Agent for imparting a sustained release property to a pesticide, a pesticide having a sustained release property and a process for the production thereof

Abstract

A sustained release pesticide comprises solid pesticidal particles comprising a solid, pesticidally active ingredient, substantially the whole surface of the pesticidal particles being coated with a hydrophobic substance.

Description

TECHNICAL FIELD

This invention relates to an agent for imparting a sustained release property to a pesticidally active ingredient having solid particulate form in a pesticide or a pesticide preparation containing the solid particles of the pesticidally active ingredient, and this invention also relates to a new pesticide having the sustained release property and containing the pesticidally active ingredient which has been treated with the agent for imparting the sustained release property thereto, and further this invention includes a process for the production of such solid particles of a pesticidally active ingredient which have gained a sustained release property. More particularly, this invention is directed to a technique for controlling the release of a pesticidally active ingredient from the pesticide by covering the particle surfaces of said pesticidally active ingredient of solid particulate form with fine particles or powder of a hydrophobic substance.

BACKGROUND ART

Hithereto, many efforts have been made to impart a sustained release property to various kinds of pesticidally active ingredients having solid form or liquid form. When largely classified, the prior art methods for preparing a pesticide having the sustained release property include (1) a method comprising encapsulating a pesticidal active ingredient in micro-capsules (see Japanese patent application first publication "Kokai" No. 58-144204 gazette and Japanese patent application first publication "Kokai" No. 59-20209 gazette); (2) a method comprising converting a pesticidally active ingredient into an inclusion compound with cyclodextrin (see Japanese patent application first publication "Kokai" No. 58-21602 gazette and Japanese patent application first publication "Kokai" No. 59-53401 gazette); (3) a method comprising granulating solid particles of a pesticidally active ingredient for use in a pesticide preparation such as granules and powders etc., alone or together with a filler etc., and coating the resultant particulate cores with wax or one of various resins (see Japanese patent application first publication "Kokai" No. 57-126402 gazette and Japanese patent application first publication "Kokai" No. 60-202801 gazette), and others. Hitherto, however, no attempt was made to achieve an improvement in the art by depositing and adhering fine particles of a hydrophobic substance onto the particle surfaces of a pesticidally active ingredient having a solid particulate form so as to cover the particle surfaces of the active ingredient with the fine particles of the hydrophobic substance, and thus controlling the dissolution and release of said pesticidally active ingredient.

When a pesticide preparation having a solid state in the form of granules and powders is brought into contact with water after the application of said pesticide preparation for use, in some cases the active ingredient present in said preparation can rapidly dissolve out and be released from the pesticide preparation so that the concentration of the active ingredient as released exceeds such a concentration just required for the active ingredient to display its biological effects. In these cases, the active ingredient can occasionally bring about kill of the leave of crop plants or a phytotoxicity such as suppression of the growth of crop plants; and the active ingredient once released can be degraded or disappear fastly in water or soil; and also it can disappear due to its degradation under the action of light, with consequences that the period of time of the lasting of the biological activities of the active ingredient can be shortened. For these reasons, these various troublesome problems can be solved if such a measure is provided to ensure that the pesticidally active ingredient continues to release gradually over a prolonged period of time from the pesticide preparation only in minimum amounts of the active ingredient just required to achieve the control of a pest. Further, when the sustained release property can be imparted to a pesticide, the necessity of repeated applications of such pesticide at several times can be eliminated, and the pesticide can be utilized highly economically with serving to prevent the enviromental pollution. However, any of the known pesticides having the sustained release property as mentioned above are advantageous in some aspects but disadvantageous in another aspects in solving the aforesaid various troublesome problems.

Thus, certain pesticidal compounds cannot be encapsulated into micro-capsules or cannot be converted into the inclusion compound with cyclodextrin according to the nature of the pesticidal compounds, and for these reasons there exist such pesticidal compounds which cannot be processed into a pesticide preparation having the sustained release property. Even if the prior art methods for producing the pesticide preparations having the sustained release property are applicable, there often occur some cases where a satisfactory sustained release property cannot be obtained; where the pest-controlling activities of the resulting pesticide preparation are not displayed fully; and/or where lasting and prolongation of the biological activities as well as the reduction in the phytotoxicity of the active compound which are aimed at for one of the purposes of the pesticide having the sustained release property are not attainable to a full extent. Besides, for the reasons why the technique for production of a pesticide having the sustained release property is complicate and troublesome and the raw materials used therefor are expensive; and for another reasons, there are still remaining many problems that are to be solved in the technical aspect or in the economic aspect. As described in the above, therefore, the prior art technique for the production of a pesticide having the sustained release property has not yet been developed to a full extent, and a development of a novel technique therefor is now desired.

In account of the above situations, we, the present inventors, have paid attention on a technique of modifying or improving the structure of the surfaces of particles of such a pesticidally active ingredient having solid particulate form, and we have made researches in attempts to provide a novel agent which is able to give the desired sustained release property to a pesticide of the solid particulate form, and to provide such a pesticide having the sustained release property as obtained using said agent, and also to provide a process for the production of such sustained-releasing pesticide.

DISCLOSURE OF THE INVENTION

We, the present inventors, have made eargerly studies in order to solve the above-mentioned technical problems. As a result, we have found that an appropriate sustained release property can be imparted to the particles of the pesticidally active ingredient by modifying the surfaces of the particles of the pesticidal active ingredient having the solid particulate form so that the particle surfaces of the active ingredient become exhibiting a higher hydrophobic property than the original property inherently shown by the particle surfaces of the active ingredient. When this is explained more concretely, it has now been found by us that when the whole surfaces of the particles of a pesticidally active ingredient having solid particulate form are coated evenly either with such an outer layer consisting or composed of fine particles of a hydrophobic substance which have a particle diameter of not greater than one-fifth of the average or mean particle diameter of said pesticidally- active ingredient and have been adhered or fixed onto the aforesaid surfaces of the particles of the pesticidally active ingredient, or with such a continuous or cohesive coat-film which has been formed by integrating and binding the above-mentioned adhered or fixed individual particles of the fine particles of the hydrophobic substance with each other, it is possible to produce such composite particles of the pesticidally active ingredient that are each containing a solid particle of the pesticidally active ingredient as a central core within each composite particle and also are each provided with a surrounding outer layer consisting of the fine particles of the hydrophobic substance or consisting of a coating film as made of the integrated and bound particles of said hydrophobic substance. At this time, it has further been found that where the total amount of the fine particles of the hydrohobic substance employed is adjusted to be of such a proportion that the hydrophobic substance is present in an amount ranging from 0.05 parts to 1 part by weight for 1 part by weight of the pesticidally active ingredient, and when the above-mentioned composite particles are placed in water, the pesticidally active ingredient is able to dissolve out gradually from the core portion of said composite particles through the surrounding outer layer made of the hydrophobic substance, and thus the resulting composite particles of the pesticidally active ingredient can exhibit the sustained release property for the pesticidal active ingredient.

Furthermore, it has now been found that the composite particles of the pesticidal active ingredient which are produced as described in the above may be, similarly to the conventional pesticides, formulated into such forms as powders, granules, wettable powders, suspensions, pastes and the like, by mixing with auxiliary additives and fillers, and that the pesticide formulations so made can exhibit an appropriate sustained-releasing effect on the active ingredient and hence exhibit the biological activity inherent to the pesticidal active ingredient in a lasting way and over a prolonged period of time, with consequences that some merits such as a remarkable reduction in the phytotoxicity of the active ingredient are obtained.

In a first aspect of this invention, therefore, there is provided an agent for imparting a sustained release property to a pesticide containing solid particles of a pesticidally active ingredient, characterized in that said agent comprises or is fine particles of a hydrophobic substance.

In a second aspect of this invention, there is also provided a pesticide having a sustained release property, characterized in that either said pesticide contains such composite particles containing a pesticidally active ingredient and each comprising a central core of the pesticidally active ingredient and an outer layer consisting of fine particles of a hydrophobic substance surrounding said core, which composite particles are produced by adhering to and over the particle surfaces of solid particles of the pesticidally active ingredient fine particles of the hydrophobic substance having an average or mean particle diameter of not greater than one-fifth of the average or mean particle diameter of solid particles of said pesticidally active ingredient or by partially embedding and thus fixing individual particles of the fine particles of the hydrophobic substance into the particle surfaces of the particles of the pesticidally active ingredient; or said pesticide contains such composite particles containing the pesticidally active ingredient and each comprising a central core of said pesticidally active ingredient and a continuous or cohesive coat-film made of the hydrophobic substance surrounding said core, which composite particles are produced by adhering said fine particles of the hydrophobic substance to and over the particle surfaces of solid particles of the pesticidally active ingredient or partially embedding and thus fixing individual particles of the fine particles of the hydrophobic substance into the particle surfaces of said pesticidaly active ingredient and then integrating and binding the so adhered or fixed individual particles of the fine particles of the hydrophobic substance with each other by application of impacting force and/or heat of friction to make the integrated and bound particles of the hydrophobic substance to coat the surfaces of the core particles of the pesticidally active ingredient, and that the total amount of the fine particles of the hydrophobic substance used is of a proportion in the range of 0.05 parts to 1 part by weight of the hydrophobic substance per 1 part by weight of the pesticidally active ingredient.

In a third aspect of this invention, this invention include a process for the production of a pesticide in the form of composite particles each comprising a central core of a pesticidally active ingredient and either an outer layer consisting of fine particles of a hydrophobic substance surrounding said core or a continuous or cohesive coat-film made of the hydrophobic substance, characterized in that the process comprises using fine particles of the hydrophobic substance having an average or mean particle diameter of not greater than one-fifth of the average or mean particle diameter of solid particles of the pesticidally active ingredient in such a proportion that the total amount of the hydrophobic substance employed is in a range of 0.05 parts to 1 part by weight per 1 part by weight of said pesticidally active ingredient, and adhering fine particles of the hydrophobic substance to and over the particle surfaces of solid particles of the pesticidally active ingredient or alternatively partially embedding and thus fixing individual particles of the fine particles of the hydrophobic substance into the particle surfaces of said pesticidally active ingredient, and further, if desired or if appropriate, integrating and binding the so adhered or fixed individual particles of the fine particles of the hydrophobic substance with each other by application of impacting force and/or heat of friction to make the integrated and bound particles of the hydrophobic substance to coat wholly the surfaces of the core particles of the pesticidally active ingredient.

BEST MODE FOR WORKING THE INVENTION

The hydrophobic substance which constitutes the fine particles of the hydrophobic substance usuable in this invention is not limited specifically, if it is a substance having a water-repellent property to water. Where one drop of water is fallen onto a top horizontal surface of a plane plate which has been made by shaping the fine particles of a hydrophobic substance under compression, and if the hydrophobic substance then used is hydrophobic to the required extent, the fallen water drop does then neither wet the surface of said plane plate nor spread over the plate surface, with retaining the shape of one single drop of water. At this time, as the "angle of contact" of said hydrophobic substance is defined such an angle which is formed between the surface of the solid plate and the liquid surface of water drop at the place where the free surface of the stationary water drop is contacting with the surface of the plane plate. When this angle of contact is greater, it can be assumed that the hydrophobic property of the hydrophobic substance is higher.

In accordance with this invention, the "angle of contact" of a hydrophobic substance to water, which is taken as a criterion of the hydrophobic property of a hydrophobic substance, may be measured by the following method of measurement:

A disc in the form of a tablet of 8.5 mm in diameter which is made of a hydrophobic substance and weighing 100 mg is prepared by shaping fine particles of said hydrophobic substance into tablet under compression (200 kg/cm.sup.2) in a tablet-shaping machine. On the top surface of this tablet is then placed by dropping through a micro-syringe 5 .mu.l of water which has been deionized by ion-exchange resins. One minute after the dropping, the angle of contact formed between the water droplet and the tablet surface is measured by means of a goniometer (Type G-1, produced by Elma Optical Company).

Where a hydrophobic substance shows a hydrophobic property to such a degree that the angle of contact formed between the free surface of the water drop and the tablet surface of said hydrophobic substance is 70.degree. C. or more when measured by the above-mentioned method of measurement, this hydrophobic substance may be very much effective to be used in this invention.

The hydrophobic substances usuable in this invention include the under-mentioned substances, for example, to which this invention is not limited, of course.

(1) Higher aliphatic acids

These acids include stearic acid, palmitic acid, lauric acid, myristic acid and the like, for example.

(2) Metal salts of higher aliphatic acids

These salts include aluminum stearate, magnesium stearate, calcium stearate and the like, for example.

(3) Titanium dioxide treated with metal salts of higher aliphatic acids

These treated titanium dioxides include titanium dioxide treated with aluminum laurate, titanium dioxide treated with aluminum stearate, and the like, for example.

(4) Hydrophobic white carbon, namely hydrophobilized silica

These materials include an alkylsilylate silica, especially silicon dioxide treated with dimethyldichlorosilane, and the like, for example.

(5) Hydrophobic synthetic polymers

These polymers include polystyrenes, polyamides, silicones and the like, for example.

For these hydrophobic substances, commercially available hydrophobic substances may be utilized as such. If necessary, however, commercially available hydrophobic substances may be finely ground before their use in order to ensure that the average or mean particle diameter of the hydrophobic substances is adjusted to be not greater than one-fifth of the average or mean particle diameter of a pesticidally active ingredient as employed.

The average particle diameter of a hydrophobic substance used in this invention may vary according to the average particle diameter of a pesticidally active ingredient as employed, but it is necessary that the hydrophobic substance has an average or mean particle diameter of not greater than one-fifth of the particle diameter of the pesticidally active ingredient. It is preferable that the hydrophobic substance has an average or mean particle diameter of not greater than one-tenth of the particle diameter of the active ingredient. Where the hydrophobic substance has an average particle diameter of greater than one-fifth of the particle diameter of the active ingredient, it becomes difficult to adhere or fix the fine particles of the hydrophobic substance uniformly into the particle surfaces of the pesticidally active ingredient or to apply the hydrophobic substance as a continuous or cohesive coat-film of a uniform thickness onto the particle surfaces of the active ingredient, so that the hydrophobic substance will then display incompletely its function to impart the sustained release property to the active ingredient.

Further, it is desirable that the composite particles of the pesticidally active ingredient which each comprise a core of said pesticidally active ingredient and an outer coating layer or sheath of the hydrophobic substance surrounding said core have an average or mean particle diameter of not more than 50 microns. If the composite particles have an average or mean particle diameter of more than 50 microns, it is involved that the pesticidally active ingredient does not display its desired biological activity to a full extent. As a tentative guideline, the average or mean particle diameter of the solid particles of the pesticidally active ingredient which form the core in the composite particles may be in a range of 5 microns to 500 microns but is not restricted to this particular range. However, the average particle diameter of the solid particles of the active ingredient may generally vary according to the nature of the active ingredient compound and according to the forms of the pesticide formulations. Again, the average or mean particle diameter of the hydrophobic substance may be in a range of 0.01 microns to 100 microns but is not restricted to this particular range.

Furthermore, the amount of the hydrophobic substance which is applied onto the surfaces of the solid particles of the pesticidally active ingredient may vary according to the average particle diameter of the pesticidally active ingredient and according to the average particle diameter of the fine particles of the hydrophobic substance, but it is necessary that the hydrophobic substance is applied to the particle surfaces of the active ingredient in such a proportion that the hydrophobic substance applied is in a range of 0.05 parts to 1 part by weight for one part by weight of the pesticidally active ingredient. Of course, it is admittable that the ratio of the amount of the hydrophobic substance to the amount of the pesticidally active ingredient may appropriately be changed within the above-mentioned range in order to obtain an optimal degree of the sustained-release property for the active ingredient. However, if the amount of the fine particles of the hydrophobic substance is less than 0.05 parts by weight, it will be not fully achievable to adhere or fix the fine particles of the hydrophobic substance uniformly to and over the whole surfaces of the particles of the pesticidally active ingredient, or to apply the hydrophobic substance as a uniform coat-film to the surfaces of the particles of the active ingredient, so that the effects of imparting the sustained release property will not be attainable completely. On the contrary, if the amount of the hydrophobic substance used is more than 1 part by weight so as to bring about an excessive application of the fine particles of the hydrophobic substance to and around the particles of the pesticidally active ingredient, the effects of imparting the sustained release property can be displayed but it is then invoked that the biological activity inherently possessed by the pesticidally active ingredient can be reduced. Accordingly, it is not desirable that the fine particles of the hydrophobic substance are used excessively over the amount just required for the intended purpose.

The pesticidally active ingredient having solid particulate form usuable in this invention is not restricted to a particular sort, and any sort of the pesticidally active ingredient may be usuable as long as it is an active ingredient compound which has been used for conventional pesticides or pesticidal preparations. Examples of such pesticidally active ingredient include the under-mentioned pesticidal compounds, for example, to which this invention is not limited, of course.

EXAMPLES OF INSECTCIDES

Pyridafenthion, chlorpyrifos-methyl, chlorpyrifos, vamidothion, dimethoate, phosalone, PMP, DMTP, CVMP, dimethylvinphos, acephate, salithion, DEP, EPN, NAC, MTMC, MIPC, BPMC, PHC, MPMC, XMC, ethiofencarb, pirimicarb, bendiocarb, resmethrin, rotenone, CPCBS, kelthane, chlorobenzilate, chloropropylate, phenisobromolate, tetradifon, quinomethionate, amitraz, benzomate, binapacryl, tricyclohexyltin hydroxide, namely cyhexatin, fenbutatin oxide, polynactin complex, methyl isothiocyanate, mesulfenfos, morantel tartrate, endosulfan, cartap, thiocyclam, methomyl, oxamyl, butoxycarboxim, diflubenzuron, buprofezin and the like.

EXAMPLES OF FUNGICIDES AND BACTERIOCIDES

Copper sulfate, basic copper sulfate, basic copper oxychloride, cupric hydroxide, copper oxinate, captan, zineb, maneb, maneozeb, polycarbamate, propineb, ziram, thiuram, milneb, captafol, dichlofluanid, TPN, fthalide, tolclofos-methyl, thiophanate-methyl, benomyl, thiabendazole, iprodione, vinclozolin, procymidone, blasticidin S, kasugamycin, polyoxins, validamycin A, streptomycin, oxytetracycline, nobobiocin, mildiomycin, PCNB, hydroxyisoxazole, dazomet, chloroneb, triphenyltin hydroxide, MAF, MAFA, dithianon, phenazine oxide, CNA, dimethirimol, anilazine, oxycarboxin, mepronil, probenazole, isoprothiolane, methasulfocarb, fluoroimide, triforine, triadimefon, tricyclazole, fosetyl, guazatine, metalaxyl and the like.

EXAMPLES OF HERBICIDES

MCP, MCPP, MCPB, phenothiol, naproanilide, DNBP, ioxynil, CNP, chlomethoxynil, bifenox, MCC, IPC, phenmedipham, MBPMC, DCPA, alachlor, napropamide, diphenamid, propyzamide, asulam, DCMU, linuron, siduron, dymron, methyl dymron, karbutilate, isouron, simazine, atrazine, propazine, simetryn, ametryn, prometryn, cyanazine, metribuzin, terbacil, bromacil, lenacil, PAC, norflurazon, bentazone, oxadiazon, pyrazolate, paraquat, diquat, trifluralin, benfluralin, nitralin, pendimethalin, MDBA, picloram, TCTP, TCA, tetrapion, amiprofos-methyl, SAP, glyphosate, fosamine-ammonium, bialaphos, glufosinate, ACN, DBN, DCBN, acephenon, alloxydim, chlorphthalim, triclopyl, DSMA, sodium chlorate, sodium cyanate, sodium sulfamate, methy 2- {[(4,6-dimethoxypyrimidine-2-yl)aminocarbonyl]aminosulfonylmethyl} benzoate, 3,7-dichloro-8-quinoline carboxylic acid, N-(1,1-dimethylbenzyl)-2-bromo-t-butylacetamide, 2-(1,3-benzothiazole-2-yl-oxy)-N-methylacetamide and the like.

EXAMPLES OF PLANT GROWTH REGULATING AGENT

Ancymidol, indolebutyric acid, ethychlozate, 2-chloroethyl phosphonic acid, oxyethylene higher alcohol, hydroxyquinolin sulfate, cloxyfonac, chlormequat, dichlorprop, dikegulac, 1-naphthaleneacetamide, nicotinic acid amide, phenoxyacetic acid, benzyl aminopurine, maleic hydrazide, mefluidide and the like.

These pesticidally active ingredients may be used either alone or in a mixture of two or more of them. Common names of the compounds of the above-mentioned pesticidally active ingredients are given in accordance with the "Pesticide Handbook, 1985-version" (published from Zaidan Hojin Nihon Shokubutsu Boeki Kyokai on 30 Jan. 1986).

In carrying out this invention, a method by which fine particles of the hydrophobic substance can be adhered or fixed in the form of a uniform outer layer made of them to or into and over the whole surfaces of individual particles of the pesticidally active ingredient having solid particulate shape, as well as a method by which fine particles of the hydrophobic substance can be applied in the form of a coat-film made of mutually integrated and bound particles of said hydrophobic substance to and over the whole surfaces of the particles of the active ingredient may be used without being limited to particular ones, but these methods may be, for example, the following methods:

(1) A method wherein given amounts of solid particles of a pesticidally active ingredient and fine particles of a hydrophobic substance are placed in a ballmill of centrifugal rotary type and these particulate materials are rotated together with the balls in the mill. In this method using the ball-mill of centrifugal rotary type, the raw materials are rotated together with the balls made of a metal within the mill and are forced to impact against the inner wall of the mill and against the balls, whereby the raw materials are mixed together uniformly, the fine particles of the hydrophobic substance smeare and adhere evenly onto the surfaces of the particles of the pesticidally active ingredient, and the particles of the hydrophobic substance together with the particles of the active ingredient are further subjected to mechanical actions of compression, shearing and impacting, so that individual particles of the finely particulate hydrophobic substance can be rendered to adhere to and over the surfaces of the particles of the pesticidally active ingredient. Or, at the same time as this adhesion or after this adhesion, the individual particles of the hydrophobic substance are partially embedded into the surface layers of the particles of the pesticidally active ingredient to provide such state that the particles of the hydrophobic substance are rooting into the surface layers of the particles of the active ingredient; and thus the particles of the hydrophobic substance are fixed into the particles of the active ingredient. As these processes proceed further, the fine particles of the hydrophobic substance which have been adhered to and/or fixed into the surfaces of the particles of the pesticidally active ingredient can further be subjected to the actions of compression, shearing and impacting as well as the actions of heat of the friction, and as a result, such fine particles of the hydrophobic substance are integrated with each other to form a continuous or cohesive coat-film which surrounds each particle (the core) of the pesticidally active ingredient.

(2) A method of acting the impacting forces in a gas stream flowing at high speed, wherein particles of a pesticidally active ingredient and fine particles of a hydrophobic substance are suspended in their given amounts in a stream of a gas flowing at high speed and these solid particles are then subjected to mechanical actions mainly comprising the impacting forces as produced by collision of the particles, the action of heat of the friction as produced by collision of the particles, and other external application of energy.

In this method, the fine particles of the hydrohobic substance are again subjected to the mechanical actions of compression, shearing and impacting as well as the actions of heat of the friction and thus can be adhered to the surfaces of the particles of the pesticidally active ingredient or fixed into the surfaces of the particles of the active ingredient in the same way as described in the above, and occasionally the processes proceed further until the fine particles of the hydrophobic substance are integrated with each other to form a continuous or cohesive coat-film which surrounds the particle of the active ingredient.

As the devices for working out the above method of acting the impacting forces in high-speed gas stream, there may be used a commerically available "Hybridization System" (a tradename of a device for modifying surfaces of a powdery material in a dry system which is provided from Nara Kikai Seisakujo Co., Ltd.) and a commercially available "Mechanofusion System" (a tradename of a device for fusing surfaces which is provided from Hosokawa Micron Co., Ltd.), and others.

It may be added that heating and cooling can be effected if necessary, when the above-mentioned methods (1) and (2) are worked out.

Pesticide formulations comprising a sustained-releasing pesticide according to this invention may be in the form of dust, DL (driftless) dust, flo-dust, wettable powder, fine granules F, fine granules, granules, suspension concentrates, water-dispersible granules, paste and the like, to which this invention is not limited. Methods for preparation of these formulations may be carried out by mixing the composite particles of the pesticidally active ingredient as obtained according to the present invention with auxiliary additive(s) and filler(s) in a conventional apparatus according to conventional formulation techniques.

The auxiliary additives usable in the formulation of the sustained-releasing pesticide according to the present invention may be a variety of auxiliary additives which have been used conventionally in the preparation of the pesticidal formulations. Examples of such auxiliary additives include anionic surface active agents such as alkyl sulfates, alkylaryl sulfonic acids, alkyl sulfonic acids, polyethylene glycol ethers, polyethylene glycol esters, polyol esters; and non-ionic surface active agents, as well as various kinds of antioxidants, ultraviolet absorbers, inhibitors of hydrolysis, modifiers of physical properties and others.

The fillers which may be used in this invention may also be those which have been used conventionally in the preparation of the pesticidal formulations. Examples of such fillers include mineral materials such as clay, kaoline, sericite zieclite, talc, acidic clay, calcium carbonate, magnesium carbonate, gypsum, diatomaceous earth, pumice, zeolite, perlite, vermiculite, attapulgite and bentonite; natural materials such as starch and cellulose; organic solvents such as xylol, methyl alcohol, ethyl alcohol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, propylene glycol monomethylether and methyl naphthalene; and water, etc.

EXAMPLE

This invention is now illustrated with reference to the following Examples to which this invention is not limited. In these Examples, all parts are given by weight.

EXAMPLE 1

Dust

Into a ball-mill of the centrifugal rotary type (a commercially available mixer of the ball-mill type which is sold under a tradename of "Mechanomill" and produced by Okada Seiko Co., Ltd.) were placed 4 parts of kasugamycin powder (with a purity of 72.0% and a mean particle diameter of 30 .mu.m) and 1 part of hydrophobic titanium oxide MT-100S (a tradename of a titanium dioxide treated with aluminum laurate which is produced by Teikoku Kako Co., Ltd. and which is a hydrophobic substance having a mean particle diameter of 0.015 .mu.m and an angle of contact of 145.degree. against water droplet. The mixture of these powders was set at a temperature of 50.degree. C. and mixed for 30 minutes at 400 rpm. In this way, the composite particles of kasugamycin (which were each composed of an outer layer of the hydrophobic titanium dioxide as applied onto the surface of the core particle of kasugamycin) were obtained. 0.35 Parts of the composite particles of kasugamycin (with kasugamycin content of 57.6%), 1.0 part of white carbon, 0.3 parts of isopropyl acid phosphate (a modifier of physical properties) and 98.35 parts of clay were mixed in a hammer-mill to give a dust having the sustained release property and containing 0.2% of kasugamycin.

EXAMPLE 2

Fine granules F

After mixing 0.18 parts of the composite particles of kasugamycin (with kasugamycin content of 57.6%) as prepared in Example 1 with 0.5 parts of a polyvinyl alcohol and 99.32 parts of clay in a hammer-mill, the resulting mixture was added with 5 parts of water and granulated in a tumbling granulator. After drying, the granules were screened and thus adjusted for their granular size (65 to 250 mesh). Fine granules F having the sustained release property and containing 0.1% of kasugamycin were obtained.

EXAMPLE 3

Wettable powder

2.1 Parts of the composite particles of kasugamycin as prepared in Example 1 were mixed with 5 parts of white carbon, 3 parts of sodium lauryl sulfate, 2 parts of calcium ligninsulfonate and 87.9 parts of finely divided clay in a hammer-mill to give a wettable powder having the sustained release property and containing 1.2% of kasugamycin.

EXAMPLE 4

Suspension

2.1 Parts of the composite particles of kasugamycin as prepared in Example 1 were mixed with 15.3 parts of phthalide (with a purity of 98.5%), 2 parts of polyoxyethylene nonyl phenyl ether, 0.2 part of xanthan gum and 70.4 parts of water in a mixer under stirring. A suspension containing 1.2% of kasugamycin and 15% of fthalide was prepared.

EXAMPLE 5

Dust

Using a ball-mill of the centrifugal rotary type (Mechanomill) same as that employed in Example 1, 4 parts of validamycin A (with a purity of 48.5%, and a mean particle diameter of 30 .mu.m) and 1 part of Aerosil R-972 (a tradename of a silicon dioxide treated with dimethylchlorosilane which is produced by Nippon Aerosil Co., Ltd. and which is a hydrophobic substance having a mean particle diameter of 0.016 .mu.m and an angle of contact of 155.degree. against water droplet) were charged in the ball-mill and mixed in the same manner of operation as described in Example 1. There were obtained composite particles of kasugamycin which were each composed of an outer layer of Aerosil R-972 as evenly adhered to and fixed into the surface of the particle of validamycin A.

0.78 Part of the composite particles of validamycin A (with validamycin A content of 38.8%) as prepared in the above were mixed with 1 part of white carbon, 0.3 parts of isopropyl acid phosphate and 97.92 parts of clay in a hammer-mill. A dust having the sustained release property and containing 0.3% of validamycin A was obtained.

EXAMPLE 6

Wettable powder

Using a ball-mill of the centrifugal rotary type (Mechanomill) same as that employed in Example 1, 4 parts of acephate (with a purity of 98.5% and a mean particle diameter of 30 .mu.m) and 1 part of hydrophobic titanium oxide MT-100T (a tradename of a titanium dioxide treated with aluminum stearate which is produced by Teikoku Kako Co., Ltd. and which is a hydrophobic substance having a mean particle diameter of 0.015 .mu.m and an angle of contact of 140.degree. against water droplet) were charged in the ball-mill and mixed for 120 minutes. There were obtained composite particles of acephate which were each composed of an outer layer of the hydrophobic titanium oxide MT-100T (the fine particles of the hydrophobic substance) as evenly adhered onto the surface of the particle of acephate.

63.5 Parts of the composite particles of acephate (with acephate content of 78.8%) as prepared in the above were mixed with 5 parts of white carbon, 2 parts of polyoxyethylene nonyl phenyl ether, 2 parts of calcium ligninsulfonate and 27.5 parts of finely divided clay in a hammer-mill to afford a wettable powder having the sustained release property and containing 50% of acephate.

EXAMPLE 7

Granules

After mixing 6.4 parts of the composite particles of acephate as prepared in Example 6 with 1 part of a polyvinyl alcohol and 92.6 parts of clay in a hammermill, the resulting mixture was added with 15 parts of water and kneaded. The kneaded mixture was then granulated in an extruding granulator, and the granules were dried and screened and thus adjusted for their granule size (14 to 32 mesh). Granules having the sustained release property and containing 5% of acephate were obtained.

EXAMPLE 8

Dust

Into a device sold under the tradename of "Hybridization System" were placed 4 parts of NAC (with a purity of 99.0% and a mean particle diameter of 7 .mu.m) and 1 part of Aerosil R-792, followed by operation of the device. There were obtained composite particles of NAC which were each composed of an outer layer of Aerosil R-972 (fine particles of the hydrophobic substance) as evenly applied onto the surface of the particle of NAC.

2.6 Parts of the composite particles of NAC (with an NAC content of 79.2%) were mixed with 1 part of white carbon, 0.3 part of isopropyl acid phosphate and 96.1 parts of clay in a hammer-mill to afford a dust having the sustained release property and containing 2% of NAC.

EXAMPLE 9

Granules

Into a device sold under the tradename of "Hybridization System" were placed 4 parts of bifenox (with a purity of 96.5% and a mean particle diameter of 15 .mu.m) and 1 part of stearic acid (with a mean particle diameter of 3 .mu.m), followed by operation of the device. There were obtained composite particles of bifenox in which the surfaces of the particles of bifenox were coated with a coat-film of stearic acid.

After mixing 6.5 parts of the composite particles of bifenox (with bifenox content of 77.2%) with 5 parts of sodium ligninsulfonate, 20 parts of bentonite and 68.5 parts of clay in a hammer-mill, the resultant mixture was added with 12 parts of water and granulated in a tumbling granulator. After drying, the granules were screened and adjusted for their granule size (14 to 32 mesh) to give granules having the sustained release property and containing 5% of bifenox.

EXAMPLE 10

Dust

0.78 Part of the composite particles of validamycin A as prepared in Example 5, 2.6 parts of the composite particles of NAC as prepared in Example 8, 1 part of white carbon, 0.3 part of isopropyl acid phosphate and 95.32 parts of clay were mixed together in a hammer-mill to obtain a dust having the sustained release property and containing 0.3% of validamycin A and 2% of NAC.

The pesticide having the sustained release property according to this invention may be of some types such as insecticidal agents, fungicidal/bactericidal agents or plant growth regulating agents, etc., according to the nature of the pesticidally active ingredient present therein. Firstly, when the pesticide of this invention is applied to foliages of plants, into soil or into water, this pesticide is able to release the active ingredient gradually therefrom and consequently is able to continue to display the excellent activity sustaining over a prolonged period and exhibit a reduced phytotoxicity to crop plants, as compared to the pesticides having no sustained release property. Secondly, when the amount of the fine particles of the hydrophobic substance as applied to the surfaces of the particles of the pesticidally active ingredient as well as the diameters of these particles and other related conditions are appropriately chosen as described hereinbefore, the rate of release or dissolution of the active ingredient out of the pesticide can be controlled optionally to be increased or decreased. Thirdly, it is readily workable to formulate the sustained-releasing pesticide of this invention by mixing with auxiliary additives, similarly to formulation of conventional pesticide preparations. Fourthly, the sustained-releasing pesticide of this invention can be produced by a dry process without using any solvents, and therefore this invention is applicable to a wide variety of the pesticidally active ingredients and exhibits a wide applicability.

Test Examples are described below to demonstrate the utilities of this invention as described in the above.

Test Example 1

Test for estimating the dissolution-out, namely release of pesticidally active ingredients into water (Test for the sustained release property)

In a flask of 1l-capacity was placed 500 ml of water which has been deionized by ion-exchangers. Into the pool of water in the flask were introduced such composite particles of a pesticidally active ingredient as prepared similarly to the Examples 1, 5, 6, 8, and 9, in such amount that the quantity of the pesticidally active ingredient added was corresponding to 250 mg. Using a testing device for estimating the dissolution-out or release of compounds (of NTR-VS6 type which is provided from Toyama Sangyo Co., Ltd.), the temperature of the water pool was kept at 20.degree. C. and the content of the flask was agitated at 200 rpm. Samples of water were taken out from the flask at pre-determined time intervals, and each sample was assayed to determine the concentration (ppm.) of the active ingredient in the water. Rate (%) of dissolution-out, namely release of the active ingredient was calculated according to the following equation: ##EQU1##

These tests for estimating the release of active compound have revealed the following: If the sustained release property is imparted to the composite particles of pesticidally active ingredient, it can be observed that the determined rates (%) of release of active ingredient are less than 100% at the initial stage of the test but the rates of release of active ingredient will increase gradually with lapse of time.

The test results obtained are as shown in Table 1 below. Through these test results, it is evidently found that the pesticide of this invention has been imparted with the sustained release property.

TABLE 1 Amount of hydrophobic substance used (weight Particle diameter Angle of contact ratio of hydrophobic Rate (%) of Release Run Fine particles of (.mu.m) of hydro- of hydrophobic substance/pesticidally Active After After After After After No. hydrophobic substance phobic substance substance (degree) active ingredient Example ingredient 1 hour 2 hours 3 hours 5 hours 24 hours 1 Titanium oxide MT-100S 0.015 145 0.05 1 Kasugamycin 35 42 48 52 56 2 Titanium oxide MT-100S 0.015 145 0.1 1 Kasugamycin 30 38 43 48 50 3 Titanium oxide MT-100S 0.015 145 0.25 1 Kasugamycin 27 35 41 45 47 4 Titanium oxide MT-100S 0.015 145 0.5 1 Kasugamycin 20 32 39 42 44 5 Titanium oxide MT-100S 0.015 145 1.0 1 Kasugamycin 15 27 34 40 41 6 Titanium oxide MT-100S 0.015 145 0.05 5 Validamycin A 9 14 17 20 23 7 Titanium oxide MT-100S 0.015 145 0.25 5 Validamycin A 6 10 12 16 18 8 Titanium oxide MT-100S 0.015 145 0.5 5 Validamycin A 5 8 10 12 15 9 Titanium oxide MT-100S 0.015 145 1.0 5 Validamycin A 3 5 7 10 12 10 Titanium oxide MT-100S 0.015 145 0.05 8 NAC 27 32 36 36 39 11 Titanium oxide MT-100S 0.015 145 0.25 8 NAC 23 28 31 31 35 12 Titanium oxide MT-100S 0.015 145 0.5 8 NAC 20 25 28 30 33 13 Titanium oxide MT-100S 0.015 145 1.0 8 NAC 18 22 23 25 29 14 Titanium oxide MT-100T 0.015 140 0.05 6 Acephate 34 43 48 52 56 15 Titanium oxide MT-100T 0.015 140 1.0 6 Acephate 31 40 44 48 52 16 Titanium oxide MT-100T 0.015 140 0.25 6 Acephate 27 38 43 45 49 17 Titanium oxide MT-100T 0.015 140 0.5 6 Acephate 24 35 40 41 45 18 Titanium oxide MT-100T 0.015 140 1.0 6 Acephate 19 30 34 36 41 19 Titanium oxide MT-100T 0.015 140 0.05 1 Kasugamycin 31 34 39 46 52 20 Titanium oxide MT-100T 0.015 140 0.25 1 Kasugamycin 26 30 35 41 49 21 Titanium oxide MT-100T 0.015 140 0.5 1 Kasugamycin 23 27 32 38 45 22 Titanium oxide MT-100T 0.015 140 1.0 1 Kasugamycin 18 21 27 32 39 23 Titanium oxide MT-100T 0.015 140 0.05 9 Bifenox 18 19 22 25 33 24 Titanium oxide MT-100T 0.015 140 0.25 9 Bifenox 15 18 20 22 28 25 Titanium oxide MT-100T 0.015 140 0.5 9 Bifenox 10 13 15 17 24 26 Titanium oxide MT-100T 0.015 140 1.0 9 Bifenox 9 10 11 12 18 27 Aerosil R-972 0.016 155 0.05 5 Validamycin A 7 9 10 13 16 28 Aerosil R-972 0.016 155 0.1 5 Validamycin A 2 5 6 7 8 29 Aerosil R-972 0.016 155 0.25 5 Validamycin A 1 3 3 4 5 30 Aerosil R-972 0.016 155 0.5 5 Validamycin A 1 2 3 4 5 31 Aerosil R-972 0.016 155 1.0 5 Validamycin A 1 2 3 4 5 32 Aerosil R-972 0.016 155 0.05 1 Kasugamycin 11 13 15 18 28 33 Aerosil R-972 0.016 155 0.25 1 Kasugamycin 6 9 10 14 23 34 Aerosil R-972 0.016 155 0.5 1 Kasugamycin 5 8 9 12 19 35 Aerosil R-972 0.016 155 1.0 1 Kasugamycin 5 8 7 9 15 36 Aerosil R-972 0.016 155 0.05 8 NAC 29 41 51 53 59 37 Aerosil R-972 0.016 155 0.25 8 NAC 24 36 46 48 53 38 Aerosil R-972 0.016 155 0.5 8 NAC 20 33 42 43 49 39 Aerosil R-972 0.016 155 1.0 8 NAC 15 28 37 39 44 40 Stearic acid 3.0 90 0.05 9 Bifenox 36 41 44 47 52 41 Stearic acid 3.0 90 0.1 9 Bifenox 30 35 38 39 45 42 Stearic acid 3.0 90 0.25 9 Bifenox 28 32 34 36 42 43 Stearic acid 3.0 90 0.5 9 Bifenox 25 29 30 33 39 44 Stearic acid 3.0 90 1.0 9 Bifenox 20 23 24 28 36 45 Stearic acid 3.0 90 0.05 6 Acephate 33 38 42 49 58 46 Stearic acid 3.0 90 0.25 6 Acephate 30 34 37 42 51 47 Stearic acid 3.0 90 0.5 6 Acephate 28 32 35 39 49 48 Stearic acid 3.0 90 1.0 6 Acephate 27 30 31 35 42 49 Palmitic acid 5.0 85 0.05 1 Kasugamycin 36 39 42 47 56 50 Palmitic acid 5.0 85 0.1 1 Kasugamycin 31 35 36 42 50 51 Palmitic acid 5.0 85 0.25 1 Kasugamycin 29 32 34 39 47 52 Palmitic acid 5.0 85 0.5 1 Kasugamycin 26 30 31 36 44 53 Palmitic acid 5.0 85 1.0 1 Kasugamycin 21 25 27 31 40 54 Lauric acid 5.0 90 0.05 5 Validamycin A 19 20 22 28 34 55 Lauric acid 5.0 90 0.1 5 Validamycin A 14 15 18 22 28 56 Lauric acid 5.0 90 0.25 5 Validamycin A 12 14 17 19 25 57 Lauric acid 5.0 90 0.5 5 Validamycin A 10 11 14 16 22 58 Lauric acid 5.0 90 1.0 5 Validamycin A 7 8 9 12 19 59 Myristic acid 1.0 75 0.05 8 NAC 35 37 41 43 54 60 Myristic acid 1.0 75 0.1 8 NAC 30 32 35 38 46 61 Myristic acid 1.0 75 0.25 8 NAC 27 29 31 35 41 62 Myristic acid 1.0 75 0.5 8 NAC 24 26 28 32 38 63 Myristic acid 1.0 75 1.0 8 NAC 20 21 23 25 32 64 Aluminum stearate 2.5 130 0.05 1 Kasugamycin 39 44 46 50 59 65 Aluminum stearate 2.5 130 0.1 1 Kasugamycin 35 39 42 45 54 66 Aluminum stearate 2.5 130 0.25 1 Kasugamyci n 32 35 38 40 48 67 Aluminum stearate 2.5 130 0.5 1 Kasugamycin 29 33 35 36 44 68 Aluminum stearate 2.5 130 1.0 1 Kasugamycin 24 28 30 31 39 69 Aluminum stearate 2.5 130 0.05 9 Bifenox 24 28 30 34 47 70 Aluminum stearate 2.5 130 0.25 9 Bifenox 22 25 27 31 40 71 Aluminum stearate 2.5 130 0.5 9 Bifenox 18 22 23 27 35 72 Aluminum stearate 2.5 130 1.0 9 Bifenox 13 15 18 20 30 73 Magnesium stearate 4.0 120 0.05 5 Validamycin A 28 30 32 34 41 74 Magnesium stearate 4.0 120 0.1 5 Validamycin A 23 25 27 29 35 75 Magnesium stearate 4.0 120 0.25 5 Validamycin A 20 22 24 27 33 76 Magnesium stearate 4.0 120 0.5 5 Validamycin A 18 20 22 24 36 77 Maguenium stearate 4.0 120 1.0 5 Validamycin A 13 16 17 19 29 78 Calcium stearate 1.0 140 0.05 8 NAC 34 38 42 46 57 79 Calcium stearate 1.0 140 0.1 8 NAC 30 32 37 39 48 80 Calcium stearate 1.0 140 0.25 8 NAC 26 29 33 35 44 81 Calcium stearate 1.0 140 0.5 8 NAC 24 27 30 32 46 82 Calcium stearate 1.0 140 1.0 8 NAC 20 22 25 28 40 83 Polystyrene resin 5.0 115 0.05 6 Acephate 39 45 49 54 60 84 Polystyrene resin 5.0 115 0.1 6 Acephate 35 40 44 48 55 85 Polystyrene resin 5.0 115 0.25 6 Acephate 32 37 41 45 51 86 Polystyrene resin 5.0 115 0.5 6 Acephate 30 34 37 41 48 87 Polystyrene resin 5.0 115 1.0 6 Acephate 25 29 32 36 43 88 Polyamide resin 5.0 125 0.05 1 Kasugamycin 22 24 26 31 40 89 Polyamide resin 5.0 125 0.1 1 Kasugamycin 27 29 32 37 46 90 Polyamide resin 5.0 125 0.25 1 Kasugamycin 29 32 34 39 48 91 Polyamide resin 5.0 125 0.5 1 Kasugamycin 26 30 31 37 45 92 Polyamide resin 5.0 125 1.0 1 Kasugamycin 25 27 29 30 40 93 Silicone resin 2.0 150 0.05 9 Bifenox 12 15 18 19 26 94 Silicone resin 2.0 150 0.1 9 Bidenox 17 20 22 24 30 95 Silicone resin 2.0 150 0.25 9 Bifenox 14 17 18 20 26 96 Silicone resin 2.0 150 0.5 9 Bifenox 11 12 13 16 23 97 Silicone resin 2.0 150 1.0 9 Bifenox 9 10 11 13 18 98 No use (an active -- -- -- Comparative Kasugamycin 100 ingredient alone used) Example 1 99 No use (an active -- -- -- Comparative Validamycin A 100 ingredient alone used) Example 2 100 No use (an active -- -- -- Comparative NAC 100 ingredient alone used) Example 3 101 No use (an active -- -- -- Comparative Acephate 100 ingredient alone used) Example 4 102 No use (an active -- -- -- Comparative Bifenox 100 ingredient alone used) Example 5 103 Titanium oxide MT-100S 0.015 145 0.03 Comparative Kasugamycin 85 93 100 Example 6 (1) 104 Titanium oxide MT-100S 0.015 145 0.03 Comparative Validamycin A 80 86 92 100 Example 7 (5) 105 Titanium oxide MT-100S 0.015 145 0.03 Comparative NAC 86 95 100 Example 8 (8) 106 Titanium oxide MT-100T 0.015 140 0.03 Comparative Acephate 88 96 100 Example 9 (6) 107 Titanium oxide MT-100T 0.015 140 0.03 Comparative Kasugamycin 87 98 100 Example 10 (1) 108 Titanium oxide MT-100T 0.015 140 0.03 Comparative Bifenox 82 86 94 100 Example 11 (9) 109 Aerosil R-972 0.016 155 0.03 Comparative Validamycin A 74 80 86 94 100 Example 12 (5) 110 Aerosil R-972 0.016 155 0.03 Comparative Kasugamycin 78 82 88 97 100 Example 13 (1) 111 Aerosil R-972 0.016 155 0.03 Comparative NAC 84 92 100 Example 14 (8) 112 Stearic acid 3.0 90 0.03 Comparative Bifenox 90 100 Example 15 (9) 113 Stearic acid 10.0 90 0.25 Comparative Acephate 92 100 Example 16 (6) 114 Palmitic acid 5.0 85 0.03 Comparative Kasugamycin 89 100 Example 17 (1) 115 Palmitic acid 7.0 85 0.25 Comparative Kasugamycin 94 100 Example 18 (1) 116 Lauric acid 8.0 90 0.25 Comparative Validamycin A 92 100 Example 19 (5) 117 Aluminum stearate 8.0 130 0.25 Comparative Kasugamycin A 88 94 100 Example 20 (1) 118 Magnesium stearate 8.0 120 0.25 Comparative Validamycin A 86 92 100 Example 21 (5) 119 Polystyrene resin 7.0 115 0.25 Comparative Acephate 82 90 100 Example 22 (6) 120 Titanium dioxide 0.015 60 0.25 Comparative Kasugamycin 100 Example 23 (1) 121 Titanium dioxide 0.015 60 0.25 Comparative Validamycin A 100 Example 24 (5) 122 Titanium dioxide 0.015 60 0.25 Comparative Acephate 100 Example 25 (6) 123 Titanium dioxide 0.015 60 0.25 Comparative Bifenox 100 Example 26 (9) 124 Silicon dioxide 0.012 20 0.25 Comparative Kasugamycin 100 Example 27 (1) 125 Silicon dioxide 0.012 20 0.25 Comparative NAC 100 Example 28 (8) 126 Methacrylate resin 0.4 65 0.25 Comparative Kasugamycin 100 Example 29 (1) 127 Methacrylate resin 0.4 65 0.25 Comparative Acephate 100 Example 30 (6) Note 1: In comparative Examples 1 to 5, a bulk powder of the active ingredient compound was tested alone as such in the tests for estimating the release of active compound. Note 2: Number given in the brackets shown below comparative Examples 6 t 30 denotes that composite particles tested there were prepared in a similar manner to the procedures of Examples having the corresponding Number.

TEST EXAMPLE 2

Tests for estimating the effects of controlling blast disease in rice plant (for confirmation of the sustaining of the fungicidal activity)

Seeds of a rice plant (Variety: Akihikari) were immersed in water until the seeds begun to germinate. These seeds were then sown along lines in a farm field which was prepared in a greenhouse made of polyvinyl chloride resin.

On 28 days after the seed sowing, the young seedlings of rice plant at the three-leaf stage were treated by applying thereto a dust preparation having the sustained release property which contained the composite particles of kasugamycin as prepared similarly to Example 1. This application of the dust preparation was made at a rate of application of 3 kg/10 ares of the dust with using a simple device for application of a dust preparation. On the other hand, another leave of rice plant were inoculated with the phytopathogenic fungus of rice blast disease (Pyricularia oryzae) and incubated to a stage of formation of spores, and the resultant fungally infected leave were cut into pieces of about 3 cm-squares. These pieces of the infected leave were scattered and placed over the entire area of the test plots 2 days after the application of the dust preparation and served to act as the source of inoculation, while the rice plants were always kept under such conditions that they were susceptible of being infected with the rice blast disease. Within the greenhouse, there were always existing a moisture. The estimation of the infection was made in such a way that the rate (%) of the area of infection of the rice blast disease on the leave of rice plant (against the total area of the leave of rice plant) were measured with lapse of time at intervals of 3 to 4 days from 7 days after the fungal inoculation and that rates (%) of disease control were evaluated according to the following equation: ##EQU2##

These tests were carried out in three-replicates with each test plot of 1 m.sup.2 in area, and an averaged value of the rates (%) of disease control was calculated.

As the comparative agent was tested such a dust preparation having no sustained release property which was prepared by using an untreated bulk powder of kasugamycin in place of the composite particles of kasugamycin of Example 1.

The results are shown in Table 2 below.

TABLE 2__________________________________________________________________________ Amount of hydrophobic Rate (%) of Disease Control Particle Angle of contact substance used (weight 7 days 11 days 14 days 17 days 20 days Fine particles diameter (.mu.m) of hydrophobic ratio of hydrophobic after after after after afterRun of hydropho- of hydropho- substance substance/pesticidally inocu- inocu- inocu- inocu- inocu- Phyto-No. bic substance bic substance (degree) active ingredient) lation lation lation lation lation toxicity__________________________________________________________________________ 1 Titanium 0.015 145 0.05 95 93 90 85 60 Not oxide observed MT-100S 2 Titanium 0.015 145 0.25 95 93 90 85 59 Not oxide observed MT-100S 3 Titanium 0.015 145 0.5 94 92 91 84 62 Not oxide observed MT-100S 4 Titanium 0.015 145 1.0 95 92 91 85 62 Not oxide observed MT-100S 5 Aerosil R-972 0.016 155 0.05 96 94 91 82 63 Not observed 6 Aerosil R-972 0.016 155 0.25 95 93 90 86 62 Not observed 7 Aerosil R-972 0.016 155 0.5 94 92 90 85 62 Not observed 8 Aerosil R-972 0.016 155 1.0 94 92 90 85 62 Not observed 9 Palmitic acid 5.0 85 0.05 95 93 89 82 63 Not observed10 Palmitic acid 5.0 85 0.25 95 93 90 83 60 Not observed11 Palmitic acid 5.0 85 0.5 96 94 90 86 59 Not observed12 Palmitic acid 5.0 85 1.0 96 93 91 86 60 Not observed13 Aluminum 2.5 130 0.05 95 92 89 85 60 Not stearate observed14 Aluminum 2.5 130 0.25 95 92 89 85 62 Not stearate observed15 Aluminum 2.5 130 0.5 95 92 90 82 62 Not stearate observed16 Aluminum 2.5 130 1.0 94 91 90 81 62 Not stearate observed17 Polyamide 5.0 125 0.05 96 94 90 82 59 Not resin observed18 Polyamide 5.0 125 0.25 96 93 89 85 60 Not resin observed19 Polyamide 5.0 125 0.5 95 93 90 85 60 Not resin observed20 Polyamide 5.0 125 1.0 95 93 90 84 60 Not resin observed21 Comparative -- -- -- 95 85 65 40 20 Not agent observed22 Untreated -- -- -- 0 0 0 0 0 -- plot (13) (34) (58) (84) (95)__________________________________________________________________________ Note: Numerical figures given in the brackets for the tests of the untreated plot denote such rate (%) of the area of infection as evaluated in the untreated plot.

Test Example 3

Tests for estimating the effect of controlling sheath blight disease in rice plant (for confirmation of the sustaining of the fungicidal activity)

Rice plants (Variety: Nihonbare, ten rice plants per pot and at 5 to 6-foliage stage) which had been cultivated in pots of 9 cm in diameter were treated by applying thereto such a dust preparation having the sustained release property which contained the composite particles of validamycin A as prepared similarly to Example 5. This application of the dust preparations was done at a rate of application of 3 kg/10 ares of the dust with using a simple device for application of a dust. On the other hand, a phytopathogenic fungus of rice sheath blight disease (Rhizoctonia solani) was incubated for 7 days (at 28.degree. C.) in a culture medium comprising wheat bran and further containing 0.5% peptone added, so that the fungal culture was obtained. One gram of this fungal culture was used as an inoculum and placed on the soil at the bases of the rice plants in each pot at a time of 3 days, 7 days or 15 days after the application of the dust preparation. After the inoculation, rice plants were maintained at 28.degree.-30.degree. C. for 10 days within a greenhouse for development of the infection, where a humidity of not lower than 90% was prevailing. Thereafter, the rice plants were removed out of the greenhouse and the length (cm) (an averaged value) of the lesions of infection of rice sheath blight disease on the leave of rice plant was measured. Rate (%) of disease control was calculated according to the following equation: ##EQU3##

These tests were carried out in three-replicates, and an averaged value of the rates (%) of disease control was calculated.

As comparative agent was tested such a dust preparation having no sustained release property which was prepared in the same manner as in Example 5 but using an untreated bulk powder of validamycin A in place of the composite particles of validamycin A of Example 5.

The results are shown in Table 3.

TABLE 3__________________________________________________________________________ Particle dia- Angle of contact Amount of hydrophobic substance Rate (%) ofFine particles meter (.mu.m) of of used (weight ratio of hydro- Disease ControlRun of hydropho- hydrophobic hydrophobic sub- phobic substance/pesticidally After After AfterNo. bic substance substance stance (degree) active ingredient) 3 days 7 days 15 days Phytotoxicity__________________________________________________________________________1 Titanium 0.015 145 0.05 100 90 60 Not observed oxide MT-100S2 Titanium 0.015 145 0.25 99 89 65 Not observed oxide MT-100S3 Titanium 0.015 145 0.5 99 90 60 Not observed oxide MT-100S4 Titanium 0.015 145 1.0 99 90 58 Not observed oxide MT-100S5 Aerosil R-972 0.016 155 0.05 99 85 62 Not observed6 Aerosil R-972 0.016 155 0.25 100 87 65 Not observed7 Aerosil R-972 0.016 155 0.5 99 90 65 Not observed8 Aerosil R-972 0.016 155 1.0 99 90 62 Not observed9 Comparative -- -- -- 99 30 5 Not observed agent10 Untreated -- -- -- 0 0 0 -- plot (16.5) (16.6) (16.7)__________________________________________________________________________ Note: Numberical figures given in the brackets for the tests of the untreated plot denote such average value of lengths (cm) of the lesions o infection as evaluated in the untreated plot.

Test Example 4

Test for estimating the sustaining property of the isecticidal activity against cabbage spinach aphis

Cabbage plants (Variety: Chyusosei, at 10 to 11-foliage stage) which were cultivated in pots were treated by spraying thereto such a test liquid which had been prepared by diluting with water such a wettable powder having the sustained release property and containing the composite particles of Acephate as produced similary to Example 6. The dilution of the wettable powder with water was conducted using the volumes of water which were such many times as much as the volume of the wettable powder as corresponding to the times of dilution (folds) given in Table 4. The spraying application of the test liquid was made at a rate of application of 150 l/are by means of a spray-gun while the cabbage plants were placed on a turning table. Thereafter, the cabbage plants treated were placed in a glass chamber. Several days later, the leaf of cabbage plants was cut into pieces of leaf by means of a leaf-puncher of 8 cm in diameter. The pieces of leaf were placed in a dish made of a plastic resin and having a diameter of 9 cm, along with adults of spinach aphis (Myzus persica) of apterous forms. The insects were left to move in the dish for 48 hours at a constant temperature of 25.degree. C., and thereafter the rates (%) of the insects killed was evaluated with lapsed time.

These tests were carried out in three-replicates, and an averaged value of the rates (%) of the insects killed was calculated.

As comparative agent was tested such a wettable powder having no sustained release property which was prepared in the same manner as in Example 6 but using an untreated bulk powder of Acephate in place of the composite particles of Acephate of Example 6.

The results are shown in Table 4.

TABLE 4__________________________________________________________________________ Amount of hy- drophobic sub- stance used Angle (weight ratioFine Particle dia- of contact of of hydrophobic Rate (%) of insects killed particles of meter (.mu.m) of hydrophobic substance/pesti- Times of afterRun hydrophobic hydrophobic substance cidally active dilution treat- After After After After Phyto-No. substance substance (degree) ingredient) (folds) ment 7 days 14 days 21 days 28 toxicity__________________________________________________________________________ 1 Titanium 0.015 140 0.05 1000 100 100 100 100 93 Not oxide observed MT-100T 2 Titanium 0.015 140 0.05 2000 100 100 100 97 83 Not oxide observed MT-100T 3 Titanium 0.015 140 0.05 4000 100 100 93 70 50 Not oxide observed MT-100T 4 Titanium 0.015 140 0.25 1000 100 100 100 100 93 Not oxide observed MT-100T 5 Titanium 0.015 140 0.25 2000 100 100 100 97 83 Not oxide observed MT-100T 6 Titanium 0.015 140 0.25 4000 100 100 97 67 47 Not oxide observed MT-100T 7 Titanium 0.015 140 0.5 1000 100 100 100 100 93 Not oxide observed MT-100T 8 Titanium 0.015 140 0.5 2000 100 100 100 97 77 Not oxide observed MT-100T 9 Titanium 0.015 140 0.5 4000 100 100 97 70 47 Not oxide observed MT-100T10 Titanium 0.015 140 1.0 1000 100 100 100 100 97 Not oxide observed MT-100T11 Titanium 0.015 140 1.0 2000 100 100 100 97 83 Not oxide observed MT-100T12 Titanium 0.015 140 1.0 4000 100 100 97 80 50 Not oxide observed MT-100T13 Aerosil R-972 0.016 155 0.25 1000 100 100 100 100 93 Not observed14 Aerosil R-972 0.016 155 0.25 2000 100 100 100 97 80 Not observed15 Aerosil R-972 0.016 155 0.25 4000 100 100 97 63 43 Not observed16 Stearic acid 3.0 90 0.25 1000 100 100 100 97 90 Not observed17 Stearic acid 3.0 90 0.25 2000 100 100 100 93 77 Not observed18 Stearic acid 3.0 90 0.25 4000 100 100 97 77 50 Not observed19 Polystyrene 5.0 115 0.25 1000 100 100 100 100 93 Not resin observed20 Polystyrene 5.0 115 0.25 2000 100 100 100 97 83 Not resin observed21 Polystyrene 5.0 115 0.25 4000 100 100 97 93 45 Not resin observed22 Comparative -- -- -- 1000 100 100 97 63 30 Not agent observed23 Comparative -- -- -- 2000 100 100 70 37 10 Not agent observed24 Comparative -- -- -- 4000 100 83 43 7 0 Not agent observed25 Untreated -- -- -- -- 0 0 3 0 3 -- plot__________________________________________________________________________

Test Example 5

Tests for estimating the sustaining character of the insecticidal activity against small brown planthopper

Rice plants (Variety: Nihonbare) were cultivated in pots having a diameter of 11 cm with five rice plants being grown together in the form of a bundle or stock in each pot, and the cultivated rice plants at 4-leaf stage were treated by applying to them a dust preparation having the sustained release property which contained the composite particles of NAC as produced similarly to Example 8. This application of the dust preparation was made at a rate of application of 3 kg/10 ares of the dust by means of Midget-duster. After this, the rice plants treated were placed in a glass chamber, and several days later, the rice plants were covered with a cylindrical pipe made of polyvinyl chloride resin and having a diameter of 11 cm and a height of 30 cm, followed by introducing 10 adults (female) of small brown planthopper (Laodelphax striatellus) into the cylindrical pipe. 24 Hours after the introduction of the insects, the numbers of the insects killed and the surviving insects were calculated and the rates (%) of the insects killed was periodically evaluated.

These tests were carried out in three-replicates, and an averaged value of the rates (%) of the insects killed as evaluated in the replicate tests was calculated.

As comparative agent was tested such a dust preparation having no sustained release property which was produced in the same manner as in Example 8 but using an untreated bulk powder of NAC in stead of the composite particles of NAC of Example 8.

The results are shown in Table 5.

TABLE 5__________________________________________________________________________ Amount of hydrophobic Angle of substance used (weight Rate (%) of insects killed Fine particles Particle diameter contact of ratio of hydrophobic DirectlyRun of hydrophobic (.mu.m) of hydro- substance substance/pesticidally after After After AfterNo. substance phobic substance (degree) active ingredient) treatment 3 days 7 days 14 days Phytotoxicity__________________________________________________________________________1 Titanium oxide 0.015 145 0.05 100 100 97 47 Not observed MT-100S2 Titanium oxide 0.015 145 0.25 100 100 97 47 Not observed MT-100S3 Titanium oxide 0.015 145 0.5 100 100 93 50 Not observed MT-100S4 Titanium oxide 0.015 145 1.0 100 100 97 50 Not observed MT-100S5 Aerosil R-972 0.016 155 0.25 100 100 97 47 Not observed6 Myristic acid 1.0 75 0.25 100 100 97 53 Not observed7 Calcium stear- 1.0 140 0.25 100 100 93 47 Not observed ate8 Comparative -- -- -- 100 83 40 10 Not observed agent9 Untreated plot -- -- -- 0 0 0 0 --__________________________________________________________________________

Test Example 6

Tests for estimating the herbicidal effect and phytotoxicity to plants

Pots each having a size of 1/5000 ares were filled with a soil of paddy rice fields (alluvial soil) and the soil in each of the pots was admixed with 3 g of a chemically compounded fertilizer (with nitrogenous content, phosphatic content and potash content at ratios of 17:17:17) as a base manure. Water was poured into the pots so that the pots were kept under water-flooding conditions.

(1) Test for Phytotoxicity

Young seedlings of an aquatic rice plant (Variety: Nihonbare) at 2-leaf stage were transplanted in the soil at a rate of 3 seedlings per pot. On third day after the transplantation of rice plants, the herbicidal treatment was done by scattering into the pots such a granular preparation having the sustained release property which contained the composite particles of Bifenox as produced similarly to Example 9. The granular preparation was applied at a rate of application of 3 kg per 10 ares. Water was poured into the pots to a depth of the flooding water of 5 cm. The estimation of the phytotoxic effect was made on 21th day after the application of the herbicidal agent by measuring the lengths of such browning regions of the third leaf of rice plants where the regions having brown discoloration could clearly be observed, and then evaluating an average value of the lengths (cm) of the browning regions of leaf.

These tests were carried out in three-replicates, and an averaged value of the lengths (cm) of the browning regions of leaf as evaluated in these replicate tests was calculated.

Furthermore, as comparative agent 1 was tested such a granular preparation having no sustained release property which was formulated in the same manner as in Example 9 but using an untreated powder of Bifenox in place of the composite particles of Bifenox of Example 9.

The results are shown in Table 6.

(2) Test for Herbicidal effect

The herbicidal treatment was conducted by scattering the same granular preparation as described in the above into another pots each having a size of 1/5000 ares which had been kept under the water-flooding conditions. This granular preparation was applied at a rate of application of 3 kg per 10 ares. 10 Days, 20 days, 30 days, 40 days or 50 days after the herbicidal treatment, germinating seeds of barnyard grass were sown at a rate of 20 seeds per pot, followed by pouring water into the pots to a depth of the flooding water of 3 cm. The estimation of the herbicidal effect was made 24 days after each date of sowing the grass seeds by extracting the grass from the soil and measuring of dry weight (g) of the extracted weed. Rate (%) of kill of weed was evaluated according to the following equation: ##EQU4##

These tests were carried out in three-replicates, and an average value of the rates (%) of kill of weed as evaluated in these replicate tests was calculated.

The results are tabulated in Table 6.

TABLE 6__________________________________________________________________________ Amount of hy- Ratio of phyto- Angle drophobic substance toxicity (length ofFine particles Particle dia- of contact used (weight ratio brown-discolored Rate (%) of kill of weed of meter (.mu.m) of hydropho- of hydrophobic sub- leave to that 10 days 20 days 30 days 40 50 daysRun hydrophobic of hydropho- bic substance stance/pesticidally in comparative after after after after afterNo. substance bic substance (degree) active ingredient) agent-treated plot seeding seeding seeding seeding seeding__________________________________________________________________________1 Titanium 0.015 140 0.05 15 100 100 100 90 78 oxide MT-100T2 Titanium 0.015 140 0.25 14 100 100 100 88 79 oxide MT-100T3 Titanium 0.015 140 0.5 15 100 100 100 88 80 oxide MT-100T4 Titanium 0.015 140 1.0 16 100 100 100 90 77 oxide MT-100T5 Silicone resin 2.0 150 0.05 18 100 100 100 89 786 Silicone resin 2.0 150 0.25 18 100 100 100 90 787 Silicone resin 2.0 150 0.5 17 100 100 100 90 808 Silicone resin 2.0 150 1.0 15 100 100 100 88 789 Stearic acid 3.0 90 0.25 16 100 100 100 88 7710 Aluminum 2.5 130 0.25 18 100 100 100 90 78 stearate11 Comparative -- -- -- 100 100 100 100 70 48 agent 1 (length of brown- discolored leave: 9.0 cm)12 Comparative -- -- -- 85 100 100 98 75 52 agent 213 Comparative -- -- -- 87 100 100 97 73 50 agent 314 Untreated -- -- -- -- 0 0 0 0 0 plot (0.21) (0.21) (0.20) (0.22) (0.21)__________________________________________________________________________

For Table 6:

Note 1): Numerical figures given the brackets in the tests of untreated plot denote dry weights of barnyard grass grown there.

Note 2): Comparative agent 2 (according to an invention of Japanese patent application first publication "Kokai" No. 126402/82). This comparative agent 2 was granular preparation of Bifenox which was obtained by spraying the granules of the comparative agent 1 with a solution containing a polyethylene resin and an polyethylene-acetic acid copolymer resin, followed by drying the so sprayed granules to produce such granules of Bifenox which were each coated with 1% by weight of the mixture of polyethylene resin and polyethylene-acetic acid copolymer resin (at weight ratio of 53:47).

Note 3): Comparative agent 3 (according to an invention of Japanese patent application first publication "Kokai" No. 202801/85). This comparative agent 3 was a granular preparation of Bifenox which was obtained by spraying the granules of the comparative agent 1 with a liquid emulsion containing wax and an acrylic resin, followed by drying the so sprayed granules to produce the granules of Bifenox which were each coated with 2% by weight of the mixture of wax and acrylic resin (at weight ratio of 6:1).

INDUSTRIAL UTILITY OF THE INVENTION

As be described in the above, this invention can provide such a pesticide having the sustained release property which is useful in that the pesticidally active ingredient can be released or dissolved out from said pesticide gradually with the release of the active ingredient lasting or sustaining over a prolonged period of time, and hence in that said pesticide can display a sustaining biological activity of the pesticidally active ingredient.

Claims

1. A process for the production of a pesticide in the form of composite particles, each composite particle comprising a solid central core of a solid, pesticidally active ingredient and either an outer layer consisting of fine particles of a hydrophobic substance surrounding said core or a continuous coat-film made of said hydrophobic substance, said process comprising

providing fine particles of the hydrophobic substance having an average particle diameter of not greater than one-fifth of the average diameter of said solid core of the pesticidally active ingredient in such a proportion that the total amount of the hydrophobic substance employed is in a range of 0.05 parts to 1 part by weight per part by weight of said pesticidally active ingredient, and

adhering said fine particles of the hydrophobic substance to the surfaces of said solid core of the pesticidally active ingredient or partially embedding individual particles of the fine particles of the hydrophobic substance into the surfaces of said solid core of the pesticidally active ingredient such that the hydrophobic substance wholly coats the surfaces of the core of the solid pesticidally active ingredient.

2. A sustained release pesticide comprising solid pesticidal particles, each of said pesticidal particles comprising

a core of a solid, pesticidally active ingredient, and

a hydrophobic coating layer comprising fine particles of a hydrophobic substance, each of said fine particles having an average diameter of not greater than one-fifth of the average diameter of said solid core, said hydrophobic coating layer substantially surrounding said core, the total amount of the hydrophobic substance in said coating layer being 0.05 parts to 1 part by weight per part by weight of the amount of pesticidally active ingredient in said core.

3. A sustained release pesticide according to claim 2 wherein said active ingredient is selected from the group consisting of insecticides, fungicides, bactericides, herbicides, and plant growth regulating agents.

4. A sustained release pesticide according to claim 2 wherein said active ingredient is water soluble.

5. A sustained release pesticide according to claim 2 wherein said hydrophobic layer is provided by hydrophobic particles having an average or mean particle diameter of not greater than one fifth of the average or mean particle diameter of said pesticidal particles.

6. A sustained release pesticide according to claim 2 wherein said hydrophobic particles have an average or mean particle diameter of not greater than one tenth of the average or mean particle diameter of said pesticidal particles.

7. A sustained release pesticide according to claim 2 wherein said hydrophobic substance is selected from the group consisting of higher aliphatic acids, metal salts of higher aliphatic acids, titanium dioxide treated with a metal salt of a higher aliphatic acid, hydrophobic white carbon, and hydrophobic synthetic polymers.

8. A sustained release pesticide according to claim 2 wherein said hydrophobic substance is selected from the group consisting of stearic acid, palmitic acid, lauric acid, myristic acid, aluminum stearate, magnesium stearate, calcium stearate, titanium dioxide treated with aluminum laurate, titanium dioxide treated with aluminum stearate, alkylsilylated silica, silicon dioxide treated with dimethyldichlorosilane, a polystyrene, a polyamide and a silicone.

9. A sustained release pesticide according to claim 2 wherein said hydrophobic particles are fixed into the surface of the pesticidal particles.

10. A sustained release pesticide according to claim 2 wherein the pesticidal particles have an average or mean particle diameter in the range of 5 to 500 microns.

11. A sustained release pesticide according to claim 2 wherein said hydrophobic particles have an average or mean particle diameter in the range of 0.01 to 100 microns.

12. A sustained release pesticide according to claim 2 wherein the coated pesticidal particles, including said hydrophobic layer, have an average or mean particle diameter of not more than 50 microns.

13. A process according to claim 1 further comprising subjecting said fine hydrophobic particles adhered to or partially embedded in the surface of said core of each of said composite particles to impacting force or heat of friction or both to integrate and bind the fine hydrophobic particles.

14. A process according to claim 1 wherein each of said fine hydrophobic particles has an average or mean particle diameter not greater than one tenth of the average or mean diameter of said core.

15. A process according to claim 1 wherein said active ingredient is selected from the group consisting of insecticides, fungicides, bactericides, herbicides, and plant growth regulating agents.

16. A process according to claim 1 wherein said active ingredient is water soluble.

17. A process according to claim 1 wherein said hydrophobic substance is selected from the group consisting of higher aliphatic acids, metal salts of higher aliphatic acids, titanium dioxide treated with a metal salt of a higher aliphatic acid, hydrophobic white carbon, and hydrophobic synthetic polymers.

18. A process according to claim 1 wherein the pesticidal particles have an average or mean particle diameter in the range of 5 to 500 microns.

19. A process according to claim 1 wherein said hydrophobic particles have an average or mean particle diameter in the range of 0.01 to 100 microns.

20. A process according to claim 1 wherein the coated pesticidal particles, including said hydrophobic layer, have an average or mean particle diameter of not more than 50 microns.