Vanishing honeybee colonies continue to trouble Virginia

More than 2,000 beekeepers in Virginia face the possibility of losing entire bee colonies to the Colony Collapse Disorder, but through Virginia Cooperative Extension, they have access to the latest research-based information about the problem.

The term Colony Collapse Disorder, which was coined by scientists in 2007, is being used to describe the sudden disappearance of adult bee populations, an unexplained phenomenon that has plagued honeybee colonies around the world.

'The disorder is characterised by an absence of adult bees in colonies with few, if any, dead bees in the hive or in the front of the hive,' said Rick Fell, Extension bee specialist and professor of entomology in Virginia Tech's College of Agriculture and Life Sciences. 'We frequently see the presence of capped brood in the colony along with food reserves such as honey or pollen. Strangely, the colonies have not been robbed, and pests such as wax moths have not attacked the hives. Some colonies have small clusters of remaining bees with a laying queen, but the bees do not respond to simulative feeding.'

According to Fell, bee losses are not uncommon. Before Colony Collapse Disorder entered the scene, an average of 31 percent of Virginia's bee colonies would die because of winter loss, usually from starvation, lack of a sufficient number of winter bees, poor bee health, disease, and mite parasites. But, last year more than 50 percent of bee colonies disappeared, an increase attributed to the disorder.

'Most colony losses are from factors other than [Colony Collapse Disorder], but [it] continues to be a problem that we do not understand,' Fell said.

Researchers have not pinpointed a single cause for the disorder and instead point to a variety of contributing factors, most of which are related to colony health. Varroa mites, for example, are a major problem, both as a parasite and as an organism known to transmit disease. Beekeepers have used miticides to control the mites, but recent evidence suggests that the miticides may also cause problems to colony health. Lisa Burley, virology lab manager for the Fralin Biotechnology Centre and one of Fell's graduate students, has shown that miticides can reduce sperm production and viability in male honeybees.

'What we have found is that when we use miticides, we might not only be controlling the mites - we might also be causing significant reproductive problems in our bee populations,' said Fell. He added that sperm viability is extremely important because honeybee queens only mate once during their lifetimes and store sperm for later use during egg-laying. Decreased sperm viability can increase queen failure and colony problems.

Miticides are not the only suspects, however. After the Greene Infectious Disease Laboratory at Columbia University conducted genetic sequencing of tissue samples from bees in Colony Collapse Disorder-affected colonies last year, researchers discovered a new microorganism now known as the Israel Acute Paralysis Virus, a pathogen that beekeepers may have imported from outside the United States.

'In the past few months, it has been found that the Israel Acute Paralysis Virus plays a bigger role in [Colony Collapse Disorder] than we originally thought,' Fell said. 'Although the virus is not the definitive cause for collapsing colonies, it does add to colony stress and possibly weakens the honeybee immune system.'

Other possible factors contributing to the disorder include the Nosema ceranae pathogen recently discovered in U.S. bee populations, chemical residues and contamination, parasite loads in bees and brood, nutritional fitness of adult bees, stress levels, and lack of genetic diversity. Also, though once suggested as a possible cause, the use of genetically modified crops is not considered a likely factor because European countries that use few genetically modified crops are experiencing similar colony losses.

Each year, Virginia honeybees produce more than one million pounds of honey and farmers rent more than 12,000 Virginia honeybee hives for crop pollination. In addition to providing workshops for beekeepers and training for its local agents, Virginia Cooperative Extension is dealing with the disorder and its possible impact on the economy and agriculture by fine-tuning the pest management approaches for the control of mites and improving beekeeper education.

'Beekeeper colonies can be saved with aggressive management practices such as reducing miticide use in colonies, more actively managing colonies in the fall and early spring, and replacing the queen frequently, especially with hygienic or mite-resistant stock,' Fell said.