Presented by: Eng. Agr. Jorgelina Lezaun
Agribusiness & Marketing Consultant
jorgelina.lezaun@gmail.com
November 2024
The active ingredients of agrochemicals are highly concentrated in their pure form and this can increase their toxicity and create risks when handling them.
In addition, they may present altered physicochemical properties (such as solubility and stability), which is why after they are obtained from industrial extraction or synthesis processes, they must be prepared in mixtures or formulations for the sale of the agrochemical that will be applied as we know it.
The formulation consists of an active ingredient (a.i.) plus other inert ingredients (auxiliary substances or carriers) such as surfactants (also known as wetting agents), solvents, stabilizers, defoamers, colorants, etc.
Formulating a pesticide then consists of preparing its active components in the appropriate concentration with the addition of auxiliary substances.
Three factors must be considered in the formulation:
- Physicochemical properties of the additions
- Application form
- Nature of the surface to which the product will be applied
FAO and the World Health Organization (WHO) in the “Manual on the development and use of pesticides” establish specifications for each type of formulation to be met in their manufacture.
Components of a formulation
A.- Active ingredient (a.i.)
The active ingredient (a.i.) is the product that kills or controls the pest or disease. It is known by its chemical name, common name, trade names and registration number.
Pure product and technical grade
- Pure product is the “isolated” active ingredient separated from the impurities that accompany it.
- Technical grade product (industrial quality) is the pesticide out of the factory as it results from the manufacturing process, accompanied by impurities and related compounds.
In the preparation of commercial formulations, “technical grade products” are used, which are cheaper due to less industrial processing. Once formulated, these are used as phytosanitary products for agricultural, veterinary and household use.
B.- Inert or Carrier ingredients
They are substances that accompany the active ingredient
- They lack pesticide activity
- They improve product performance
- They make their application and handling easier
- They help it dissolve in water
- They improve penetration and adhesion to leaves and soil, and stabilize the product during storage and transport
Inert ingredients or auxiliary substances can be classified as:
B.1- Solvents
They are key ingredients in the formulations of emulsifiable concentrates and solutions. It is important to consider that the solvent should not be phytotoxic when applied to crops.
Most active ingredients are insoluble in water, so the solvent must also be insoluble in water. Otherwise, when the product is added to the tank with water in the sprayer, the solvent will mix with the water, but will leave the product as a crystalline precipitate.
B.2- Surfactants
They are added to the active ingredients to ensure their storage and to facilitate their mixing with water in the sprayer. They serve as coupling agents, joining two phases and depending on the state of the phases they join, they are called:
- emulsifier: unites phases: liquid/liquid, for example water and oil.
- Humectant or wetting agent: unites phases: liquid/solid, used to “wet” the solid.
- foaming agent: combines phases: liquid/air and can form foam
B.3- Diluents or solvents
They are inert or transporting agents that are important in the functioning of the formulated product. In the case of liquids, they must be good solvents, otherwise the formulation could become compacted during storage.
Types of Formulations
Formulations may be liquid or solid, taking into account the physical state in which they are marketed.
A. COMMON FORMULATIONS
A.1.- Liquid formulations:
expressed as weight in volume, i.e. grams of active ingredient in 100 cm3 of formulation. The same for the concentration of the rest of the components.
Since this concentration refers to a pure product but they work with a technical product, it is necessary to know the standard (purity) of the technical product (industrial quality).
A.1.1.- Solutions (SL) - Soluble Liquids
These include active ingredients that are miscible in water or diesel fuel. They may be concentrated solutions or “solutions for direct use”.
Concentration of the active ingredient: between 20% and 80%, depending on its solubility in the solvent used.
A.1.2.- Emulsifiable concentrates (EC) - Emulsifiable liquids
These formulations are designed to be applied as a spray and mixed with water to form an emulsion.
The active ingredient (a.i.) is solubilized in non-polar solvents (not miscible with water) derived from petroleum, forming a translucent solution together with the auxiliary substances - emulsifier - to keep the product suspended in water.
When adding the formulation to the water in the application equipment, a stable milky emulsion of fine drops of one liquid dispersed in another is formed, both being immiscible.
The emulsifier (surfactant) facilitates the application of water-insoluble or water-miscible solvents using water as a vehicle with common spray equipment, either hand-held or backpack, as well as with large ground sprayers, low-volume equipment, foggers and aerial applications.
ECs may contain 25 to 50% pesticide weight/weight.
Concentration of the active ingredient: may contain 25 to 50% of the toxic substance weight/weight.
A.1.3.- Concentrated or dispersible suspensions (SC or FL)
They are crystals of active ingredient in water, but they are “suspended” in it. That is, dispersions of a finely divided solid (active ingredient insoluble in water) in a liquid medium, generally water, but it can be oil.
Most “hydrophobic” particles are dispersed dissolved in water, so the active ingredient must be insoluble in water to allow its dispersion in water and not decompose during storage.
When the formulation is added to the water in the application equipment, a colloid is formed.
The presence of the dispersant allows the homogeneous dispersion and suspension of the particles in the aqueous medium, maintaining colloidal stability, meaning that the particles do not precipitate or dissolve, which is why they present a certain turbidity.
This is because the hydrophilic polar part of the surfactant is directed towards the water and the hydrophobic part towards the interior of the particle.
It can be applied aerially.
Concentration of the active ingredient: varies between 30% and 60%.
A.1.4.- Microemulsions (ME)
Micro emulsions are formulations designed to improve undesirable characteristics of emulsifiable liquids (EC) such as the content of toxic and highly polluting flammable solvents. Organic solvents are not used in this type of formulation.
In micro emulsions, the oily active ingredient is dispersed in water with various surfactants. These require high-speed mixing until stable and fine dispersions of water-insoluble active ingredients are obtained. It is less likely to separate into phases than any emulsion, which makes it more stable.
They do not take on a milky appearance, they are clear liquids of low viscosity and are thermodynamically stable.
For pre-plant, under no-till stubble, a ME adheres more to the stubble than a common emulsion, due to the small oil droplets.
Concentration of active ingredient: greater than 30%
A.1.5.- Water-concentrated emulsions (EW) Emulsified liquids
The formulation is a preformed emulsion with emulsifiers that have water in their composition that are further diluted in water.
The active ingredient is solid or a viscous oil soluble in paraffinic oil; direct emulsion in water with surfactant (oil in water) mixed at high speed, small particles (<50F); thermodynamically unstable; oil in water dispersion with emulsifiers.
A.1.6.- Suspoemulsions (SE)
One or more active ingredients soluble in solvents in emulsion phase with another insoluble active ingredient dispersed in aqueous phase. Mixture of active ingredients.
A.1.7.- Ultra low volume liquids (ULV)
They are formulations that are presented ready to use from undiluted technical grade material. Its special viscosity, density and volatility characteristics allow these drops to reach their destination without being affected by high temperatures and low relative humidity when applications are made in summer.
They are EC designed to be applied without dilution or with carriers such as diesel oil or water. They are applied as an extremely fine aerosol generated by special sprayers or aerial equipment.
A.1.8.- Micro encapsulated (MC)
The active ingredient is enclosed in many millimetric-sized solid capsules; it is therefore a suspension (solid dissolved in liquid).
Microcapsules remain stabilized in an aqueous medium, and in the presence of water there is no release of the active substance contained within. This situation occurs both in the commercial packaging, where the microcapsules are in aqueous suspension, and in the spray tank, where water acts as a dissolution and dispersion medium.
Once deposited on the surface of the crop, the microcapsules remain stabilized due to the aqueous medium provided by the spray water, and by surface tension they remain adhered to the surface of the plant.
In pre-plant, it is advisable to use an MC formulation due to greater residuality if it touches the stubble or falls directly to the soil.
A.2.- Solid Formulations:
expressed as weight over weight in grams per 100 grams of formulation both for the concentration of the active ingredient and the rest of the components.
Powders usually contain a mixture of only two ingredients: the inert diluent and the active ingredient, the latter representing only 1 to 10% of the mixture. The diluent must be poorly adsorbed to avoid inactivation of the pesticide, such as talc or clay.
Its appearance is that of a fine, loose powder. They are used as they are sold commercially.
A.2.1.- Dusting powders, Powders (P or DP)
These are formulations that are generally used as they are presented in the packaging. They are very subject to wind drift. They are practically not used in extensive agriculture, but they are frequently used in treatments for livestock and domestic animals, as well as in environmental sanitation and, occasionally, in gardening.
A.2.2.- Wettable powders (PM or WP)
More commonly used formulation in agriculture, and is composed of: Active Ingredient + Inert Diluent (usually clay) + Wetting Agent. The active ingredient usually comprises between 25 and 75% of the mixture.
These are used after dispersion in water. In water they wet spontaneously and disperse, forming relatively stable suspensions.
The active ingredient is ground and subsequently mixed with inert earth and surfactant (wetting agent and dispersant) at high speed.
The addition of wetting agents allows the finely divided solid particles that make up the formulation to become wet and suspended in water due to the decrease in interfacial tension between water and the particles, by increasing the wetting power of the latter. Dispersants prevent the formation of agglomerates of solid particles, thus promoting their suspensibility in water. They are applied with common spraying equipment.
A.2.3.- Soluble powders
Similar to wettable powders, but they form a solution with water. Auxiliary substances improve their application and retention conditions.
There are few water-soluble active ingredients. These powders form true solutions that are applied with commonly used sprayers. In this formulation the technical grade material is a finely ground solid which is added to the tank of the spray machine and dissolves rapidly.
Concentration of the active ingredient: generally high
A.2.4.- Dry granules (GR)
The granular formulation is similar to the powder formulation, the difference lies in the particle size that contains the active ingredient which prevents the risk of inhalation during handling. They differ from those in the size of the particles (between 100 and 6000 F). They are used as they are sold commercially. They are frequently used as soil insecticides.
The formulation is the result of extruding the active ingredient with the carrier, obtaining a paste and drying it. Due to their size, they can be distributed evenly and not be exposed to drift. The active ingredient must be released from the granule to exert its action either by diffusion or disintegration of the particle and dispersion.
Concentration of the active ingredient: low, from 1 to 15%
A.2.5.- Water dispersible granules (WDG)
They are formulations that are added to the water in spraying equipment and form suspensions similar to those produced by wettable powders or dispersible liquids.
They are handled as liquids, are expensive and require agitation. They are a modern version of wettable powders.
The active ingredient is mixed with solid carriers and surfactants, extruded as a paste and then dried, forming a uniform cylindrical shape (0.5-1 mm diameter); they disintegrate easily and are dispersed in water by dilution
Concentration of active ingredient high
B.- SPECIAL FORMULATIONS
In solid and liquid form, some formulations are presented as pills, pellets, cartridges, blocks, tablets, plates, strips, baits, liquids to generate gases that in general, due to their composition and purpose, are classified as special formulations.
B.1- Gels
These are high viscosity liquid formulations, using water as a base (GW) or solvent (GL). They are intended for alternative markets to agricultural use and have different uses (toothpaste, detergents, pharmaceuticals, etc.) High development costs and expensive packaging.
B.2- Fumigants
The active ingredient is used or acts in the form of gas or vapor, regardless of the state in which it is applied. They can be classified as solid, liquid and gaseous.
- Solids are made up of the active ingredient, vehicle and adjuvant (Naphthalene, aluminum phosphide tablet: phosphine).
- Liquids are made up of the active ingredient plus the solvent (Methane sodium; volatile liquids or liquids that are released by environmental humidity or heat)
- Gaseous are made up of the active ingredient plus warning gas (methyl bromide).
Broad spectrum control since they affect all pests, very high penetration capacity and ability to eradicate pests. Given their high toxicity, gas leaks must be prevented. Serious risks for humans and domestic animals, need to use complete protective equipment.
B.3- Smokers
They consist of the active ingredient mixed with combustible substances (organic matter that burns easily) and oxidizers (which cause or activate combustion; potassium chlorate or sodium nitrate), producing lethal fumes. Once ignited, incomplete combustion is generated, releasing smoke or gases that drag or carry the active ingredient with them (mosquito coils).
B.4- Liquid Aerosol
It refers to a dispersion of solid or liquid particles in a gaseous medium (pressurized gas or liquid). The active ingredient (solid or liquid) is dissolved in an organic solvent, a synergist is added and then it is packaged with a propellant gas (deodorized butane or propane). The active ingredient is released with a propellant gas.
B.5- Tablets (TB)
The active ingredient is solid and micronized cellulose plus a dispersant are added to it. They disperse in water (effervescent additive improves dispersion). They are safe to handle and dose; simple packaging and high cost.
B.6- Baits (B)
Toxic substances to which palatable or attractive substances are added and then pelletized. The active ingredient is mixed with food or attractive substances. They have a low concentration of active ingredient, ready to use, and compete with other foods. We can mention baits for ants, snails and slugs, and control of vertebrates and birds, rodenticides, etc. Attractants differ depending on the species to be controlled.
These can be: cereal grains, cassava starch, mandarin essence, blood meal, corn meal, orange peel, etc.
Importance of formulations when applying phytosanitary products
The formulated product is dispersed by spraying, fumigation, dusting or by manual distribution (granulated baits) in order to effectively fulfill its biological purpose (prevent, destroy or control pests). In formulations for dilution, the formulated product is diluted in an application vehicle (water or diesel) and then applied by spraying.
These conditions must also be maintained during storage and transport. Ready-to-use formulations, such as granulated baits or dusting powders, will be dispersed without application vehicles.
Presentation
It is the way in which the product is delivered to the user.
For liquid formulations, the most common are one-liter bottles and 5, 10 and 20-liter resistant plastic drums.
As for dry formulations, airtight bags or “sachets” of variable weight are normally used.
Sources:
- org/es/current/articles/I-do-read-the-labels-and-safety-sheets-of-phytosanitary products-or-phytosanitary products
- SENASA Argentina Applicators Manual
- INTA Efficient application of phytosanitary products
- FAO Manual on the preparation of pesticides
- INTA Pergamino Pesticide formulation Agr. Eng. Pedro Daniel LEIVA Nov 2013
- INTA Good Practices Guideline for the Management of Phytosanitary Products L. Brambilla Edited and collaborated by V Gómez Hermida MP Bogliani
- University of Comahue Argentina Formulations Prof.HU Gentle
