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Fertilizers disrupt flower electrical fields and confuse bees

Bumblebees use several different cues to locate and identify suitable flowers from which to harvest pollen and nectar. They home in on flower scent and color, but are also sensitive to the electrical field around a flower. These tiny electric fields form from the imbalance of charge between the ground and the atmosphere, and are unique to each species, depending on the plant’s distance from the ground and the shape of the blooms. Flowers use electric fields as an additional means by which to advertise themselves to pollinators, but it seems that human activities can change these electrical cues and make it more difficult for pollinators to sense the presence of suitable flowers.

A study published in the journal PNAS Nexus has investigated the effects, on bumblebees, of spraying plants with fertilizers and pesticides. These chemical sprays cause alterations to the electric fields around flowers for up to 25 minutes after exposure, which is far longer than the fluctuations caused by natural phenomena, such as wind. The researchers found that bumblebees were less likely to land on flowers that had been sprayed with fertilizers or pesticides, and that this resulted in a reduction in bee feeding effort.

Dr. Ellard Hunting of Bristol’s School of Biological Sciences, and his team, noted that fertilizers did not affect the bees’ vision or sense of smell, and so they set out to mimic the electrical changes caused by fertilizers and pesticides in the field by manipulating flowers electrically. The results of their experiments showed that bumblebees were able to detect and discriminate against the small and dynamic electric field alterations that are caused by the chemicals.

“We know that chemicals are toxic, but we know little about how they affect the immediate interaction between plants and pollinators. Flowers have a range of cues that attract bees to promote feeding and pollination. For instance, bees use cues like flower odor and color, but they also use electric fields to identify plants,” explained Dr. Hunting. “A big issue is thus – agrochemical application can distort floral cues and modify behavior in pollinators like bees.”

And it is not only bumblebees and sprays of fertilizer or pesticide that are involved here: various other airborne particles such as nanoparticles, exhaust gasses, nano-plastics, and viral particles may have similar impacts, affecting a wide array of organisms that use the electric fields that are virtually everywhere in the natural environment.

“What makes this study important is that it’s the first known example of anthropogenic ‘noise’ interfering with a terrestrial animal’s electrical sense. It’s much like motorboat noise that hinders the ability of fish to detect their predators, or artificial light at night that confuses moths; the fertilizers are a source of noise to bees trying to detect floral electrical cues,” said study co-author Sam England.

“This widens our understanding of the multifaceted ways in which human activity is negatively impacting the natural world, which can seem quite depressing, but it will hopefully allow us to introduce or invent solutions to prevent the adverse effects that these chemicals may be having on bees.”

“The fact that fertilizers affect pollinator behavior by interfering with the way an organism perceives its physical environment offers a new perspective on how human-made chemicals disturb the natural environment,” concluded Dr. Hunting.

The project was funded by the European Research Council and the Swiss National Science Foundation.

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By Alison Bosman, Staff Writer

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