On the London Beekeepers Association face book page Dr Karin Alton of the University of Sussex – Laboratory of Apiculture and Social Insects (LASI) posted-
hello! Latest research results from LASI indicate that between the dates of 10th december and christmas is the optimal time for oxalic acid treatment. Please check for sealed brood and destroy any, say, 48 hours before applying acid.
This is not published yet and perhaps she was jumping the gun by posting it but as someone who has managed perfectly well without the need to treat with oxalic find this advice just crazy.
The unpublished work at LASI was presented and discussed at their Open Day this last summer.
The project was to compare the relative efficacy and relative risks of vaporising, trickling and spraying Oxalic.
It was on different ways of using Oxalic, not about whether, or when, to use it.
In order to 'level the playing field' between the experimental colonies, it was necessary to zero out all varroa sheltering in sealed brood cells.
This also maximises the anti-varroa treatment's effectiveness.
HOWEVER -
- I don't believe that the research compared different treatment timings, treatment weather conditions, or 'control' non-brood-culled colonies.
- and I don't believe that the scope of the research included much, if any, follow-up on the performance of the colonies - let alone proper comparison with any non-brood-culled but treated colonies.
In conversation, Mr Garbuzov was strongly of the opinion that (full inspection and) brood culling to increase effectiveness of the anti-varroa treatment was well worth any downside, but did not offer any evidence on that score.
I would note that any
comb-spraying treatment (whether Lactic or Oxalic) necessarily involves frame removal, and that sealed-brood-culling would not add great additional disruption to that.
I'm not sure what the point might be of doing such sealed brood culling in a different inspection, 2 or 3 days before treatment. Perhaps it was simply more convenient for the experimenters' schedule?
However, it is important to note that there was no mention whatsoever of any research being (or having been) done as to comparative application dates... (ADDED - for treatment efficacy, let alone comparing dates against colony outcomes in the year ahead)