Alarming Long-Term Effects of Insecticides on Ants

Researchers from the Institute of Bee Health at the University of Bern have shown in a study that even low residues of neonicotinoid insecticides cause lasting damage to ants. The researchers question the current use of chemical pesticides and call for more sustainable solutions in agriculture.

«In recent years, a worldwide decline in the quantity and diversity of insects has been observed. Ants are also affected — species that play an irreplaceable role in our ecosystems and help to maintain our natural biodiversity», says Daniel Schläppi of the Institute of Bee Health at the University of Bern, lead author of the current study.

One cause of the global loss of insects that researchers identify is pesticides. «Due to their chemical properties, neonicotinoid insecticides contaminate soils and groundwater and can already be detected in areas where they have not even been used», explains co-author Gaétan Glauser of the University of Neuchâtel. Low quantities of neonicotinoids are not lethal, but the study documents serious long-term effects that had not previously been investigated.

The negative effects only become apparent in the second year of colony development, as data collected at the University of Bern in collaboration with Agroscope and the University of Neuchâtel show. According to the authors, this study underscores the importance of striving for sustainable agriculture in order to prevent irreparable damage to our environment. The study was published in the journal «Nature Communications Biology».

Concerning Long-Term Effects

The neonicotinoid insecticide thiamethoxam is used in agriculture to combat pests. As several studies have already demonstrated, these substances also harm beneficial insects, such as bees. "As we have now been able to show, ants are unfortunately also affected by these chemicals", says Schläppi. For the study, queen ants of the black garden ant (Lasius niger) were collected and observed in the laboratory over 64 weeks during colony founding.

At the start of the first overwintering period, colonies chronically exposed to a pesticide and colonies from the control group showed no differences in colony size. In the following year, however, it became apparent that the colonies in the pesticide group comprised significantly fewer workers. Since a large number of workers is a decisive factor in the success of an ant colony, the survival of these colonies is therefore at risk. "When we consider how important ants are to our ecosystems, it becomes clear that the use of neonicotinoids poses a threat to our environment", emphasises Schläppi.

A call for sustainable solutions

«Long-term effects of neonicotinoid insecticides on ants are alarming", says Prof. Dr. Peter Neumann from the Institute of Bee Health at the University of Bern. "Our study illustrates how long it can take for the effects of such low residues of agricultural chemicals, with potentially far-reaching consequences, to become visible."The authors therefore emphasise the importance of considering ants as model organisms and of incorporating long-term effects into future risk assessments. This, they argue, should help to ensure a more sustainable agriculture on a lasting basis.