Pesticide Formulation: Step-by-Step Guide

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Formulating pesticide preparations is a key step in achieving maximum efficacy, stability, and safety during application. Properly selected active ingredients, adjuvants, and carriers can significantly influence the final product quality, its shelf life, and economic efficiency. This article focuses on the practical aspects of formulation—from selecting suitable raw materials through laboratory testing to industrial mixing and quality control. The process requires not only expert knowledge of chemistry but also compliance with technical and legislative requirements, such as REACH or CLP/GHS regulations.

1. Selection and Characterization of the Active Ingredient

The first step in formulating a pesticide product is selecting a suitable active ingredient based on the target pest, crop, and application method. The active ingredient must meet requirements for biological activity, stability, and compatibility with other formulation components. It is important to verify its physico-chemical properties, such as solubility in water and organic solvents, melting point, vapour pressure, and stability at different pH levels. These parameters affect not only efficacy but also safety and product shelf life.

Before starting the formulation, it is necessary to study the active ingredient’s registration documentation, particularly data on toxicity, ecotoxicity, and environmental behaviour. According to REACH and CLP/GHS regulations, the substance must be properly classified and labelled. It is also essential to consider possible interactions with adjuvants, which may affect the penetration of the active ingredient into the plant or its distribution on the treated surface. Without this information, the next step—selecting the formulation type—cannot be undertaken.

2. Selecting the formulation type based on the application method

The formulation type significantly influences the efficacy, stability, and application properties of a pesticide product. The most common types include emulsifiable concentrates (EC), suspension concentrates (SC), water-dispersible granules (WG), or microencapsulated formulations (CS). The choice depends on the physico-chemical properties of the active ingredient, the target organism, and the technical possibilities of application. For example, emulsifiable concentrates are suitable for substances soluble in organic solvents, while suspension concentrates are used for insoluble solid substances.

When selecting a formulation, practical aspects must also be considered, such as ease of mixing with water, storage stability (resistance to sedimentation, crystallization, or phase separation), and compatibility with adjuvants. For example, in spray applications, the ability of the product to form a stable dispersion with minimal risk of nozzle clogging is crucial. For granulated formulations, mechanical strength and dissolution rate in water are important. The right choice of formulation type can significantly reduce application costs and enhance biological efficacy.

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3. Optimizing composition with adjuvants and auxiliary substances

Adjuvants and auxiliary substances play a key role in improving the application properties and efficacy of pesticide formulations. The most commonly used adjuvants include wetting agents (e.g., surfactants), which reduce the surface tension of droplets and enhance coverage of the treated surface. Other adjuvants used include penetration agents to increase the absorption of the active ingredient into plant tissues, adhesives for better adhesion to waxy leaf surfaces, or antifoaming agents to prevent foam formation during mixing.

When selecting adjuvants, it is essential to consider their compatibility with the active ingredient and other formulation components. For example, some surfactants may cause phase separation or reduce suspension stability. It is also important to test the effect of adjuvants in combination with water of varying hardness, as calcium and magnesium ions can affect the efficacy of wetting agents. Laboratory tests, such as determining the wetting angle or measuring surface tension, help optimize the composition for a specific application.

4. Stability and Efficacy Testing Prior to Registration

The final step before registering a pesticide formulation is comprehensive stability and biological efficacy testing. Stability is verified at various temperatures (e.g., 0 °C, 25 °C, and 54 °C) for a minimum of 2 years, monitoring changes in appearance, pH, viscosity, sedimentation, or degradation of the active ingredient. For suspension concentrates, a critical parameter is particle size, which should not exceed 5–10 micrometers to prevent nozzle clogging.

Biological efficacy is tested under controlled conditions on target organisms, both in the laboratory and in field trials. It is important to verify efficacy at different dosages and environmental conditions (temperature, humidity, UV radiation). Additionally, compatibility tests with other preparations that may be applied simultaneously must be conducted. The results of these tests are crucial for registration documentation and ensure that the product will be safe, stable, and effective throughout its shelf life.

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5. Consideration of physicochemical properties during mixing and homogenization

When formulating pesticide preparations, it is crucial to respect the physico-chemical properties of individual components to avoid undesirable interactions or loss of efficacy. For example, surfactants with a low HLB (hydrophilic-lipophilic balance) value below 10 mix better with oil phases, while surfactants with an HLB above 13 are more suitable for aqueous systems. When mixing, the order of component addition must be observed: active ingredients are dissolved first in the appropriate solvent (e.g., aromatic hydrocarbons for lipophilic substances), followed by the addition of emulsifiers and stabilisers. The mixing speed should be sufficient for homogenisation but not too high to prevent foaming or degradation of sensitive components – the optimal range is usually 300–600 revolutions per minute.

Temperature during mixing also plays a key role. Most adjuvants and surfactants are mixed at a temperature of 20–30 °C, but some waxes or polymeric thickeners require heating to 50–70 °C to achieve uniform dispersion. For suspension concentrates (SC), it is important to maintain a constant temperature during milling to prevent recrystallisation of the active ingredient. To monitor homogeneity, it is recommended to regularly take samples and measure viscosity (e.g., using a rotational viscometer) or particle size (laser diffraction). Any deviations can be corrected by adding thickeners (e.g., xanthan gum) or diluting with solvent.

6. Ensuring compatibility with application technology and protective equipment

The pesticide formulation must be compatible not only with the target pest but also with the application technology that farmers will use. For example, spray liquids for low-pressure sprayers (up to 3 bar) require low viscosity (1–10 mPa·s), while high-pressure systems (above 10 bar) can use more viscous mixtures (up to 50 mPa·s). For granular preparations (GR), mechanical strength is critical to prevent crumbling during handling or application. Standardised methods are used for testing, such as the abrasion resistance test (e.g., according to ISO 14780) or simulation of storage under various temperatures and humidity levels.

Another aspect is compatibility with protective equipment, such as filters in sprayers or materials of hoses and nozzles. Some solvents (e.g., N-methyl-2-pyrrolidone) or strong acids/bases may damage plastic or rubber components of the equipment. Therefore, it is recommended to perform compatibility tests with commonly used materials (PE, PP, PVC, EPDM) for 24–48 hours at a temperature of 40 °C. For water-dilutable concentrates (EC), it is necessary to verify whether phase separation occurs when diluted with hard water (Ca²⁺ and Mg²⁺ content above 300 ppm), which can be addressed by adding complexing agents (e.g., EDTA).

7. Documentation and Preparation of Materials for Registration Procedures

Before submitting an application for the registration of a pesticide product, it is necessary to compile comprehensive documentation demonstrating its safety, efficacy, and stability. The key document is the Product Technical Data Sheet, which must include the exact composition (including the weight percentages of individual components), physico-chemical properties (pH, density, viscosity, flash point), instructions for safe handling, and first aid measures. Additionally, results of accelerated aging stability tests (e.g., 6 months at 40 °C and 75% relative humidity) and real-time storage tests (12–24 months at 25 °C) must be provided.

For registration in the EU, it is crucial to comply with the requirements of Regulation (EC) No 1107/2009 and the CLP Regulation (GHS), which mandate the classification and labeling of the product according to its hazards. This includes determining the hazard class (e.g., acute toxicity, irritancy, ecotoxicity) and assigning appropriate pictograms, signal words ("Danger" or "Warning"), standardized hazard statements (H-phrases), and safety instructions (P-phrases). Furthermore, it is necessary to submit efficacy reports from field tests demonstrating the product's effectiveness against target pests at recommended dosages. These tests must be conducted at multiple locations with varying climatic conditions to ensure the representativeness of the results.

Need Help Selecting Raw Materials?

Every pesticide formulation requires an individual approach and precise selection of components. GCG Group provides detailed technical data sheets and safety data sheets (SDS) for all supplied raw materials and assists with optimizing formulations according to your specific requirements. Contact us – or browse our catalog of over 1,300 products right away.