WEED CONTROL METHOD AND MIXED AGROCHEMICAL COMPOSITION FOR SOIL TREATMENT

Abstract

The present invention is aimed at providing a weed control method and a mixed agrochemical composition for soil treatment, which, in a soil treatment of farmland with pyroxasulfone, not only can inhibit or reduce crop injury caused by absorption into cultivated crops, without being influenced by heavy rainfall, soil type, seeding depth and the like, but also are effective against a wide range of weed species. The weed control method includes a soil treatment step of performing a soil treatment on farmland with an agrochemical composition for soil treatment, which contains pyroxasulfone, and with a protoporphyrinogen oxidase inhibitor, simultaneously or sequentially, the method being characterized in that the agrochemical composition for soil treatment further contains a masking substance that masks the pyroxasulfone, and the pyroxasulfone is microencapsulated in or coated with the masking substance. The mixed agrochemical composition for soil treatment is characterized by containing the agrochemical composition for soil treatment and a protoporphyrinogen oxidase inhibitor.

Claims

1. A weed control method, comprising a soil treatment step of performing a soil treatment on farmland with an agrochemical composition for soil treatment, which comprises pyroxasulfone, and with a protoporphyrinogen oxidase inhibitor, simultaneously or sequentially, wherein the agrochemical composition for soil treatment further comprises a masking substance that masks the pyroxasulfone, and the pyroxasulfone is microencapsulated in or coated with the masking substance.

2. The method according to claim 1, wherein the protoporphyrinogen oxidase inhibitor is selected from the group consisting of saflufenacil, sulfentrazone, flumioxazin, flumiclorac-pentyl, fluthiacet-methyl, lactofen, fomesafen, acifluorfen and salts thereof, bifenox, chlomethoxyfen, oxyfluorfen, halosafen, cinidon-ethyl, carfentrazone-ethyl, azafenidin, benzfendizone, butafenacil, tiafenacil, pyraflufen-ethyl, fluazolate, thidiazimin, oxadiazon, oxadiargyl, chlorphthalim, pentoxazone, pyraclonil, flufenpyr-ethyl, and profluazol.

3. The method according to claim 1, wherein the protoporphyrinogen oxidase inhibitor is selected from the group consisting of saflufenacil, sulfentrazone, and flumioxazin.

4. The method according to claim 1, wherein crystal particles of the pyroxasulfone are directly coated with the masking substance.

5. The method according to claim 1, wherein the pyroxasulfone is enclosed and microencapsulated in a wall material composed of the masking substance.

6. The method according to claim 1, wherein the agrochemical composition for soil treatment has an average particle size of 0.1 to 150 μm.

7. The method according to claim 1, wherein the content ratio of the masking substance is 0.1 to 50 parts by mass with respect to 1 part by mass of pyroxasulfone.

8. The method according to claim 1, wherein the masking substance is selected from the group consisting of polyureas, polyurethanes, polyamides, polyesters, ethyl cellulose, poly(meth)acrylate-based copolymers, carnauba wax, montanic acid ester waxes, hardened oils and fats, polylactic acids, gelatin, cross-linked melamine, polystyrenes, polystyrene-based copolymers, waxes, yeast cell walls, alginates, polyglycolic acids, polyethylene glycol-based copolymers, and shellac.

9. The method according to claim 1, further comprising performing a soil treatment with an agrochemical active component other than the pyroxasulfone and the protoporphyrinogen oxidase inhibitor, simultaneously or sequentially with the agrochemical composition for soil treatment.

10. The method according to claim 1, wherein the agrochemical composition for soil treatment has a dosage form of a dust, a granule, a wettable powder, a water-dispersible granule, an aqueous suspension formulation, or an oily suspension formulation.

11. The method according to claim 1, wherein the soil treatment step is performed before sprouting of a cultivated crop.

12. The method according to claim 11, wherein the cultivated crop is a bean plant.

13. The method according to claim 12, wherein the bean plant is soybean (Glycine max), peanut (Arachis hypogaea), azuki bean (Vigna angularis), common bean (Phaseolus vulgaris), or black-eyed pea (Vigna unguiculata).

14. A mixed agrochemical composition for soil treatment, comprising: an agrochemical composition for soil treatment, which comprises pyroxasulfone; and a protoporphyrinogen oxidase inhibitor, wherein the agrochemical composition for soil treatment further comprises a masking substance that masks the pyroxasulfone, and the pyroxasulfone is microencapsulated in or coated with the masking substance.

15. The mixed agrochemical composition for soil treatment according to claim 14, further comprising an agrochemical active component other than the pyroxasulfone and the protoporphyrinogen oxidase inhibitor.

Description

EXAMPLES

[0113] The present invention will now be described in detail by way of Examples and Test Examples; however, the present invention is not restricted by these Examples at any rate. In the below-described Examples, “part(s)” means part(s) by mass, and “%” means % by mass.

Preparation Example 1

[0114] A mixture was obtained by stirring 5 parts of phenylxylylethane (trade name “HISOL SAS-296”, manufactured by Asahi Petrochemicals, Co., Ltd., viscosity at 20° C.=lower than 10 mPa.Math.s (measured by a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.); the same applies below)) with 0.05 parts of a polyester block copolymer (trade name “ATLOX RHEOSTRUX 100-PW(MV)” manufactured by Croda International Plc) under heating at 80° C. using a dissolver (trade name “TK ROBOMIX”, manufactured by PRIMIX Corporation). The thus obtained mixture had a viscosity of 52 mPa.Math.s at 20° C. To this mixture, 5.1 parts of pyroxasulfone was added, and the resulting mixture was stirred at 30° C. for 15 minutes at a peripheral speed of 9,425 mm/s, after which 15 parts of an isocyanate (trade name “CORONATE 1130”, manufactured by Tosoh Corporation) was further added, and the resulting mixture was stirred at a peripheral speed of 9,425 mm/s. Then, 68.51 parts of a 1% aqueous polyvinyl alcohol solution and 0.1 parts of a silicone-based antifoaming agent (trade name “ASAHI SILICONE AF-128”, manufactured by Asahi Dyestuff MFG. Co., Ltd.) were further added, and the resulting mixture was stirred at a peripheral speed 25,133 mm/s for 10 minutes to obtain a suspension solution. Subsequently, the thus obtained suspension solution was stirred at a peripheral speed of 628 mm/s with heating from 30° C. at a heating rate of 1° C./min for 30 minutes, and then further stirred at a peripheral speed of 628 mm/s for 2.5 hours while the temperature was maintained at 60° C., followed by addition of 2.0 parts of a polyoxyethylene polyoxypropylene block copolymer (trade name “EPAN 410”, manufactured by DKS Co., Ltd.) and further stirring for 1 hour. After the completion of reaction, 4.0 parts of sodium salt of a naphthalene sulfonic acid formaldehyde condensate (trade name “DEMOL SN-B”, manufactured by Kao Corporation) was added at room temperature, and the resulting mixture was stirred at a peripheral speed of 3,142 mm/s for 5 minutes, followed by addition of 0.2 parts of xanthan gum (trade name “KELZAN”, manufactured by SANSHO Co., Ltd.) and stirring for 10 minutes, after which the resultant was screened through a sieve having openings of about 300 μm (48 mesh), whereby a microencapsulated pyroxasulfone-containing agrochemical composition for soil treatment, which contained a polyurea as a masking substance, was obtained. This composition was in the form of spherical particles having an average particle size of 15.4 μm.

Preparation Example 2

[0115] A mixture was obtained by stirring 5 parts of phenylxylylethane (trade name “HISOL SAS-296”, manufactured by Asahi Petrochemicals, Co., Ltd., viscosity at 20° C.=lower than 10 mPa.Math.s (measured by a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.); the same applies below)) with 0.05 parts of a polyester block copolymer (trade name “ATLOX RHEOSTRUX 100-PW(MV)” manufactured by Croda International Plc) under heating at 80° C. using a dissolver (trade name “TK ROBOMIX”, manufactured by PRIMIX Corporation). The thus obtained mixture had a viscosity of 52 mPa.Math.s at 20° C. To this mixture, 5.1 parts of pyroxasulfone was added, and the resulting mixture was stirred at 30° C. for 15 minutes at a peripheral speed of 9,425 mm/s, after which 15 parts of an isocyanate (trade name “SUMIDUR 44V10”, manufactured by Sumika Bayer Co., Ltd.) was further added, and the resulting mixture was stirred at a peripheral speed of 9,425 mm/s. Then, 68.51 parts of a 1% aqueous polyvinyl alcohol solution and 0.1 parts of a silicone-based antifoaming agent (trade name “ASAHI SILICONE AF-128”, manufactured by Asahi Dyestuff MFG. Co., Ltd.) were further added, and the resulting mixture was stirred at a peripheral speed of 31,416 mm/s for 5 minutes to obtain a suspension solution. Subsequently, the thus obtained suspension solution was stirred at a peripheral speed of 628 mm/s with heating from 30° C. at a heating rate of 1° C./min for 30 minutes, and then further stirred at a peripheral speed of 628 mm/s for 2.5 hours while the temperature was maintained at 60° C., followed by addition of 2.0 parts of a polyoxyethylene polyoxypropylene block copolymer (trade name “EPAN 410”, manufactured by DKS Co., Ltd.) and further stirring for 1 hour. After the completion of reaction, 4.0 parts of sodium salt of a naphthalene sulfonic acid formaldehyde condensate (trade name “DEMOL SN-B”, manufactured by Kao Corporation) was added at room temperature, and the resulting mixture was stirred at a peripheral speed of 3,142 mm/s for 10 minutes, followed by addition of 0.2 parts of xanthan gum (trade name “KELZAN”, manufactured by SANSHO Co., Ltd.) and stirring for 10 minutes, after which the resultant was screened through a sieve having openings of about 300 μm (48 mesh), whereby a microencapsulated pyroxasulfone-containing agrochemical composition for soil treatment, which contained a polyurea as a masking substance, was obtained. This composition was in the form of spherical particles having an average particle size of 8.8 μm.

Comparative Preparation Example 1

[0116] After adding and mixing 50 parts of pyroxasulfone, 3 parts of sodium alkylnaphthalene sulfonate, 2 parts of polyoxyethylene alkylphenyl ether, 5 parts of sodium lignin sulfonate, 18 parts of diatomaceous earth and 22 parts of clay, the resulting mixture was pulverized and subsequently kneaded with an addition of water in an appropriate amount. Thereafter, the resultant was extrusion-granulated through a screen of 0.7 mm in mesh size using an extrusion granulator and then size-sorted, followed by drying at a product temperature of 60° C. and sieving, whereby a pyroxasulfone-containing wettable powder was obtained.

Test Example 1: Herbicidal Effect Evaluation Test on Weeds by Soil Treatment

[0117] In a greenhouse having an average temperature of 25° C. (highest: 30° C., lowest: 25° C.), field soil (sandy loam) was filled in a plastic pot of 11 cm in length, width and depth, and twenty seeds of each of barnyard grass (Echinochloa crus-galli) and redroot amaranth (Amaranthus retroflexus) were sowed and covered with the same soil at a thickness of 1 cm. Subsequently, the agrochemical composition for soil treatment which was obtained in Preparation Example 1 or the wettable powder obtained in Comparative Preparation Example 1 and a PPO inhibitor were weighed such that the amount of pyroxasulfone per hectare would be as shown in Table 1, and then diluted with water and uniformly sprayed to the soil using a small sprayer. On the day of this chemical treatment, a total of 2-mm rainfall was artificially applied in 30 minutes using an artificial rain maker. Thereafter, barnyard grass and redroot amaranth were grown and, on Day 18 after the treatment, the growth conditions of barnyard grass and redroot amaranth were observed and examined. The rates of reduction in the plant height and the number of leaves relative to an untreated area were each calculated, and the herbicidal effect was determined as a value obtained by adding the thus calculated rates of reduction and dividing this value by 2 for evaluation of the degree of the herbicidal effect. For example, the herbicidal effect is 90% when the plant height was decreased by 90% and the number of leaves was reduced from 10 to 1, while the herbicidal effect is 75% when the plant height was decreased by 70% and the number of leaves was reduced from 5 to 1. The results of the examination are shown in Table 1. It is noted here that, in Table 1, each value of the herbicidal effect represents an average value of two herbicidal effect evaluation tests.

TABLE-US-00001 TABLE 1 Barnyard Redroot Amount of grass amaranth component Day 18 after Day 18 after (g/ha) treatment treatment active (4.2 L)*.sup.1 (4 L)*.sup.1 Comparative 1 Preparation Example 1 90 100 97 Examples 2 pyroxasulfone) (microencapsulated 180 100 97 3 Comparative Preparation 90 100 94 4 Example 1 (pyroxasulfone) 180 100 94 5 Flumioxazin*.sup.2 70 100 100 6 140 100 100 7 Saflufenacil*.sup.3 25 15 100 8 50 65 100 9 Sulfentrazone*.sup.4 160 100 100 10 320 100 100 Examples 1 Preparation Example 1 + 90 + 70 100 100 2 flumioxazin 180 + 140 100 100 3 Preparation Example 1 + 90 + 25 100 100 4 saflufenacil 180 + 50  100 100 5 Preparation Example 1 +  90 + 160 100 100 6 sulfentrazone 180 + 320 100 100 Comparative 11 Comparative Preparation 90 + 70 100 100 Examples 12 Example 1 + flumioxazin 180 + 140 100 100 13 Comparative Preparation 90 + 25 100 100 14 Example 1 + saflufenacil 180 + 50  100 100 15 Comparative Preparation  90 + 160 100 100 16 Example 1 + sulfentrazone 180 + 320 100 100 *.sup.1The leaf stage at the time of examination is shown in parentheses. *.sup.2flumioxazin water-dispersible granule (trade name “VALOR SX”, manufactured by Valent LLC) *.sup.3saflufenacil aqueous suspension formulation (trade name “SHARPEN”, manufactured by BASF Japan, Ltd.) *.sup.4sulfentrazone aqueous suspension formulation (trade name “SPARTAN FL 4F”, manufactured by FMC Corporation)

Test Example 2: Evaluation Test of Crop Injury to Soybean by Soil Treatment

[0118] In a greenhouse having an average temperature of 25° C. (highest: 30° C., lowest: 25° C.), field soil (sandy loam) was filled in a plastic pot of 11 cm in length, width and depth, and a single seed of soybean (Glycine max) was sowed and covered with the same soil at a thickness of 2 cm. Subsequently, the agrochemical composition for soil treatment which was obtained in Preparation Example 1 or 2 or the wettable powder obtained in Comparative Preparation Example 1 and a PPO inhibitor were weighed such that the amount of pyroxasulfone per hectare would be as shown in Tables 2 to 5, and then diluted with water and uniformly sprayed to the soil over the soybean using a small sprayer. On the day of this chemical treatment, a total of 15-mm rainfall was artificially applied in 30 minutes using an artificial rain maker. Thereafter, the soybean was grown and, on Day 15 and Day 39 after the treatment or on Day 13 and Day 26 after the treatment, the growth conditions of the soybean were observed and examined in terms of the plant height and the number of leaves. The rates of reduction in the plant height and the number of leaves relative to an untreated area were each determined, and the thus determined rates of reduction were added and then divided by 2 to calculate the growth inhibition rate for evaluation of the degree of crop injury. For example, the growth inhibition rate is 10% when the plant height was decreased by 10% and the number of leaves was reduced from 10 to 9, while the growth inhibition rate is 25% when the plant height was decreased by 30% and the number of leaves was reduced from 5 to 4. The results of the examination are shown in Tables 2 to 5. It is noted here that, in Tables 2 to 5, each growth inhibition rate represents an average value of two crop injury evaluation tests.

[0119] In this Test Example 2, an effect lower than a formal sum of the crop injury levels caused by the individual use of two chemical agents, i.e., the agrochemical composition for soil treatment or the wettable powder and a PPO inhibitor, was observed with a combination of the present inventions. The values observed in the test each indicated an effect lower than the expected value calculated by the following Colby formula at a preferable dosage (see S. R. Colby, Weeds 15(1967), pp. 20-22). Colby's formula defines the expected value (E) as follows for the use of a combination of two chemical agents:

(E)=X+Y−XY/100

[0120] wherein X represents the growth inhibition rate of an agent a at a concentration of x, and Y represents the growth inhibition rate of an agent b at a concentration of y.

TABLE-US-00002 TABLE 2 Soybean growth inhibition rate Amount of (%) active Day 15 Day 39 component after after (g/ha) treatment treatment Comparative Preparation Example 2 90 10 5 Example 17 (microencapsulated pyroxasulfone) Comparative Comparative 90 10 13 Example 3 Preparation Example 1 (pyroxasulfone) Comparative Flumioxazin 70 15 5 Example 5 Example 7 Preparation Example 90 + 70 15(24)*.sup.5 5(10)*.sup.5 2 + flumioxazin Comparative Comparative 90 + 70 25(24)*.sup.5 20(17)*.sup.5 Example 11 Preparation Example 1 + flumioxazin *.sup.5The Colby expected value is shown in parentheses.

TABLE-US-00003 TABLE 3 Soybean growth inhibition rate Amount of (%) active Day 15 Day 39 component after after (g/ha) treatment treatment Comparative Preparation Example 2 180 10 8 Example 18 (microencapsulated pyroxasulfone) Comparative Comparative 180 15 13 Example 4 Preparation Example 1 (pyroxasulfone) Comparative Flumioxazin 140 25 10 Example 6 Example 8 Preparation Example 180 + 140 20(33)*.sup.5 5(17)*.sup.5 2 + flumioxazin Comparative Comparative 180 + 140 65(36)*.sup.5 25(22)*.sup.5 Example 12 Preparation Example 1 + flumioxazin *.sup.5The Colby expected value is shown in parentheses.

TABLE-US-00004 TABLE 4 Soybean growth Amount of inhibition rate (%) active Day 13 Day 26 component after after (g/ha) treatment treatment Comparative Preparation Example 1 90 10 5 Example 1 (microencapsulated pyroxasulfone) Comparative Comparative 90 10 10 Example 3 Preparation Example 1 (pyroxasulfone) Comparative Flumioxazin 70 8 10 Example 5 Comparative Saflufenacil 25 20 30 Example 7 Comparative Sulfentrazone 160 25 20 Example 9 Example 1 Preparation 90 + 70  5(17)*.sup.5 5(15)*.sup.5 Example 1 + flumioxazin Example 3 Preparation 90 + 25  20(28)*.sup.5 18(34)*.sup.5 Example 1 + saflufenacil Example 5 Preparation 90 + 160 20(33)*.sup.5 20(24)*.sup.5 Example 1 + sulfentrazone Comparative Comparative 90 + 70  25(17)*.sup.5 20(19)*.sup.5 Example 11 Preparation Example 1 + flumioxazin Comparative Comparative 90 + 25  40(28)*.sup.5 40(37)*.sup.5 Example 13 Preparation Example 1 + saflufenacil Comparative Comparative 90 + 160 70(33)*.sup.5 60(28)*.sup.5 Example 15 Preparation Example 1 + sulfentrazone *.sup.5The Colby expected value is shown in parentheses.

TABLE-US-00005 TABLE 5 Soybean growth Amount of inhibition rate (%) active Day 13 Day 26 component after after (g/ha) treatment treatment Comparative Preparation 180 15 10 Example 2 Example 1 (microencapsulated pyroxasulfone) Comparative Comparative 180 15 10 Example 4 Preparation Example 1 (pyroxasulfone) Comparative Saflufenacil 50 30 30 Example 8 Comparative Sulfentrazone 320 18 15 Example 10 Example 4 Preparation 180 + 50  35(41)*.sup.5 25(37)*.sup.5 Example 1 + saflufenacil Example 6 Preparation 180 + 320 25(30)*.sup.5 15(24)*.sup.5 Example 1 + sulfentrazone Comparative Comparative 180 + 50  45(41)*.sup.5 40(37)*.sup.5 Example 14 Preparation Example 1 + saflufenacil Comparative Comparative 180 + 320 65(30)*.sup.5 60(24)*.sup.5 Example 16 Preparation Example 1 + sulfentrazone *.sup.5The Colby expected value is shown in parentheses.