Blowing Bubbles to Pollinate Flowers

Researchers in Japan have developed a soap bubble-based pollination method that is as effective as doing it by hand.

As wild insect populations decline and commercial honeybee colonies suffer maladies, farmers are seeking new ways to pollinate their crops. Some hire alternative insects, like blue orchard bees. Others drive huge pollen-spraying rigs, or daub each flower by hand with a paintbrush.

In the future, some may blow bubbles. In a study published Wednesday in iScience, researchers describe a type of soap bubble which, when laced with pollen, can propagate fruit as well as any of these other methods, save perhaps for bees themselves.

Eijiro Miyako, an associate professor in the School of Materials Science at the Japan Advanced Institute of Science and Technology, has spent years looking for a better artificial pollination method — especially one that could replace hand pollination, which he said farmers have told him is “really hard work and annoying.”

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In 2017, he and some colleagues built a new tool: a tiny drone lined with horsehair coated in a special gel. But the machine was clumsy and difficult to control: “It sometimes broke the flowers,” Dr. Miyako said.

More recently, during a day in the park with his son, it occurred to Dr. Miyako that soap bubbles are much gentler. They also have a large surface area, are easily dispersed, and don’t cost very much. He and a postdoctoral researcher, Xi Yang, headed to the lab to build a better bubble.

The first task was mixing the right soap. (As any enterprising former child knows, you can make bubbles out of a lot of different kinds.)

It was a balancing act: too little soap, and you can’t make very many bubbles at once. But too much, or the wrong kind, and the soap interferes with the pollen. The sweet spot was a 0.4 percent concentration of a surfactant called lauramidopropyl betaine, common in baby shampoo.

The researchers settled on a pollen concentration that worked out to about 2,000 grains per bubble. They also juiced the solution with substances previously shown to enhance aspects of pollen germination — and a polymer that strengthened the bubbles.

They took their superbubbles to a pear orchard, and blew them at each of 50 pear flowers. Ninety-five percent of the flowers later bore fruit. This was the same success rate as hand-pollinated pears but required less time and effort, and much less pollen — about 1/30,000th the amount, Dr. Miyako said.

The bubble-based approach “does appear to have potential,” said Dave Goulson, a biology professor at the University of Sussex in England and an expert in pollination.

But, he added, there are still many things bees can do that bubbles can’t, like collecting pollen in the first place, which is half the job. Dr. Goulson is also concerned that if farmers no longer rely on insects, they might start using more pesticides.Can You Pick the Bees Out of This Insect Lineup? How can we save the pollinators if we don’t even recognize them?

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This harms wild pollinators, which are responsible for keeping alive the vast majority of the world’s non-crop plants. (They help crops a lot, too. In the pear field experiment, 58 percent of the flowers in the supposedly untouched control group also produced fruits, “probably because of the influence of naturally pollinating insects,” the authors wrote.)

“It concerns me that our response to the pollination crisis is to find ways to do without pollinators, rather than investing our efforts in looking after our environment better,” Dr. Goulson said.

Lila Westreich, a doctoral candidate in pollinator ecology at the University of Washington, fears that the bubble solution itself could harm local insects, as well as the bacteria that naturally occurs on flowers, which “plays an important role in the microbiome and health of native bees,” she said. But she thinks bubble pollination could be a good alternative to trucking in nonnative pollinators.

Dr. Miyako is formulating an organic superbubble with a lower environmental impact: “You can drink it, actually,” he said.

He is also working on combining his two inventions by mounting a bubble gun on an autonomous drone and using it to pollinate whole fields. When testing it, he added more stabilizer to the bubbles, which led to another mystical sight: Some of the bubbles floated, unpopped, for five hours.

Overall, the method “sounds like a childhood fantasy,” he said. “But it’s fully effective.”

By Cara Giaimo

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