UD Researchers Look to Honeybees’ Natural Behavior for Solutions to Improve Hive Health
August 9, 2012 | Noelle Swan
Across the nation, beekeepers, entomologists, and farmers have watched in horror as colony after colony of the country’s precious honeybees have died or just plain disappeared. While researchers all over the country have been scrambling to pinpoint the cause of the massive bee deaths, scientists at the University of Delaware have been wondering if the honeybees themselves might have a solution.
While no single culprit has been identified as the cause of colony collapse, a tiny mite, or Varroa destructor owns at least a share of the blame, says Debbie Delaney, UD assistant professor of entomology and wildlife. Varroa mites attach themselves onto bee larva, also known as the brood, and feed on their blood through the bees’ various stages of development. By the time the bees grow up to become drones, the mites have drained much of their protein, reduced their sperm levels, and left them unable to fly. Additionally, the varroa mite can carry viruses and pathogens into the hive.
Many beekeepers keep varroa mites in check by applying a miticide to the hive, a risky proposition considering mites and bees hail from the same phylum, or division of insects. “Anytime you target an arthropod on another arthropod, there is going to be some level of sublethal effect,” Delaney explains. Recent studies have shown that beeswax is remarkably absorbent. Chemicals applied directly to the hive as well as those picked up inadvertently by foraging bees remain in the wax for years. Delaney worries that as miticides, insecticides, and fungicides accumulate and interact with each other, the wax itself could become toxic to bees. She believes there is another way.
Following the Honeybees’ Lead
Delaney has set her sights on a honeybee behavior that frequently infuriates beekeepers. Honeybees manage population growth and overcrowding by dividing the hive in two and sending a swarm of half the colony away to start a new hive. In preparation for a swarm, bees create special queen cells, or pockets within the hive for new queens to grow. This original queen of the hive then gathers her growing army of drones into a buzzing cluster that moves across land as a superorganism in search of a new hive. Chances are that hive will not be conveniently located in the same bee yard.
Typically, beekeepers discourage their bees from swarming by providing large enough boxes to accommodate population growth, destroying queen cells at a key point in development, or preempting the swarm by relocating half of the bees, their queen, and their food to a new hive. Back in the original hive, over the next month, the candidates for queen that have been growing in those queen cells come of age and fight for the throne. During that time, no nectar is gathered and no new brood of baby bees is laid (bad for varroa mites).
Delaney believes that by imitating this process and intentionally splitting the hive, beekeepers can stay ahead of the varroa mites without applying chemicals. She has tried it in her backyard hives with success and is now conducting controlled trials at the UD research apiary in Newark, Del. She and Katy Evans, the UD graduate student heading the project, are closely monitoring the impact of both swarming and hive splitting on varroa mites at the apiary. Delaney expects that she and Evans will find substantially fewer varroa mites in the newly established hives. Only time will tell if the process of swarming and splitting will also impact the number of mites in the original hive.
In recent years, beekeepers have been exploring more natural hive management practices, says Bill Leitzinger, president and CEO of the Delaware Beekeepers Association. He says that he has been using a variety of natural tactics, including hive splitting, to keep varroa mites in check in his hives for the past ten years. “I’m trying to be proactive and not allow the varroa mite to get to a problem level rather than treating the hives that have a problem.” In addition to hive splitting, Leitzinger routinely gives his hives a powdered sugar bath. By sifting powdered sugar into the hives, he encourages the bees to groom themselves. In the process of cleaning the sugar off each other, they knock off many of the mites. He also encourages his queens to lay their brood in removable frames that he can freeze to kill off any mites living off the brood. He says that the combination of these methods has been so effective, that he has stopped testing for mites in his hives.
For Leitzinger, natural hive management is a labor of love. For commercial beekeepers, with pollination contracts from area farmers, the time investment involved in natural hive management is more cumbersome. Delaney admits that even if she is able to prove that hive splitting is effective, it would be impossible to employ on a commercial scale. Still, many of the nation’s honeybees live in the backyards of hobbyists like Leitzinger. She hopes that her research will encourage more small-scale beekeepers to address the dreaded varroa mites naturally.