Andy Natchbaul says it is not known how many mites per given quantity of bees should be a treatment level for varroa. He may well be correct for conditions in the USA especially as there so many regional variations in climate etc. In the UK the Ministry of Agriculture's Central Science Laboratory has just published a pamphlet entitled Varroa jacobsoni: monitoring and forecasting mite populations within honey bee colonies in Britain. It is based upon a computer simulation model which can estimate both the number and distribution of mites within a colony at any time. This allows monitoring methods to be quantified and changes in the mite population to be forecasted. It is used in conjunction with a circular slide rule which gives an idiot's guide as to whether to treat or not depending on the estimated number of mites in the colony and the time of year. It is emphasised that the beekeeper must monitor the mite population and the leaflet gives intructions how to do this. The advantage is that unnecessary treatments are avoided as they involve loss of time or money and may increase mite resistance and residues in honey, but the beekeeper must be confident that the colony will not collapse if treatment is delayed. The Varroa Mite Model means that a beekeeper can assess the present scale of the problem and forecast the future level of infestation. This increases the efficience of mite control and saves both time and money. Chris Slade