Winter staples.
Previous winters I have seen wetness and dripping staples, which I presume isn’t great for the bees. Of course, neither is varroa…. However, I have been shifting to vented base boards, and combined with narrow staples last winter I saw a lot less dampness.
.......
3. Both the above points lead to the staples having less solution in them when winter really hits. I think there is less GL in them to attract water.
It is a misconception that OA/Glycerine strips would make hives more damp. Yes, glycerine is very hygroscopic, it is in some applications even used to extract water from air, but it does not make the air more humid, on the contrary: it dries the air out because water is being removed (for a short while, at least, until the glycerine is saturated).
The pure glycerine in the strips attracts water and the strips drip as long as the humidity of the air is higher than what balances out a glycerine/water mix. Venting makes the hive atmosphere more in equilibrium with the outside, and it will vary accordingly and so dripping may happen even a few weeks after the strips have put in (at least in Dunedin...
).
There are no very firm data on Relative Humidity (RH) inside a hive, again it depends on the circumstances, time of the year, location, ventilation, size of the colony and so on and numbers between 50 and 85% have been mentioned in the scientific literature.... But perhaps a 60-70% RH is considered an ok average. Under those conditions the glycerine takes up ~ 30 volume % of water. The strips can not hold that volume, regardless of how many layers are used, it is a volume %age after all. So they drip.
If humidity decreases the strips will lose water and the powdery OA will dissolve again. Swiss beekeeper Gerhard Brüning's data suggest that the powder is active and ends up on varroa's feet, poisoning them. This is after all also what kills varroa when OA is sublimed into the hive entrance.
I made the strips this season with ~ 25% water, 75% glycerine (v/v) instead of 100% glycerine. Some of the OA will crystallise because the 40-50% OA solution is almost saturated when made with pure glycerine and OA is less soluble in water than in glycerine or mixes thereof. This makes the surfaces a bit powdery, which happens anyway also with strips made with pure glycerine when they have spent a while inside the hive, for obvious reasons. Saves on glycerine too (yes, I am Dutch.... originally...
). Higher %ages of water might be interesting but make it impossible to make a solution of 40% OA in the liquid. Whether that is a bad thing? I doubt it to be frank, as long as the suface is powdery the strips should be fine.
Just under a month ago I put some cardboard oxalic staples into a hive I'm monitoring at home. It had around 25 mites per 400 bees in an alcohol wash. (I know 400 is not the normal number but that is what I'm using because that is what the container I chose holds). Today I replaced the strips even though they weren't particularly chewed up with eight new strips and did another alcohol wash. This time it was 125+.
I had high hopes for oxalic\glycerin strips but this has certainly dented my enthusiasm. I will check them again in a couple of weeks.
Surprisingly the hive still looks pretty healthy with just the odd bit of deformed wing showing up.
I agreed wih Alastair. As long as the production capacity of new bees (and varroa) exceeds the slaughtering capacity by OA, varroa numbers will continue to go up, but they would go up even more in the absence of such treatment. When brood numbers go down at the end of the season that is when OA will start to win! I apply my strips early Feb when I find >5 mites on the sticky board over 24 hrs.
OA is a slow poison, so it needs to be presented to the infested colonies under the best conditions to reach a good outcome. Monitoring on a very regular basis is key, to make sure the strips still hang over the frames and have not been pulled off by the bees and allow Varroa numbers to continue to go up exponentially. There are many observations and opinions about the success rate of OA, and some failures may be due to such events.
Staples <> strips? I use just one layer of Gib tape, so strip would be a more appropriate use in my case I suppose. I have followed in Otto's footsteps, never used anything else than what we call OA/GLYs and very happy with the reults so far. Yes, I am a novice and as a biologist I realise i will always be a novice when it comes to understand and align with Nature.