Varroa history
The varroa mite (Varroa destructor) was first discovered in 1904 by A. C. Oudemans. At the time, it was a parasite of the Asian honeybee (Apis cerana). The varroa mite is very closely related to Varroa jacobsoni, the two only being differentiated in 2000 due to genetic testing. Because of this, early records can be confusing. The primary difference between these two mites is that both will parasitize the Asian honeybee, but only varroa mites parasitize the European honeybee.
Through movement of the western honeybee in and out of Asia in the 1940s, the varroa mite was able to move through Europe and Africa, spreading around the world in honeybee colonies. It wasn’t detected in the United States until 1987, but it has been a growing problem in the decades following.
The threat
The varroa mite is completely dependent on honeybees for its life cycle and cannot exist without coming into contact with them. Varroa mites have two life stages – phoretic and reproductive. The phoretic stage is when the mite is attached to a honeybee, feeding off their hemolymph (analogous to blood for insects). During this stage, the mite may move between hosts, spreading diseases and weakening more members of the same colony, or finding new colonies to infect. This significantly decreases a worker’s weight and their energy levels. Infected worker bees tend to live shorter lifespans than healthy workers. Because of their more lethargic state, infected bees are also more likely to drift into nearby hives, spreading the mites further.
Varroa mites are vectors for at least five diseases that affect honeybees – deformed wing virus, Acute Bee Paralysis Virus, Kashmir Bee Virus (KBV), Israeli Acute Paralysis Virus (IAPV), and Parasitic Mite Syndrome (PMS) are all associated with high levels of varroa mite infestation.
Varroa is such a threat to European honeybees because they are a newer threat. European honeybees haven’t had enough time to develop more resistance to them. A western honeybee colony infected with varroa but is not treated will die within one to three years (source).
