Deformed wing virus

Definition

Present at low levels in many colonies without causing harm. Varroa acts as a vector and amplifier, injecting the virus directly and bypassing the bee's ordinary defences, and the resulting viral load produces bees with shrivelled wings that cannot fly. Colonies die of viral disease vectored by varroa far more often than from the mite's feeding damage alone.

Where the word gets used loosely

Varroa is usually blamed directly. The mite is the delivery mechanism; the virus does the killing, which is why mite counts matter as a proxy for viral risk rather than as a measure of direct harm.

Guide records that discuss this

• Varroa and the health of a honey bee colonyOne parasitic mite explains most of what has gone wrong for managed honey bees in the last forty years. It is not a mystery, it is not colony collapse disorder, and it is not the reason wild bees are declining.