Colony collapse disorder is a term for a particular pattern of colony loss described in the mid-2000s. The term is now used far more loosely than the original definition warrants.

The original description

What distinguished the pattern was not that colonies died, but how:

• The adult bees disappeared
• Few or no dead bees in or around the hive
• Stores and brood left behind
• The queen often still present with a small cluster
• The abandoned stores were not immediately robbed by neighbouring colonies

That last point was among the most striking: the hive stood full and untouched.

Why the term causes confusion

Calling every winter loss "colony collapse disorder" stops the search for the actual cause.

Most winter losses do not fit the description. If there are dead bees in the hive, heads in the cells, or plenty of honey with few bees, the cause lies elsewhere — and it is usually identifiable.

What is known

No single cause has been established. The consensus points to combinations of factors:

• Varroa and the viruses it transmits
• Poor nutrition and lack of forage diversity
• Pesticide exposure, including sublethal effects on navigation
• Pathogens such as nosema
• Stress from transport and management

The sublethal navigation effect is one plausible explanation for bees that leave and never return.

What is more useful than the label

Examining the dead colony. The picture in the hive usually says what happened:

• Heads in cells, no honey → starvation
• Few bees, plenty of honey → Varroa and viruses
• Wet hive, mould → ventilation or a leaking roof
• Raised drone brood → queenlessness
• Almost no dead bees, stores and brood intact → this is the pattern originally described

The practical position

Whatever the label, the measures that reduce losses are the same: control Varroa before winter bees are reared, feed adequately, keep the hive dry, provide varied forage, and keep records.