[Shelleyanne]

I am going to try icing sugar as a treatment for varroa but I have read that it is not good for the bees if the icing sugar has cornflour in it. Ours in NZ does so I tried to blend sugar in the blender but some of it is fine with a few larger grains in it. Would it be harmful to the bees to use this or is it imperitive that every single particle is fine like icing sugar. Its certainly alot finer than regular sugar.

 

[Phoebee]

We had a similar discussion a few months back. Be aware that in the US we call it "powdered sugar" or "confectioners' sugar", so you may not get a lot of responses if they don't recognize "icing sugar".

I was concerned about the corn starch (corn flour) content as well, but the consensus of the discussion seemed to be that the bees don't eat the sugar you powder them with, they just discard it, and the corn content will not harm them.

Our last brand with no corn starch in it now has corn starch.

I did read one university study that tested powdered sugar and determined that it is ALMOST harmless. It has only one bad effect, which is that it can harm larvae that are about to cap. However, you have to nearly fill the cells with sugar to harm them. A gentle and uniform dusting should be harmless, except to varroa.

 

[tomkat]

Since the sugar you have blended does not contain corn flour I would use it.

 

[AR Beekeeper]

The cornstarch in powdered sugar will not harm your bees when you dust for varroa mites. You will not be dusting the bees when they are unable to fly, and that is the problem with cornstarch used for feeding bees during winter. If the bees can't fly and take a dump, the cornstarch builds up in their gut and causes diarrhea.

The sugar particles must be fine or they will not cause the mites to fall off. Moisture in the air causes the particles to enlarge and leftover sugar is not as effective as powdered sugar when it first comes out of the bag. I store leftover sugar in ziplock plastic bags, and I double bag it. I use a blender to re-grind the powdered sugar the night before, or in the morning that I plan to use it.

The only time the powdered sugar dusting works well is when the mites are riding the adult bees, even then I think I only cause about 20 to 30% to fall with each dusting. Mainly, I use a combination of PSD and drone brood removal to clean up a caught swarm, or to clean up a new nuc made with very young larvae that the mites will not have entered.