To Sugar Roll or Alcohol Wash, That is the Question

A dead bee after a sugar roll

In honeybee keeping, varroa mites are the most common pest and must be tested for continuously in order to ensure proper treatment for them. Not only are there a variety of mite treatments, there are a variety of ways to test for them. The most traditionally accepted, and the most accurate method is the alcohol wash, wherein isopropyl alcohol and water are used to instantly kill bees upon submersion, and then you shake the bee-alcohol mixture to dislodge the mites. Another popular testing method is the sugar roll, wherein bees are placed in a jar with about 2 tbsp of powdered sugar, and they are shaken to dislodge the mites, left to sit for a few minutes, and then the sugar and bees are separated, and finally the sugar is dissolved in water in order to allow the beekeeper to see and count the bees. A less common testing practice is placing a sticky board to catch varroa that fall to

A side view of the abdomen of a bee post-sugar roll under a dissecting scope

the bottom of the hive. The sugar roll and alcohol wash are by far the two most common methods, the main difference is arguments for or against them. An alcohol wash immediately kills all 300 bees for the mite count, so while it is more accurate some claim it is less humane. The sugar roll

doesn’t immediately kill all the bees that are used in the test, but the sugar roll is less accurate, most powdered sugar contains cornstarch (which can clog the bee’s gut), and there is some thought that it could clog the tracheal tubes of the bee (how it breaths).

Dissecting scope image of the underside of a bee's abdomen

Currently in the bee yard there is a running experiment to test the questions “does the sugar roll just kill bees more slowly or is it really that much more humane?” and “is the sugar roll as accurate as the alcohol wash in testing your mite load in your hive?” To test the first we are taking advantage of the small observation hive we have access to so that we can separate the bees that have undergone a sugar roll from the rest of the hive. A sugar roll is then preformed with a kit specially designed for mite

Dissecting scope image of a dead bee after a sugar roll

testing by the Bee Squad from the University of Minnesota. After an allotted amount of time the bees are released from the observation hive and the dead or dying bees are then counted to give us the number of bees lost. Additionally, in order to test the second question, we preform a secondary mite testing procedure on the same hive using an alcohol wash so that we can compare the two results. While we haven’t been able to preform this experiment many times due to weather constraints and now the winter weather, in the few data sets I have, it’s not a stretch to say that (from our anecdotal evidence) the sugar roll is both less effective in counting the mites and does cause mortality that is simply more drawn out rather than quick.

Dissecting scope image of a bee's head and underside of the thorax after a sugar roll under a dissecting microscope

Having the opportunity to design an experiment and then spearhead its execution while still in undergraduate has been a fantastic opportunity. Not only is it incredibly rewarding to see what you’ve hypothesized and designed in theory turn into actual numbers and data, I have discovered that the longer you spend working on and thinking about an experiment the more ideas you come up with that are tangential to it. Hopefully once it gets warm, we will be able to get more significant numbers through repetition of the experiment that will give something more statistically sound and less anecdotal to report. But even for now it is becoming clear that while a sugar roll may make a beekeeper feel better because they aren’t killing their bees, there are other consequences of the sugar roll that are likely just causing a slower death that the beekeeper just doesn’t see.