5 Mistakes in Pesticide Mixing That Reduce

Photo: marcelo guarnieri / Unsplash

Pesticide formulations are the result of precise chemical balance, where even a seemingly minor error can mean the difference between effective application and wasted resources. Yet, in practice, we often encounter repeated mistakes—from incorrect order of ingredient addition to ignoring temperature limits or incompatible adjuvant combinations. These errors not only reduce the biological efficacy of the products but can also lead to the formation of hazardous byproducts, sprayer clogging, or even endanger the health of workers. In this article, we focus on five of the most common risky situations that recur in agrochemical production and application, and we show how to systematically prevent them.

1. Incorrect Adjuvant Compatibility: When Additives Do More Harm Than Good

When formulating pesticides, the selection of adjuvants plays a crucial role – poor choices, however, can dramatically reduce the efficacy of the product or even cause phytotoxicity. Adjuvants such as surfactants, oils, or penetration agents improve the distribution and absorption of the active ingredient, but their mutual incompatibility can lead to chemical reactions, precipitation, or pH changes. For example, anionic surfactants may react with cationic substances to form insoluble complexes, which clog application equipment and reduce coverage of the target surface.

Always verify the compatibility of adjuvants with the active ingredient and among themselves according to technical data sheets before mixing. It is recommended to perform a small-scale compatibility test: mix the components in a ratio corresponding to the final formulation and observe changes such as cloudiness, sedimentation, or foam formation. Ideally, consult with the raw material supplier, who has experience with specific combinations and can recommend proven practices.

2. Temperature fluctuations during storage: How heat and frost destroy formulation stability

Pesticide formulations are sensitive to temperature extremes, which can disrupt their physical and chemical stability. High temperatures (above 30 °C) accelerate the degradation of active ingredients, particularly in emulsifiable concentrates (EC) or suspension concentrates (SC), where phase separation or crystallization may occur. Conversely, low temperatures (below 0 °C) can cause freezing of aqueous formulations, leading to irreversible damage to the structure and loss of homogeneity.

Store preparations in dry, ventilated areas at temperatures between 5–25 °C, away from direct sunlight and heat sources. For water-dilutable formulations (e.g., suspensions), it is critical to prevent freeze-thaw cycles—these processes disrupt particle dispersion and may cause irreversible sedimentation. Regularly monitor storage conditions and, if temperature damage is suspected, perform a homogeneity and efficacy test before use.

Photo: TECNIC Bioprocess Solutions / Unsplash

3. Incorrect dilution sequence: Why the order of adding components determines mixture quality

An apparently simple process of diluting pesticide concentrates can end in failure if the correct order of adding components is not followed. For example, directly mixing an emulsifiable concentrate with hard water without prior dilution can lead to the formation of clumps or an unstable emulsion. Similarly, adding an adjuvant to an already diluted solution instead of the concentrate reduces its effectiveness, as it does not integrate sufficiently into the system.

The basic rule is: first dilute the concentrate in a small amount of water (ideally soft or deionised), then gradually add adjuvants, and only finally top up with the remaining water. For suspension concentrates, continuous stirring during dilution is crucial to prevent sedimentation. Always follow the manufacturer’s instructions and use calibrated measuring containers – even a small deviation in the ratio can lead to a non-homogeneous mixture and uneven application.

4. Neglecting pH and Water Hardness: How the Aqueous Environment Affects Pesticide Efficacy

The quality of water used to dilute pesticides has a fundamental impact on the stability and efficacy of the final mixture. Hard water (with a high content of calcium and magnesium ions) can react with anionic surfactants or phosphates to form insoluble salts, which reduce the dispersion of the active substance. Conversely, excessively acidic or alkaline pH can accelerate the hydrolytic degradation of certain pesticides, particularly esters or carbamates.

Before dilution, measure the pH and water hardness using test kits. The optimal pH for most pesticide formulations ranges between 5.5–7.0. If the water is hard, use softening agents (e.g., chelating agents such as EDTA) or choose hard-water-resistant adjuvants. For sensitive active ingredients, consider using deionized water. Regular testing of the water environment is a simple but often overlooked step that can prevent efficacy losses of up to 30%.

Photo: Adrian Sulyok / Unsplash

Exceeding the recommended storage period: When expiration leads to loss of efficacy and safety risks

Every pesticide formulation has a defined shelf life during which it retains its declared properties. Exceeding this period is not merely an administrative issue—it can lead to chemical changes that reduce the active ingredient's efficacy or increase the risk of phase separation. For example, emulsifiable concentrates (EC) may lose homogeneity after expiration, resulting in uneven dispersion in the spray tank and consequently ineffective coverage of target areas. In the case of suspension concentrates (SC), sedimentation or clumping may occur, which can clog filters and spray nozzles.

Safety risks arise from the potential degradation of additives such as stabilizers or corrosion inhibitors, which may lead to undesirable reactions with packaging materials or the formation of toxic degradation products. For instance, some organophosphates decompose during long-term storage into compounds with higher volatility, increasing the risk of worker exposure. It is recommended to regularly inspect stored stocks, adhere to the FIFO (first in, first out) system, and conduct a small-scale stability test before using expired formulations. If in doubt, consult the manufacturer or analyze the active ingredient using standard laboratory methods.

Contamination from Residues of Previous Products: How a Minuscule Amount Can Ruin an Entire Batch

Residues of pesticides or cleaning agents in containers, mixing equipment, or application machinery pose a frequent but often underestimated problem. Even microscopic amounts of contaminants can trigger chemical reactions leading to precipitation, pH changes, or inactivation of the active ingredient. For example, residues of copper-based fungicides may react with certain glyphosate-based herbicides, resulting in the formation of insoluble complexes and loss of efficacy. Similarly, residues of strongly alkaline cleaning agents can destabilize emulsions or cause hydrolysis of sensitive active ingredients.

Preventing contamination requires thorough cleaning of all equipment between individual batches. It is recommended to use suitable cleaning agents that are compatible with subsequently processed formulations, followed by a thorough rinse of the system with clean water. For critical applications, it is advisable to perform a compatibility test on a small sample of the mixture before full-scale mixing. It is also important to separate storage areas and equipment for different types of pesticides, especially when dealing with preparations with different chemical bases (e.g., organophosphates vs. pyrethroids).

Inappropriate Choice of Packaging Material: How the Wrong Container Can Ruin a Quality Formulation

The choice of packaging material is not just a matter of logistics but also chemical stability. Some pesticide formulations react with the packaging material, leading to degradation of the active ingredient or contamination of the product. For example, organic solvents in emulsifiable concentrates can compromise low-density polyethylene (LDPE) plastic containers, resulting in the migration of plastic additives into the formulation or the leakage of volatile components. Metal containers, on the other hand, may corrode in the presence of acidic or chlorinated formulations, leading to rust contamination and deterioration of product quality.

When selecting packaging material, chemical compatibility with the formulation, mechanical resistance, and gas permeability must be considered. For most liquid pesticides, containers made of high-density polyethylene (HDPE) or specially treated metals with a protective coating are recommended. For solid formulations (granules, powders), barrier protection against moisture is crucial, which is why multilayer films with an aluminum layer are often used. It is also important to follow the manufacturer’s instructions regarding storage conditions, as even compatible packaging can fail under extreme temperatures or mechanical stress.

How to Avoid Mistakes in Your Formulation?

Every agrochemical raw material requires a specific approach – from proper storage to optimal mixing conditions. GCG Group provides detailed Safety Data Sheets (SDS) and technical specifications for every product supplied, helping to eliminate risks already at the planning stage. If you have any doubts about component compatibility or storage conditions, do not hesitate to contact our experts. Get in touch with us – or browse our catalogue of over 1,300 products right away.