Re: What is the efficacy of powdered sugar as a mite treatment
Powdered sugar will remove 20 to 30% of the varroa mites on adult bees, but 70% or more of the mites is in capped brood. The only time you could expect any success is when there is no capped brood in the hive. If you have no capped brood then you could expect to remove 90% of the mites, or better, by dusting 4 times. This is labor intensive unless you have a small number of hives. A combination of sugar dusting and trapping mites with drone brood would be a better method to remove mites.
When cleaning up a natural or a shaken swarm, a dusting with sugar and a frame of proper age drone brood for trapping mites, followed by another dusting and frame of drone brood at one week, usually results in a clean swarm that builds rapidly and need no further treatments.
Naturally, if using powdered sugar, you need to have a screened bottom board. If the mites fall onto a solid bottom they just hitch a ride on the next passing bee of the proper age.
42 + years - 24 colonies - IPM disciple - Naturally Skeptic