Winter losses – Micheál C. Mac Giolla Coda (spring 2008)

It is disappointing to hear of exceptionally severe losses in certain parts of the country.  This is particularly sad news for those of us who are dedicated to the conservation and preservation of our native Irish bees.  It is bad enough to have to lose all our wild or feral colonies through varroa, but when managed stocks in whole localities are decimated, it is a very serious loss to the gene pool of our native dark bees.  It is vitally important that a bee can be bred that will cope naturally with varroa.  In this respect, feral colonies and local strains of bees are very important, as they will contribute significantly to the genetic pool, and the more diverse that this pool can be maintained the better the security for the survival of the subspecies.

Before the advent of varroa, an acceptable level of losses over winter would have been about 10%.  Since varroa arrive, this level of losses has increased considerably and especially so in the early years.  In former years, these losses could be attributed to acarine, nosema, dysentery, dampness, severe cold, or starvation.  In recent years we have had a rather high incidence of queenlessness or drone-laying queens in spring.  We also find occasional colonies with no bees either alive or dead even though there may be abundant stores.  At present, much research is being carried out in other countries to find the reasons for those strange phenomena but no definite cause has yet been determined.  We can only conclude that these severe losses are due to the presence of varroa and the related viruses that seem to persist for some time after the mites have been diminished by treatment.  When control over varroa becomes maintained and mite numbers are kept at a low level throughout the year, thereby preventing the build-up of viruses, we do not seem to suffer as many losses.

How can members of GBBG help in replacing those winter losses in our own apiaries and how can we alleviate the shortage of bee stocks being experienced by our colleagues who have been more severely smitten?  One can no longer depend on the availability of swarms in this country as we did in the past.  One of the most convenient methods of replacing winter losses is by producing nuclei.  If these are not required for replacing losses in our own apiaries or for expansion, they can be sold to those that need them. Of course, it is especially important to provide nuclei to fill beginners’ needs.  It is good bee husbandry to maintain a certain proportion of nuclei at all times, and we should have at least a ratio of 1:10 of nuclei as followers to our full size colonies. It is said that any beekeeping problem can be solved by taking something out of or putting something into a nucleus.

Traditional methods of stock division in spring can be used to replace winter losses.  Strong stocks can also be split after removal of the honey crop and fed and treated for over-wintering.  When queen cells are found, artificial swarms can be made and the parent colony divided into nuclei.  Indeed, artificial swarms disrupt the life cycle of varroa and so reduce the level of mites in a colony.  Unlike honey producing colonies, nuclei can be treated with Bayvarol or Apiguard in summer, as they do not have honey supers.

Leave a Reply

Your email address will not be published. Required fields are marked *