How Do Pesticide Metabolites Affect Plants
Corn, soybeans, and sunflowers are consistently profitable crops that help farmers generate income even in challenging wartime conditions. Therefore, some agricultural producers often return them to the same field, disregarding crop rotation.
This is reported by AgroReview
This, among other things, means the regular use of products from the same chemical group. This can lead to the accumulation of certain active substances and their metabolites in the soil due to violations of cultivation technology, specialists from the Ukravit Institute emphasize.
“Metabolites are derivatives and transformation products of pesticide active substances,” says the head of the service and technology department at Ukravit, Serhiy Salnikov. “They are components of residual amounts of pesticides and can persist in environmental objects for a long time. One active substance can have 5–10 main metabolites, not to mention secondary compounds. Thus, their effect on plants is difficult to predict.”
Unlike direct herbicide exposure, metabolites act somewhat differently, explains the specialist, causing chronic stress in crops. Firstly, they can bind to the same active sites of plant enzymes as the original active substance and block them. Secondly, they can disrupt transpiration in crops: the plant expends energy on detoxifying residues instead of forming a harvest. Under unfavorable weather and stressful conditions, the plant becomes severely suppressed or may even die. Thirdly, metabolites of different active substances can exhibit synergy and amplify damage to plants. For example, metabolites from corn herbicides and fungicides can enhance each other’s effects, creating an unpredictable outcome.
Today, farmers most often turn to the Ukravit Institute for the identification of mesotrione in the soil. This is because products based on it are widely used in corn cultivation.
“Mesotrione belongs to the triketone group and is a classic HPPD inhibitor,” explains Serhiy. “According to scientific data from the EU, the half-life of mesotrione (DT50) in soil under field conditions is up to 44 days, while its DT90 (the period for the active substance to degrade by 90%) can be up to 80 days; in the plant, the half-life is recorded after the 5th day. After mesotrione is applied to the soil, the microbiota begins its transformation, breaking it down into a series of metabolites, the main product of which is MNBA (4-methylsulfonyl-2-nitrobenzoic acid). This is what poses a danger to subsequent crops. Unlike the parent molecule, MNBA is considered non-phytotoxic to most crops. It does not block the HPPD enzyme as effectively as mesotrione itself, but is significantly more stable in the soil – as noted in scientific sources, for over 120 days. If the degradation is not completed (due to drought or low pH), the next crop shows specific signs of damage, even after more than a year.”
In light of this, specialists from the Ukravit Institute recommend adhering to crop rotation, avoiding violations of cultivation technologies, and controlling the presence of hazardous residues in the soil through laboratory methods. The institute’s researchers have been studying the impact of metabolites on soils for over 3 years and have extensive experience in identifying and addressing this issue.