Behavioral alteration in insects caused by pesticides

Over the past decade, numerous reports have highlighted alarming declines in insect biodiversity globally, likely driven by habitat loss due to agriculture and urbanization, the advance of global climate change, and the extensive use of pesticides.

Sublethal doses of pesticides (pesticide concentrations too low to kill) have emerged as a significant but understudied factor in this decline.

Previous research has shown how sublethal doses of agricultural chemicals can alter various aspects of insect biology, such as metabolism, development, reproduction, immunity and behavior. However, safety evaluations of these products typically focus on lethal doses, and systematic experimental studies on the subtle and chronic effects of sublethal doses in non-target species remain scarce.

In an attempt to mitigate this knowledge gap, a team led by Lautaro Gandara of the European Molecular Biology Laboratory in Heidelberg, Germany, developed a system that uses the fly Drosophila melanogaster (a well-established model for toxicological evaluations), to analyze the physiological, behavioral and fitness impacts of sublethal exposure to various agrochemical molecules.

Gandara and his colleagues used a chemical library of 1,024 different agrochemicals and found that 57% of these products (many without known insect-specific actions) significantly altered larval behavior.

In addition to behavioral changes, the study authors have identified widespread alterations in proteins with phosphate groups attached, indicating deeper physiological impacts.

Tests with combinations of chemicals at sublethal concentrations common in natural habitats also showed a reduction in the speed of development and reproductive capacity of D. melanogaster individuals, compromising their long-term survival.

Furthermore, the results have revealed that slightly elevated ambient temperatures amplify the toxicity of pesticides.

This raises fears that global warming will accentuate the problem.

Gandara and his colleagues also found that similar behavioral alterations occur in other species exposed to sublethal doses, including mosquitoes and butterflies, suggesting that the ecological repercussions are broader than might appear.

A pollinating insect, specifically a bumblebee, flying over a flower. (Photo: Mike Tome/USGS)

The study is titled “Pervasive sublethal effects of agrochemicals on insects at environmentally relevant concentrations.” And it has been published in the academic journal Science. (Source: AAAS)