Like the opposite of good perfume, the chemicals humans use to protect crops can have unintended side effects that make certain bees less attractive to mates, potentially threatening the populations of these key pollinators.
The common insecticide meconazole is classified as relatively safe for bees because it specifically targets the fungus (taxonomically very different from bees) and exposure to it usually does not kill bees directly. Previous study found pesticides considered ‘low risk’ to bees still affect their development, eating behavior and learning; Fungicides such as meconazole have not been extensively studied but are considered unlikely to be harmful.
Samuel Boff, lead author of the new study inside Journal of Applied Ecology, and his colleagues wondered whether fenbuconazole — commonly used in wheat, apples and grapes — could have subtle effects on bees. “We did it [the study] Because this fungicide is used so often,” says Boff, an ecologist at the University of Würzburg in Germany. “We didn’t expect to see an effect. “
But in fact, there was a surprising effect: Benzbuconazole exposure altered two distinct components of the courtship ritual of male horned mason bees. The male will usually vibrate his chest seductively and rely on his scent to attract females. Exposure to the biocide reduces the frequency of vibrations (possibly by affecting muscle contractions), in addition to altering the males’ chemistry, changing their scent. Women seem to be bored by the changes. They prefer unexposed males. The study’s authors speculate that this female mating avoidance may reduce the number of hornwort and other species with similar mating systems.
The study “is important because it gives us a mechanism for decline,” said Susan Willis Chen, a bee researcher at the University of Guelph in Ontario who was not involved in the study. “It’s a great paper.” Boff hopes his team’s findings will prompt greater scrutiny of the use of fungicides and possibly lead to the emergence of alternative pest control methods.
This article was originally published as “Buzzkill” in Scientific American 327, 2, 15 (August 2022)