As it is now becoming fashionable to expose your bees to the fumes of vapourised Oxalic acid rather than the trickling of acid in syrup that we’ve been doing for years, I thought I’d give it a try.
I found in my shed a length of copper pipe, about 7/8″ in diameter and cut off a length of a little over a span. I found a stick of hazel, trimmed it, and it was a perfect fit to block one end and provide a handle. The other end was placed in a vice and squoze until it was narrow enough to fit into a hive entrance and stay there unsupported. I tested in some empty hives in the garden. I bent the lid of a cat food tin to make a funnel to help pour the acid crystals into the spout.
Next job was to do a test run. I asked on the BBKA Facebook page what was the dose to apply and misread the 2.3 grammes as 23! I measured this amount on the kitchen electric scale and it was about 3 heaped teaspoons, about as much as would make a half gallon of the syrup treatment!
I revisited FB and discovered my mistake. Unfortunately my scales aren’t sensitive enough to measure that amount so I had to dig out my see-saw powder scale which measures in grains. By an on-line conversion table I discovered that 2.3 grammes equal 35.49 grains so I set my scale to that and added oxalic crystals until the bar of the see-saw balanced horizontally. I don’t intend to do this every time, so transferred to acid to the usual measure, a tea spoon, and found that it equals half a level teaspoonful.
I poured the acid into the applicator and took it for a test run, wearing goggles and mask and making sure that there was no wind in my direction. I lit my small camping gas stove, applied heat to the part of the pipe where the crystals would be, and started counting mentally. It was about 30 seconds before I saw anything at the spout and, rather than the gush of acid steam that I’d been expecting there was just a mist drifting out and around. It diminished after about 2 minutes.
I went to the nearest hive with a Varroa board, did a count of mites which was at the usual around three a day and reduced entrances with cloth, leaving a gap the size of the spout.
Later, I went back with all the kit and gave the hive and the one next door doses of half a level teaspoonful each. Today, roughly 24 hours later, I checked the Varroa floor again and found 13 dead mites, roughly 4 times as many as usual, so it had had some effect but nothing like the massive drop I’d been hoping for.
Only one of the mites appeared dented, but there was also a paler one, suggesting an immature mite. There were far more bits of bee ‘skeleton’ than usual, suggesting that the bees may have been sweeping their floor to get rid of the intruding chemical.
I think I’ll leave it for a couple of days, doing further mite counts and then repeat the process using the usual trickling method to compare and contrast.