A COMPOSITION FOR APPLICATION TO A PLANT LOCUS

Abstract: A composition for agricultural application which contains a major amount of water and a minor amount of an alkaline earth metal alginate gel uniformly dispersed through the water. The composition may include an active ingredient such as a herbicide, pesticide, fungicide, fertiliser or the like. The composition may also contain a suitable wetting agent to assist in spreading it on a surface to which it is applied.

Description: This invention is concerned with a thixotropic composition for application of an agricultural chemical to a plant locus. Agricultural chemicals such as herbicides, fertilisers, insecticides, fungicides and the like are applied in a variety of formulations and compositions. The compositions may take the form of dusting powders or granules, dispersible powders or granules, aqueous dispersions or emulsions and sprays and aerosol formulations. The active ingredients for such formulations are dispersed in a variety of mediums or carriers depending on the nature of the formulation. FR-A-1,521,308 describes the use of calcium alginate in water-based phytosanitary and herbicidal compositions. The alginate is described as a "protective colloid" and its function is to maintain the active phytosanitary or herbicidal agent which is, by definition, insoluble in water, in suspension. GB-A-1,271,575 describes the use of an aqueous alginic acid/alginate system to which salts, such as calcium salts, can be added, the resulting composition being used as a fertiliser composition for application to the soil. Alginate gels are derived from seaweed and are used in various food products in a highly purified form, i.e. less than 0.1 percent by weight of + 10 µm insolubles. According to the present invention, there is provided a thixotropic composition for application of an agricultural chemical to a plant locus, which comprises a major amount of water and a minor amount of an alkaline earth metal alginate gel matrix and bentonite uniformly dispersed through the water, the water being present in an amount of at least 90 percent by weight of the composition and the alginate gel matrix being present in an amount of up to 5 percent by weight of the composition, the composition containing at least 0.05 percent by weight of - 70 µm insolubles, and the weight ratio of the alginate gel matrix to bentonite being in the range 1:1 to 1:10. According to another aspect of the invention, there is provided a method of treating a plant locus, which comprises the step of applying to that locus a composition according to the invention. It has been found that the composition adheres well to surfaces such as soil, and leaves and other foliage of plants. These adherent or sticking properties of the composition allow it to be used in a number of applications. For example, the composition contains a considerable amount of water and that water is retained on the surface to which the composition has been applied for a long period. This property may be used for fighting fires or preventing the spread of fires in forests and other agricultural areas. Active ingredients such as herbicides, fertilisers, insecticides, fungicides, and the like may be included in the composition. These active ingredients will be retained on the surface to which the composition has been applied. The composition has particular application for sprays. The alginate gel of the composition is thixotropic which means that although it is thick and viscous, it will spray easily either from the ground or from the air at high concentrations. Due to the polymer structure of the gel, spray particles of a uniform size are produced and drift is substantially reduced. The composition may be used for spraying herbicides, pesticides, fertilisers and foliar compositions. The preferred alkaline earth metals for the alginate gel are calcium, magnesium and mixtures thereof. The gel may be formed by bringing together a solution of a soluble alginate, for example sodium alginate, and a pre-swelled bentonite. Bentonite is a montmorillonite which swells when wetted with water. The weight ratio of the soluble alginate to bentonite should, as previously stated, be in the range 1:1 to 1:10. It is important that in producing the gel there is a slow reaction between the soluble alginate and the bentonite which provides the alkaline earth metal salt as otherwise an insoluble fibrous alginate may well form. The soluble alginate may be produced by boiling seaweed in an alkaline salt solution, such as a sodium carbonate solution, milling the thus treated seaweed, and then removing, for example by filtration, large, e.g. + 150 µm, insolubles. After bringing together the pre-swelled bentonite and the soluble alginate, the combination is left for a time to allow the alkaline earth metal ions of the bentonite to react with the soluble alginate and form an alkaline earth metal alginate gel. The gel may then be treated, e.g. by filtration, to remove + 70 µm insolubles. The resulting product is a coloured alginate gel containing at least 0.05 percent, generally at least 0.5 percent, by weight of - 70 µm insolubles. Such a gel, while suitable for agricultural applications, is totally unsuitable for food applications. The composition of the invention may also contain a wetting agent. The wetting agent assists in improving the spreadability of the composition on the surface to which it is applied. Preferred wetting agents are anionic surface surfactants. Non-ionic surfactants may also be used. Examples of suitable non-ionic surfactants are linear primary alcohol ethoxylates, polyoxyethylene dodecyl phenol, polyoxyalkylene nonyl phenol, polyoxyethylene octyl phenol, ethoxylated castor oil, polyoxyethylated sorbitol, polyoxyethylene stearate, sorbitan monolaurate, sorbitan monostearate and sorbitan monooleate. Examples of suitable anionic surfactants are alkylaryl sulfonates, lauryl polyoxyethylene salts, dioctyl sodium sulfosuccinate, salts of lignosulfonic acids, salts of sulfate ester of nonylphenoxypoly (ethylenoxy) ethanol, polyoxyethylene nonylphenol phosphate esters, tall oil and salts of alkyl sulfates. The composition of the invention may also include an active ingredient such as a herbicide, pesticide, fertiliser, fungicide or the like. The amount of active ingredient present will vary according to the nature of the active ingredient and the application to which the composition is to be put. Examples of suitable active ingredients include mancozeb, paraquat, fenthion and malathion. The composition of the invention will typically be applied to a plant locus by spraying. To this end, the composition will generally be diluted with water to the desired concentration. The dilution will vary according to the application. In one particular form of the invention, the composition includes a thripsicide, such as a salt of an antimony carboxylic acid having an alpha monohydroxy group or nicotine sulphate. The preferred thripsicide is tartar emetic which has the chemical name potassium antimony tartrate. The composition is applied to citrus fruit where thrips, also known as Scirtothrips Aurantii Sauri , causes considerable damage to the fruit by eating the tissue around the calyx when the fruit is still young and small. This damage then heals as a scar which stretches as the fruit grows and causes unsightly discolouration to the skin around the calyx. In many cases these fruits are unsaleable. The composition containing the thripsicide is applied to the citrus trees. The alginate gel provides a non-phytotoxic protective coating for the thripsicide active ingredient which nevertheless allows the thripsicide to function effectively. Typical uses and compositions of the invention are set out in Table 1. Use Composition Dilution In Use (Amount of Composition Added to 100ℓ Water) Active Ingredient Alginate Gel (% by weight) Wetting Agent (% by weight) Thripsicide 100 0 250 to 1000ml Tartar emetic 400g plus sugar 400g Red Spider Remedy 40 to 75 0.5 to 1 1 to 5ℓ Organophosphate (optional) Soil Penetration Inhibitor 30 to 60 1 to 30 50 to 250ml Atrazine Forest Fire Fighting 50 to 90 2 to 10 100 to 1000ml None Wetter/Sticker Adjuvant for Sprays 30 to 60 10 to 30 50 to 250 Trace Elements Fungicide, Pesticide or Herbicide COMMENTS 1. The sugar which is added to the thripsicide is present as a bait. 2. For the red spider remedy, the composition when diluted is applied to an infested locus and in effect acts to drown the pest. Thus, the organophosphate or other active ingredient is optional. 3. For soil penetration, the composition of the invention acts to retain water in the surface of soil to which it is applied. Thus, if an active ingredient such as atrazine is applied to a crop, residual atrazine which falls on the soil is held there and is effectively prevented from being leached to underground water systems until it has been biodegraded. The invention will be illustrated further by the following specific examples. EXAMPLE 1 A mixed calcium and magnesium alginate gel was made in the following manner. Seaweed of the Laminaria type was brought to the boil with sodium carbonate solution and then milled in a high shear mixer to produce a slurry containing the milled seaweed. The slurry contained approximately one percent by weight sodium alginate. The slurry was filtered to remove + 150 µm insoluble weed body. To the filtered slurry was added finely particulate bentonite which had been pre-swelled with water to give a composition containing about 8 percent by weight bentonite. The bentonite had the following composition: Ion exchange occurred over a period of about 30 minutes producing a mixed calcium and magnesium alginate gel of good gel strength. The thus produced gel was filtered again to remove + 70 µm insolubles. The final composition was as follows: Component Amount (per 250ℓ) Alginate (predominantly calcium) 1,3 kg Bentonite 6,0 kg Water 241 ℓ Other seaweed solubles & insolubles 2,0 kg - 70 µm insolubles 0,2 kg EXAMPLE 2 A mixed calcium and magnesium alginate gel in a water base was made in the manner set out in Example 1 except the seaweed used was of the Ecklonia Max . type. EXAMPLE 3 The composition of Example 1 had added to it sodium dioctyl sulfosuccinate (a wetting agent), silicon 1520 (a de-foamer from Dow Corning) and acetic acid. The final composition had the following constituents: Ingredient Percent by Weight Sodium Dioctyl Sulfosuccinate 10 Alginate Gel 20 Silicon 1520 0,4 Acetic Acid to pH 7,2 Water balance This composition was an excellent wetter/sticker adjuvant for various spray applications and can be used in the manner set out in Table 1 above. EXAMPLE 4 250ml of a composition as produced in Example 1 was added to 100ℓ water. Also added to the water was tartar emetic and sucrose each in an amount of 400g. The diluted composition was thoroughly mixed. The composition was then delivered to a spray nozzle for application to a citrus crop. It was found that an excellent application of the composition to the citrus crop was achieved with the composition being firmly adhered to the leaves and fruit of the trees. Further, good control of the thrips was achieved. It was noted that the composition was not removed by rain from the trees.

Claims: A thixotropic composition for application of an agricultural chemical to a plant locus, which comprises a major amount of water and a minor amount of an alkaline earth metal alginate gel matrix and bentonite uniformly dispersed through the water, the water being present in an amount of at least 90 percent by weight of the composition and the alginate gel matrix being present in an amount of up to 5 percent by weight of the composition, the composition containing at least 0.05 percent by weight of - 70 µm insolubles, and the weight ratio of the alginate gel matrix to bentonite being in the range 1:1 to 1:10. A composition according to claim 1, in which the alkaline earth metal is calcium or magnesium or a mixture thereof. A composition according to claim 1 or 2, which contains at least 0.5 percent by weight - 70 µm insolubles. A composition according to any of claims 1 to 3, which also comprises a wetting agent. A composition according to claim 4, in which the wetting agent is an anionic surfactant. A composition according to any of claims 1 to 5, which also comprises a herbicide, pesticide, fertiliser, or fungicide. A composition according to any of claims 1 to 6, which also comprises a foaming agent. A composition according to claim 7, in which the foaming agent is present in an amount of 1 to 10 percent by weight of the composition. A method of applying a herbicide, pesticide, fertiliser, or fungicide to a plant locus which comprises the step of applying to that locus a composition according to claim 6. A method according to claim 9, in which the application is by spraying. A method of treating a burning plant locus, which comprises the step of applying to that locus a composition according to claim 7 or claim 8.

Inventors: BEWSEY, JOHN ARTHUR
Applicants: HARVEST CHEMICALS (PROPRIETARY) LIMITED
Application year: 1987
Main classification: A01N25
IPC codes: C05G3, C05F11, A01N25