Agrochemical Adjuvants: How to Choose the Right Type for Maximum Pesticide Efficacy

Photo: Dibakar Roy / Unsplash

Pesticide formulations often rely on adjuvants to enhance the properties of active ingredients—from improved wetting and adhesion to increased resistance to rain wash-off. Choosing the wrong type, however, can lead to uneven distribution, reduced efficacy, or even phytotoxicity. In this article, we focus on the key parameters to consider when selecting adjuvants and how to properly combine their properties with the requirements of specific crops and application techniques. Practical tips will help you optimize costs while maximizing plant protection results.

What Are Agrochemical Adjuvants and Why Are They Key to Pesticide Efficacy

Agrochemical adjuvants are special substances added to pesticide formulations or application mixtures to improve their physicochemical properties and thereby enhance their biological efficacy. Their role is to optimize processes such as wetting, penetration, adhesion, or evaporation of active ingredients. Without a properly selected adjuvant, pesticide wastage, reduced efficacy, or even damage to target crops may occur. Typical categories of adjuvants include wetting agents, penetration agents, adhesives, foaming agents, defoamers, pH stabilizers, or rainfastness enhancers.

The selection of the right type of adjuvant depends on several factors: the type of pesticide (herbicide, fungicide, insecticide), the target crop, application technology (sprayer, aerial application), and environmental conditions (temperature, humidity, wind). For example, systemic herbicides require penetration adjuvants that facilitate the entry of the active ingredient into plant tissues, while contact fungicides benefit more from wetting agents and adhesives that ensure even coverage of the leaf surface. The correct combination of adjuvants can increase pesticide efficacy by up to 30–50%, directly resulting in cost savings and reduced environmental impact.

Main types of adjuvants and their specific use in agricultural practice

Among the most commonly used adjuvants are wetting agents, which reduce the surface tension of spray droplets and improve their spread across the leaf surface. Typical representatives include surfactants based on alcohol ethoxylates or organosilicones, which are effective even at low concentrations (0.01–0.1% in the application mixture). To enhance the penetration of active ingredients, oil-based adjuvants such as methylated vegetable oils or mineral oils are used, which disrupt the leaf cuticle and facilitate the uptake of systemic pesticides. These adjuvants are particularly essential for herbicides with low mobility within the plant.

Another important group consists of adhesives that increase the spray's resistance to wash-off by rain. Polymers such as polyvinyl alcohol or acrylates, which form a protective film on the leaf surface, are frequently used here. Buffers are added to regulate the pH of the application mixture, ensuring the stability of active substances – for example, citric acid or sodium phosphate. Last but not least, defoamers are crucial as they prevent foam formation during mixing, ensuring uniform dosing. The selection of a specific adjuvant type should be based on pesticide manufacturer recommendations and verified field tests.

Photo: Dibakar Roy / Unsplash

How to choose the right adjuvant supplier: criteria for professional buyers

When selecting a supplier of agrochemical adjuvants, it is crucial to evaluate several aspects that influence the quality, reliability, and economic efficiency of the purchase. The first criterion is technical support and expert advice. A reputable supplier should provide detailed technical data sheets with information on composition, recommended dosage, compatibility with pesticides, and results of field tests. It is also important to verify whether the supplier has laboratory facilities for testing samples and developing custom formulations.

Another factor is compliance with legislative requirements, particularly REACH and CLP/GHS regulations. Adjuvants must be properly registered and labeled in accordance with current legislation, including safety data sheets and labels with hazard pictograms. A quality supplier also guarantees stable product quality, which can be verified through certificates according to applicable standards or long-term cooperation with reputable manufacturers. Price should not be the only deciding factor—low prices may indicate compromises in raw material quality or insufficient technical support. The ideal choice is a supplier with a flexible approach, allowing for sampling, testing, and adaptation of products to the specific needs of the customer.

Practical tips for testing and optimizing adjuvants in field conditions

Before deploying a new adjuvant in full-scale operations, it is essential to conduct field tests to verify its efficacy and compatibility with the pesticides used. The foundation is to select a representative area with homogeneous conditions (same variety, growth stage, soil type) and apply the tested mixtures under standard conditions. It is recommended to compare several adjuvant variants at the same dosage and monitor key parameters: leaf coverage, resistance to rain wash-off, penetration rate, and biological efficacy against the target pest or weed.

For objective evaluation, it is advisable to use visual assessment (e.g., measuring leaf coverage with fluorescent dyes) or quantitative methods, such as determining residues of the active substance in plant tissues. It is also important to monitor potential phytotoxic effects, which may manifest as yellowing, necrosis, or leaf deformations. Test results should be documented and compared with a control variant without the adjuvant. Based on this data, the dosage and combination of adjuvants can be optimized for specific conditions. For long-term monitoring of effectiveness, it is advisable to implement a monitoring system that allows evaluating the impact of adjuvants on yield and harvest quality.

Photo: Dibakar Roy / Unsplash

Influence of physicochemical properties of adjuvants on the penetration and distribution of pesticides

The effectiveness of pesticide application depends not only on the active ingredient but also on the adjuvant's ability to modify the physical properties of the spray liquid. A key role is played by surface tension, which adjuvants can reduce by 50–70% compared to pure water. This improves the wetting of the leaf surface, especially on waxy or hairy surfaces where droplets would otherwise bounce off or run off. For optimal penetration, viscosity is also important – too low leads to rapid evaporation, while too high impairs droplet dispersion. The ideal adjuvant should maintain viscosity in the range of 1.5–3 mPa·s at 20 °C, ensuring even coverage of the target area.

Another critical parameter is the cloud point, which determines the temperature stability of the adjuvant in the aqueous phase. For nonionic surfactants, commonly used in agrochemistry, the cloud point ranges between 40–70 °C. Exceeding this temperature leads to phase separation, reducing effectiveness and potentially clogging nozzles. For hot climatic conditions, adjuvants with a higher cloud point or special stabilizers are therefore recommended. It is also important to consider the pH of the spray liquid – some adjuvants (e.g., organosilicones) are sensitive to acidic environments and may degrade, reducing their ability to lower surface tension.

Compatibility of adjuvants with pesticide formulations and other agrochemicals

When selecting an adjuvant, it is essential to verify its compatibility not only with the pesticide but also with other components of the tank mix, such as fertilizers, microbial preparations, or additional adjuvants. Some combinations may lead to undesirable chemical reactions, such as precipitation, gel formation, or inactivation of the active ingredient. For example, anionic surfactants can react with cationic pesticides (e.g., certain glyphosate-based herbicides) and form insoluble complexes. Before mixing, it is advisable to perform a simple compatibility test in a small volume – if no cloudiness, sedimentation, or color change appears after 24 hours, the mixture can be considered stable.

Special attention must be paid to adjuvants containing oils or organic solvents, which can disrupt the structure of certain pesticide formulations, particularly suspension concentrates (SC) or emulsifiable concentrates (EC). These formulations risk droplet coalescence or phase separation, leading to loss of efficacy and uneven coverage. To minimize risks, it is recommended to follow the order of adding components to the tank: first water, then adjuvant, followed by pesticide, and finally other additives. This procedure ensures uniform dispersion and stability of the mixture throughout the application.

Ecological and Regulatory Aspects of Adjuvant Selection: Requirements for Modern Products

The selection of adjuvants can no longer be assessed solely in terms of efficacy—ecological and regulatory requirements now play a key role. In the European Union, all adjuvants must comply with the REACH regulation, which ensures safety for humans and the environment. This includes evaluating toxicity, biodegradability, and bioaccumulation potential. For example, adjuvants based on alkylphenol ethoxylates (APEO) are banned in the EU due to their persistence and endocrine-disrupting effects, despite their previously widespread use for excellent wetting properties. Modern alternatives, such as alcohol ethoxylates or fatty acid esters, offer comparable efficacy with a lower environmental impact.

Another important aspect is the impact of adjuvants on pesticide residues in soil and watercourses. Some adjuvants can increase pesticide mobility, leading to leaching into groundwater. To minimize this risk, adjuvants with low affinity for soil particles and high biodegradability are recommended. Certifications such as "Eco-label" or "Green Chemistry" can serve as indicators of environmental friendliness, although they are not mandatory for agrochemical adjuvants. When selecting a supplier, it is therefore advisable to request documentation confirming compliance with applicable environmental standards and transparent information on product composition.

Need help selecting adjuvants?

Every adjuvant supplied by GCG Group is accompanied by detailed technical and safety data sheets to help you assess its suitability for your application. Our experts will be happy to advise you on the selection and optimization of formulations according to the specific needs of your operation. Contact us – or browse our catalog of over 1,300 products right away.