This is a question I’d rather sidestep, but it keeps insinuating itself into my inbox. So I’ve finally decided to take a quick stab at this complex (and oftentimes heated) debate.
The theory behind powdered sugar dusting is that the bees will groom the sugar off themselves and the hapless mites will drop from the bees and fall through the screened bottom board and out of the hive. Mites on the ground soon become food for something else. Good riddance. Any inert powder applied to the bees will have a similar effect, but powdered sugar is a good choice because it is readily available, inexpensive, and harmless to the bees.
Most sources I consulted recommend one cup of powdered sugar per brood box. However, those who use bellows-type applicators use less. Those who use powdered sugar dropped through a food strainer use considerably more. As I said, the sugar is harmless to the bees, and even the small amount of corn starch found in commercial powdered sugar has no ill effects.
Powdered sugar also has no harmful effect on mites. Some folks think the sugar makes it harder for the mites to hold onto the bee, others say it makes no difference. Most think it is just the act of grooming that dislodges the mites. Consequently, most mite drop after a powdered sugar application occurs within the first few hours and decreases quickly after that.
So far, I’ve given you all the good news. Now, the rest:
Powdered sugar only affects phoretic mites—those mites that are riding around on the bodies of honey bees. By far the most mites, especially during spring and summer, are inside the cells of capped brood. These mites are oblivious to blizzards of powdered sugar.
That means that powdered sugar must be applied regularly to the hive in order to remove mites as they hatch along with brood. In his experiments, Randy Oliver found that the more treatments you applied, the more mites you “killed” (dropped out of the hive). Treatments every week killed more mites than treatments every two weeks, which killed more mites than treatments every month. Oliver found that the only treatment schedule that effectively suppressed mites over long periods was once per week.
Another factor is the method of application. Some experiments have shown the best coverage is achieved by removing every frame from the hive, treating both sides, and then replacing the frame. This is an egregious amount of work and a huge disruption of the colony, especially if done on a once-per-week schedule. In fact, except for hobbyists with just a few colonies, it would be virtually impossible. Other experiments have shown that dusting the top bars is more effective, as long as at least some of the sugar immediately falls through to the bottom of the hive.
Another issue is humidity. Powdered sugar is amazingly hygroscopic, meaning it has an attraction for water. If you keep bees in a humid climate, or if your hives are full of moisture, the sugar will clump on the bees instead of dusting them, a situation that reduces the efficacy of the treatment.
In spite of the negatives, sugar dusting has been found to significantly reduce adult mite populations at times when little brood is present. Colonies in a summer nectar dearth or loosely clustered winter bees may be effectively treated with powdered sugar. Also packaged bees, swarms, and shook swarms—units without brood—may benefit from the treatment as well.
My own opinion is that powdered sugar dusting is effective only when used in combination with other Varroa management protocols such as drone trapping, queen removal, splitting, and the use of organic acids. Except under the most onerous treatment regimens, powdered sugar dusting by itself is probably insufficient for long-term Varroa management.
I’m new to beekeeping, will get my first two hives in spring 2013 (on order now). I want to use very little as possible of any chemical treatment. I have seen on YouTube a man (fatman) fogging his bees with mineral oil and a few drops of pure wintermint oil. He did it on warm days in winter. Is this a good treatment? What is the best non-chemical treatment? I know that in classes they have said to rotate the chemicals and not to use some behind each other because it will kill bees. Boy what a catch 22 . . . thank you.
I don’t have experience with FGMO, but you should read this post written by my friend, Maggie. She worked with a beekeeper in New Zealand who was experimenting with it and had good results. It’s worth it to read the comments as well: https://www.honeybeesuite.com/a-fight-with-the-varroa-mite-in-new-zealand/.
Many beekeepers manage to keep honey bees without resorting to chemical treatments. If you go that route just remember that it requires more time and more hive manipulation; also you will probably have more losses in the beginning. Over time, however, you can develop a line of bees with higher resistance than average and fewer losses.
I consider myself to be middle-of-the-road on mite treatment. I do not use hard chemicals or pesticides at all, but I do use the so-called “soft chemicals” made from plant extracts such as thymol (from thyme), hop beta acids (from hops), and wintergreen. I consider FGMO to be in this category.
Other methods such as drone trapping, splitting, queen sequestration, and powdered sugar are mechanical in nature and therefore the least damaging to bee health. Unfortunately, they are also the least damaging to mite health.
Roy, like everyone else, surely, I’m working my way through every single word of your sageness on this site, but I notice a typo in the first paragraph. Being such an eloquent and erudite wit, I know this will bother you.
OK. …one clue.
It’s actually in the second paragraph.
Thank you. And you are correct, those errors bug me no end.
Can you recommend a book that has the information on the mite managment techniques you mention (the ones you like/use) in this thread? Thank you.
I actually can’t think of one. The options keep changing, which is part of the problem.
Rusty, I am currently feeling like an abject failure as a first year beekeeper. I have hummed along happily since May watching my two colonies grow and seem happy and healthy. I got VERY busy with work for the last few months and took this for granted. Last week I found a few small hive beetles so I put in traps but then I remembered to check for mites. Based on the sticky board test, both my hives are positively overrun, hundreds of drops per day. Given the lateness of the hour, what can I do? I still have lots of bees with a steady stream of traffic in and out at the right times of the day.
It may be too late, but you can purchase something to treat them with. You can use one of the organic acid treatments such as ApiLife Var, Miteaway Quick Strips, Hop Guard, or oxalic acid. Or else you can go with a commercial pesticide such as Apivar. Whatever you decide on you have to follow the directions. Some need to applied within certain temperature ranges.
Rusty I cannot seem to find the Varroa mite count charts that tells how to count and divide for the % of Varroa mites. (I intend to use the sugar shake method) Can you publish one or point me in the right direction? What are your thoughts on mites vs Russian Bees? I have inherited 2 hives of those little mean, communist, election rigging, KGB, American hating Russian bees and have heard that they deal with mites real well. The hives are way small in population so I decided to feed them sugar syrup with Super B Healthy and pollen patties to try to get them to build up. I got Apiguard to treat for Varroa and Tracheal mites but am holding off applying because they are so weak. I will decide after I test for Varroa mites. I sure would like to hear any advice you may have concerning Russian bees.
The directions for the Sugar Roll Test say this, “If you know how many bees were in your sample, you can estimate the number of mites per 100 bees. If there is brood in the colony when you sample, you should double this number to factor in the amount of mites in worker brood. For example, if there are 5 mites/100 bees, the total infestation is probably 10 mites/100 bees. If your colony has over 10-12 mites/100 bees, you should consider treatment.”
I’ve only had Russian bees one time (one year/three colonies). I could not tell any difference between them and my Carniolans. But that may be because I had no way to keep them from crossbreeding with other bees in my area, so the genetics probably washed out quickly. It’s impossible to maintain genetic purity if your bees are within flying distance of other hives unless you instrumentally inseminate all your queens.
My personal opinion is that locally adapted bees are the best.