Queen marking colour for 2017 - YELLOW

Winter Varroa treatment - Message from Peter West

Just a reminder to those obtaining Api-Bioxal oxalic acid solution from me, the method of application is outlined below. Please note that solution made with Api-Bioxal may have a faint brown tinge compared to previous solutions. This is nothing to worry about.

Many people have been caught out, thinking that they have very little Varroa.  Inserting a Varroa tray and doing a mite drop count every couple of days for a week after treatment is instructive, and gives you a good idea of how many mites are waiting to get into the brood cells when the queen restarts laying in January/February.

Oxalic solution damages the Varroa mouthparts, so they cannot suck your bees haemolymph and over the next few days fall off.

Treatment with oxalic solution does not affect the honey made in the Spring.  In fact oxalic acid is found naturally in honey in small quantities.

Oxalic acid only affects the Varroa on the bees. Normally 85% of the Varroa are inside the sealed brood and are safe.  Treatment around Christmas / beginning of January aims to catch the Varroa when there is no brood to hide in.


The solution should not be too cold, nearer blood heat would be good.  The day can be frosty with the bees well clustered.

Ideally draw up 50ml solution in a syringe.

Have a lit smoker handy (but should not be needed if crown board removed very carefully).

Between the brood frames are 'seams' of bees. Use 5ml for each seam of bees.  Only treat the bees, do not put the solution down empty seams/gaps.  So if there are only 4 seams of bees only use 20 ml.

Practice with water beforehand so that you know how to deliver 5 ml along each seam.  I find that 5 ml is a continuous series of little drops.

If you have a super on top of the brood box and you know the cluster is below it, you can remove the super gently to treat the bees.

Best wishes for a Happy Christmas and a Productive New Beekeeping Year!  Peter

Thermal Properties of Hives

Derek and Elaine Mitchell, Feb 2017

Elaine is the beekeeper and Derek is the mathematician. Between them they have completed research concerning hive temperature and humidity and the impact on the colony and have submitted their paper for publication.

Much of the original work on hive ventilation was done more than 50 years ago when none of the modern hive materials such as polystyrene were available. Thin walled wooden hives were cold, leading to condensation, so ventilation was essential to avoid mould growth. Putting match sticks under the crown board was standard winter preparation in those days.

Studying the thermal properties and ventilation of the bees nest in hollow trees lead Derek to conclude that we, as beekeepers, could do a lot better. They tested 8 hive types, 12 hives in total, against a natural tree cavity. The temperature rise for a standard 20 watt input was recorded for each hive.

Bearing in mind that the tree cavity could be surrounded by 6” of solid wood with only a small hole for ventilation it is not surprising this came top of the list. Interestingly a skep covered with cow dung gave a result similar to modern day polystyrene hives, probably because the cluster fits the shape well with no dead space to waste heat.

At the bottom of the performance list were wooden National hives. The message is that a well insulated cavity allows the colony to heat and ventilate their home the way they want to with minimal use of stores.

Leading on from these ideas there are some important points for beekeepers to recognise.

A well insulated hive mimicking a tree nest will enable the colony to achieve a higher temperature more easily AND maintain the higher temperature. Lower ventilation

Photo courtesy of Derek Mitchell

will result in higher humidity. Overall the winter stores will be consumed more slowly promoting colony survival.

The sweet spot for temperature and humidity in a bees’ nest is 35-36°C / 90%RH. These conditions have been shown to enhance egg survival, reduce varroa mite viability, suppress nosema and chalk brood, avoid damp and mouldy conditions plus reduce mortality due to chilled brood.

Elaine described her beekeeping with well insulated National-style hives. She no longer finds it necessary to treat her colonies for varroa. Checks for mites show low numbers that do not seem to cause any problems.

These low numbers may partly be due to the high temperature/humidity conditions allowing the bees to remain unclustered for much of the winter which in turn enhances grooming and varroa control. It was also mentioned that under these conditions brood rearing may be delayed until later thereby increasing the brood break, leading to further reduction in varroa breeding.

Counter intuitively, high insulation could be more important in summer than in winter as bees need far more energy for foraging and nectar ripening than they do for winter survival. To ripen nectar and turn it into honey stores large quantities of moisture have to be removed before the honey can be capped.

This moisture can be removed more efficiently at higher air temperatures. Thus energy saved by insulation can be more usefully employed in honey making.

Bees in modern polystyrene hives have been shown to produce more honey than bees in equivalent thin-walled wooden hives and many bee farmers in the UK and on the Continent use them.

Improving insulation further, Elaine showed examples of her hives made with modern house insulation sheet material. The only ventilation was the front entrance and there was no varroa mesh floor. The insides of these hives were kept in almost immaculate condition over winter due to the bees being able to move around in the high temperature conditions.

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East Devon Beekeepers

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