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Varroa


Varroa destructor (Anderson and Truman) previously described as Varroa jacobsoni (Oud) (a closely related mite) is a parasitic mite of honey bees, capable of devastating honey bee colonies. According to results of scientific research projects, the main cause of honey bee colony loss is this mite, which can be found in almost every apiary in Europe. This mite is an external parasite that attaches to the body of Apis species, and breeds within the colony by laying its eggs within capped brood and feeding on Apis larvae. The mite is also a known disease vector.

The adult female mites commonly seen within the hive and on the bees have flat, reddish-brown oval bodies, greater in width than length (1.6 x 1.1mm).  The native host of V. destructor is the Asian honeybee (Apis cerana). In the past hundred years or so V. destructor has become the most serious pest of Western honeybees across the globe. Unlike Apis cerana the Western honeybee has no or limited natural defences to the varroa mite. If left untreated an infested colony will usually die within 2-3 years. Varroa is present on all continents with the exception of Australia. It was first found in the UK on the 4th April 1992 in Devon. The technical name of an infestation of varroa mites is 'Varroosis'.

Depending on climatic conditions, the damage caused by V. destructor appears from autumn to early spring during the overwintering phase, leading to general weakening and often complete losses of colonies. High level infestations can be a direct cause of colony loss, but the mite is also a vector of a number of viruses. Although bee viruses usually persist as unapparent infections and cause no overt signs of disease, they can dramatically affect honey bee health and shorten the lives of infected bees under certain conditions.

Even with proper management it is impossible to keep apiaries 100% free from V. destructor mites. Nevertheless, some strategies have proven to be successful, the most efficient being collective action within an entire area with coinciding treatments, but require extensive knowledge in order to manage the possibilities and limitations of the different treatments.


Present Status
Within the UK, Varroa is now endemic in England and Wales; present and widespread on both mainland Scotland and in Northern Ireland.  It is also widespread in the Republic of Ireland. The first honey bee colony losses attributed to the Varroa mite were reported in the Far East during the 1960's; the mites have since spread to most areas of the world where Apis mellifera are kept. In temperate regions infested Apis mellifera colonies usually collapse within one to three years if Varroa is not controlled in some way. Since Varroa cannot be eradicated, every beekeeper with infested colonies must practice effective mite control. It is the major challenges that beekeepers and beekeeping face today.

More information about Varroa, including monitoring methods, resistance management and treatment information, is available in the current advisory leaflet "Managing Varroa".  If you would like a hard copy please contact us directly.

Life Cycle
Varroa is an external parasite that lives exclusively on honeybees, feeding on their haemolymph (blood). To breed, a mated adult female mite enters a brood cell just before the cell is capped over, where she remains in the brood food until the cell is sealed. She then feeds on the immature bee and begins to lay eggs.

Mating between mite offspring (usually brother and sister) occurs within the cell. Mature female mites leave the cell when the host bee emerges. Males and any remaining immature females die, unable to survive outside the sealed cell. With heavy infestations numerous female mites may enter the same cell to breed. The mites have a preference for reproducing within drone brood (in fact in the ir original host they are only able to reproduce within the drone brood, but are also well suited to infest worker cells of the Western honeybee.

In winter, when brood rearing is restricted, mites over-winter solely on the bodies of the adult bees within the winter cluster, until brood rearing commences the following spring. During the summer, female varroa mites may live for 2-3 months. During the winter, or broodless periods, they can live much longer, feeding on adult bees. Mites cannot survive more than a few days without bees to feed on (e.g. on combs or equipment). As well as causing physical damage by weakening the larvae and adults by feeding directly upon them they also act as a vector for a number of honey bee viruses and the feeding process may stimulate latent infections to become highly virulent to the bees they affect.

The attached document is designed to give an overview of Integrated Pest Management for Varroa, available treatments and sources of further information.