Chemistry professor Matt Kiesewetter and entomology professor Steve Alm are putting their heads together to develop better ways to protect honeybees from varroa mites.
By Lauren Rebecca Thacker
When Matt Kiesewetter was promoted to associate professor of chemistry in 2018, he breathed a sigh of relief and thought it might be time to find himself a hobby that had nothing to do with his work. So, on a whim, he ordered bees.
“Why bees?” he offers, and quickly answers, “I have no damn clue. I can’t tell you why. But when I was growing up, I raised butterflies in the yard. Back then, in the country, you could grab milkweed from the side of the road and raise some monarchs. I guess that sparked my interest in insects. So, I got bees.”
Now, five years later, he’s got four hives in his backyard and more honey than he knows what to do with. And in that time, he realized that beekeeping didn’t give him the break from chemistry he was looking for, but instead gave him a new focus: controlling the honeybee’s enemy. Enter, the varroa mite.
Varroa mites, Kiesewetter explains, are the number one stressor of honeybee hives. If you’re a bee- and honey-lover, but not a beekeeper, you may be surprised by this. What about colony collapse disorder, the mysterious and widely reported phenomenon that causes worker bees to flee their hives, leaving their queen to die? Well, that’s certainly a problem, but it’s not as prevalent as it used to be. The Environmental Protection Agency reports that incidents of colony collapse disorder have dropped dramatically since the disorder’s height in 2008. If you’re a backyard beekeeper, varroa mites are probably your biggest headache.
Female mites enter and lay eggs in a honeybee brood cell—where the eggs, larvae, pupae, and adult bees develop. Mites develop alongside the growing bees, eventually attaching to a honeybee’s fat body, a type of insect tissue that is analogous to the liver in mammals. There are seven confirmed diseases that the mites bring to hives and at least a dozen more suspected—all determinantal, some fatal. The mites cannot exist without the honeybees. So, the problem of varroa mites presents a conundrum: Beekeepers, amateur or professional, must combat the mites to ensure their hives’ survival, but mites can only be treated within the hives.
Kiesewetter contended with varroa mites in his own hives using the standard methods: synthetic chemicals, like pyrethroid and organophosphate miticides, and naturally occurring chemicals, like formic and oxalic acids, and even powdered sugar. They work, but there are risks: Synthetic miticides can lead to the development of miticide resistance, while some natural miticides are less effective and difficult to administer. And, Kiesewetter explains, most pesticides on the market are broad spectrum, meaning that they can kill many different organisms. Which means that they can kill bees, too.
“These chemicals just happen to be a little less toxic to bees than mites,” says Kiesewetter. “But there are sublethal effects, and some people suspect that these pesticides are harming the hives. We don’t know. But my question is, can we design a pesticide that is essentially nontoxic for bees while hitting the target—the mites—that we want?”
As a graduate student at Stanford University, Kiesewetter was interested in polymer synthesis and renewable plastics. In particular, his research considers how materials, including plastics, can be more sustainable. He carried that interest through a postdoctoral fellowship at Massachusetts Institute of Technology and then to the University of Rhode Island, where he arrived in 2013.
Kiesewetter realized his experience in organic chemistry could help him develop new miticides that can evade resistance, in addition to plastic-based delivery systems that could make natural options safer and more effective. What if, for example, he could construct a hive using plastic that degrades to produce a mite-controlling agent? But, while he was a pro at chemistry, he was an amateur when it came to honeybees.
Steve Alm is no bee amateur. The professor of plant sciences and entomology is an expert in pollinators of all kinds, from the honeybee to the estimated 250 native bee species buzzing around Rhode Island. Kiesewetter heard through the grapevine that Alm had hives at URI’s East Farm.
The roughly 85-acre spread of East Farm is the place for URI students and faculty to experiment with flora and fauna. The location, about a mile southeast of the Kingston Campus, facilitates bobcat and coyote research; efforts to develop stronger breeds of rhododendrons, azaleas, and apples; and studies on Atlantic salmon. It’s also home to beehives and pollinator meadows.
“I’m picturing it right now,” Alm says, remembering his first meeting with Kiesewetter. “I was in Woodward Hall teaching a course on bees and pollination. Matt came in, and he had this idea for controlling varroa mites. He had the chemistry, and I had the bees.”
Thus, a collaboration began.
Kiesewetter says, “I found Steve by accident, and I couldn’t have found a better collaborator if I had tried. He has been so willing to do this work and is just great. And it’s been a lot of fun.”
Alm explains the risks inherent in the process of treating a hive with standard commercial products with formic or oxalic acids, both naturally occurring chemicals. “Products with formic acid say right on the package that they may kill your queen and up to 1,500 bees. So yeah, that’s very rough on a colony. And with oxalic acid, you need to wear a special respirator, so it’s noxious for beekeepers, as well. Sometimes the cure is almost as bad as the disease. We’re trying to find safer materials for the bees and the beekeepers.”
One particularly challenging aspect of studying varroa mites is their short lifecycle. Mite populations are at their peak in August, September, and October. Scientists want to study mites during this peak, but three months isn’t much time.
“My question is, can we design a pesticide that is essentially nontoxic for bees while hitting the target— the mites—that we want?”
Casey Johnson, M.S. ’22, a research associate, adds that while there are methods to rear varroa mites outside of a honeybee colony and their natural lifecycle, “It’s very work-intensive and not foolproof. With our methods, we can get them to live for 24 hours in the lab outside of a hive, but that’s it.”
And then there are the additional challenges of maintaining the hives and controlling the scale of experiments, things Kiesewetter had to adjust to when turning his attention to honeybees.
“You think about a hive being 50,000 bees and you’re like, ‘Oh gosh, this is great,’” he says. “But it’s only one hive. Fifty thousand bees are a data point of one. If you have five experimental hives and five control hives, you can see how things can get out of hand, real fast. Our initial tests are meant to figure out if we should scale up.”
Julia Vieira ’21, M.S. ’23, a student in Alm’s lab, tells us about a recent experiment designed to address these challenges, saying, “The idea was, could we get another species that is comparable to varroa, and has a similar mortality rate, that we could use for preliminary bioassays when we don’t have access to varroa populations?”
It turns out, the answer was yes. In 2022, Kiesewetter, Alm, Vieira, and Johnson, along with colleagues Elizabeth Varkonyi, M.S. ’22; Howard Ginsberg, scientist emeritus with the U.S. Geological Survey’s Eastern Ecological Science Center; and Kassie Picard, Ph.D. ’23, published a paper demonstrating their findings.
The research, published in the Journal of Economic Entomology, tested four organic acids at a variety of concentrations on varroa mites and three insect species. The results showed that varroa had levels of mortality consistent with the other species, suggesting that other, more easily managed test subjects can be used when testing varroa mite treatments.
Kiesewetter is pleased with the experiment, which also tested methods of applying the various acids.
“These organic acid treatments are very popular,” he says, adding that he uses them in his own hives. The research gives insight into how they work and paves the way for more experimentation. “In the future, we’ll experiment with some synthetic pesticides that are less toxic to bees and more toxic for mites. We’re trying to scale up and see what kind of plastic-based delivery systems can have good effects.”
The beekeeping community must contend with varroa mites in order for hives to survive. And Johnson points out that varroa mites are a problem for honeybees now but says, “There are documented cases of pathogen spillover from managed honeybees to native bees. Beekeepers,” she explains, “have a responsibility to monitor and treat varroa to help mitigate the spread of diseases into our native wild bee populations.”
There are different perspectives on how best to treat the mites and ensure a healthy honeybee population. One approach is what Kiesewetter calls Darwinian beekeeping: using no controls, in order to develop a strain of bees with inherent mite resistance. But that’s a long game, and Kiesewetter isn’t sure it’s a realistic approach. Other beekeepers are interested in physical methods, like heating hives to a temperature that harms mites but not bees; and using powdered sugar to coat bees, then shaking them until the mites release their hold. But research, including a soon-to-be-published paper by Johnson, shows that powdered sugar is effective for monitoring mite populations, but not for eradicating them. And studies on heat treatments are in the early stages. So that leaves chemicals, synthetic and natural.
“It might sound like, ‘Oh, of course the chemist wants to use chemicals,’ but it’s not really like that,” Kiesewetter says. “Pesticides work. They have sustained the beekeeping world for decades. But if people stop using them or if mites develop resistance, that would be catastrophic for the beekeeping community.”
As a chemist and a beekeeper, Kiesewetter wants to keep his hives healthy, and yours, too. Even if beekeeping didn’t end up being the nonscientific hobby he first imagined, it has meant a lot to him over the years. It gave him a new direction and exciting collaborations across URI. And don’t forget the honey. So much honey.
“Last year, I got about 200 pounds,” he says, laughing. “In the summer, people are probably tired of seeing me show up because I’m just carrying jars of honey around. I try to give it all away.”
These Bees Are Locals
Since the emergence of colony collapse disorder in 2006, interest in backyard beekeeping has grown among people looking to support global bee health and local ecosystems. While keeping bees is a worthwhile hobby, there are other, less labor-intensive ways to support pollinators.
Honeybees are not native to North America—they were brought over by honey-craving colonists in 1622. Before that, plants were pollinated by native species, including the much-loved bumblebee and the much-maligned wasp, a group of insects that Johnson calls “incredibly misunderstood” and that she lauds for their pollinating and pest-control abilities.
We need all pollinators—not just honeybees—for a healthy world. Of all the crops grown worldwide, about 75% require pollination. Without pollinators, we wouldn’t have pumpkins, raspberries, tomatoes, onions, or many, many others.
Kiesewetter and Alm recommend that Rhode Islanders looking to support native pollinators fill their gardens and flowerpots with native plants. Consider blueberries, bee balm, goldenrod, beardtongue, native milkweeds, hyssop, and asters. To convert your turf lawn into a bee lawn, incorporate clovers (especially medium red clover), selfheal, or creeping thyme.
If those aren’t your style, don’t worry. You can still nourish your local pollinators.
“A very simple equation is: more flowers equals more bees,” Alm says.
For more information on ongoing research and pollinator gardens, visit the Bee Lab at uri.edu/beelab.