Assessment of the toxicity of pesticide mixtures on soil microorganisms

Within the ARISTO project, which aims to increase the understanding of the effect of pesticides on soil microbes, my project has a focus on pesticide mixtures.

My first goal is to identify and develop methods, procedures and tools to assess the toxicity of pesticide mixtures on soil microorganisms. My project will specifically address how the mixture of pesticides affect the abundance and diversity of soil microorganisms in interaction with free-living nematodes.

Evaluation of the effect of pesticides mixtures on soil microbial community and free-living nematodes.

Although soil organisms are exposed to complex mixtures of pesticide residues, most of the ecotoxicology studies towards soil microorganisms are still done testing one active substance by one, and not considering neither complex mixtures, nor interactions with macro-organisms. My work will be carried out under a lab-to-field experimental design with a two-tier scenario of exposure.

Fig. 1: The plots of the field experiment.
Fig. 2: Soil sampling during the field experiment.

I have performed lab experiments at INRAe with planted soil microcosms exposed to heavy rainfall simulation or heat stress and treated with a pesticide mix of 3 active ingredients: clopyralid, cypermethrin and pyraclostrobin. The objective of this study is, therefore, to evaluate the compounded effect of global change related environmental disturbances and pesticides on soil microbial community structure and functioning.

Fig. 3: Extraction of free-living nematodes from the soil.
Fig. 4: A picture taken during nematodes identification.

In the field experiment at ECT Oekotoxikologie I studied the impact of pesticides mixtures on the bacterial and fungal communities. I have also evaluated the effect of the mixture on nematode abundance. We selected 3 formulated products containing the active ingredient previously applied in the microcosms experiment. This experiment was performed in cooperation with two students from another Marie Curie project (PRORISK)

In a last lab experiment performed at ECT Oekotoxikologie, I tested the effect of a mixture of a bio-insecticide and an insecticide on soil nematodes community and on the microbial community. This experiment has a main focus on the nematodes community that I have taxonomically identified to the family level. This experiment was performed in cooperation with another ARISTO fellow, Alexandre Pedrinho.

Fig. 5: Alex and I preparing the nematodes samples during nematodes counting in our joint experiment.
Fig. 6: Presentation of the preliminary results of the experiment performed at INRAe at Setac 2022: “Evaluating the compounded effect of disturbances and pesticides on soil microbes”.