Thursday, 21 November 2013

Defining CCD - Colony Collapse Disorder

One of the problems with the current media attention on bee problems and colony failures is that the media often implies that all colony failures are due to CCD. And while all causes of colony failures are sad and need research to help us prevent them, CCD is actually a specific type of colony failure. Indeed, I'd actually prefer the disorder were called Colony Collapse Syndrome, because we have a list of very specific symptoms that mark out CCD (or CCS) against other colony failures, but we have very little understanding of the underlying mechanisms which cause the colony to fail.

So, what is CCD, exactly? I can't find any one article that scientifically lays out a set of symptoms, so I'll attempt to define its symptoms as best I can here:

  1. The colony should have been previously healthy - there should have been no indicators of poor colony health in the days (or even hours) prior to the collapse event.
  2. The colony must collapse in a timescale of a few hours up to a couple of days
  3. There must be no dead bees in or near the hive (it is normal to find some dead bees in or near a healthy hive - this number should not be statistically greater than expected for a healthy hive) - this implies that the bees did not die in or near the hive, but abandoned the hive before dying.
  4. Small number of living workers (far below the threshold required to maintain a stable brood nest temperature of 35-37°C) and often the queen left in the hive (the strictest definitions of CCD require a live queen to confirm a diagnosis of CCD - as the live queen indicates that the colony was still able to produce young workers - a colony which dies from being queenless is not considered CCD)
  5. Food stores intact - absconding bees did not consume honey/pollen stores before abandoning the hive
  6. Brood nest intact but abandoned - brood in all stages (egg, larva, pupa) abandoned in the hive, but left to die as the brood nest requires a large number of bees to incubate using wing muscle thermoregulation.
  7. Other honeybee colonies are reluctant to rob the food stores of the dead hive, wasps are reluctant to rob the hive, honeybee pests such as wax moth and small hive beetle are reluctant to lay eggs in the hive. This contrasts with other colony failures, where other colonies and wasps will eagerly steal the remaining food supplies in the dead hive, and wax moths etc. will keenly take up residence to reproduce on the wax comb.

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