Common Mistakes and Good Practices When Preparing Pesticide Mixtures in Brazil


“…information should be sought in the literature about interactions between the active ingredients of the products that will be applied…”

Marcelo Hilário Figueira Garcia is the chemist responsible for R&D at Sell Agro, graduated in industrial chemistry from the Federal University of Rio de Janeiro, with a specialization in polymer chemistry from the State University of Rio de Janeiro and in soil science and plant nutrition from the Escola Superior de Agricultura “Luiz de Queiroz” (ESALQ/USP).

Sell Agro operates in the formulation and manufacturing of agricultural adjuvants, with headquarters in Rondonópolis, State of Mato Grosso.

Marcelo Hilário, chemist responsible for R&D at Sell Agro

AgriBrasilis – What does it mean to say that the spray solution “broke” in the field? What should be done in this situation?

Marcelo Hilário – This means that a reaction occurred between two or more ingredients in the solution, leading to the formation of a solid/gel. This causes operational problems, meaning that the mixture cannot be applied.

Before preparing the solution, a bottle test must be carried out to check if the reaction occurs. If so, it is necessary to use an agent that makes the ingredients compatible and prevents the reaction.

AgriBrasilis – What are the main mistakes made when preparing pesticide mixtures?

Marcelo Hilário – Common mistakes are: using too little water in the pre-mix, adding the mixture ingredients in the wrong sequence, and not enough stirring when preparing the solution.

AgriBrasilis – Which products are the most complex to mix? Is there an order for adding products?

Marcelo Hilário – The correct order in which products are added is based exactly on their complexity, in terms of their “difficulty in combining with water”, which means their solubilization . Thus, solids are initially added, then the concentrated suspensions, then emulsions, and finally solutions and macro and micronutrients.

AgriBrasilis – What precautions should be taken to avoid a loss of product efficiency? How important is the pH and factors such as water hardness?

Marcelo Hilário – Firstly, information should be sought about interactions between the active ingredients of the products that will be applied. These interactions can be synergistic or antagonistic. It may even be that no interaction occurs in relation to the efficiency of the products.

Mixing all the products, each with its own pH, generates a final mixture with a pH that must be at a value that encompasses the ideal pH range of at least the majority of the solution ingredients, to avoid the loss of efficiency by hydrolysis.

Water hardness is nothing more than the presence of calcium and magnesium in the water. High hardness values are a risk when applying acidic herbicides, such as glyphosate and 2,4-D, for example, which combine with these metals, ceasing to act as herbicides. To avoid this inconvenience, it is necessary to use adjuvants that contain chelating agents in their formulation, to sequester calcium and magnesium and prevent them from interacting with the herbicides.

AgriBrasilis – Why is bleach cleaning for spray tanks inappropriate? What is the correct method for cleaning?

Marcelo Hilário – Bleach is a product used to disinfect surfaces. Its chemical composition does not guarantee the correct cleaning of tanks and spraying equipment. The correct cleaning method is to use an alkaline detergent, which cleans dirt and neutralizes pesticide residues due to the increase in the pH of the washing water.

AgriBrasilis – What does the legislation say about mixing pesticide products in the spray tank?

Marcelo Hilário – Current legislation (IN40 – MAPA – 11/2018) authorizes the recommendation and application of a mixture of phytosanitary products in spray tanks, which must be prescribed in an agronomic reccomendation/ prescription by a qualified professional.



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