FR2533415A1 - NOVEL PESTICIDE GRANULES, THEIR PREPARATION AND THEIR USE - Google Patents

Abstract

THE OBJECT OF THE INVENTION IS NEW FLUENT AND WATER-FLOATABLE GRANULES CONTAINING A PESTICIDE, FOR EXAMPLE A BIOLOGICAL LARVICIDE AGAINST MOSQUITOES, THE PREPARATION OF THESE GRANULES AND A PROCESS FOR COMBTING MOSQUITOES USING THESE GRANULES.

Description

The present invention relates to pesticide granules, for example

organic pesticides,

  their preparation and use.

  Organic pesticides have sparked in-

  growing interest in recent years. They are more or less sensitive to a large number of factors such as heat, light, chemicals and other factors which they may be confronted with when they are found outside their original environment Stability (under heat, in the light and

  storage) of bioldgic pesticides is therefore a pre-

  major cupation and a prerequisite.

  For similar use, organic pesticides therefore offer less flexibility in preparing formulations than synthetic chemical pesticides. Granulated pesticide formulations have

  great interest in combating pests.

  Until now, the granulated formulations of unstable pesticides such as the biological pesticides Dne did not meet the requirements of stability. against mosquito larvae), at least 20% of which sink in water and prepared from conventional materials intended to form the nucleus of the granule, such as vermiculite and clay Biological pesticide granules prepared with these materials classics lose a significant part of their effectiveness during the week

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following their preparation.

  The present invention relates to a form of granules which is suitable for use with stable pesticides but also with unstable pesticides, in particular the latter, especially biological pesticides. The present invention also relates to a form of granules suitable for application in water, for example from an airplane, which can release the pesticide essentially on the water surface The Applicant has found that this latter property is of great interest in combating mosquito larvae 'in the water The present invention therefore relates to a fluent pesticide which can be floated on water in the form of granules, said granules consisting of a) a core of solid wax or a core coated with solid wax having a density less than that of l water which is inert towards the pesticide, and b) a pesticide attached to the wax core or the coated core

  of wax by a matrix which is inert with respect to the weight

  who is able to release the pesticide

in contact with water.

  The use of wax as the core of the granule or as a coating material makes it possible not only to prepare a floatable granule, but also to provide the means for a pesticide release system having stable efficacy and a number of other desired properties. for a pesticide in the form of granules, in particular for

  a pesticide in the form of granules used in water.

  The expression "buoyant" indicates that the density of the granules of the invention must be less than

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  that of the water and that, even in contact with the water, the granules must remain on the surface for a sufficient time to allow the release of the pesticide on the surface of the water; appropriately at least 95% of the granules of the invention must remain on the surface of the water

24 hours after application.

  The expression "wax" as used in the description,

  denotes any hydrophobic substance meeting the criteria of the invention (lighter than water, solid and inert with respect to the pesticide). As suitable examples of such waxes, mention may be made of silicones and paraffin waxes,

especially the latter.

  The expression "solid" used in connection with the wax core or the wax-coated core indicates that the wax core or the wax coating must be solid at room temperature and have a melting point above 30 ° C. , preferably at least 40 C The preferred waxes have a melting point of between 45 C and

   C, more preferably between 50 C and 75 C.

  The wax used must be inert, i.e.

  state that it must not affect the pesticide intended to be incorporated into the granule Special attention must be paid to said requirement

  if the pesticide in question is a biological pesticide.

  If necessary we can easily check the inertia by

  method of successive approximations However, the sub-

  Paraffinic stanzas are generally inert with respect to biological pesticides and it is preferred to use paraffinic waxes as core material for the granules of the invention Paraffinic waxes having points of

  fusion of the desired magnitude are easily dis-

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  available on the market in a finely divided form ("spherules") such as for example the Sun Wax 4412 (F = 600 C) and the Sun Wax Antichek (F = 670 C), from the firm

  Sun Petroleum Products, Wayne, Pennsylvania.

  The core of wax or core coated with wax, hereinafter referred to as "core", may be essentially composed of solid wax or may be a body containing an internal base surrounded by solid wax to which the matrix is fixed. In the latter case , the only requirement will be that the wax more or less completely coats the internal base and that this coating has a sufficient thickness so that the internal base does not damage the pesticide and that the water does not penetrate into the coating of wax, this that would sink all of the pellet at least before the pesticide it contains has been fully released onto the surface

some water.

  Various finely divided products or products in the form of particles can be used as a base material intended to be coated with wax, hereinafter referred to as "base material", to form the core of particles coated with wax. Such basic materials have themselves advantageously have a density lower than that of water and can be of a mineral nature, such as vermiculite, or of an organic nature, such as corn cobs but finely divided, for example the material known as granules of

roundups of evils.

  The main advantage of using a base material is a reduction in costs The amount of base material compared to the wax in such wax-coated cores can vary quite widely and the base material

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  *, * t E can easily form most of the nucleus whatsoever

by weight or by volume.

  Therefore, it is generally preferred that such cores contain from 10 to 60% wax and 40 to 90% base material by weight, more preferably from 35% by weight of wax and 65 to 85% base material. base, provided that the wax coats the

basic material.

  For example one can use, as basic material for granules, roundups of & mals to form a nucleus

  coated with wax containing 75-90% corn cob and 10-

  % of wax by weight The particle size of the base material used to form such nuclei of base particles coated with wax is preferably

  between 0.3 and 3.0 millimeters (mm), more preferably

between 1 and 2 mm -

  The wax-coated cores can be prepared according to the usual methods for coating particles with

  Using normally liquefied solid material.

  In general, we prefer first of all to liquefy the wax by heating it well above its melting point, for example at least 500 ° C. above its

  melting point, preferably between 750 C and 1250 C above

  above its melting point, and then distribute the molten wax in the mass of the base material constituted by the particles, for example by spraying, mixing in order to ensure a homogeneous and more or less uniform coating of the wax over the basic material Intensive mixing is desirable and is continued until the temperature of the wax is well below its melting point, for example practically at room temperature, in order to avoid agglomeration

  undesirable from the resulting individual nuclei.

  The mixture can be heated either by external means) or by the application of an inert gas

  heated directly in the mass to ensure

  uniform partition of the wax before cooling

  the mass to form the desired nuclei.

  The particle size of the "core" is advantageously between 0.5 and 5 mm When the core is formed from wax, the dimension is preferably between 0.5 and 3.0 mm, more preferably between 1 and 2 mm. dimension of the wax-coated cores is preferably between

  1 and 4 mm, more preferably between 2 and 3.5 mm.

  As already indicated, the granules of the invention contain the pesticide which is located inside a

  matrix itself attached to the "core".

  The expression "matrix" as used above

  after, designates any system capable of fixing the pesticide to the wax core; such a matrix is advantageously

essentially dry.

  The expression "essentially dry" used in connection with the matrix indicates that the properties of the matrix must allow good fluidity of the

granular mass.

  The matrix can be directly attached to the "core" or can be indirectly attached by one or more layers

an appropriate inert coating.

  By matrix, a distinction must be made between the "coating material serving as matrix" which essentially serves to

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  fix the pesticide directly or indirectly to the nucleus, and the "encapsulation matrix" which is above all a protective matrix indicating a complete incorporation or coating of the pesticide in the matrix although a small proportion of the pesticide may be (and the is it-

  if present) or exposed on the surface of the matrix.

  Note that the use of an encapsulation matrix

  is particularly suitable when pre-

  serving the stability of the pesticide Whereas, in the case of the simplest granules of the invention, the pesticide can be considered to be encapsulated in its nearest matrix or in its adjacent matrix, the expression "matrix" will be used ci -after to indicate the essential matrix and the overall matrix having a general encapsulation effect and comprising or consisting of a coating matrix. The material serving as a matrix can be uniform (or homogeneous) or can be composed of various materials serving as matrices which can each coat the core thus forming a multiple layer, and / or consist of a heterogeneous mixture of various materials serving

  matrix, comprising, for example, several

  encapsulation inside the coating material serving as a matrix The action of water on the various matrices can therefore be different and the various release systems can vary accordingly Each of the materials serving as matrix can be either dispersible in

  water, either water-soluble, or essentially non-

  water-wettable The matrix material may incorporate the pesticide in whole or in part or may be formed from various matrix materials including several or more

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  only one of them can fully incorporate the pesticide and the other or the others only partially incorporate it.

  For example, pesticide particles in-

  wettable capsules, for example dispersible in water (such as biological pesticides), can be

  combined with a matrix coating which is essential-

  slightly non-wettable or insoluble in water, to cause the release of the pesticide by wetting the fraction of particles dispersible in water on the surface of the granule Such an action on the surface will expose

  generally other wettable particles or particles

  originally located inside the pellet, at wetting and releasing so that

  additional amounts of pesticide may be released

  berées. However, it is generally preferred to use, in

  especially in the case of pesticide particles

  encapsulated in a water dispersible matrix, a

  casing serving as matrix essentially wettable in water, for example soluble or dispersible in water so that the entire matrix is released from the nucleus by

some water.

  The particular material which can be used as a matrix material will depend on the particular pesticide to be developed and on various choice factors. While a large choice of matrix material and coating vehicles are available for pesticides other than biological pesticides, the selection of such materials is more critical when a biological pesticide is used as an active ingredient Specific materials suitable for use with biological pesticides are carbohydrates, proteinaceous materials of animal or plant origin and materials of synthetic origin Suitable carbohydrates include starches such as corn starch and various cellulosic materials such as ethylcellulose. Suitable protein materials include, for example, casein,

  carrageenan, partial vegetable seed proteins-

  partially hydrolyzed, such as soy protein, and partially hydrolyzed animal protein Representative plastics usually include

  solid polyethylene glycols and poly alcohol resins

  vinyl The particular material suitable as a matrix and-

  providing the most inert and stable environment for a particular pesticide is usually known when it

  is not, as is the case with new bio-

  logic, the appropriate matrix material can be determined by routine experiments In general, proteinaceous materials provide a stable environment for biological pesticides such as bacteria, viruses and fungi

usually be used.

  As already indicated above, the matrix of

  matrix filler must be used to fix the pesticide on

  the core of wax particles Because of this, and in particular

  In the variants in which the coating matrix is fixed directly to the "core", the fixing is essentially carried out by a surface bond which is generally due to the adhesive properties of the materials used in the

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  coating matrix and such materials are further

rely chosen accordingly.

  The term "adhesive" as used below includes the various properties by which adhesives can achieve bonding including properties and capacities such as adhesion, penetration and the like, and in addition cohesion as it is obtained for example from adhesives

forming a film.

  When a coating material serving as a matrix producing water-dispersible coatings or other non-filming coating materials is used, adhesion becomes more important; greater attention must then be paid to maintaining the adhesion of such coatings by tolerating an appropriate residual moisture content and storing them under conditions which do not cause a rapid decrease in

residual moisture.

  When using coating materials forming a film, this constitutes a particularly effective element for bonding the coating matrix directly or indirectly to the "core", even if this film can be partially interrupted by non-homogeneous particles.

it contains.

  The use of a coating matrix forming

  a film is therefore a preferred variant of the

  vention Suitable film-forming coating materials are water-soluble adhesive materials such as hydrolyzed animal proteins (a

  known component of envelope glue).

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  When the pesticide is a bio-pesticide

  logic, the matrix material may already be present in the biological product that was manufactured as a result of the raw materials used for its preparation -, or may be chosen from a separate source or both, - For example, bacteria and fungi used

  as pesticides are usually prepared industrially-

  Lement by fermentation in a nutritive medium comprising water, carbohydrates, proteins and various compatible mineral salts. The resulting product in the dry state usually contains a large portion, generally at least 80% by weight of carbohydrate and protein residues which are at least partially dispersible in water and these products can advantageously be used as such, as a material serving as a matrix or as a component thereof for the preparation of the granules of the invention.

  fermentation in which the protein residue represents

  feels alone at least 50% by weight of the product in the dry state are common, and can advantageously be used alone or mixed with one or more materials serving as matrix to form a coating composition. Such batches of fermentation products can be used as a coating when the water content of these products has been brought up to the desired level, for example

by vacuum evaporation.

  On the other hand, the batch of dried fermentation product, for example by spraying according to the

known methods, produces a-

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  dry granular mass in which the particles constitute the biological pesticide encapsulated in a

  matrix composed of the residue from the iron's nutrient medium

  mentation (as an appropriate example of such particles, mention may be made of a bacterial insecticide in the form of

  powder such as Bacillus thuringiensis Israeliensis).

  Such a granular mass can be mixed with water to form a sticky, pasty composition which can be coated on the "core" to form a granule in which the biological active material is fixed in a coating matrix consisting of the nutritive residue. In addition, and according to the particularly preferred variants of the invention, the dry powder obtained for example by spray drying of the fermentation batch is a particularly suitable form to be applied to the particles of the "core" while it is still wet. following the first coating. Such a preferred variant can be applied to biological pesticides which are not usually prepared by fermentation, for example to virus-based pesticides, for example using fines

  particles containing a virus-based pesticide

  encapsulated in a protein matrix dispersible in

the water.

  A subject of the invention is also a process for preparing the granules of the invention comprising the following steps i) the application to the "core" of a liquid composition intended to form the coating matrix optionally containing the pesticide and ii ) adding the pesticide in solid form only

$ 253,341

  when step i) is complete, step ii) being optional in the case where the composition of the matrix

coating contains the pesticide.

  The coating can be carried out according to the coating methods known per se using, for example, a) known coating methods using liquid materials as a matrix containing the pesticide in the form

  of essentially dry particles which are either non-in-

  baked or which have a dry coating (see variant A below), b) known methods of coating dry pesticide particles on the particles of the "core" which are still wet following a prior coating (see variant B),

  then by drying to obtain a fluent mass.

  The method used for variant A is advantageously carried out by thoroughly mixing the pesticide or the material containing the pesticide with a liquid material serving as matrix. This mixture is then coated

  -directly or indirectly in the "core".

  According to the method used for variant B, the material containing the pesticide in solid form, for example in the form of particles or powder is coated on the core and / or absorbed by the "core" while still being

  wet after previous coating -

  The term "pesticide-containing material" as used below indicates that said material may consist essentially of the pesticide or may be in the form of a composition, for example in the form of a wettable powder or may be encapsulated in a suitable inert matter,

  (for example in the form of an encapsulation matrix).

  When a liquid coating is used, the solvent or release vehicle is advantageously water, although organic solvents can be used. The matrix material used for variant A should preferably be dispersible or soluble in water. , in order to allow the release of the pesticide on contact

some water.

  According to a more preferred variant of the

  vention, the fine and dry particles encapsulating the pesticide in an encapsulation matrix are coated and at least partially incorporated in the wet coating

  of the matrix that was previously applied to the "core".

  According to this process, the material of the "core" which is preferably in the form of particles, for example spherules, is mixed, for example by stirring in a suitable mixer, and the coating material serving as a matrix is

  then sprayed> advantageously in the form of a solution

  tion or is applied to the mass of the "core" and the mixture is continued in order to completely coat the matrix of e O robage over the entire surface

  "kernels" In most cases, concentra-

  trations of the solution on the order of 20 to 50%, preferably 30 to 40% in a weight / volume ratio

  suitable for spray application.

  The coating is advantageously carried out - more or less at room temperature or below the melting point of the wax. The amount of coating material serving as matrix in the dry state can vary depending on a certain number of factors. such as the material used, the desired thickness of the coating, the capacity

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  coating and the like Generally, the amount of coating is very small relative to the weight of the "core" material and may also be relatively minor compared to the amount of pesticide added thereafter, for example an encapsulated biological pesticide

  finely divided For example, the coating matrix pre-

  fairy of the invention may represent from 0.5 to 5.0% in

weight of the "core".

  The mixing time required to coat the core with the coating solution forming the matrix is variable and this operation can be carried out in a relatively short time,

  from 1 minute to 20 minutes, more precisely from 3 minutes to 10 minutes.

  When this coating is finished, the mixing or stirring of the mass of particles coated with the liquid wax is

  continued to avoid unwanted agglomeration.

  Addition of the pesticide in dry form (in finely divided encapsulated form or in powder form)

  can be done immediately after the end of the

  or after a short delay depending on the characteristics

  drying characteristics of the coating matrix and of the desired amount of fixing - or of the degree of adsorption of the coating matrix The addition of the pesticide is carried out by controlled introduction and / or

  intermittent or by distribution in the mass of the parties

  coated "core" cells which are stirred, in order to obtain a more or less uniform coating of the particles

  of pesticide on the particles of the coated "core".

  The addition time of the pesticide can be of the order of 1 to 20 minutes, more precisely 2 to 10 minutes; this operation is preferably carried out at room temperature and advantageously in

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  below the melting point of the wax core or of the wax coating the base material The amount of matrix material (dry weight) on or in which the pesticide is coated may be relatively small compared to the amount of pesticide material; it can, for example, represent from 3.0 to 25%, more precisely from 5.0 to 20% by weight of the pesticidal material. The appropriate quantity to be used as a pesticide will depend, inter alia, on the capacity of the still wet matrix of absorb the pesticide, final product characteristics (such as efficacy) and practical considerations such as the time required to dry the product and the need to avoid unwanted agglomeration of particles in

the mass of particles.

  When the addition of the pesticide is complete, the resulting mass of particles is kept under

  stirring and is dried in order to obtain a fluent product.

  Such drying can advantageously be carried out with a heated inert gas, such as heated air, which is introduced into the mass with stirring. In the case of a biological pesticide, it is generally necessary to control the temperature.

  drying or gas heated to moderate temperatures.

  In general, the air temperature is advantageous.

  between 380 C and 710 C, more preferably between 430 C and 600 C It is usually not necessary to dry the mass completely and a satisfactory product can be obtained by reducing the moisture content by no more than 10%, preferably not exceeding 8% As already indicated, maintaining a certain amount

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humidity may be desirable.

  The drying time can vary depending on particular situations and can be between

  minutes and 3 hours, for example 1 hour.

  Drying can be facilitated or carried out at

  a reduced temperature, for example around

  rature ambient, by adding a material absorbing moisture in significant quantities, for example from 50% to

  % by weight of the mass of the product in the form of granules.

  Such a material can also serve as a diluent for

  product As a suitable material to fulfill this ob-

  jectif mention may be made of corn cob granules (not coated with wax), even if this material is not suitable as a core material when it is not coated with wax Any agglomerate formed during drying can

  be broken, for example by hand. The particle size of the product can

  vary considerably, for example from 0.5 to 5 millimeters.

  When using the commercially available forms of wax (spherules), the particle size of the final product can vary from approximately 0.5 to 4 millimeters, more preferably from 1 to 2 millimeters When using cores consisting of a filler coated with wax, the size of the final products varies from 1 to 5 millimeters

  more particularly from 2 to 4 Millimeters.

  The resulting product can then be mixed and coated with a small amount, for example from 0.1 to 4.0% by weight of the granule, preferably between 0.5 and 2%, of a lubricating agent such as stearate. calcium, various silicas such as High Sil, Aerosil

and the like.

  According to a preferred variant in which the fine particles of the encapsulated biological pesticide are coated in the wax which is wetted with a coating material serving as matrix, the exact nature of the final product depends on various factors such as the amount of encapsulated material applied to the coating material serving as a matrix The use of small quantities of encapsulated and finely divided biological pesticide can cause a more or less complete incorporation in the coating of the matrix of particles containing the biological pesticide The application of more

  large quantities of biological pesticide up to the capa-

  city of fixation of the coating liquid used to form the matrix means that a significant part of the particles containing the biological pesticide is incompletely incorporated and in certain cases, they adhere as much to each other as to the coating matrix. product allows a staggered release of a high or maximum dose of particles with a high content of product When using a coating material forming a film and serving as a matrix, some encapsulated particles containing the biological pesticide can penetrate the matrix without greatly affect the cohesion of said coating film serving as a matrix These systems, in particular that which uses coatings serving as matrix soluble in water, produce a granule of the invention which is particularly suitable The invention allows the preparation of granules releasing to the minus 80% of the pesticide they contain within 24 hours The particularly preferred granules of the invention, including s those with wettable coatings serving as matrix, are already capable of releasing at least% of the pesticide which they contain after 3 hours and

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% after 6 hours.

  The present invention is particularly suitable for biological substances having use as pesticides, for example bacteria, viruses and fungi. Bacterial insecticides, in particular of the bacillus type such as Bacillus thuringiensis (berliner) and Bacillus sphaericus, represent an important class having a particular interest to be used in the granules of the invention The current products existing on the market using Bacillus thuringiensis are represented by the varieties Kurstaki and Israelensis The invention is

  particularly interesting to be used with-

  known as Israelensis (B t i) which is the biological pesticide of choice to fight mosquitoes, simulids and other organisms harmful to the state of larvae that are

found near water.

  The present invention also relates to a process for combating the larvae of mosquitoes (culicidae) and other similar harmful organisms evolving in an aquatic environment, which consists in applying to this place

  an insecticidally effective amount of a gra-

  void of the invention containing a biological larvicide

against mosquitoes.

  The amount to be applied will depend on various factors such as the method of application, the larval development stage, the habitat and the effectiveness of the granules. The quantities required are greater for an aerial application than for a ground application When the 1st, 2nd and 3rd larval stages predominate, the doses of application required are lower than those used when the end of the 3rd and the

  beginning of the 4th larval stage predominate among insects.

  The effectiveness of the granules will depend among other things,

  the quantity and effectiveness of the bio- insecticide

  logic introduced in the granules; it can be determined by biological tests and can, for example, be expressed in Aedes Aegypti Units (UAA) per mg of formulated product (biological test method accepted by the Federal Agency for Environmental Protection in the United States ) The amount to be applied will therefore also depend on the efficiency, that is to say the activity in UAA per mg of the granules. In general, satisfactory results are however obtained when the granules of the invention are applied at a dose. between 2 and 7 kg per hectare, for example between 2 and 3 kg / ha in running water, standing ponds, ditches, and canals, between 3 and 5 kg / ha in lagoons, tidal waters and salt marshes, and between 5 and 7 kg / ha in waters polluted by sewage The suitable granules have, for example, an efficiency which is between 200 and

600 UAA per mg.

  The granules having an efficiency of between and 300 UAA / mg, for example of 260 UAA / mg, allow good distribution of the active material The granules having an efficiency of between 300 and 600 UAA / mg, for example of 520 UAA / mg , do not necessarily allow a reduction in the application dose, although they

have better persistence.

  Although the invention refers to the applications

  cations in aquatic environments, it is obvious that pesticides in the form of granules can also

  be used in non-aquatic environments if necessary.

  Note that the matrix fixing the pesticide

  the wax core does not necessarily encapsulate the weight

  suicide unless it is necessary to preserve its stability in one way or another, provided that a

  biological pesticide needs to be protected in this way.

  However, using coating compositions serving as a matrix in which the agent is intimately mixed, essential encapsulation of the pesticide will occur inside the final granule in a matrix attached to the wax core, particularly when the wettable powder pesticide is attached to the "core" When the wettable powder surrounding the agent is a water-dispersible matrix, it is attached to the wax core in a matrix

  which is preferably soluble in water.

Examples and additional information

* In the following examples, the death tests

  They were made by filling 12.5 x 27.5 x 32.5 cm plastic tubs with 8 liters of non-chlorinated tap water to have a depth of 10 cm and an area of 0.093 m 2 For each test we introduce Aedes Aegypt larvae (in the 2nd or 4th larval stage) into the tank We also add 25 mg of brewer's yeast per liter of water to feed the larvae The test is carried out by spreading on the surface of water a pre-determined quantity of the granules being studied and the mortality of the larvae is evaluated by a percentage related to all the larvae originally present, 18 to

  24 hours after the addition of the granules.

  The following examples illustrate the invention

  without limiting its scope; in these examples, the indi-

  cations of parts and percentages are by weight and temperatures are given in degrees Celsius

unless otherwise stated.

Example 1

  95 parts of Sun Wax Antichek paraffin wax in the form of spherules (from Sun Petroleum Products, Wayne Pennsylvania) are added to a coating mixer.

  add 20 parts of a composition to the mass with stirring

  pasty sition prepared by homogeneously mixing parts of water and 5 parts of a technical powder of Bacillus thuringiensis israelensis (B ti) which is at least partially wettable and has an efficiency of 2300 UAA / mg The powder of B ti is prepared according to

  usual methods of preparing a powder of B t.

  technique by draining the content of the fermentation tank (* originally around 6% solids in an aqueous medium) until a solids content of 14 to 18% is obtained, of which around 40 to 60% are proteinaceous materials and 1 to 10% are starch, the temperature being 40 and under a vacuum of 625-750 mm Hg (Torr) and then at

  dries the resulting mixture by spraying.

  The entry temperature of the spray dryer is 1771 and the exit temperature is 660. The mixing is continued after the addition of B t i for approximately 3 minutes.

  in order to evenly coat the paste of B t i on the wax.

  While continuing to mix, heated air is introduced for approximately 30 minutes at approximately 520 and the fluent mass of granules is recovered. The granules are stored for 4 weeks at 40 and then subjected to the mortality test by making float the particles on the surface, which gives a 100% mortality rate for the 4th larval stage 24 hours after application

at a rate of 3.36 kg / ha.

Example 2

  S parts of mo 6 uillable powder of B.t i, prepared according to the method described in Example 1, are mixed with 10 parts of molten polyethylene glycol sold on the market.

  under the name of Polyglycol E 4000 by the company Dow Chemical Cy.

  We continue to mix for another 2 minutes at 40.

  The resulting molten mixture is added to a functioning coating mixer containing 85 parts of Sun Wax Ant-ichek paraffin wax (spherules) and mixed again for approximately 3 minutes. The resulting granules are then stored at 40 for 2 weeks and they are then subjected to the mortality test; we obtain a mortality rate of 100% for the 4th larval stage 24 hours

  after application of a rate of 3.36 kg / ha.

Example 3

  In a Stockes type coating machine, 22.7 kg of Sun Wax Antichek paraffin wax (spherules) are introduced. The rotor is started and 500 ml of an aqueous protein collo Pdes solution is slowly added to the particles with stirring. This solution is prepared by mixing 198 g of partially hydrolyzed animal proteins obtained under the name of Colloid N 1-V from the firm Swift Adhesives & Coatings, with enough water heated to 60 to form a solution at 36% by weight of materials solids Addition of solution

  protein protein lasts about 3 minutes and.

  continue to agitate for a further 3-5 minutes afterwards to evenly coat the wax granules with the

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  the protein solution To the granules of wax coated with protein are then added slowly with stirring 3000 g of B ti in the form of a wettable powder prepared according to the method described in Example 1 The addition lasts about 10 minutes and the process continues. shake for minutes to spread the Bt i more or less uniformly as a wettable powder over the protein-coated wax particles. While continuing to mix, the resulting particles are treated for approximately 30 to 45 minutes with heated dry air. to 500 in order to reduce the moisture content below 8% Any agglomerate contained in the mass is removed by hand

  resulting and sieved to remove all the agglomerates

  resulting merats The resulting product consists of

  brownish granules with no excess formation

  powder sive, is fluent and the individual particles of this product float on water The final formulation consists of 87.2% wax, 12.0% B ti in the form of wettable powder and 0.8% protein collids and the specific gravity is 1.88 liters per kg The final particle mass has an efficiency of 520 UAA / mg and after 4 weeks of storage at 40, the mortality is 100% for the 4th larval stage 24 hours near the application of

  produced at a rate of 3.36 kg / ha according to the death test

  Lity Adding High Silica (1.0% of the resulting product) improves the storage possibilities of

  granules avoiding their agglomeration.

Example 4

  To a helical mixer (Day Model 758) operating at 280 revolutions / minute and containing 80 parts (about 45 kg) of No. 2 mash cob granules (1.5 3 mm), 20 parts of paraffin wax are added per portion (the same wax as that used in Example 1) which were added in approximately 4-6-portions from containers of which

  content was evenly distributed over the granular mass

  mash stalks stirred for about 4 minutes after adding all the melted wax interval during which the melted wax more or less uniformly coats the individual granules of mash stalks and solidifies to form a coating of dry wax Then place a charge of 88 parts of

  corn cores wrapped in wax in a blender-

  similar helical mixer and they are mixed, while distributing them uniformly, over 4.5 parts of

  the protein solution of collo Tdes used in Example 1.

  Mixing is continued for approximately 5 minutes after this addition, in order to distribute the solution evenly.

  protein collo Pdes on the wax surface of the nuclei.

  While continuing to mix, 10 parts of B ti are uniformly distributed over the resulting mass in the form of a wettable powder prepared as described in Example 1 and the mixing is continued for a further 3-5 minutes to ensure homogeneous coating of the powder over the protein-coated wax nuclei 100 parts of the N 2 corn cob granules (not coated with wax) and 0.4 part of hydrophobic silica sold under the name Aerosil R 972 are then added, and further mixing is carried out,

  for 5 minutes to obtain a uniform mixture.

  The addition of unrefined wax pellets facilitates the drying of the mass and serves as a diluent in the product. The resulting mass is sieved through a

  N 6 mesh sieve (0.33 cm) to obtain the final granules.

  The mortality test reveals that these granules cause a mortality rate of 100% in the 4th larval stage

  24 hours after application of a dose of 2.24 kg / ha.

  After storage for 3 weeks at 40 the mortality rate revealed by the mortality test is 85% and 100% at the 4th larval stage when the granules are applied respectively at a dose of 2.24 and 4.48 kg / ha When applied to water by air 98% of the coated granules remain on the water surface for 24 hours

after application.

Claims (1)

CLAIMS 1 Fluid granules floating on water containing a pesticide, characterized 'in that they consist of a) a solid wax core or a core coated with solid wax having a density lower than that of the water and which is inert towards the pesticide, and b) a pesticide fixed to the wax core or to the core coated with wax by a matrix which is inert towards the pesticide and which is capable of releasing the pesticide to the water contact. 2 A granule according to claim 1, characterized in that the wax which it contains is a paraffin wax having a melting point of at least 400 C. 3 A granule according to claim 2, characterized in that the material of the wax-coated core is a granule of males cob. 4 A granule according to any one of claims 1 to 3, characterized in that the pesticide is a biological pesticide. A granule according to claim 4, characterized in that the biological pesticide which it contains is a biological larvicide against mosquitoes. 6 A granule according to claim 5, characterized in that the pesticide is a Bacillus thuringiensis of the Israelensis type. 7 A granule according to any one of claims 1 to 6, characterized in that the matrix material represents from 0.5 to 5% by weight of the core and from 3.0 to 25% by weight of the pesticidal material. 8 A process for combating the larvae of mosquitoes and other similar harmful organisms evolving in an aquatic environment, characterized in that a pesticide-effective amount of a granule as specified in claim 5 is applied to this place. A method according to claim 8, characterized in that the mode of application is a mode of application by air.   1 O A process for preparing granules   specified in any one of claims 1 to 8,   characterized in that it comprises i) the application to the core of a liquid composition intended to form the coating matrix possibly containing the pesticide, and ii) the addition of the pesticide in solid form only when step i ) is complete, step ii) being optional in the case where the composition of the matrix coating contains the pesticide.