Bee Health - Varroa
Varroosis is an infestation caused by varroa, a serious Asian parasitic mite of honey bees. Originally confined to the Asian honey bee, Apis cerana, it has spread in recent decades to the European honey bee, Apis mellifera. The mites feed on both adult bees and brood, weakening them and spreading harmful pathogens such as bee viruses. Infested colonies eventually die out unless control measures are applied.
Since its discovery in England in 1992 the parasitic mite, Varroa destructor, has spread to infest colonies of honey bees throughout the UK; its management has now become a routine part of bee husbandry. Since it is now endemic, varroa is no longer notifiable under bee health legislation in England.
The advisory leaflet 'Managing Varroa' describes the biology of the mite, how it can be recognised and monitored, the latest approaches beekeepers can use to control infestation in their hives, and a look ahead to the future.
Pyrethroid Resistant Mites
The recent development of strains of varroa mites resistant to treatments used against them poses new challenges to beekeepers. The first known case in the UK of resistant varroa mites was found in Devon in August 2001 during routine field screening for resistance to pyrethroid by the Central Science Laboratory's National Bee Unit (NBU). Pyrethroid is the active ingredient in Apistan and Bayvarol, until 2003, the only treatments authorised for use in the UK to control varroa. Further cases of pyrethroid resistant varroa have been detected in apiaries in England since 2001.
In June 2003, a new treatment, Apiguard, was given market authorisation in the UK for use against varroa. Apiguard is not based on a pyrethroid active ingredient and is therefore effective against pyrethroid resistant mites. It is recommended that this treatment be used in conjunction with other controls during the year and with periodic monitoring of infestation levels - ideally as part of an IPM (Integrated Pest Management) approach.
The NBU's message to beekeepers is that they should remain alert to resistant mites in their colonies and consider the following general advice:
- Avoid movement of bees out of the affected areas - this will only hasten the spread of resistance. If you are thinking of moving bees then you should be aware of the risks and thoroughly test them prior to their movement.
- Check for evidence that pyrethroid treatments are working by regularly monitoring mite populations. If significant numbers of mites remain after treatment this may indicate resistance and you need to investigate urgently.
- Use pyrethroid treatments (Apistan and Bayvarol) no more than you have to. Alternate their use with non-pyrethroid treatments (Apiguard) and biotechnical methods. Make sure you strictly follow the label instructions of any varroa treatment - this will maximise their useful working life.
- Learn to test your own colonies for resistance using a resistance field test. If you think this is too difficult for you, then be prepared to ask for help from more experienced local beekeepers or from bee inspectors.
- Learn about Integrated Pest Management (IPM) - control of varroa using a variety of methods applied at different times in the year in conjunction with monitoring of varroa mite levels.
- When you find evidence of mite resistance stop using pyrethroid treatments (Apistan and Bayvarol). They will no longer provide effective control of varroa and their use will only make the resistance problem worse. Instead you should use a non-pyrethroid varroacide (Apiguard) ideally in conjunction with biotechnical methods as part of an Integrated Pest Management programme.
Details, including advice to beekeepers wishing to undertake resistance testing on their own colonies, are available on the National Bee Unit website.
Some documents are in Portable Document Format (), a copy of the Adobe Acrobat Reader is available free of charge.
Page last modified:
8 April 2008
Page published: 10 March 2005