Initial assessment of powdered sugar vs. alcohol wash in recovery of Varroa from adult honey bees

Contributed by Jim Orem and Kristen Giesting

The goal of this study is to determine the effectiveness of using powdered sugar to detect varroa mites on adult honey bees. The standard protocol used by many beekeepers is an alcohol wash, which is said to be more effective, but also requires sacrificing 300 bees. Some bee keepers are unwilling to do this, thus, we are interested in determining how accurate and effective the sugar shake method is in comparison.

The goal of this study is to determine the effectiveness of using powdered sugar to detect varroa mites on adult honey bees. The standard protocol used by many beekeepers is an alcohol wash, which is said to be more effective, but also requires sacrificing 300 bees. Some bee keepers are unwilling to do this, thus, we are interested in determining how accurate and effective the sugar shake method is in comparison.

We utilized Tim Schuler’s sugar shake method: His method suggests 2 tablespoons of powdered sugar per ~300 bees, but we decided to use a ¼ cup since we didn’t have an accurate measuring spoon with us in the field. Otherwise, we followed his procedure as closely as possible, collecting ~300 bees from a frame with various stages of brood, into a glass jar. We shook ¼ cup of powdered sugar through the mesh lid of the jar. Schuler’s instructions suggested that we only needed to shake the jar gently to coat the bees in sugar; however, we had some issues with clumping of the sugar onto the walls of the jar. This may have been attributable to the high humidity*. We shook the jar fairly vigorously, to coat the bees as best as possible, and then let the jar sit for four minutes, as per Schuler’s instructions (to allow the sugar to warm, and the mites to loosen). After four minutes, we shook the sugar through the mesh lid over a bowl of water (the sugar dissolves into water and mites float to top). Again, due to the sugar clumping in the jar, we had to shake fairly vigorously for a minute or two, rather than a gentle shake for 30 seconds as recommended by Schuler. We also decided to strain the water through a T-shirt placed in a colander, as a way of double-checking the number of mites we had counted in the bowl of water.

In order to gain some understanding of the effectiveness of the powdered sugar shake method, as compared to the more commonly used alcohol wash, we used the same sample of bees to perform a subsequent test with alcohol. We poured alcohol onto the sample of bees, which still had some sugar clinging to them (and to the jar, likely due to humidity). We performed the alcohol wash for about a minute, although we did not time this step. The first four alcohol washes were performed gently, with the screened lid still on top. The next two washes were done in the same way, and then followed by a water wash, in which the dead bees were submerged in water and then dumped into a white shirt plus colander, as another check for mites. This method was implemented because the sugar did not fully dissolve in the gentle alcohol wash, and we felt that adding a third step may catch more mites, which it did the two times we used it. However, we soon realized that by replacing the solid (rather than screened) lid for the alcohol wash, we could shake more vigorously, thereby dissolving the remaining sugar more thoroughly, and perhaps removing more mites. Three tests were performed in this way, and it

was determined that this should be the method for future research, although using a final water wash is also recommended as part of the research protocol, to triple check the mite count for each sample.

We tested 9 samples of bees, each from a different hive. Eight of these samples came from the same apiary; the additional sample was taken at a different location 2 days later. Each sample was tested for mites using both the powdered sugar and alcohol wash methods. An average of 1.9 mites per sample were recovered using the sugar method, ranging from 0 to 4 mites per sample. Since our post-sugar shake methods were somewhat variable (doing only alcohol for some, alcohol and water tests for others, and using the solid lid alcohol wash for others), it is difficult to assess results. However, the average number of mites recovered for tests done after the sugar shake was 0.7, ranging from 0 to 2 mites per sample. Thus, these preliminary results suggest that the sugar shake method recovers the majority of mites in a sample, as compared to the alcohol wash. If performing only the sugar shake, then one might consider adding 1 or 2 mites to the total number recovered, in order to obtain a number more in line with what an alcohol test might provide.

The article at this link indicates the sugar shake is about 90% as effective as the alcohol wash at recovering varroa mites. This is consistent with our findings. Therefore, a beekeeper could choose to use ONLY the sugar shake method, and simply divide the mite count by 90%, to get a good idea of what the mite count would have been with the alcohol wash method. By using the sugar shake method to test for mites, a beekeeper can avoid killing bees, and still obtain useful information about the mite population within the hive.

*The sugar shake method was tested at a different location two days later, using two tablespoons of powdered sugar from a different bag. During this test, there was much less caking of the sugar, and it stuck only minimally to the sides of the jar. Due to this, it was easier to shake the sugar from the bees more gently, and also appeared to coat them more effectively. This difference may be attributable to lower humidity on the testing date; however, this was not measured.

Editors note: At SIBA, we have preached the necessity of using an alcohol wash to measure and deal with varroa mites. We think it's great that people are looking at various ways to do it. Sugar shakes are considred easier on bees because they don't kill the bees being sampled, but various studies suggest that both alcohol (and soap) washes give a slightly more accurate count. See here on Honeybee Suite, and Randy Oliver's site. This is NOT to discount the sugar shake in any way. In fact, the Honeybee Suite article linked above suggests a formula to account for the small percentage of mites it may miss. We believe that those who are monitoring mites will be better off than those who don't. Share your thoughts below, or bring them to a meeting!

3 Responses

  1. I believe that the alcohol wash has become the standard for industry because it is fast. It need not be the standard for less intensive beekeeping
    • Jason
      Hi Sharon, as more of a small-time beekeeper myself (20 hives) I feel it is the standard for all beekeepers. It's just oo easy to get an accurate idea of the number of mites in the hive. Whether you run 20 hives, or even 2 hives, a beekeepers biggest concern is to keep the colony outbreeding the mites. Since I have been keeping a diligent eye on mites via washes,... and actually doing something about any high-mite counts, I have not lost any hives over the winter for the last two years. I may not be clear when you say "less intensive beekeeping" but will preach that doing washes on the hives you have can't go wrong. Cheers.
  2. […] yourself using either an alcohol wash (that kills the bees you will use for your sample) or a powdered sugar method (that doesn’t kill your bees, but coats them in powdered sugar and allows you to dump them […]
  3. I did a two sugar rolls a couple of weeks ago. I shook the sugar onto a ruled off sampling board and sprayed it with water to dissolve the sugar. Zero mites. Not too surprising, since they were both new colonies with a recent brood break. On thinking back, however, I realize that there was a ring of clumped sugar left in the bottom of the jar that I didn't count. I now believe that mites detaching from the bees may have been trapped in this sugar, and not counted. In future I will wash the jar after dumping the bees, and strain it to see if there are additional mites. Unless things change, I will continue to use a sugar roll partly because I can test a nuc without putting a dent in the population and results will be consistent with my other testing. My ultimate goal is to put my colonies into Winter with a sustainable mite population, and long term, work towards mite and disease resistant bees.

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