Varroa resistant bees
The United States Department of Agriculture (USDA) has shown that it is possible to select honey bees with Varroa Sensitive Hygiene (VSH) behavior: these bees can detect reproducing Varroa in brood. As these VSH bees remove the infested brood, no Varroa offspring is produced. Selection has only been limited to this trait and no resources were available yet to structurally integrate this trait in a broader base of the honey bee population.
The next step in the breeding program, starting in the 2015 season, will be to further select towards 100% VSH in the EU breeding stock. Once this level is reached, normal sized, multi-drone colonies will be created and thoroughly tested on other important traits like honey production, gentleness and swarming tendency. Also the selection has to be done in as many different lines of honey bees as possible to ensure a rich biodiversity and to enable its broad application in the beekeeper community worldwide. >>>Read more>>>
Still a queenless colony?
We asked John Everett yesterday what he would recommend if a colony has swarmed and the remmaining colony still seems to be queenless after maybe 5 weeks. His answer:
It can take up to 5-6 weeks until a new queen starts laying. So there’s still a chance that in Sue’s hive a new queen is present but has not yet started laying.
If the next inspection doesn’t show any fresh brood, just add a frame with brood from another colony and check it after 2-3 days. There will be 2 possibilities:
- If there is NO queen present,they will have started building new queen cells.
- If there IS a queen present, nothing will happen – they’ll just look after the brood.
If (1) proves true, we should merge this colony with a queen right one. We should use the newspaper technique described here:
How to unite two colonies (http://www.somersetbeekeepers.org.uk/unite.html)
There comes a time when it is beneficial to the bees, or the beekeeper, to join two colonies together. This may be to save the bees in a colony, which is hopelessly queenless, or to cull a queen with undesirable traits, or to save equipment, or simply to reduce stocks. This is a relatively simple operation, requiring the minimum equipment.
Bees will not unite naturally for two basic reasons.
- They can recognise by smell any intruder who is not a member of their colony.
- A large influx of intruders would immediately put them in defensive mode, resulting in excessive fighting and deaths.
For uniting to be successful therefore, it must be done in such a way as to disguise the odour, and reduce the risk of putting the bees on the defensive.
There are many suggested ways of doing this, including the use of talcum powder or flour, water or sugar syrup sprays, or shaking all the bees in a heap in front of the hive, and letting them run in together, in the hope that this will neutralise the odour. All these methods are either messy or violently disruptive to the bees. The simplest and most successful method involves the use of a sheet of newspaper.
The principal is to place one colony on top of another separated only by newspaper. The bees will chew through the paper and unite, but this will probably take at least twenty-four hours, by which time the colony odours will be neutralised, and the bees will have had time to calm down and are no longer in a defensive attitude.
The hives to be united should be prepared during the day, when most of the flying bees are away from the hive, and the actual uniting done in the evening when all is quiet. The best time of year to unite is in early autumn, after the honey crop has been removed. It can be achieved with supers in place, but they are an added complication. If both colonies are queen right, the decision must be taken which queen to retain.
There is sometimes a “cop out” by beekeepers at this stage, not wanting to kill off perhaps a perfectly good queen, so the two colonies are united leaving the queens to “fight it out”. This is not a good practice, as although the strongest queen is usually the victor, quite often she receives injury during the confrontation.
Much better to find and destroy the unwanted queen before uniting. The colony without a queen should always be united on top of the queen right colony, not the other way around. It is therefore necessary to check and if necessary clean the bottoms of the frames in the queenless colony. As modern hive floors are deeper than a bee space, the bees are prompted to build brace comb under the bottom bars. If these are then placed on top of a sheet of newspaper, the paper will be broken, rendering the operation futile, or the frames will be pushed up, thereby raising the crown board.
Once the colony, which is to be united, has been prepared, it can be closed down until the evening, and attention turned to the receiving colony. All that is necessary here is to check that they are in fact queen right, and scrape off the top bars of the frames to provide a smooth surface for the newspaper to rest on. A single sheet of newspaper is then applied and held in place by a couple of drawing pins, or by covering with a queen excluder. The crown board and roof can then be replaced, and the hive left until the evening.
In the evening, when the bees have finished flying for the day, the roof and crown board are quietly removed. The bees are not disturbed as they are covered by the newspaper. The second hive is then quietly released from its floor, and gently placed over the newspaper. The united hive should be left completely alone for at least two days, or until crumbs of chewed up newspaper can be seen being ejected at the entrance. The colony can then be inspected, and combs moved around to place all the brood in one area, or the brood in the upper chamber simply left to emerge, after which this brood chamber can be removed.
“Varroa mites are innocent, OK” – after all, they are just doing their thing without any malevolent intent. It’s what they do. But – by feeding on the bees’ “blood” the Varroa mites unwittingly carry and inject harmful viruses and other toxic entities.
The key thing in the interaction between the Varroa mites and the bees is that the Varroa carry out their reproduction in the brood cells of our bees. The female Varroa mite enters the brood cell and lays a series of eggs. The first is always male; the second and subsequent eggs are always female. They are laid at consistent time intervals.
Bees have incubation periods that differ between the different forms of bee in a colony.
Without going into a lot of science, the incubation period for drones is two days longer than the smaller worker bees and this is long enough for the mite to lay two female eggs. The worker bee cells only yield one female mite. There is only ever one male mite and he stays in the cell and perishes in each generation, so he doesn’t matter.
The mathematics of this are key to the drone problem. For worker bees, there is only time for one female Varroa egg to be laid per cell, so in each succeeding generation there are: – 1->1->1->1->1 females; there is no increase in the female Varroa population and hence the total mite population is stable and controllable at a low level.
However, if there are two female eggs per generation the population grows explosively: – 1->2->4->8->16->32->64………but of course this is for only one mite. If there are ten, then it goes: – 10->20->40->80->160->320->640
If there are 100 to begin with we have: – 100->200->400->800->1600->3200->6400, …….and the colony soon becomes overwhelmed, not by the mites themselves, but by the viruses they carry.
This cannot happen with worker bee brood cells; there is not enough time in the incubation period for two female mite eggs to be laid. The drone brood is where the problem lies and it MUST be monitored. This means taking a sample, which regrettably results in the death of a small part of the drone brood. Despite the injustice to the drone bees, a responsible beekeeper MUST monitor and control the mite-infested drone brood in the hive. Unfair it may be but it is unavoidable if the colony is to survive. Drone bees are innocent victims. They do not deserve to be slaughtered but the numbers are inexorable. We must keep the Varroa numbers as low as we can.
Of course, if the drone brood is found by monitoring (which means killing a few drone embryos) that it is not significantly infested, then no intervention is necessary and none should be undertaken.
In a sample taken from the drone brood of one of our hives we found that about ten percent of the brood were infected with the Varroa mite. This is held to be significant but not disastrous. Five percent is considered to be a light infestation, twenty five percent is severe.
Thymol kills the Varroa mite. Thymol is not a man-made pesticide or insecticide. It is an essential oil produced from Thyme (Thymus vulgaris), which many of us have in our gardens. It is harmless to humans and has been used in medication by many ancient and modern cultures. We must use it.
As for harmony in nature, bees and mites have been co-existing for eons, so why have not all the bees either been wiped out or become resistant? The answer seems to be that in the search for greater honey production the European Bee has been selectively bred to become physically larger and in so doing the incubation period has been prolonged. In the case of the drone brood this has enabled to mite to produce two progeny instead of one. Man has destroyed the balance of nature. (Text written by Peter Horsefield)
How is varroa spread to other colonies? (from: Adventures in Beeland)
- Foragers carrying mites drifting into, or robbing from, other colonies
- Drones carrying mites visiting other colonies
- The beekeeper moving brood frames between hives or transporting infected colonies to new areas
- Varroa mites have been found on flower-feeding insects such as certain species of bumble-bees, scarab beetles and flower-flies. Although the Varroa mite cannot reproduce on these insects, its presence on them may be a means by which it spreads short distances and finds new honey bee hosts.
Below are a couple of monitoring methods beekeepers can use to help monitor how bad infestation is.
- Drone trapping
Varroa mites prefer to breed in drone brood. Drones take 24 days to develop whereas workers take 21, so drones give the mites time to fit in more breeding cycles. The mites identify the drone brood by its different smell, which is a result of the more protein rich diet fed to drones.
In England drone trapping can be used as a method of varroa monitoring and/or control during April, May and possibly June. To do this put a drawn super frame into the brood box, to encourage them to build drone comb in the gap underneath, or a frame with drone foundation or drawn drone comb, depending on the size and strength of the colony. Put the super frame at the side of the brood nest, not the middle.
Once the drone comb is sealed, cut it off the super frame. You can do this 2-3 times during the summer. Before you destroy the drone brood you can uncap some to see how many mites are inside.
- Varroa board monitoring
Draw a grid with several squares on your monitoring board and smear it with vaseline, then put it under your open mesh floor for a week. The grid pattern makes it easier to count mites and the vaseline ensures the mites stick to the vaseline and aren’t blown off when you inspect the board. A week later, count the number of mites and work out an average daily drop count. If there is a lot of debris which makes it hard to count mite numbers, put the debris in a jar with a lid before mixing with methylated spirits and shaking vigorously: once the debris settles, the wax, propolis and other debris will sink, the mites will float.
To assess how bad the problem is based on the daily drop count, the season and the type of hive must be taken into account – UK colony collapse thresholds would be a daily drop of 6 in May, 10 in June, 16 in July and 20 in August. The Beebase varroa calculator is a helpful tool which can tell you how bad the problem is based on the time of year.
What treatments for Varroosis are permitted in the UK? A detailed account of how to carry out four forms of treatment.
I have a blog post explaining how a shook-swarm works, ‘A successful shook swarming‘. Ideally this is carried out in early spring, in late March – early April. The bees are shaken onto new foundation frames and all the old brood comb, containing lots of mites taking advantage of the new spring brood to breed, is burned. Sugar syrup is fed so the workers can draw out new comb quickly. This is a helpful non-chemical anti-varroa treatment because a large percentage of the mites are destroyed, followed by a short break in the queen laying while new comb is drawn out, which further cuts down on mite reproductive cycles.
- Icing sugar
The advantages of this method are that it’s cheap and easy to do. It can also be done with supers on, unlike thymol based treatments like Apiguard which might taint the honey with their smell. The icing sugar works in two ways – by reducing the electrostatic charge by which the varroa cling to adult bees and by inducing the bees to groom. A flour dredger or a honey jar with holes punched in a lid work well. Work in pairs to do the treatment, with one person holding out each frame horizontally and another person dusting the sugar over each side.
As the treatment doesn’t kill mites, but only knocks them off, it is only any good in a hive with an open-mesh rather than a solid floor. Since it only affects phoretic mites clinging onto adult bees, which only make up about 30-40% of the mite population, it is a low efficiency treatment and generally only reduces mites by about 20-30%. This may sound good, and is better than nothing, but really an 80% effective treatment (such as Apiguard or oxalic at the appropriate times of the year) is needed to have any real effect on mite numbers.
You cannot rely on sugar dusting alone to keep varroa levels down; if you do your colonies are likely to die. This is true generally of varroa control: you cannot rely on one treatment alone, but should use several different methods throughout the year.
Apiguard, a natural thymol based treatment, can be given in August once your supers have been removed (otherwise your honey will stink of thyme). Starting Apiguard in August allows the hive to produce several generations of healthy bees before going into the winter. Two 50g treatment packs are given, one initially and the second 10-15 days later. Small colonies or nucleuses can be given a half dose.
The treatment works because the worker bees dislike the heavy thymol scent. They start removing the gel to clean the hive and remove the foreign smell, distributing it round the colony and killing off varroa mites in the process. Both adult mites and developing mites inside capped cells are affected, but honey bee larvae are safe. Tape up your varroa monitoring board whilst treating so the fumes stay in the hive. Apiguard should be done while the weather is still warm, as it is most effective – 90-95% effective – in the optimum conditions of an external ambient temperature of more than 15°C and active bees. This is because distribution of the Apiguard gel depends on the bees transporting it round the hive during the process of hive cleaning, and this activity increases as the external temperature rises.
- Oxalic acid
This treatment can be carried out once either in December or January whilst brood levels are either non-existent or low. It works by damaging the proboscis of the varroa mites, preventing them from sucking haemolymph from the host bees. Oxalic acid can be purchased pre-mixed in a sugar solution, which is the safest method.
Choose a bright and warm winter’s day when the bees are loosely clustered, so that as they move inside the cluster they distribute the chemical onto the mites. Put a varroa monitoring board over the mesh-floor, as it feels good to count the number of dead mites dropped onto it over the next few days; sometimes I’ve counted over a hundred in a week. Warm the product slightly until it’s lukewarm, remove the hive roof and crown-board, and trickle 5ml over each seam of bees. Do this very quickly to avoid chilling the bees too much. If the colony has been treated before and still has the same queen, it is unwise to use it again as it may harm the queen.
copyright top two pictures: http://adventuresinbeeland.com/2012/10/21/3rd-honey-bee-pests-diseases-and-poisoning-revision-post-the-lifecycle-of-varroa-destructor-and-monitoringtreatment-techniques/
Come and see a real beehive in action
Sunday 19 July, from noon till 3pm at Trunch Open Gardens Day
Watch through a glass-walled beehive how bees work in their comb, filling cells with nectar, honey and brood. Get interesting information about these fascinating insects, which are so important for our everyday life!
- When? 19 July, Trunch Open Gardens, From noon till 3pm
- Where? Glebe Lodge, Gunthorpe Lane (last property on left on Knapton Road)
- Who? Norfolk master-beekeeper John Everett will introduce you to some fascinating facts about the life and work of bees
- Cost? Free with access armband to the Open Gardens
- Extras? Buy John’s delicious honey & some Trunch Beekeeping coasters