Varroa Mite

For years now, the mite Varroa destructor has plagued bee colonies in many parts of the world. Indeed, infestations of this mite have now become an epidemic of global proportions, threatening to destroy entire populations of honey bees in the Western world. There are only a few treatments available to control this pest.

The Varroa mite.

For thousands of years, Varroa mites have been parasites on the Asian honey bees Apis cerana, giving this species the opportunity to learn to live with the mites. Unfortunately, the European honey bee (Apis mellifera) did not have any time to adapt to this pest, which was accidentally introduced in Europe by international trade in 1977 and then later in North Africa, America and New Zealand as well. Scientists have intensively studied this parasite. They have researched the biology of the mites, its potential as a vector for disease and specific approaches to control. This, in turn, has led to the development of effective, safe medicines the strategic use of which has helped to prevent even greater damage to honey bee populations.

Development of the Varroa mite.

The development of this reddish-brown mite is perfectly adapted to the lifecycle of the honey bee. Female mites (foundresses) have a flat-shaped body roughly 1.6 mm wide and 1.1 mm long, allowing them to fit between the overlapping abdominal segments, where they feed on the bees’ hemolymph.

The foundresses enter the brood cell shortly before the cell is capped, preferring to infest drones. This is an effective strategy as the roughly three-day additional development period of the drones provides the mites with extra time to reproduce. In the brood cell, the mite feeds on the hemolymph of their hosts, after which it lays its eggs. The eggs develop into young mites in the closed cells and then mate. Following this, the female offspring then leave the cell with the young bees and seek a new host to continue to the cycle of reproduction.

Double damage.

Varroa mites not only cause significant damage to the bees by feeding on their hemolymph, but also act as a vector for viral diseases like Acute Paralysis Virus (APV) and Chronic Paralysis Virus (CPV). The wounds inflicted by mites may also be contaminated with bacterial or fungal organisms. These secondary infections can be recognized based on typical symptoms associated with them and often lead to severe damage to the colony. In order to prevent this, it is crucial that colonies are monitored for Varroa infestation regularly and that measures to control the infestation are taken when necessary.