Since its introduction into the U.S. in 1987, this mite has reduced the quality and quantity of bee colonies available for honey production and pollination. Therefore, it is important to determine if honey bees have any natural, heritable defense mechanisms against the mite that may be readily incorporated into breeding programs. The mite leaves the adult bee to enter a cell with an immature bee. The offspring mate within the cell and mated female mites leave when the bee emerges as an adult. Parasitized bees have reduced life-spans and may be deformed.
Severe infestations lead to both individual and colony mortality.
A balanced host-parasite relationship has evolved between Varroa and its natural host, Apis cerana, in Asia. While grooming, adult bees remove mites from themselves or from nestmates, damaging mite legs and cuticle in the process. The removal of infested pupae interrupts the reproductive success of the mites. Hygienic bees have the ability to detect, uncap and remove diseased brood from the nest before the causative organisms reach the sporulating stage. A two-way selection program for hygienic behavior was initiated at the University of Minnesota in 1992.