With the help of two major grants from the National Science Foundation and the U.S. Department of Agriculture, a team in Montana State University’s College of Agriculture is furthering investigations of honeybee antiviral defense mechanisms with the goal of developing strategies to reduce honeybee colony deaths.
According to Michelle Flenniken, a professor in MSU’s Department of Plant Sciences and Plant Pathology and co-director of the university’s Pollinator Health Center, annual honeybee colony losses have averaged roughly 38% in the U.S. in the past 15 years. Despite these losses, beekeepers in the U.S. have maintained the number of bee colonies at roughly 2.5 million by dividing one colony to make two – a process called “splitting.”
While splitting helps to offset some of the impact of colony losses, Flenniken said the core problem of population decline is concerning. Many factors, including mite infestation, chemical exposure and pathogens – including viruses – contribute to those losses. In Montana, Flenniken said, beekeepers maintain over 250,000 honeybee colonies for honey production and crop pollination, both in and out of the state. Therefore, pollinator health is a crucial area of research for Montana and beyond.
Many of the viruses that affect honeybees cause observable symptoms for which they are named, such as deformed wing virus. However, scientists have learned that many virus-infected bees don’t exhibit symptoms, even when they harbor high viral loads. The impact of these asymptomatic infections on honeybee health is not clear, Flenniken said, and since viruses use the cellular and energetic resources of their host to replicate, she hypothesized that these overlooked infections may be more detrimental to honeybee health than is currently appreciated.
Supported by a $1.4 million grant from the NSF, Flenniken’s team of graduate and undergraduate student researchers is working to better understand the impact of virus infections on honeybee health. One study, by MSU doctoral student Naomi Kaku, is using flight performance as an indicator of overall bee health. Kaku uses flight mills, machines to which an individual bee is attached by a leash, measuring its flight distance and speed. The mills were made by associate professor Mark Jankauski in MSU’s Department of Mechanical and Industrial Engineering. Kaku’s research compares the flight distance, duration and speed of healthy bees to virus-infected bees.
So far, Kaku has found that bees infected with some viruses don’t fly as far or as fast as healthy bees. The reduced flight distance in infected bees may reduce the ability of forager bees to obtain nectar and pollen to feed their colony, extending the impacts of infection to a community of roughly 30,000 bees. In addition, Kaku and Flenniken are examining the role of the honeybee heat shock stress response in combatting viral infection.
“Flight generates heat, and we know that for at least some viruses, that heat shock response can reduce infections,” said Kaku, who is in her fifth year of doctoral studies in Flenniken’s lab.
In addition to investigating that hypothesis, Flenniken’s team is researching the potential of two supplements to boost honeybee immune strength, a project supported by a $680,000 grant from the USDA’s National Institute of Food and Agriculture.
Previous research in the Flenniken lab, as well as data from other labs, indicated that the honeybee immune system is activated by double-stranded RNA, which is produced by replicating viruses. Therefore, Flenniken’s team is experimenting with the use of synthetic dsRNA to stimulate the immune response, which in turn is expected to reduce virus infection levels.
Similarly, thyme oil and thymol, which are naturally produced by thyme plants, have been shown to activate honeybee immune responses. Therefore, members of the Flenniken lab, including doctoral student Hunter Charles in MSU’s Department of Microbiology and Cell Biology, are carrying out studies to determine the potential virus reducing efficacy of these compounds.
“Research in our lab is aimed at understanding how bees have evolved to fend off viruses on their own,” Flenniken said. “By better understanding that process, we hope that will lead to strategies that we could use to promote bee health.”
These strategies may include the development of feeding supplements, but for now Flenniken encourages bee enthusiasts to plant for pollinators; a list of pollinator-supporting plants can be found on MSU’s Pollinator Health Center’s resource page. In addition, she encourages members of the community to join her team at volunteer events held every summer at MSU’s Pollinator Garden, which is the home of MSU’s own honeybee colonies.
“We love having groups come, learn about bees and volunteer in the garden,” Flenniken said.
Opportunities to volunteer will be posted to the MSU Calendar. The team also welcomes donations that support undergraduate and graduate students working on honeybee research.