Oxalic Acid Vaporiser Treatment on September 20th

After the high count in Aqua from the drone trap last week – 50:100 and the Defra advisory on incidences of high Varroa infestations I decided to use my new vaporiser and apply Oxalic Acid to the home apiary colonies. Will do the Mole Valley ones next week.

Oxalic Acid Vaporiser - completed

Bit of a faff removing the entrance blocks especially as it was the middle of the day and as the weather has continued to be warm the bees were very active. Didn’t see the vapour coming out of the top of the hives but certainly seems effective based on the drop counts. Very easy to use and found the on/off switch to be useful, also liked the fact the battery is relatively light weight so easy to move around the apiary.

Put in Varroa slides before applying the treatment and the 24 hour drop counts were shocking:

  • Aqua – 132 – surprised at how high as this the colony that I have been very focused on drone trapping during the season
  • Blue – 212 mites, might be down to the poor start it got during the season
  • Cyan – 180 mites – very active so after the other results not too surprising
  • Denim – 37 mites, surprised how low it was compared to the others; hopefully the treatment was applied correctly This has been a very active colony throughout the season
  • Honeydew – over 300 mites. Very surprised as this was a new colony this year but I obviously haven’t been managing it for Varroa very effectively. I thought the it would be one of the lowest as it was set-up as a nuc and I didn’t use drone trapping.

Second count 48 hours after treatment not much better (either the treatment is really effective or my colonies are in a very bad state!):

  • Aqua – 85 mites
  • Blue -180
  • Cyan – 60
  • Denim – 10
  • Honeydew – 260

With such high counts I will treat again in 3 weeks. This is one of the advantages of using the Vaporiser is that the treatment can be repeated.

Making an Oxalic Acid Vaporiser – Part 1

Since reading about the effects of applying Oxalic Acid in a sublimate form (vaporised) rather than the trickle method I have been using I decided to look at acquiring a vaopriser. I was horrified to see what they cost for a commercial one and so set about making my own.

I couldn’t find a design that seemed to be tried and tested so experimented with various prototypes and have ended up with one that works for me – see under plans for the details of the build. This post is about my experiments and conclusions about what worked for me. I wanted to make it cheaply and if possible using tools that I have.

My initial design criteria:

1) Fit into a hive without removing entrance block

2) Use 12v power supply

3) Administer 2g dose within 3 minutes

4) Use my pillar drill and router to machine the materials.

Prototype 1:

I worked out the volume that 2g of Oxalic acid would take up and produced a Sketchup design for one that could be  heated by a diesel glow plug. Using my router I made the recess that would hold the Oxalic crystals to the correct dimensions . Then tapped 2 holes to take the glow plug and handle. Finished version of the block shown as 1 in photo. Found it very difficult to rout out the recess with a router bit in my pillar drill. Definitely not recommended and forced me to look at alternatives for the other versions I made. The drawback with this design is that it was relatively quite a large block of aluminium (50mm x 50mm x 19mm) and weighed 120g and took ages to heat up – over 5 minutes to boil off some water, so no good.

Prototype 2:

For this design, 2 in photo, I decided to try and use a PTC element to heat a slimline block. The idea being that using the PTC element would mean that I could keep the height of the unit to 9mm and so fit into the hive without removing the hive entrance block. Overall size was 60mm x 60mm x9mm and weighed around 60g. Because the tolererances for the various holes needed to be much tighter than I could achieve with my basic tools, I got a friend to CNC the block for me. The PTC element was cheap about £5.00 and could reach a temperature of 170°C, more than hot enough to vaporise the Oxalic Acid (157°C).  The drawback was that the PTC element heats up quite slowly. It couldn’t boil off the water I used as a test in less than 8 minutes, so I didn’t even bother to test with Oxalic.

Prototype 3:

Design 3 in photo. I set out to minimise the size of the block and went back to using a glow plug as the heat source. My friend CNC’d 2 for me so I had a spare if I messed up drilling the hole for the glow plug (he drilled and tapped the hole for handle). Overall the block is 42mm x 36mm x 12mm and weighs 45g

My first try was to use a 8mm aluminium tube for the handle as I wanted to pass the wires from the battery through the tube rather than have them taped to the side. This meant the wires had to be thin gauge to fit into the diameter of the tube. However on testing it showed the wires were not capable of carrying the current required to power the glow plug. Took about 3 minutes to boil the water off and the wires themselves were warm to the touch a sure sign they were not up to the job.

So my final version was to use a 10mm tube which could take wires rated at 13 amps (glow plug seems to draw about 5 amps).  I finished off the build with a wooden handle into which I  fitted a rocker switch. The acid test (forgive the pun) was that it managed to vaporise the Oxlic Acid in 2mins 15 seconds.

Oxalic Acid Vaporiser - completed

So my conclusions for anyone considering making their own vaporiser. Keep the size of the block as small as possible. I could probably shave about 10g off my version if I pare down the size a bit more. Use a glow plug as the heat source as it heats up really quickly and is cheap, around £5 for a new one. Beware the glow plug thread is fine  pitch, most taps seem to be for standard pitch.


Feeding Honey Back to The Bees

I know it’s not recommended but I had a super of old  honey, most of it crystallised in the combs. Rather than just bin it I decided to feed it back to my bees. So I uncapped 4 frames and put them into a super and left it about 15m from the hives. The bees found it and took about 2 days to clear the frames out. They made a mess of the foundation and a lot of wax debris was deposited on the ground. The condition of the drawn combs was such that they couldn’t be re-used and I put them in the solar wax melter. The whole process seems to have made the bees in all the hives very aggressive. I guess what I had unwittingly caused was a form of robbing activity and the colonies were taking measures to protect their own stores.

I was still left with another 5 frames, but didn’t want to repeat the process of leaving the frames in the open. I decided to uncap the frames and split these between two hives  and put them in a super above the crownboard. The bees cleared them in 2 days and when I removed the empty combs the bees were still very aggressive. But on the plus side they hadn’t destroyed the drawn combs and I will be able to re-use them.

So at least I have learnt one lesson – put the combs back on to a strong colony above the crownboard for best results.

Bait Hive – Success As Swarm Takes Up Residence

I put a bait hive out for the first time last year but didn’t have any luck attracting a swarm, but then I didn’t have much luck with anything beekeeping related last year. The main reason for doing it was to hopefully stop swarms from my own colonies causing problems with the neighbours.

About 4 weeks ago I decided to relocate it from it’s westerly facing position on a  flat roof to the top of my south facing porch – about 3m off the ground. The bait hive consists of a 14 x 12 brood box fitted with a solid floor and a restricted entrance of about 30mm in one corner, topped with a crownboard and roof. Inside the box were a couple of old frames and a dummy board – as it’s a 14 x 12 box I wanted to make the internal volume appear smaller. All the research I did indicated that bees seemed to prefer around 30-36 litres so using a dummy board meant I could adjust the internal space to the recommended volume.

I smeared a couple of drops of lemongrass oil across the tops of the frames and put some on a wad of tissue inside a freezer bag that I placed in a corner on the floor.

Got back after being away for the week-end to find that a swarm had occupied it. As I hadn’t inspected  my own bees I was a bit concerned that one of my colonies might have swarmed whilst I was away. However, after inspecting my colonies it looks like it’s a swarm of somebody else’s bees.

From a cursory look I can see it’s a large swarm and has already started to fill the old combs and drawn a new comb down from the crown-board and the bees look to be good tempered. As it had been there for about 3 days I took it down and sited it in my apiary. I have added some additional frames of foundation and put in a frame feeder in case they are short of stores and to encourage them to draw out the new foundation. At the week-end I will do a proper inspection and look to put them in a normal brood box so I can re-use the bait hive.

Really pleased so far with the results as it’s always nice to get something for nothing, hopefully they will turn out to be a productive colony and expands to be able to take them through the Winter as a full size colony.

My advice for anybody contemplating setting up their own bait hive is go for it. Make sure that the location you choose is one that you can access easily as you will need to able to carry a box full of bees down from it. At first I wasn’t sure if I would be able to do this as I had originally set the hive up by carrying the individual components up a ladder one by one. It’s a different story trying to lug a full size box back down again.



Observations of a Warm Spring

After a number of seasons where the start of Spring has been either cold, wet or even both it makes a pleasant change to have a warm and settled period of weather to the start of a season. This year, 2014, looks to be about 4 weeks ahead of last year and about 2 weeks ahead of what could be considered an average Spring. The bees are certainly active when the mid-morning temperature gets above 12C and it has been getting to 17C on quite a few days. What has been interesting to observe is that my strongest colony, Aqua, has raced ahead of the others. It’s been expanding at the rate of one additional 14×12 frame of brood per week. So it has virtually doubled in size in the space of 6 weeks, which means I can add a second brood box and use it for queen rearing. The other colonies are expanding much more slowly, probably about 1/2 a brood frame a week.


Also what has surprised me has been the emergence of drones very early in the season, at least this means that if the bees do start to show signs of producing new queens they can get mated.

The other issue that appears to be one that will need to be tackled is varroa. As the Winter was very mild this means that the colonies were rearing brood over the whole of Winter giving the varroa ample opportunity to continue their breeding cycles in the larval cells.  I haven’t started to remove capped drone brood yet. I think that because it’s a bit early the bees have been drawing the comb out as worker cells rather than drone cells. I will put in the varroa slides to monitor the mite drop and see how bad the problem is likely to be.