Insects retain more heavy pesticides, and for long than previously thought

Insects appear to hold on to much heavier crop protection agents, and for longer than was previously thought. German scientists found an average of 16 pesticides per area on flying insects from 21 nature reserves that were studied. On insects from one location, they even found a mix of 27 toxins, writes Jean-Pierre Geelen in the Volkskrant in response to a scientific publication.

It was already known that individual pesticides can have an effect on the insect population. In their article in Scientific Reports, the German researchers point out the dangers of a mix of several crop protection agents, called 'toxins' in the article. Until now, residues of poisons in agriculture and horticulture were mainly determined on the basis of plant remains and soil samples. The research team from the University of Koblenz-Landau caught flying insects in 21 protected nature areas - comparable to the Dutch Natura 2000 areas - with so-called Malaise traps.

This is the same method with which German researchers in 2017 came to the shocking conclusion that the total biomass of flying insects in German nature reserves had decreased by more than 75 per cent since 1989. The new study seems to underline the main reason for this.

The captured animals were preserved in ethanol, after which not the insects, but the ethanol was examined for toxins. In total, the researchers found traces of 47 different types of pesticides.

Remarkably, the researchers found the substance thiacloprid in sixteen areas. This is a so-called neonicotinoid, which is so harmful that the EU has now banned it. Based on their research, the scientists say there are gaps in the EU approval process: pesticides are usually tested for their individual active ingredients. This leaves unexplained the effect that the accumulation of so many different pesticides as currently measured has on insects.

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