GB2040684A - Pesticidal composition and method for treating seeds prior to planting - Google Patents

Abstract

Liquid slurry formulation contain- ing active pesticide and adhesive sticker in admixture with suspending agents, surface active agents, and other adjuvants, is applied to seeds to yield seeds with an adherent coating in which active pesticidal agent is dispersed. Preferred stickers are hydroxypropyl cellulose and polyvinyl acetate, and a preferred pesticide is 2,3-dihydro- 2,2-dimethylbenzofuran-7-yl methylcarbamate (carbofuran). The seeds are dried after treatment to provide an adherent coating.

Description

SPECIFICATION Pesticidal composition and method for treating seeds prior to planting This invention pertains to the protection of crops from plant pests, particularly from pests which attack crop seeds and seedlings.

Crop pests which attack seeds and seedlings have been controlled by applying formulations of pest control agents to the soil at planting, and after planting before emergence from the soil, or after emergence from the soil. It is particularly efficacious to apply the formulations of pest control agents to the seeds before planting, thereby placing the pest control agents at the site where pest attack will occur and eliminating the waste attendent upon treating of the entire cultivated acreage.

Treatment of seeds with a systemic pest control agent affords protection to the seed itself, to emerging roots and upward growth of seedlings vulnerable to attack by soil insects and nematodes, and to the seedlings newly emergent from the soil which are especially vulnerable to attack by above-ground insects and other pests.

Application of formulations of pest control agents to crop seeds has been carried out in a multiple-step process by first applying a coating of adhesive sticker to the seed and then causing a formulation of pesticide dust to adhere to the sticky surface of the coating. A subsequent coating with adhesive sticker has often been found necessary to prevent loss of the pesticide dust through attrition and abrasion.

Formulation of adherent coating and active pesticide together so as to permit application to seeds in a single step offers an attractive advantage, except that levels of active pesticide obtainable by this method have in some instances been too low to yield the protection desired.

The present invention comprises storage-stable liquid slurry formulations containing active pesticide and adhesive sticker in admixture with suspending agents, surfactants, and other components. The invention comprises the process for applying said slurry formulations to seeds, followed by drying to remove excess liquid, so as to yield an adherent seed coating in which active pesticidal agent is dispersed. The invention comprises seeds with an adherent pesticide-containing coating obtained by this process.

The coating is resistant to loss of active pesticide by attrition or abrasion, does not significantly reduce the rate of germination of the seed, and provides levels of active pesticide which give adequate protection against crop pests.

The adhesive sticker must be water dispersible, with good film-forming and adhesive properties, yet the resultant dried film must not interfere with respiration of the seed, so as to cause a decrease in germination rate of the seed.

The formulation must be stable in storage for long periods, preferably in excess of one year, during which period agglomeration of solids does not occur, and components which separate are easily redispersed by shaking or stirring.

Adhesive stickers efficacious in the practice of this invention include materials such as hydroxypropylcellulose and emulsions of polyvinyl acetate.

Suspending agents efficacious in the practice of this invention include xanthan gum (a complex polysaccharide with molecular weight above one million), purified, colloidal, sodium-modified montmorillonite, and organically refined smectite clay.

Surface active agents may be nonionic or anionic. Nonionic polyalkylene glycol ethers and anionics such as free acid of oganic phosphate esters or the dioctyl ester of sodium sulfosuccinic acid have been found useful. It is contemplated that other nonionic and anionic surface active agents may also be used.

It is contemplated that a variety of pesticides effective against soil insects and nematodes may be formulated by the method of the invention. Agents capable of systemic action are preferred for use in the invention. An especially preferred systemic insecticide/nematicide is 2,3-dihydro-2,2-dimethylbenzofuran-7yl methylcarbamate ("ca rbofu ran"). It is also contemplated that fungicidal agents may be incorporated in order to protect seeds against fungal attack which the insecticidal and/or nematicidal agent may not effectively combat.

Commercially manufactured insecticides ("technical product") are ordinarily admixed with clays and other adjuvants in order to improve handling characteristics and to reduce dusting and/or caking tendencies of the undiluted technical product. In addition to being unpleasant for personnel who handle the technical product, dustiness increases exposure to inherent hazards of the pesticide. Atypical carbofuran "dustless base" containing approximately 75% active ingredient will comprise, for example: Carbofuran, technical (95% purity) 79.0% Inerts (clays and adjuvants) 21.0 Total 100.0% Preparation of liquid seed treater formulations containing carbofuran 75% dustless base is described in the following examples, intended to be illustrative of the invention, but not limiting thereof.

EXAMPLE 1 Preparation of a seed treater formulation containing 30% carbofuran (formulation D) To 273.72 g of tap water was added 0.42 g of xanthan polysaccharide gum. Mixing with a Lightnin' mixer was continued until the polysaccharide gum was completely dispersed. To the mixture were then added 3.00 g of anionic phosphate ester surfactant, 6.00 g of polyalkylene glycol ether surfactant and 0.06 g of dimethyl siloxane antifoam agent. After dissolution was complete, 72.00 g of stabilized polyvinyl acetate emulsion and 242.40 g of carbofuran 75% dustless base were added and mixed for 10 min. Rhodamine B dye (2.40 g) was added and mixed for 5 min. The formulation was passed through a 100 mesh (0.149 um opening) screen to insure all agglomerates were dispersed. Viscosity ofthis formulation as measured by Zahn cup #3 was 24.0 sec.; its density was 1.1274 g/ml; and it contained 338.2 g of carbofuran/1.

EXAMPLE 2 Preparation of a seed treater formulation containing 25% carbofuran (formulation G) To 616.6 g of water were added 5.00 g of anionic phosphate estersurfactant, 10.00 g of polyalkylene glycol ether surfactant and 0.10 g of dimethyl siloxane antifoam agent. After these surfactants had completely dissolved, 35.00 g of hydroxypropylcellulose was added. Mixing continued until the hydroxypropylcellulose completely dissolved. Carbofuran 75% dustless base (333.3 9) was added, and the mixture was stirred for 5 min. The formulation was passed through a 100 mesh screen to assure that all agglomerates were dispersed.

Rhodamine B dye (4.00 g) was added to the formulation which was then placed in a one-liter jar on a mechanical roller four 12 hours. The formulation had a viscosity af 42.0 sec. as measured by Zahn cup #3 and was found to contain 24.9% carbofuran.

EXAMPLES 3 THROUGH 9 Formulations A, B, C, E, F, H, and I were prepared in essentially the manner as Examples 1 and 2. The formulations and the properties of each formulation are shown in Table 1. Samples of each formulation were placed in 250-ml wide mouth jars for storage stability tests. One sample was stored at room temperature and the other in an oven at 500C. Observations of the amount of phase separation, the settling out of solids, and the tendency of the formulation to jell were made periodically, usually after 1,3, 6, and 12 months of storage.

Tables 2 and 3 show the storage stability of Formulations Athrough I.

EXAMPLE 10 Treatment ofwheatseed with formulation G (treated seed formulation 5) Formulation G (Example 2) (1.20 g) was diluted with 1.20 g of water. After adequate mixing to insure uniformity, the diluted formulation was added to 97.60 g of Yorkstar wheat seed. The treated seed was mixed with a spatula until all of the seed was wet. It was then placed on a mechanical roller for 10 min. The treated wheat seed was placed in an evaporating dish and allowed to air dry for 48 hours. The calculated amount of carbofuran on the seed was 0.3 wt %. No germination study was done on this treated seed. It was found that 0.0037 g of dust could be collected from 20 g of treated seed. The amount of dust was determined by placing 20 g of treated seed in a Kjeldahl connecting bulb which was attached to a rotary evaporator. A special glass apparatus made from a 5.5 cm diameter screw-top glass jar with the bottom replaced by a standard glass taper seal joint was placed at the outlet of the Kjeldahl connecting bulb. The cap of the jar was thoroughly perforated with 1.6-mm holes. A tared 5.5 cm Whatman #1 filter paper was placed in the cap, and the cap was used to close the open end of this special glass apparatus. The inlet of the Kjeldahl connecting bulb was connected to an air supply flowing at 9000 ml/min that was controlled by a rotameter. The rotary evaporator was turned on for 10 min with the air stream passing over the tumbling seed and then through the filter paper. The weight gain of the filter paper during this operation represented the dust from the 20 g sample of seed. The properties of wheat treated with Formulation G and other selected formulations are summarized in Table 4.

EXAMPLE 11 Treatment of corn seed with formulation G (treated seed formulation 11) To 310.45 g of corn seed was added 19.80 g of Formulation G (Example 2). This was mixed with a spatula until the formulation was evenly distributed on the corn seed. The mixture was transferred to an evaporating dish to air dry for 12 hours. An additional 19.75 g of Formulation G was added to the corn seed and mixed with a spatula. The mixture was placed in a 2-liter jar and put on a mechanical roller for 10 min. It was then placed in an evaporating dish to air dry for 3 days. A good coating on the seeds resulted, but the seeds adhered to each other to an unacceptable extent. Only 0.0004 g of dust was found per 20 g of seed. An assay determined that 4.65 wt % of carbofuran was coated on the seed. A germination test after 6 months storage showed that 82% of the seeds germinated. No phytotoxicity was observed in the seedlings. Table 5 summarizes the properties of corn treated with Formulation G and other selected formulations. Tables 6 and 7 list other seeds treated with Formulation G and other selected formulations. Seeds which were treated and then had adequate rates of germination either initially or after 6 months storage include sorghum, red fescue, alfalfa, and soybeans. The soybeans were wrinkled by the treatment and there was stunting of the plants in the initial germination test. The treatments for rye and oats could not be judged accurately because of the low rate of germination of the control sample of untreated seeds.

It is apparent that various modifications may be made in the formulation and application of the novel seed treater formulations of this invention, without departing from the inventive concept herein, as defined in the following claims.

TABLE 1 Slurry formulations of carbofuran seed treater Formulation, % A B C D E Carbofuran 75% Base 46.67 42.66 42.66 40.40 40.40 Xanthan poly saccharide gum .06 .07 .06 Colloidal mont morillonite 1.00 Smectite clay Polyalkylene glycol ether 1.00 2.00 2.00 1.00 1.00 Anionic phos phate ester 1.00 .50 .50 Sodium dioctyl sulfosuccinate 1.00 1.00 Polyvinyl ace tate emulsion 8.00 12.00 12.00 Hydroxypropyl cellulose .60 2.50 Dimethyl siloxane .01 .01 .01 .01 Rhodamine B .40 .40 Water 49.33 46.27 51.83 45.62 46.03 Active ingred.

% intended 35 32 32 30 30 % assayed 31.9 32.1 29.2 Viscosity* (sec.) 37.0 18.5 15.5 24.0 20.0 Agglomerates (on 100 mesh) Nil Nil Nil Nil *Zahn cup - No. 3 Formulation, % F G H Carbofuran 75% Base 40.40 33.20 26.70 26.67 Xanthan poly saccharide gum .10 Colloidal mont morillonite 1.00 Smectite clay 0.13 Polyalkylene glycol ether 1.00 1.00 1.00 1.00 Anionic phos phate ester .50 .50 .50 .50 Sodium dioctyl sulfosuccinate Polyvinyl ace tate emulsion 12.00 12.00 Hydroxypropyl cellulose 3.49 3.00 Dimethyl siloxane .01 .01 .01 .01 TABLE 1 (Cont.) Slurry formulations of carbofuran seed treater Formulation, % F G H Rhodamine B .40 .40 .40 .40 Water 44.69 61.40 59.29 68.29 Active ingred.

% intended 30 25 20 20 % assayed 24.9 19.6 19.2 Viscosity* (sec.) 21.0 42.0 20.0 27.0 Agglomerates (on 100 mesh) Nil - Nil Nil *Zahn cup - No. 3 TABLE 2 Stability ofcarbofuran seed treater formulations storage at ambient temperatures Formulation A B C D E After 1 month Separation 3% 5%a Settling out Nil Nil Gel tendency Nil Nil After 3 months Separation 20%b 23% 24% 5% 9%C Settling out Nil Nil Trace Nil Trace Gel tendency Mod. Nil Nil After 6 months Separation 26% 20% 25% 10% 17%d Settling out Nil Nil Nil Trace SI.

Gel tendency Mod. Nil Nil After 11 months Separation 25% 25% Settling out Trace Trace a - 2 months b - 3.5 months c - 4 months d - 7 months Formulation F G H After 1 month Separation 6% 42%a 40% Settling out Nil Nil Nil Gel tendency V. SI. SI. Nil After 3 months Separation 10% 43% 11%C 46% Settling out Nil 57% Nil Nil Gel tendency SI. Hard Nil Nil After 6 months Separation 16% 22% 53% Settling out Nil Nil Nil Gel tendency Mod. Nil SI.

After 11 months Separation Settling out a - 2 months c - 4 months TABLE 3 Stability of carbofuran seed treater formulations storage at 500C Formulation A B,C D E After 1 month Separation 12%a 18% 9% Settling out Nil Nil Nil Gel tendency Mod. V. SI. Nil Agglomerates SI. N Trace SI.

Viscosity* (sec.) 50.0 0 19.0 17.0 After3 months Separation 21%b R 12% 18% Settling out Nil E Nil Trace Gel tendency Heavy A V. SI. Nil Agglomerates - D SI.

Viscosity* (sec.) 47.0 1 17.0 15.0 After 6 months N Separation 16% G 28% 30%d Settling out Nil S Trace Nil Gel tendency Mod. Nil Nil Agglomerates Mod. SI. Mod.

Viscosity* (sec.) Paste 14.0 13.0 * Zahn cup - no. 3 a - 1.5 months b - 3.5 months c - 4 months d - 7 months Formulation F G H After 1 month Separation 5% 45% 44% Settling out Nil Nil 56% Gel tendency SI. SI. Mod.

Agglomerates Trace Nil Nil Viscosity* (sec.) 25.0 27.0 23.0 After3 months Separation 17% 35% 48%C 48% Settling out Nil Nil Nil 52% Gel tendency SI. Mod. Nil Mod.

Agglomerates SI. - Heavy SI.

Viscosity* (sec.) 17.0 23.0 12.0 31.0 After 6 months Separation 12% 50% 50% Settling out Nil Nil Nii Gel tendency Mod. Nii Mod.

Agglomerates Mod. Heavy Mod.

Viscosity* (sec.) 29.0 11.5 12.0 * Zahn cup - no. 3 c - 4 months TABLE 4 Wheat treated with carbofuran seed treater formulation Seed treatment Lot no. 1 2 3 4 5 6 Yorkstar wheat seed, % 96.00 96.67 97.50 96.66 97.60 98.00 Formulation E,% 3.33 1.00 F, % 1.00 G,% 4.00 1.20 I, % 1.50 Water, % 1.00 2.34 1.20 1.00 Active ingred ient on seed %intended 1.00 1.00 .3 .3 .3 .3 %assayed 1.18 1.17 - Dust, 9/20 g seed .0028 .0096 .0036 .0001 .0037 .0048 Coating coverage Good Good Coating rub-off Slight Slight Germination, % 96(91)a 96(76)8 Phytotoxicity Nil Nil After 6 months Germination, % 96 98 Phytotoxicity Slight Slight After 9 months Germination, % 88 76 Phytotoxicity V.SI. V.SI.

a - Field germination result is shown in parentheses TABLE 5 Corn treated with carbofurn seed treater formulation Seed treatment Lot no. 7 8 9 10 11 12 Field corn seed, % 98.43 98.43 96.88 96.88 88.70 90.30 Formulation B, % 1.57 3.12 1.57 3.12 E, % 9.70 G, % 11.30 Active ingred ient on seed % intended .5 .5 1.0 1.0 3.0 3.0 % assayed 4.65 3.12 Dust, g/20 g seed .0004 .0005 Coating coverage Fair Good Good V.Good V.Good Good Coating rub-off Heavy Mod. Mod. Slight Seed adhesion Nil Nil Nil Nil Severe Severe Germination, % 98 92 90 96 86(90)a 82(87)a Phytotoxicity Slight Nil Nil Slight Nil Nil After 6 months Germination, % 82 96 Phytotoxicity Nil Nil After 9 months Germination, % 72 74 Phytotoxicity Nil Nil After 12 months Germination, % 92 98 94 94 Phytotoxicity Nil Nil Nil Nil After 21 months Germination, % 96 98 94 94 Phytotoxicity Nil Nil Slight Slight a - Field germination result is shown in parentheses TABLE 6 Sorghum treated with carbofuran seed treater formulation Seed treatment Lot no. 13 14 19 20 Sorghum seed, % 90.90 90.90 85.20 87.10 Formulation B, % 9.10 C, % 9.10 E, % 14.80 12.90 Active ingre dient on seed % intended 3.0 3.0 4.0 4.0 Coating coverage V. Good Excell.

Coating rub-off V. SI. V. SI.

Seed adhesion Slight Slight Germination, % 94 90 86(96)a 98(80)a Phytotoxicity Slight Slight Mod(Nil)a Mod(Nil)a After 6 months Germination, % - - 86 80 Phytotoxicity - - Slight Slight After 9 months Germination, % - - 80 80 Phytotoxicity - - Mod. Mod.

After 12 months Germination, % 90 98 Phytotoxicity Severe Mod.

After 21 months Germination, % 86 84 Phytotoxicity Mod. Mod.

a - Field germination result is shown in parentheses TABLE 7 Seeds treated with carbofuran seed treater formulation Seed treatment Red fescue Alfalfa Lot no. 15 16 17 18 Fescue seed % 88.70 90.30 Alfalfa seed % 82.00 84.20 Formulation E % 9.70 15.80 11.30 18.00 Active ingre dient on seed % intended 3.0 3.0 5.0 5.0 Germination, % 84 86 78 74 Phytotoxicity Nil Nil Slight Slight After 6 months Sermination, % 88 84 70 72 Phytotoxicity Nil Nil - Slight Slight After 9 months Germination, % 68 78 82 76 Phytotoxicity Nil Nil Slight Slight Seed treatment Rye Oats Soybeans Lot no. 21 23 25 26 Rye seed, % 94.20 Oats seed, % 94.20 Soybeans, % 92.20 93.40 Formulation E, % 6.60 G, % 3.80 3.80 7.80 Water, % 2.00 - 2.00 Active ingred ient on seed % intended 1.0 1.0 2.0 2.0 Germination, % 70(31)a 46(31)a 100(78)a 96(89)a Phytotoxicity Nil Nil Mod.(d) Mod.(d) After 6 months Germination, % 48b 22C 92 96 Phytotoxicity Slight Slight Slight Slight After 9 months Germination, % 48 26 88 94 Phytotoxicity Nil Slight Slight Slight a. Field germination result is shown in parentheses.

b. Germination rate of untreated rye seed was 66%.

c. Germination rate of untreated oats seed was 38%.

d. Stunted in field.

Claims (11)

1. A method of protecting seeds and seedlings against plant pests which is characterized by applying to seeds of plants before they are planted an aqueous suspension containing an adhesive sticker and one or more active pesticide compounds in admixture with suspending agents, surface active agents and other adjuvants, and drying the treated seeds to remove excess liquid so as to provide an adherent pesticide-containing coating on the seeds.

2. The method of claim 1 wherein the aqueous suspension contains about 0.5 to 15% adhesive sticker and about 15 to 40% active pesticide compound.

3. The method of claim 1 wherein the adhesive sticker is selected from the group consisting of hydroxypropyl cellulose and polyvinyl acetate.

4. The method of claim 1 wherein an active pesticide compound is 2,3-dihydro-2,2-dimethylbenzofuran7-yl methylcarbamate.

5. A composition for use in application as an aqueous suspension to plant seeds to protect seeds and seedlings against plant pests characterized in that it contains an adhesive sticker and one or more active nesticide comnounds in admixture with a susDendina agent. surface active agents and other adjuvants.

6. The composition of claim 5 wherein the adhesive sticker comprises about 0.5 to 15% and the active pesticide compound comprises about 15 to 40%.

7. The composition of claim 5 wherein the adhesive sticker is selected from the group consisting of hydroxypropylcellulose and polyvinyl acetate.

8. The composition of claim 5 wherein an active pesticide compound is 2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate.

9. Plant seed protected against plant pests by an adherent pesticide-containing coating, obtained by applying to the seeds an aqueous suspension containing an adhesive sticker and one or more active pesticide compounds in admixture with suspending agents, surface active agents and other adjuvants, and drying said coated seeds to remove excess liquid.

10. The plant seed of claim 9 wherein the adhesive sticker is selected from the group consisting of hydroxypropylcell ulose and polyvinyl acetate.

11. The plant seed of claim 9 wherein the adherent pesticide-containing coating contains as active pesticide 0.1 to 6% of 2,3-dihydro-2,2-dimethyl benzofuran-7-yl methylcarbamate.