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Colony collapse disorder (Rev #2)

Colony collapse disorder

Idea

Colony collapse disorder (CCD), also known as honey bee depopulation syndrome (HBDS), refers to a dramatic increase in the occurrences of almost all the worker bees disappeareing from a colony, causing it to collapse. Although this has been recorded throughout history, there appears to have been a huge increase in occurrences in North America and Northern Europe over the last two decades. As bees are the dominant polinators for many natural plants and farmed crops, this issue may have wide import.

Details

The first scientific accounts of large scale colony collapse disorder date from the start of the 1990s, but the topic has been of high interest and impact to bee-keepers and environmental scientists from the 2005 onwards. This phenomenon is significant both because of the role of honey bees pollinating crops and the lack of understanding of its precise causes.

Roles of honey bees in pollination

The honey bee is the dominant means of pollination for many food crops and other plants in northern Europe, as well as being used to pollinate some “export crops” grown in other parts of the world.

Honey bees are not native to America, so that it is crops of European extraction that require bee pollination. In 2000, the total U.S. crop value that was wholly dependent on honey bee pollination was estimated to exceed $15 billion.[They are currently responsible for pollination of approximately one third of the United States crop species, including such species as almonds, peaches, soybeans, apples, pears, cherries, raspberries, blackberries, cranberries, watermelons, cantaloupes, cucumbers and strawberries, although there are claims that this role would be fully over by other pollinating insects in the absence of bees. This is uncertain on the scale of large commercial farming.]

Possible causes of CCD

There appears to be no conclusive single cause for CCD. Some of the suspected causes are:

  • Malnutrition This is hypothesised to be due to some aspect of diet,eg, farming monoculture, deliberate feeding with high-fructose corn syrup, micronutrient defeiciency, genetically modified crops.

  • Pathogens There are various suspect pathogens, eg, Varroa mites.

  • Pesticides There are various types of pesticides hypothesised to affect bee health.

  • Antibiotics and miticides Beekeepers, particularly commercial beekeepers, use various chemicals in an attempt to optimise their health, but some suspect unintended results.

  • Bee rentals and migratory beekeeping In America, there are virtually no feral bees and travelling bee hives cross the country, stopping temporarily when paid so that the bees will pollinate local crops. There is concern that this mobility leads to both stress on the bees and leads to much wider spread of infections and parasites amongst bee populations.

  • Climate change Environmental changes and stresses due to climate change may be a contributor.

  • Electromagnetic radiation There is hypothesised to be effects on bee memory, navigation or general health due to EM radiation, primarily from mobile phones and the cell towers. The primary evidence appears to be the correlation between mobile phone spread and CCD reports, with direct experiments appearing not to demonstrating effects.

Some recent work suggests which of these causes are most important,eg, Bromenshenk et al (see references below) found the combination of Nosema fungus and invertebrate iridescent virus, but these reports neither seem to agree globally and may have methodological or conflict of interest issues.

Questions

  1. What are the factors causing of CCD, and how do they interact to cause a full collapse? Are there important emergent phenomena causing this (that may have wider applicability)?

  2. Are there effective changes in human bee management that would improve the robustness of bee colonies?

References

  • Colony collapse disorder, Wikipedia.

  • Jerry J. Bromenshenk, Colin B. Henderson, Charles H. Wick, Michael F. Stanford, Alan W. Zulich, Rabih E. Jabbour, Samir V. Deshpande, Patrick E. McCubbin, Robert A. Seccomb, Phillip M. Welch, Trevor Williams, David R. Firth, Evan Skowronsk, Margaret M. Lehmann, Shan L. Bilimoria, Joanna Gress, Kevin W. Wanner, Robert A. Cramer Jr Iridovirus and Microsporidian Linked to Honey Bee Colony Decline, DOI: 10.1371/journal.pone.0013181, PLoS One, 2010.