New research sheds light on fertilizer’s impact on bees

A bumblebee feeding on a lavender blooms By RonnySchoene/Shutterstock

Want to create a paradise for bees in your garden? Experienced gardeners know to select plants that are attractive to pollinators, emphasizing flowers with enticing colours, shapes, and smells. But gardeners should also ensure they aren’t unwittingly turning bees away from their flower beds.  

New research from the University of Bristol shows that applying chemical sprays of fertilizers to plants can discourage bees from visiting flowers. The researchers also found that it’s not the appearance or smell of the chemical fertilizers that’s a turn-off for bees; instead it’s a change in the flower’s electric field that bees are not a fan of.

“It’s basically static electricity,” explains the study’s lead author Ellard Hunting, a research associate for the School of Biological Sciences, University of Bristol. Flowers are typically electrically charged, and slightly more negative than the ground, Hunting says. Bees tend to have a positive charge.

While a flower’s electrical field is not noticeable to humans, it’s a different story for bumblebees. The insects can detect the electrical field thanks to their small body size and fine, sensitive hairs. A flower’s electrical field can provide important information and cues to a visiting bumblebee. 

But a communication breakdown occurs when synthetic fertilizers get added to the mix. The researchers found that applying sprayed synthetic fertilizers altered the electric fields of flowers by causing physiological changes in the stressed out plants. Wild bumblebees were less likely to land on the affected flowers.

Hunting compares the altered electric field as sensory overload for bumblebees. “If you look into the sun, it’s too bright, it’s too blinding,” he says. “And I think that’s what’s happening with the bees. The elevation in the electric field and the dynamics are just too much information. They decide this is not nice, and they move on.”

A negative experience at a flower could lead to bigger consequences. “Bees really learn rather quickly,” says Hunting. “If bees arrive at a field, and it was treated with chemical fertilizers, the entire hive might actually decide not to go there anymore,” he adds.

To avoid confusing bumblebees and other pollinators, Hunting suggests choosing fertilizers made from natural sources like manure or seaweed. He also encourages gardeners to apply fertilizers in the evening when no pollinators are around.

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