Paris (AFP)
Traces of three neonicotinoids, insecticides considered harmful to bees, are present in an amount dangerous to insects in plots, despite a moratorium in effect since 2013, according to a study published Wednesday.
The EU had imposed this partial moratorium, banning the use of three of these substances (clothianidin, thiamethoxam and imidacloprid) on crops that attract bees, such as maize, rapeseed and sunflower, while the populations of these insects pollinators were decimated.
France has since banned in September 2018 five neonicotinoids (the three already mentioned plus thiacloprid and acetamiprid) for any phytosanitary use.
But according to a study by researchers from the CNRS, INRA and the Institute of the Bee (Istap), published in the journal Science of the total environment residues of the three products subject to the moratorium are found in samples taken from 2014 to 2018 on samples of rapeseed nectar.
Of 536 samples collected from 291 CNRS plots in Deux-Sèvres, imidacloprid was detected every year, in total in 43% of the samples, with significant variations from one year to the next (90% of plots tested positive in 2016, against only 5% in 2015).
Researchers believe that residue levels increase especially with precipitation, "but do not seem directly related to the spatial or temporal proximity of potentially treated crops."
The mortality estimates from the surveys "suggest a significant risk for foraging bees", with between 2014 and 2016 "about 50% of the foragers likely to die of imidacloprid in 12% of the plots studied".
The authors therefore consider that their results "support the idea that imidacloprid residues persist and diffuse into the environment" and support the extension of the ban to "all outdoor crops".
© 2019 AFP