In 2006, beekeepers around the world began noticing extraordinarily high losses of their honeybees. Bees were disappearing from hives en masse, leaving behind untended queens and their brood fated to die without worker bees to care for them. Beekeepers reported alarming losses of 30 to 90 percent.
The potential loss of honey as a crop was trivial compared to the possible loss of honeybees as pollinators, because 35 percent of the global food supply depends on pollinators to reproduce crops. In fact, the majority of modern beekeepers make a livelihood by renting bees to farmers for pollination, rather than raising bees for honey production. In the US, beekeepers truck their hives from crop to crop, starting with the almond orchards in California in late winter, then to the apple orchards in Eastern Washington in early spring, followed by the berry fields in Western Washington in late spring, before heading east to North Dakota to pollinate seed oil crops like canola and sunflower each summer.
Due to concerns about an environmental and humanitarian catastrophe, the phenomenon of honeybee colony collapse disorder was immediately and intensively studied. But no single contributing factor could be identified for the loss of 30 percent of the bee population each winter between 2006-2013. Loss of pasture, pesticide use, and other environmental stressors were thought to be contributing factors to colony collapse disorder. But beekeepers and researchers both agreed that one culprit in particular could be implicated: Varroa destructor.
The Varroa mite is a parasite that attaches itself to the body of a honeybee and feeds on its fat stores, weakening the bee so that it can’t fend off sickness. These mites also transfer diseases to bees, much like mosquitoes to humans. Without intervention, a bee colony infested with Varroa mites will completely collapse within a couple of years.
Bee colonies are, by nature, extraordinarily self-reliant superorganisms, and historically beekeepers had to do little more than prevent swarms and harvest honey in the fall. But the modern beekeeper must be very hands-on. Supplemental feeding of bees is needed to offset forage loss; hives must be winterized to survive winters that are colder and harsher; intentional hive splitting is needed to offset the now-normalized annual bee losses; and all hives must be treated for Varroa mites.
Like most pests, Varroa mites are controlled with chemical pesticides, in this case formic acid, oxalic acid, or a dozen other products. But as happens with any pesticide and its target, the mites build up resistance over time. Also, oxalic acid is toxic to bee larvae and dangerous to beekeepers, who must wear a respirator during application. And not least, consumers don’t want any of these chemicals in their honey, so application timing is very important to avoid contamination.
In a 2014 TEDx Talk, beekeeper John Miller described the scourge of the Varroa mite, which showed up in the US in the late 1980s. He said, “It’s really hard to kill a bug on a bug. But if we don’t, we’re going to lose our bees.”
Killing a bug on a bug is exactly what Francesco Merola plans to do—using lasers. Merola, a senior research fellow at the University of Auckland, and affiliated with the National Council of Research of Italy, is working on a device that can be placed at the entrance of a standard Langstroth beehive—the kind that looks like stacked boxes, most commonly used in commercial beekeeping operations—to eliminate mites before they enter the hive.
Merola isn’t the first researcher to work on a laser solution for pest management. A team in Japan is working on laser extermination of the Spodoptera litura moth. Their method combines AI-based flight prediction with a low-energy blue semiconductor laser beam targeted at the moth’s thorax or face. A team in France investigated laser-based extermination of aphids using a CO2 laser at a dosage harmless to host plants to irradiate one-day-old nymphs. Bees, in some ways, are easier: they don’t have to be targeted while in flight, nor is a broadcast treatment needed. Bees can simply be cleaned off at their front door, which they enter and exit multiple times per day, like hosing the mud off a dog before letting it into the house.
Instead of a garden hose, Merola’s device employs a “laser curtain” at the hive entrance to exterminate any mites trying to gain entry on the body of a honeybee. Advanced cameras monitor the hive entrance from both outside and inside. The imager on the outside determines whether mites are present and the laser curtain needs to be activated, whereas the inside imager determines whether the treatment has been effective at eradicating the mites. The whole device uses low-cost commercially available lasers and requires minimal power—it could be powered by a small solar cell and batteries.
Though Miller noted the difficulty of trying to kill a bug on a bug, Merola promises, “I haven’t killed a single bee so far.” The parameters of the laser mean that it delivers energy to the mite only and does not harm the bee.
How exactly Merola’s laser curtain works is not yet ready to be revealed. He will finalize his prototype and file for a patent later this year. With that done, he will be able to give more thought to commercialization and distribution. He hopes the device would be accessible to hobbyist and commercial beekeepers, because ultimately, he wants his research to make a tangible difference.
“Just in New Zealand, we have 30,000 colony deaths every year. That corresponds to 40 million dollars per year of revenue loss,” he says. “So globally, it’s so much more.”
But his motivations aren’t only economic. Merola, who is an organic food advocate, ultimately hopes to eliminate chemical pesticides in agriculture. “We shouldn’t use pesticides, not just in beehives,” he says. “There are too many chemicals in our world. If I can do something to help the environment as well… that would be great.”
Gwen Weerts is the Editor in Chief of Photonics Focus.
