This is a bit of controversial question, my aim is not to cover the argument about whether we treat or not but rather to inform you about the varroa mite and what impact it has on our honey bees.
Varroa Destructor is an ectoparasitic arachnid mite; this simply means a parasite that lives on the outside of its host. The adult female mites, which are the most commonly seen within the hive and on the honey bees, have flat, reddish-brown oval bodies that are around 1.6mm wide and 1.1mm long. The female mites enter an open cell just before the cell is about to be capped. Here it will hide under the larva and it will wait for 2-3 days until the brood food has been consumed by the larva. The female mite will then begin reproduction inside the sealed cell by laying her first egg, which is usually male, she will continue to lay at intervals of around 1-2 days. The later eggs are usually all female and she will lay around seven eggs per cell. The eggs hatch into immature mites of which only two to three will reach adult stages.
The mites are trapped in the sealed cell with the pupae and are now feeding off the pupaes’ fat stores. Through the process of feeding they are not only reducing the fat stores of the bee, but they are also transferring viruses to the bee. Both of which will shorten the life span and stunt the pupa’s development. After 21 days, the worker bee emerges (24 days for drones) and any surviving mites in the cell will also be set free. The mites will have attached themselves to the underside of the honey bee where they will travel with the bee until they see a new open cell with a larva in it. They will detach themselves from the bee they are travelling on and enter the open cell and the whole process is repeated. The repeating of this process quickly accelerates the number of varroa within the colony.
Mite populations can also be transferred between colonies in the same apiary through robbing, drifting and swarming.
The Symptoms of Varroosis
Severe infestation of varroa may lead to the following that can be visually seen in the colony:
- Deformed wings; caused by a virus passed on by varroa
- Stunted abdomens; caused by varroa feeding of the developing pupae
- general weakening of the colony; caused by the lifespan of the bee being shortened
- Patchy/ pepper pot brood patterns; caused by bees removing dead and damaged pupae from cells
- High levels of infestation can be a direct cause of complete colony loss
In order to keep healthy and productive bees you must control the Varroa levels within our colonies. This can be done through treatments which fall into one of two main categories, each of which have their pros and cons and you can decide which type of treatment suits your method of husbandry.
Varroacides: Most beekeepers will chose this method to control varroa mites in their colonies as they are highly effective at killing and controlling Varroa. There are two classes of varroacides; those that contain chemicals that have been constructed if you like, and those that contain chemicals which are naturally occurring for example formic acid, oxalic acid or essential oils. Whatever treatment you do use, due care must be taken with anything that you introduce into your colony in order to prevent
contamination of honey.
The choice of treatments that are legal in the UK may differ to those in other countries. Listed below is a table of treatments available in the UK, at the time of publication, by beekeeping suppliers along with the active ingredient. It is advisable to alternate your treatments in order to reduce the risk of varroa becoming resistant.
|Name of Treatment||Active Ingredient|
|ApiLife Var||Thymol, Camphor Racemic,Eucalyptus Oil,|
|MAQS – Mite Away Strips||Formic Acid|
|Varromed||Oxalic Acid, Formic Acid|
Biotechnical Controls: These avoid the use of chemicals totally but still aim to reduce levels of mites in the colony. Some biotechnical methods exploit the fact that mites reproduce in bee brood. The most common method is to remove comb once it is sealed, mites will populate drone cells in favour of worker cells as the drone cell is bigger. The comb is then cut out and destroyed, along with the mites contained within the cells. Generally, these methods are only used during the spring and summer months when drone brood is being reared. This method can be a great way of delaying when treatments are needed. The idea is that you put one super frame in your brood box, the bees will chose to naturally draw the new comb on the bottom as drone comb, so the queen will lay all unfertilised eggs in these cells. Once capped over you simply take the frame out and cut out the drone brood. We personally do not advocate using this method because you are of course removing a big percentage of drone from the colony. This causes a reduction of the drone pool for natural reproduction of the honey bee. This method would certainly have a limit on the amount of times you could do it in a season.
Drone brood can however a useful tool in monitoring your varroa levels. By pulling a small sample of developing drone brood with an uncapping fork you will see how many mites you see on the larvae and this will give you a good indication of your levels.
There are other more effective ways to check on your varroa levels and you should learn to regular check your bees. Varroa levels will build up differently in some years to others and differently in each separate apiary.
Monitoring with an open mesh floor is a very popular method. You simply clean the varroa tray, insert it for 24 hours then go back and count the natural varroa drop. There will be other debris and detritus on the tray so you need to spend time sorting out the varroa to ensure you get a good count. There is a varroa calculator on BeeBase that you can then use to check if your levels are high or not.
Alcohol wash is also an effective way of counting varroa however you do kill the bees using this method. You need to collect around 300 bees from your colony and place them in a vessel that has a mesh separator in it and that has an amount of alcohol in it. This is then shaken vigorously for around 30 seconds to really mix things up and knock the varroa of the bees. The varroa will drop through the mesh and you will be able to count them. You obviously need some specific equipment to carry out this method of counting however, if you have a lot of colonies this may be more a manageable method for you to get an average count by apiary as you can just check a few colonies per site.
You can use icing sugar in place of the alcohol and instead of shaking you roll the vessel, the icing sugar will dislodge the varroa which will fall through the mesh. The bees are unharmed and can be returned to the hive. There is some question as to whether you get the same accuracy as using alcohol.
Another none chemical method of reducing varrao loads on your bees is by sprinkling icing sugar directly onto the bees in your colony. The icing sugar will stimulate the bees to cleanse and this in turn knocks the varrao off them. You will need to cleanse the varroa board after treatment as the mites are not killed and it is said they can climb back up. This is not an affective treatment on its own however can be used as at temporary measure until you can treat them with a proper varroaside. Just a note; do not use this method and then do a varroa count which you put in the calculator on BeeBase as you will have an unnatural mite drop count which will give you obscure results.
When do I treat?
There is no specific time that you should treat for varroa however most beekeepers will treat late Summer once they have removed the honey harvest but before they do their winter preparations. At this time the colony will be reducing in size but varroa infestation will be increasing. The aim of treating at this time is reduce the mite count so that the last few cycles of brood rearing within the colony will be protected and you will have healthy young bees reared ready to take the colony into winter. If you don’t treat at this time you will be in danger of your winter bees life span being reduced which will have a direct impact on the colonies winter survival.
Your choice of treatment may require certain conditions, for example Apiguard and ApiLife Var, which are both thymol based, need warm conditions for maximum efficacy. Oxalic acid treatments have the best efficacy on broodless colonies and are usually used during the winter months or early in the spring. You can however combine this treatment along with confining your queen which will create a broodless situation so that you get the best efficacy. Do ensure that you have a nice strong colony if you do this, no point in caging the queen on a struggling colony in April as you will only add to the stress and possibly cause the colony to totally fail. I know some beekeepers who routinely treat swarms they take in with Oxalic acid treatments as this will target any varroa the swarm has carried before they start to rear brood. If you are shook swarming your bees for any reason then you can treat the for Varroa with this method at the same time.
Most treatments cannot used during a honey flow as there is a danger that the product will contaminate the honey and this would make it unfit for consumption. Always read the instructions and warnings for the product you are using. There are a few treatments that can be used during a honey flow if necessary, MAQ’s is one of these, however this is quite an aggressive treatment and special attention should be given to the advice and instructions on the packet to avoid damage or loss to the colony.
Rotate you treatments to avoid varroa building up resistance, this is especially true of Pyrethroid based treatments. General rule of thumb is use once every three years. You must keep a log of all treatments you put onto your bees, date and batch number, if you are selling your honey.
You can find out even more information about varroa life cycles and the affects on the honey bees plus different techniques to control, resistance build up and much more on BeeBase , see their ‘Managing Varroa’ advisory leaflet, it really is jam packed full of information. Vita Bee Health also has some super information all about varroa.