These microscopic mites penetrate the tracheae of honey bees and feed on their blood. Feeding by the mites damages the tracheal walls, which blocks the bees' breathing passages. These breathing tubes supply the flight muscles with oxygen. As a result of mite feeding, the flight muscles may atrophy, and the bee may be unable to fly or control its body temperature. Pathogens also may be introduced into the bees' bloodstream by feeding mites.
High infestations can lead to colony death, particularly during winter.
The varroa mite is considered by many to be the most serious honey bee pest. This mite is an external parasite that is visible to the naked eye. Heavy parasitism results in bee mortality, subsequent weakening of colonies, and often death. Efforts to stop the spread of these two mites have been largely unsuccessful, but research into chemical controls and resistant honey bees looks promising. For more information on parasitic mite control, contact your county extension office or your university beekeeping specialist.