The National Bee Unit recommends two simple methods for counting varroa for the purpose of monitoring levels of mite infestation throughout the season. The simplest method is demonstrated in Denise’s video and has the advantages that it does not disturb the bees and gives an accurate indication of varroa levels even when there is a low level of infestation.
The only disadvantage of this method is that it takes several days to get a result. The monitoring board must be in place for a minimum of seven days. If you have a more urgent need to establish the level of infestation in a particular hive, you can use the drone uncapping method described in the Beebase fact sheet which is attached below.
When you have completed the varroa count, you can use the Beebase calculator to establish an estimation of the varroa population in your hive. http://www.nationalbeeunit.com/public/BeeDiseases/varroaCalculator.cfm
The calculator informs your decision on what to do next. For example, if you undertake a count in the autumn and the calculator suggests that no treatment is needed for at least six months, you can leave your bees alone until spring when you may decide to undertake a non-chemical treatment such as shook swarm, queen trapping or drone brood removal. On the other hand, if the infestation level is high, you may decide to use a chemical treatment providing you have already taken off your honey harvest. Sugar dusting can be carried out throughout the year, during each hive inspection if necessary.