Dealing with varroa

Any beekeeper that has kept bees for a number of seasons will understand and know, there comes a time when your colony requires assistance in dealing with varroa, or the colony will die. This is a sad fact of modern beekeeping, but, if we are going to apply good animal husbandry concepts to our bee stock, there are times when it’s necessary to intervene and try keep our stock healthy.

To begin with, when modelling mite interventions (Treatments), I have chosen two of the common organic acid methods to introduce as tools for managing mites.

Formic Flash:- The formic flash treatment is one commonly used in our area, it’s a single day application of formic acid to the colony. The benefit of the formic acid treatment over others, it will apparently effect mites under cappings as well as phoretic mites. One can read endlessly about efficacy, and eventually you realize, the numbers quoted in different sources are all over the map. I have chosen to model the formic flash treatment with a very high efficacy level, not because I believe it is this high, but to show how even with high efficacy on a treatment, an out of control mite population will still kill the hive even after a mite treatment is applied. For the purposes of this model, the formic flash treatment kills 90% of the mites under cappings and those in a phoretic state. This is a highly effective mite kill. But a huge caveat, reading at Randy Oliver’s site at scientific beekeeping, he tried multiple rounds of formic flash to try improve mite kill. A second round of formic a week after the first resulted in a dead colony. Reference available here.

Oxalic Acid Vapour:- The Oxalic Acid Vapour treatment is less effective than the formic treatment in that it only affects phoretic mites. Easily applied on a small scale using a wand style vaporizer that takes about 5 minutes per colony for a full treatment, or using a blower style of vaporizer that takes about a minute per hive when doing larger numbers. The OAV treatment puts oxalic acid crystals in the hive which work for about 24 hours killing phoretic mites. Literature suggests this treatment is about 95% effective, in that when properly applied it will kill 95% of the mites. As it lasts over roughly 24 hours, for the purposes of modelling, we kill off 95% of phoretic mites on the day it is applied, and also get 95% of the mites emerging over the next 24 hours.

The OAV treatment only gets phoretic mites, and one strategy to help with this problem that I’ve read about online a number of times is folks are trying 3 treatments a week apart with the expectation this will get all of the mites thru a brood cycle. That would be true if the mite brood cycle turns over on a weekly basis, but, it doesn’t, it turns over on a 5 day period, the amount of time a mite remains phoretic. I added two more OAV options to the model, one of them applies 3 treatments at a 1 week interval, and another that applies 4 treatments at 5 day intervals. for those with a small number of hives, these may be viable options for mite control. If your colony count is such that you cant get thru them all in 5 days of work, then these become less viable options.