2024-10-24 18:38:00
For about thirty years insects have been disappearing amid general indifference. Too often perceived as undesirable, these small creatures do not attract the same interest as mammals and are rarely the subject of conservation action. Therefore, in regions dominated by human activities, several scientific studies estimate that at least 70-80% of insects have disappeared in recent decades.
New work, published Thursday 24 October in the magazine Sciencesuggest that the effect of agrochemicals on this decline may be greater than expected. This study conducted by researchers at the European Molecular Biology Laboratory (EMBL) demonstrated that some pesticides, initially perceived as harmless, could actually hinder the development of insects.
To reach these conclusions, they tested 1,024 agricultural chemicals on Drosophila flies and their larvae. They monitored their development, behavior and long-term survival throughout their life cycle. As a result, 57% of the chemicals tested changed the behavior of insects.
“We found that for more than half of the products, exposure of the larvae even to ecologically relevant doses, i.e. very low, caused alterations in the physiological processes of the insects and had sublethal effects”explains Lautaro Gandara, first author of the study.
“Aggravating factors”
Sub-lethal effects correspond to all undesirable effects that do not lead to death, such as in particular changes in deposition rate or mobility. EMBL researchers have thus demonstrated that some pesticides (a family of products that includes, in addition to insecticides, fungicides, herbicides or parasiticides) could have consequences on the movement of insects and therefore reduce their predation capacity.
Taking these sub-lethal aspects into account, some products initially perceived as harmless have turned out to be dangerous to insects. “Dodine, a guanidine-based fungicide, is an example, advances Justin Crocker, co-author of the study. It does not pose a direct problem for adult insects, but we have shown that it significantly modifies the behavior of the larvae. »
“This study stands out for its scope, observes Colette Bertrand, researcher at the National Institute of Agronomic Research, who did not participate in the work. Both for the impressive number of molecules that are tested, but also for the consideration of aggravating factors such as mixtures between molecules. This gives a lot of solidity to this work. » This unprecedented study could change estimates of the toxicity of some pesticides. “Classical approaches primarily test lethality, continues the researcher. But in recent years there has been widespread awareness of the need to take into account the sublethal effects that determine the survival capacity of insects. »
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