Noninsecticidal agrochemicals alter insect behavior

While the prospect of fewer mosquitoes buzzing around might be compelling, insects play a crucial role in maintaining our ecosystems and supporting agriculture. Widespread use of insecticides has been implicated in the decline of beneficial insect populations, but new research published in Science suggests that hundreds of noninsecticidal agricultural chemicals could be negatively affecting insect populations too (2024, DOI: 10.1126/science.ado0251).

Justin Crocker, senior author on the paper and an evolutionary and developmental biologist at the European Molecular Biology Laboratory (EMBL), led a research team to investigate how more than 1,000 agricultural chemicals affect insect behavior. The team exposed Drosophila melanogaster, the common fruit fly and a model organism for genetics, to insecticides, fungicides, herbicides, and other chemicals and looked for behavioral changes such as modified crawling, egg-laying, and developmental patterns. “The big push here for us was actually looking at the sublethal effects of these chemicals on behaviors,” Crocker says.

The results of this study were deeply surprising to Crocker, as more than half of the chemicals altered behavioral patterns, he says. “And when you heat these systems up just a few degrees, the effects would become more amplified.” Chemicals like dodine, a fungicide, and glyphosate, a common herbicide, stuck out to Crocker because they had notable effects on fly behavior. But fruit flies aren’t broadly representative of all insects, so the team also tested a subset of the chemicals in the study on mosquitoes and butterflies, validating the results.

Leslie Ries, a butterfly researcher and global-change biologist from Georgetown University who isn’t affiliated with the study, is impressed with the scale of the research and says that the data suggest “why you would see declines in the field, even if effects are not lethal to the individual insect.”

Crocker does see a silver lining to all this research. “Maybe the majority of compounds are changing behavior, but some seem fine,” he says, referring to the chemicals that didn’t alter insect behavior. That means further study could help inform which chemicals are insect safe for agricultural use. “I don’t want this to be all be doom and gloom,” he says.