March 4, 2013
Bizarre Bee Disease Decimates Colonies
Brett Smith for redOrbit.com - Your Universe Online
As the mysterious plunge in bee populations continues, researchers are scrambling to understand the cause for the widespread decimation.
Study co-author David Tarpy, an associate professor of entomology at North Carolina State University, said IBDS was difficult to identify at first.
“Historically, we´ve seen symptoms similar to IBDS associated with viruses spread by large-scale infestations of parasitic mites,” he said. “But now we´re seeing these symptoms — a high percentage of larvae deaths — in colonies that have relatively few of these mites. That suggests that IBDS is present even in colonies with low mite loads, which is not what we expected.”
In the study, the researchers from NC State, the University of Maryland and Penn State evaluated 80 commercial colonies of eastern US honey bees over the course of 10 months — the equivalent of a full working “season” for the colonies.
The initial purpose of the study was to track shifts in colony health and identify any factors that may have contributed to colony death. In all, some 56 percent of colonies studied experienced colony collapse, many of which were attributed to IBDS.
“We found that colonies affected by IBDS had a risk factor of 3.2,” said co-author Dennis vanEnglesdorp of the University of Maryland, meaning that colonies with IBDS were 3.2 times more likely to die than the other colonies in the study.
The team also found that the occurrence of a so-called “queen event” also played a big role in colony death. A queen event occurs when a colony perceives that something is wrong with its only queen. When this happens, the workers eliminate that queen by “balling” her: meaning they will cluster around her body — allowing their collective body heat to kill her. Workers also use this technique to remove invading wasps or a foreign queen.
After the queen is dead, a protein-rich secretion called royal jelly is released from“¯glands“¯on the heads of young worker bees. The jelly supports the future queen´s larval body. Many bee keepers find that the new queen is often less prolific.
This entire queen event process is not always a smooth or successful transition. The research team found that the queen event had a risk factor of 3.1.
According to Tarpy, his team´s study is one of the most comprehensive to date in uncovering the root causes of colony collapse.
“This is the first time anyone has done an epidemiological study to repeatedly evaluate the health of the same commercial honey bee colonies over the course of a season,” Tarpy said. “It shows that IBDS is a significant problem that we don´t understand very well. It also highlights that we need to learn more about what causes colonies to reject their queens. These are areas we are actively researching. Hopefully, this will give us insights into other health problems, including colony collapse disorder.”
In their report, the authors suggested that future studies should focus on identifying the root causes for both IBDS and queen events.