Varroa Destructor – The Varroa Mite
Varroa was first found in the UK in Devon in 1992, within five years it had spread to most areas in Britain and is now present in the vast majority of colonies. The problem is that our honeybees did not evolve with the mites and therefore have no instinctive way of dealing with them, as a result the vast majority of beekeepers implement a pest control system to limit the population of mites inside a hive. Feral colonies do not have the benefit of help from beekeepers and as a result many wild colonies have simply died out. The correct name for these mites is Varroa Destructor. They are around 1mm by 1.5mm (wider than they are long).
There are a number of treatments available for Varroa mites, although none are 100% effective, however a combined treatment plan will keep the mites down to manageable levels. These treatments include the various Thymol treatments, Oxalic Acid and more organic methods, such as dusting the bees with icing sugar at inspections, this is said to encourage the bees to clean each other and remove the mites in the process.
The use of mesh floors in hives is also widely accepted as an effective part of managing Varroa, most beekeepers now use these, as they allow any mites which fall off, or are cleaned off to fall through the floor, rather than with old solid floors, landing on it and climbing back up into the brood nest.
Fortunately there are breeding programs around the country where beekeepers are trying to breed resistance into their bees. By selective breeding they seem to be making headway and developing strains of bees which actively remove the mites themselves. One of these breeding programs is happening locally to me, by the Swindon Honeybee Conservation Group you can read all about their varroa resistant honeybees on their website, or see a short clip from the BBC’s Springwatch program below:
When originally discovered in the UK around 20 years ago, it was thought that the mites feeding on the larvae caused them to weaken and this in turn caused the damage to the bees. In more recent years it has been proven that Varroa Mites themselves actually do very little harm to the bees, however by feeding on the bees they spread the
various bee viruses around a colony and it is these which damage the bees and will eventually cause the demise of a colony if left unchecked.
There is further evidence emerging, which is pinpointing Deformed Wing Virus (DWV) as the specific virus which causes the most damage to colonies, therefore in my personal view, if DWV is spotted in a specific colony immediate action needs to be taken. Whilst there is no treatment for DWV available at the moment, reducing Varroa load should slow it’s spread throughout the colony.