Pyrethrum Insecticidal Composition

Background of the invention

The invention relates to the insecticidal compositions containing naturally occurring pyrethrum are widely used to combat insect pests, such as flies, mosquitoes, gnats and the like. Frequently, the pyrethrum is employed in a solvent of the hydrocarbon or mineral oil type. The term pyrethrum is used to identify flower extracts have long been known to possess insecticidal activity. The molecular structure of the pyrethrin esters has been used by many different companies to develop synthetic compounds. These synthetic compounds, called pyrethroids are not naturally occurring and have chemical structures that differ from those of pyrethrums.

The natural pyrethrums however, have remained popular and are commonly used in a variety of formulations. Usually pyrethrins are combined with a variety of substances, called synergists, which enhance their effectiveness. One of the earliest of these synergists was sesame oil which contains the extractives sesame and sesamolin (Casida, Pyrethrum, The natural insecticide, p. 329, Academic press 1973). US2463324 describes that it is the sesame oil extractives, not the oil itself that are responsible for the enhanced activity of pyrethrins.

US4983591 describes specific fatty acid salt in combination with pyrethrins. Generally, pyrethrins are degraded in an alkaline environment and are, therefore, incompatible with fatty acid salts. However, this drawback was overcome by adjusting the pH of the aqueous mixture.

Summary of invention

It is an object of the invention to provide formulations of pyrethrums in the form of Suspension Concentrates (SC).

It is another object of the invention to provide formulations of pyrethrums in the form of Emulsion Concentrates (EC).

It is another object of the invention to provide formulations of pyrethrums in the form of Wettable Powders (WP).

It is another object of the invention to provide formulations of pyrethrums in the form of Capsule Suspensions (CS)

Detailed description of the invention

Suspension Concentrates (SC)

Pyrethrum can be formulated as a suspension concentrate.

Suspension concentrates are stable suspensions of pesticide particles in water. Suspension concentrates were developed as means for overcoming dust problems associated with WP formulations. Suspension concentrates are usually made by premixing the active powder in an aqueous solution of a wetting agent and a dispersing agent. This is followed by a wet grinding process in a bead mill, to give a particle size distribution of about 1 - 10 u with an average particle size of about 2 - 3 u.

The suspension concentrate of this invention demonstrates many favourable attributes like rapid and complete dispersion in the spray tank with minimal agitation in hard or soft water, lack of breakdown or dust formation, good re-suspension after settling and stable shelf life; enhanced biological activity; low cost of production.

The formulation may have wetting and dispersing like Sodium lignosulfonates, Aliphatic alcohol ethoxylates, EO/PO co-polymers, Sodium naphthalene sulfonates - formaldehyde condensates, Tristyryl phenol ethoxylates phosphate esters, graft co-polymers and anti-settling agents like Xanthum gum, Cellulose derivatives, Polyvinyl alcohols, Modified starches, Natural gums, Polyethylene oxide. The formulation may further contain dispersed phases like Bentonite clay, Atapulgite, Precipitated silica and fumed silica. Antifungal agents like formaldehyde solution and Proxel GXL may also be used.
Wettable Powders (WP)

Powders consist of active ingredients, wetting agents and inert carriers. Wettable powders are finely divided solid pesticide formulations which are applied after dilution and suspension in water. WP formulations are usually made from solid active ingredients which are suitable for fine grounding through a hammer or pin type mill or air jet milling for wettable powder. The formulation contains dry surfactants as powder wetting, dispersing agents and inert carriers or fillers. Average particle size of wet table powders 5u.

Wettable powders are finely divided solid pesticide formulations which are applied after dilution and suspension in water. WP formulations are usually made from solid active ingredients which are suitable for fine grounding through a hammer or pin type mill or air-jet mill.

The WP formulation may contain wetting agents such as Benzene sulfonates, Naphthalene sulfonates, aliphatic sulfosuccinates, aliphatic alcohol ethoxylates and the like; dispersing agents like Lignosulfonates, Naphthalene sulfonate - formaldehyde condensates and antifoaming agents like Silicone oil based polymers.

Emulsifiable Concentrates (EC)
Emulsifiable concentrates consist of an active ingredient, a solvent, and an emulsifier. The formulation is economical as it may be shipped in high concentrations and diluted later with water. The solvent may be chosen with respect to the solubility of the active ingredient and the emulsifier may be chosen as per its HLB (Hydrophilic Lipophilic Balance) value. The EC formulations have the advantages of good chemical stability, high biological activity, and easy pourability.

Capsule Suspensions (CS)
Capsulated suspensions consist of either wettable powder and water or suspension concentrate and water held in a capsule. Microcapsule suspensions are small spherical particles (typically 1 -20 urn in diameter) composed of a core material containing active ingredient and an outer shell wall of polymeric material, which is designed to release the core in a controlled way, as appropriate for the biologically active material. Suspensions are produced normally as aqueous concentrates that are diluted in water and sprayed conventionally.

The capsulated suspensions may contain wetting and dispersing, anti-settling agents, dispersed phases and antifungal agents.

The process for the formulation of naturally-occurring pyrethrins may profitably employ numerous species in addition to the pyrethrins. Thus, formulations according to this invention may include clays, stabilizers, surfactants, de-foaming agents and suspension agents. The arthropodicidal composition of the present invention comprises active ingredients that are derived from a pyrethrum extract. Typically the stabilizers are butylated hydroxy toluene, epoxydized soyabeen oil and epoxydized linseed oil. The emulsifiers are anionic and nonionic surfactant.

Procedure for SC formulations:
Suspension concentrates are made by premixing the active ingredient powder in an aqueous solution of a wetting agent and a dispersing agent. This is followed by a wet grinding process in a bead mill, to give a particle size distribution of about 1 - 10 [i with an average particle size of about 2 - 3 u.

Procedure for WP/ WDP formulations
Wettable powder (WP) formulations are made by blending active ingredient with surfactant wetting and dispersing agents and inert fillers, followed by grinding to the required particle size.

3. EMULSIFIABLE CONCENTRATE

Procedure for EC formulations
Active ingredient is dissolved in suitable solvents, emulsifiers to form a clear oily stable liquid, which on dilution with water forms milky emulsion.

4. CAPSULE SUSPENSIONS
Procedure for Soluble concentrates formulations

Active ingredient is dissolved in water / water miscible solvents, wetting /bio-enhancing agents and anti-freezing agents to form a homogeneous liquid.

Claim

1. An insecticidal composition of Pyrethrum in the form of suspension concentrate, emulsifiable concentrate, capsulated suspension and wettable powder.