Fertilizers may change the way flowers 'look' to bees and discourage them from pollinating, a study suggests.
Flowers attract bees using small electric fields that bees can learn to recognize. The study, published in the peer-reviewed journal PNAS Nexus on Wednesday, found that the fertilizers change these electric fields and bees seem to find these changes very weird.
Flowers lure bees with electric charges
In the study, scientists investigated whether the fertilizers affected the color, smell, or electric charge of the flower for bumblebees, a docile species of bees that are easy to use in experiments.
There are a number of cues that bees use to decide which flower to land on. Like us, they are attracted by certain smells and colors, but bees rely on an extra feature: the electric field of a flower.
As bees fly through the air, their bodies become positively charged. When they came across negatively-charged flowers, their small bodies sense the flower's electric field like a magnet.
When they pollinate, the bees change the flowers' electric field. The next bees that come along will be able to tell from the electric field that these flowers are likely tapped out, and will skip them entirely.
Fertilizers change the electric field
The study found that spraying synthetic fertilizers onto a field didn't change the color or smell of the flower.
But it did affect "magnitude and dynamics" of the electric field – essentially the way the flower's electric fields would look to the bees, Ellard Hunting, a study author and biophysicist from the University of Bristol, told Insider.
"If you imagine that in terms of vision, it's like that light is too bright and it's blinding them," Ellard Hunting, a study author and biophysicist from the University of Bristol, told Insider.
Bees aren't only attracted to the negative charge of the flower – they can also learn to read specific characteristics of the electric fields, a 2013 study from the same group showed.
That study found that bees could be trained to recognize artificial electric fields with different properties to find a sugary treat.
To test whether the sprayed flower's electric field was putting off the bees, the scientists artificially charged flowers to mimic these electric fields. They found the bumblebees were more likely to avoid these flowers.
This is likely to have a knock-on effect because bees can learn from experience, Hunter said.
"If you spray a field and bees explore a field and it seems to them like: 'okay, this is not right,' then they will not go there anymore and they will communicate that with each other," Hunting said.
Bees are crucial pollinators
Fertilizers aren't the only chemical that is likely to change the electric field, Hunter said. It's likely that other chemicals like pesticides, for instance, will have a similar effect, he said.
The fact that the fertilizers were sprayed on is also an important factor, he said. If they had been added to the soil, they would have interacted with the flowers in a completely different way.
But there's still a lot to understand about how chemicals change how bees spot flowers and that information is crucial.
Bees pollinate about a third of the world's crops. And two-thirds of fruits and seeds crops rely on pollinators, including bees, for sustained production, per the United Nations' Food and Agriculture administration.
Without bees, humans would have to abandon some of our most nutritious fruits and vegetables, including berries, apples, almonds, cucumbers, and peppers, Insider previously reported.
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