Bubble-blowing drones may one day aid artificial pollination

Drones that blow pollen-laden bubbles onto blossoms could someday help farmers pollinate their crops.

Rather than relying on bees and other pollinating insects — which are dwindling worldwide as a result of climate change (SN: 7/9/15), pesticide use (SN: 10/5/17) and other factors — farmers can spray or swab pollen onto crops themselves. But machine-blown plumes can waste many grains of pollen, and manually brushing pollen onto plants is labor-intensive.

Materials chemist Eijiro Miyako of the Japan Advanced Institute of Science and Technology in Nomi imagines outsourcing pollination to automatous drones that deliver pollen grains to individual flowers. His original idea involved a pollen-coated drone rubbing grains onto flowers, but that treatment damaged the blossoms (SN: 3/7/17). Then, while blowing bubbles with his son, Miyako realized that bubbles might be a gentler means of delivery. 

To that end, Miyako and his colleague Xi Yang, an environmental scientist also at JAIST, devised a pollen-containing solution that a drone toting a bubble gun could blow onto crops. To test the viability of their pollen-loaded bubbles, the researchers used this technique to pollinate by hand pear trees in an orchard. Those trees bore about as much fruit as trees pollinated using a traditional method of hand pollination, the researchers report online June 17 in iScience.

Among various commercially available bubble solutions, Miyako and Yang found that pollen grains remained most healthy and viable in one made with lauramidopropyl betaine — a chemical used in cosmetics and personal care products. Using that solution as their base, the researchers added pollen-protecting ingredients, like calcium and potassium, along with a polymer to make the bubbles sturdy enough to withstand winds generated by drone propellers.

The researchers blew pollen bubbles at flowers on three pear trees in an orchard. On average, 95 percent of the 50 pollinated blossoms on each tree formed fruits. That was comparable to another set of three similar trees pollinated by hand with a standard pollen brush. Only about 58 percent of flowers on three trees that relied on insects and wind to deliver pollen bore fruit.

To test the feasibility of applying this bubble treatment with flying robots, Miyako and Yang armed a drone with a bubble gun and blew pollen bubbles at fake lilies while flying by at two meters per second. More than 90 percent of the lilies were hit with bubbles, but many more bubbles missed the blooms. Making drone pollination practical would require flying robots that can recognize flowers and deftly target specific blossoms, the researchers say.

Not everyone is convinced that building robotic pollinators is a good idea. Simon Potts, a sustainable land management researcher at the University of Reading in England, sees this technology as a “piece of smart engineering being shoehorned to solve a problem which can be solved in … more effective and sustainable ways.”

In 2018, Potts and colleagues published a study in Science of the Total Environment, arguing that protecting natural pollinators is a better way to safeguard plant pollination than building robotic bees. Insects, the researchers noted, are more adept pollinators than any machine and don’t disrupt existing ecosystems. Miyako and Yang say their bubble solution was biocompatible, but Potts worries that dousing flowers in human-made substances could dissuade insects from visiting those trees.  

Roboticist Yu Gu of West Virginia University in Morgantown, who designs robotic pollinators but was not involved in the new work, says that building robotic bees and supporting insect populations are not mutually exclusive. “We’re not hoping to take over for bees, or any other natural pollinator,” he says. “What we’re trying to do is complement them.” Where there is a shortage of winged workers to pollinate crops, farmers could one day use robots “as a Plan B,” he says. No pun intended.