The Oxalic trickle process – you are supposed to trickle 5ml of the mix into every occupied seam of bees but you don’t know if there are 500 or 2000 bees in the seam so potentially some bees could get a much higher dosage than others. You may see a couple of dozen dead bees chucked out after treatment and that is likely a mix of natural wastage and drowning or chilling in the applied liquid.
Bring a thermos flask of hot water to the apiary and stand the bottle of Oxalic mix in a margarine tub of hot water to keep it tepid. You definitely do not want to trickle cold liquid over the cluster in winter. You can also apply it with a vapouriser but that can be dangerous (vapourising acid) and there is also comparative research which demonstrates that trickle method is just as effective.
The basic mix is 7.5g oxalic powder with 100g sugar and 100ml of water. That treats 4 or 5 strong colonies. You scale this up according to the number of hives you have.
Last year a ratio of 30g 400g and 400ml treated about 20 colonies and nucs and about 150 ml left over. It costs less than 10p per colony so just throw away the excess.
Thanks to Jonathan for these notes on his oxalic experience in December 2010.
Also thanks to Philip for sending me a copy of the British Beekeepers Association leaflet on Oxalic acid use: Oxalic Acid Cleansing
Tip: Treat yourself to at least 5 syringes, prefill just before opening the hive and then the hive may only be open for 1 – 2 minutes at most.