Submitted by J. Morgan
There's a lot of opinions and thoughts on sugar dusting and so on Thursday, September 16, 2010, we decided to address the topic. The associated video was our attempt to further explain and demonstrate the matter. Techniques and thoughts vary depending on who you ask or the area you are in. We hope this video is helpful to you.
What is sugar dusting?
It is a technique that Dr. Fakhimzadeh proposed as a part of his Doctoral work and is published in several journals. Google his name to find out more.
The idea is simple. Varroa have little "suction-cup" feet. When varroa fall down below a varroa screen or out a screen bottom board, they don't crawl back up. Sugar particles that are approx. 5 microns in diameter (powdered sugar or "dust") clog up the mites suction cups, and they can't hang on to the bees so they fall and eventually die and don't live to reproduce. Therefore, dusting the bees will knock off some significant percentage of the mites, keeping the population under control.
Sugar dusting may allow you to stop using Apistan strips or other toxic treatments. This treatment is both cheap and non-toxic treatment so we like it and want to explore it. Most of our club members tend to lean towards more natural beekeeping and there are many methods of mite management to choose from. See Mel Disselkoen's outbreeding mites and overwintering honey bees.
What powdered sugar to use
Thoughts are... 2% - 5% corn starch (found in Domino 10X and most other store brands) doesn't matter one bit. But it doesn't hurt to try to find the LOWEST percentage of corn starch you can.
Supposedly, "pure" powdered sugar with zero corn starch (added to keep it from clumping) exists. If you can find it, great.
Preparing the sugar
It's the very tiny sugar particles that clog up the "suction cups" on the legs of the varroa mites. But how to insure that you "dust" a minimal amount of useless larger particles, when the optimal particle size is on the order of 5 microns?
- We sifted the sugar the day I used it but you can do it ahead of time if you store it right.
- First, all sugar is sifted with a flour sifter. This removes the big lumps.
- Sift the sugar again right in to a container that you can seal tightly from moisture.
- Adding some rice to your sugar container can absorb humidity, and keep the sugar drier.
- Seal the container tightly, (canning jars work).
Note submitted by Kenny Schneider: Use powder sugar with the least amount of corn starch. I make my own powder sugar. Just put your regular sugar in a blender and in a few seconds you have powder sugar with no corn starch.
Sugar application to the hive
Application of the sugar is your choice. There are many options and whatever one can give you full coverage with less effort is good. As you see in the video, we used both a bellowed blower and a flour sifter. There are "pistols, foot-pumps and you could even use a dried baby-powder container, (where you can twist the cap to reveal tiny holes.) Again, the most important thing is that you cover all the bees. In our video, we didn't go frame by frame. Obviously doing so would give you the best coverage, but it's a huge disturbance to the hive.
Dust the bees trying not to get too much on the comb. There is a lot of debate about dusting. Some mentioned simply dusting the top bars rather than removing the frames, but the idea here is to do your best to knock down all the adult varroa in the hive.
If you google "Dr. Fakhimzadeh" you will see he says that sugar DOES NOT have a negative effect on open brood or eggs. It's said that OTC dusted with sugar was claimed to be fatal to brood, and Dr. Fakhimzadeh stated that it is the OTC itself that can kill the brood, not the sugar. Again, we only used sugar and we didn't do each frame. We'll report our results later.
Methods of mite counting
It's good to have a varroa screen or a slatted bottom board, or at least a sticky-board insert with a mesh cover. Sugar dusting will not help if the mites can crawl onto another bee after they fall. Mites can fall through a varroa screen or screened bottom board any time.
If you slide a fresh sticky board in just before you do your dusting, you can get the most accurate count. There are many methods to count. We demonstrated an "ether roll" test... but also, check out the sugar roll test.
Frequency of dusting
Again, thoughts vary. Remember, you are disturbing the hive... especially if you dust frame by frame. We read 3 consecutive treatments 1 and a half or two weeks apart. You have to use your judgement on your own hive as to how many are too many mites. Seeing only a few over a certain area is not as much of a concerns as seeing very many over the same area.
You could sugar-dust a hive every week, but think of the impact on the productivity of the bees. Maybe you can tolerate a low varroa population and do a sugar roll or an ether roll as often as you want to make the best decision when to dust.
Varroa population, should be monitored ongoing, but seems to peak between June and early September in our area. Some of our members say they will do three dustings about 2 weeks apart before winterizing the hive. Good luck.