation Example 13 Powder 10 parts of N- (4-tolylsulfonyl) -3-methylisothiazole-5-carboxylic acid amide (Compound No. 3),
90 parts of clay was uniformly mixed to obtain a dust.

Formulation Example 14 Powder N-benzenesulfonyl-3-methylisothiazole-
5-Carboxylic acid amide (Compound No. 4) 5 parts, clay 4
0 parts, 54 parts of talc and 1 part of calcium stearate were crushed and mixed to obtain a powder.

It will be specifically described with reference to test examples that the rice blast control agent according to the present invention exhibits excellent rice blast control effect. Test Example 1 Rice blast control effect test (treatment for nursery box) Rice seedlings (cultivar: Mangetsumochi; 2 leaf stage) grown in a rice nursery box (30 cm x 60 cm x 3 cm) were prepared with granules prepared according to Formulation Example 2. It processed so that it might become a predetermined amount per box.
After 3 days, it was transplanted to a Wagner pot of 1/5000 are and grown in a greenhouse. Every 30 days, 45 days, and 60 days after transplantation, 1/3 of the total pot is used, and the spore suspension is sprayed and inoculated each time, and the pot is kept at a temperature of 25 ° C. under high humidity for 1 week each, The number of lesions was investigated and the duration of the effect was examined. The control value was calculated by the following formula (Equation 1). Second result
It is shown in the table (Table 3). (6 repetitions)

[0039]

[Equation 1] Control value = (1-number of lesions in treated group / number of lesions in untreated group) × 100

[0040]

[Table 3] Control compound: N-benzyl-3-methyl-5-isothiazolecarboxylic acid amide (compound described in JP-A-5-59024)

Test Example 2 Rice blast control effect test (water application) After transplanting rice (variety: mangetsumochi; 3 leaf stage) into a Wagner pot of 1/5000 are and growing in a greenhouse for 1 week, a preparation example The granules prepared according to 2 were applied to the surface of the water in a predetermined amount per are. Drug treatment 30 days, 40
Each day, every 50 days, one-third of all treated pots are used, sprayed with a spore suspension each time, and kept at 25 ° C for 1 week under high humidity conditions. Investigate,
The duration of the effect was investigated. The control value was calculated by the following formula (Equation 2). The results are shown in Table 3 (Table 4). (6 repetitions)

[0042]

[Equation 2] Control value = (1-number of lesions in treated plot / number of lesions in non-treated plot) × 100

[0043]

[Table 4] Control compound: N-benzyl-3-methyl-5-isothiazolecarboxylic acid amide (compound described in JP-A-5-59024)

[0044]

INDUSTRIAL APPLICABILITY The isothiazolecarboxylic acid derivative according to the present invention has an extremely excellent effect on controlling rice blast disease, has a long-lasting effect, and exhibits a stable effect over a long period of time. It is useful as an agent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunichi Inami 1144 Togo, Mobara-shi, Chiba Prefecture Mitsui Toatsu Chemical Co., Ltd. 72) Inventor Atsushi Takashi, Mitsui Toatsu Chemical Co., Ltd., 1144, Togo, Mobara-shi, Chiba

Claims (4)

[Claims] 1. Formula (1) (Formula 1) (In the formula, R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or 1 to 4 carbon atoms. 4 represents an alkylthio group, and n represents an integer of 1 to 2). 2. The compound according to claim 1, wherein in the formula (1), R is a hydrogen atom or a methyl group, and Xn is a hydrogen atom. 3. Formula (1) (Formula 2) [Formula 2] (In the formula, R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or 1 to 4 carbon atoms. 4 represents an alkylthio group, and n represents an integer of 1 to 2), and a rice blast control agent containing an isothiazolecarboxylic acid derivative represented by the formula) as an active ingredient. 4. Formula (1) (Formula 3) [Formula 3] (In the formula, R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or 1 to 4 carbon atoms. 4 represents an alkylthio group, and n represents an integer of 1 to 2), and a rice blast control agent containing an isothiazolecarboxylic acid derivative represented by the formula) as an active ingredient is applied to a pathogenic bacterium or its habitat. How to control rice blast disease.