In January 2007 huge numbers of honey bee colony deaths were being reported from the United States of America. Many commercial beekeeping businesses recorded up to 90% colony losses. Around 700,000 colonies died with no discernable pattern to the losses and leaving many surviving colonies too weak to be used either for pollination or honey production. It was also worrying that colony collapses were being reported in parts of Europe.
Many North American beekeepers were noticing that when the colonies died out there were no signs of dead bees either inside or in front of the hives. Losses of colonies in other countries from time to time in the past had showed similar signs becoming known as 'disappearing syndrome'. Even given different times and places the result was similar; the undiagnosed deaths of a large number of honey bee colonies. Dramatic population collapses occur only if the brood in the colony is not able to regenerate sufficiently to replace lost adults, or if all the adult bees die or depart within a few days.
It is still not clear what has caused such large scale colony deaths but the reasons are thought to be multi-factorial. Most of the more fanciful causes have been ruled out leaving the following areas to be investigated: chemical contamination or residues, known and unknown pathogens, the effects of parasite loads, nutritional fitness of adult bees, stress levels of adult bees and lack of genetic diversity.
There are already a range of virulent pathogens widely distributed worldwide with Varroa and associated viruses being particularly damaging. Some are recently identified in Apis mellifera such as Nosema ceranae. Israeli acute paralysis virus (IAPV) emerged as a strong suspect, being found to be present in over 80% of CCD affected colonies. However, whether IAPV is a causal agent of CCD or just an effective marker is still an open question. Most experts think a single cause is unlikely, currently considering a combination of factors to be more credible.
Of course, human factors must not be neglected. People influence honey bee colonies not only by their colony management, but also by changing local environmental conditions. Industrial agricultural monocultures require intense application of pesticides - and industrial agriculture uses industrial styles of beekeeping. Both factors can have serious implications for honey bee health.
Not all honey bee deaths can be attributed to a single factor. Bees are affected by disease, starvation, careless and even well-meaning bee management, and stress caused by physical threats such as bush fires, ants or queen failure. Experienced beekeepers learn to 'read' the clues left behind by the bees activity on the honeycomb, and in the colony, to help determine the cause of the loss. Only then can steps be taken to correct it.
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