Please post an after update. Curious about doing myself. I have a fogger and heard mineral water works and gets rid of mites, but maybe the sugar dusting is the way to go in the beginning. Thanks either way, subscribing to this post.
You need to count the number of brown varroa that are on the sticky board, it is hard to tell from a photo. If the numbers are greater than those recommended for your area you will need to decide what to do about treatments.
It is best to do your dusting on a day when you have sunshine and low humidity if possible. Humid weather or rain will cause your sugar to form very small balls instead of staying in the very small powder particles. This will lessen the ability of the sugar to remove the mites. You don't have to spray the sticky board when using powdered sugar, the mites can't move well in the powdered sugar. Usually they just remain where they fall. The sugar will cause the bees to do a house cleaning, they go to work on the cells and will remove much "trash" from them.
If you are doing only a few colonies buy your powdered sugar in the small bags, it clumps if the bag is not re-sealed tightly. Remember, powdered sugar only removes the mites that are on the adult bees, and most of the mites are in the sealed brood cells. Sugar dusting gives you an idea of the number of mites, and it removes mites from the bees and this slows their population growth. I find that sugar dusting is a handy tool for treating caught swarms or when making nucs with brood less than 8 days old, but full colonies usually will need another form of treatment.
Randy Oliver's web-site, "Scientific Beekeeping", has good information on sugar dusting.
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