Following a recent question from @AmethystDragon on Twitter I asked a few of my beekeeping collegues what their opinion was on the assertion that using top bar hives led to a substantial reduction in the infestation of bees by Varroa mites.
The question had been prompted by this article on Warre Beekeeping .
Although most people felt it unlikely to make a big diference to the incidence of Varroa there is some logic to the assertion and there is a connection between this and the work of an Italian beekeeper who claims that increasing the space between frames to give a wider "Bee Space" shows a significant improvement. (Can't find a web reference for this at the moment will update later).
The theory is that top bar hives in which the bees build natural comb without wax foundation as a guide tend to use a wider space between combs. The mites travel around the hive after hatching by being transfered from bee to bee. A wider bee space may lead to fewer interactions between the bees as they pass each other over the comb and therefore statistically reduce the ability of the mites to spread.
This is only a theory and I have not been able to find any scientific peer reviewed work to back it up - anyone reading this who does know of studies please contact me and I will update this with relevant links.
Natural comb building is of course what happens in nature and there is evidence that wild colonies have been known to exist quite happily in inaccessible places when they will almost certainly have picked up mites whilst out foraging or robbing hives. This is one of the reasons that wild colonies are very important for research. Whether it is a genetic or a behavioural trait it may well hold the answer to keeping bees that are more resistant to Varroa and disease.
On a practical note. The use of top bar hives presents particular management and manipulation issues. Modern beekeeping practice requires colonies to be regularly checked for disease and most swarm control techniques requires the regular manipulation of combs. Comb without a wooden frame around it is very delicate and on a hot day could easily break whilst being examined. Extracting honey from natural comb almost certainly will require cold pressing equipment or heating to melt the wax the later being significantly detrimental to the flavour, aroma and beneficial qualities of the honey.
This I suggest would lead to the advice that one should learn beekeeping on the more usual framed system and then start experimenting with top bars once a significant level of skill and knowledge of bee behaviour and husbandry has been gained.
This is not to suggest that keeping bees in the Warre way should be dismissed out of hand. I believe that there may be substantial benefits to this system if applied properly and with the appropriate regard to disease control. I and many of my collegues are sceptical that it is the answer to varroa problems but any system which gets as close as possible to the natural environment for the bees themselves is worthy of serious consideration and should be supported by all Associations in a spirit of collaboration and research.