Powdered sugar for Varroa control

[oldenglish]

Sounds like powdered sugar could just be a myth,

Journal of Apicultural Research and Bee World 48(1): 72-76 (2009) © IBRA 2009
DOI 10.3896/IBRA.1.48.1.14
The efficacy of dusting honey bee colonies
with powdered sugar to reduce varroa mite populations.
Amanda M. Ellis1*, Gerry W. Hayes1, and James D. Ellis2
1 Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Bureau of Plant and Apiary
Inspection, Apiary Inspection Section, 1911 SW 34th St., Gainesville, FL 32614-7100, USA.
2 Honey Bee Research and Extension Laboratory, Department of Entomology and Nematology, University of Florida,
Bldg. 970 Natural Area Dr., Gainesville, FL 32611-0620, USA.
Received 5 August 2008, accepted subject to revision 15 October 2008, accepted for publication 16 December 2008.
*Corresponding author: Email: jamamellis@hotmail.com

Summary

Controlling varroa mite (Varroa destructor Anderson and Trueman) populations in honey bee (Apis mellifera L.) colonies with acaricides has been a challenge for beekeepers due to the rapid development of resistant mite populations. For this reason, many beekeepers are adopting Integrated Pest Management strategies as alternatives to chemocentric varroa control schemes. One nonchemical tool that has been used for varroa control is dusting bee colonies with powdered sugar. The objective of our study was to determine the efficacy of powdered sugar as a varroa control by comparing mite populations, adult bee populations, and brood area in untreated colonies with those in colonies dusted every two weeks for 11 months with 120 g powdered sugar per application. We found that dusting colonies with powdered sugar did not significantly affect the adult bee population (treated: 10061.72 ± 629.42;control: 10691.00 ± 554.44) or amount of brood (treated: 4521.91 ± 342.84 cm2; control: 4472.55 ± 365.85 cm2). We also found no significant differences between the total number of mites per colony (treated: 2112.15 ± 224.62; control: 2197.80 ± 207.75), number
of mites per adult bee (treated: 0.080 ± 0.010; control: 0.097 ± 0.010), or number of mites per capped brood cell (treated: 0.112 ± 0.013; control: 0.106 ± 0.018). All data are mean ± s.e. Within the limits of our study and at the application rates used, we did not find that dusting colonies with powdered sugar afforded significant varroa control.
Discussion Despite the fact that powdered sugar dusting is innocuous to colonies of honey bees and would, therefore, be a good candidate as a varroa control agent, we found that our treatment protocol did not significantly reduce the total number of mites per colony, the number of mites per adult bee, or the number of mites per capped brood cell. We reject our hypothesis that biweekly dustings with powdered sugar would significantly reduce varroa populations. Even though dusting with powdered sugar resulted in significant mite fall initially (Fakhimzadeh, 2000), we did not find an overall reduction in colony mite populations within the limits of our study. This may be attributable to the reproduction rates of varroa mites under differing population pressures. Eguaras et al. (1994) observed that at lower mite densities, the reproductive rate of varroa increases. Therefore, the mite may be able to compensate for population loss due to dusting by increasing its reproductive rate. Even though different application methods were employed, Fakhimzadeh (2000) only measured mite fall 24 h after treatment, so it is unknown how effective the treatment would be in the long term, which
was addressed by our study.
Dusting only removes mites from adult bees and not mites reproducing in sealed brood cells. We found that, on average for each sampling month except November, approximately 60 % of the total mites per colony were located in the brood. For example, since 60 % of mites may be reproducing in brood at any given time, a control method that reduces even 90 % of the mites on adult bees will only result in a 36 % reduction of mites in the entire colony. To account for that in our study, we dusted colonies every two weeks for an entire year. This should have increased the efficacy of powdered sugar because we dusted colonies during times of the year when they were relatively broodless (winter). We still did not, however, find significant differences in mite populations between dusted and undusted colonies. Our results support the conclusion of Aliano and Ellis (2005b) that isolating broodless adult bees from their nest materials and dusting them in a separate box is the only way to effectively use powdered sugar to significantly reduce varroa infestations.
In summary, dusting colonies with powdered sugar did not significantly affect colony strength or mite populations. Within
the limits of our study and at the application rates used, we did not find this method of dusting colonies with powdered sugar to effectively control varroa mites.

Acknowledgements
Tom Dowda provided technical assistance with colony care, treatment administration, and data collection. Various members of FDACS Apiary Inspection, FDACS Bureau of Methods Development and Biological Control, and UF Honey Bee Research and Extension Laboratory assisted in data collection. Funding was provided by the Florida State Beekeepers Association and the Florida State Legislature as directed by the Florida Honey Bee Technical Council.

[Kathyp]

need to see the study protocol to see how and when they did it.  was it a one time dusting, every week, two weeks, etc. 

[oldenglish]

Its in there,

dusted every two weeks for 11 months with 120 g powdered sugar per application

[Kathyp]

sorry, missed that line.  well, that's what most of us do, or less.  a little discouraging.

[indypartridge]

Interesting. Obviously my results aren't a controlled scientific study, but I dust my bees when my mite counts get high (50-to-60) in a 24-hr period and seem to have had success in reducing mite infestations.

The two-week interval they used was unexpected. I've usually read that shorter intervals are more effective with respect to mite/bee reproduction cycles. When I treat with powdered sugar, I usually do 3 treatments, a week apart.

[Brian D. Bray]

Interesting. Obviously my results aren't a controlled scientific study, but I dust my bees when my mite counts get high (50-to-60) in a 24-hr period and seem to have had success in reducing mite infestations.

The two-week interval they used was unexpected. I've usually read that shorter intervals are more effective with respect to mite/bee reproduction cycles. When I treat with powdered sugar, I usually do 3 treatments, a week apart.

That is the recommended protocal, so I would have to suspect the research.  doing the shakes at 2 week intervals allows for a lot of mites to hatch out and re-enter brood cells so the shakes wouldn't be as effect.  I think that is exactly what they proved.  I say have them do again, right.  3-4 Sugar shakes at 1 week intervals and see what the results are.

[IABeeMan]

 I dust once a month as a norm and if my counts begins to grow I dust once a week for a month. I have used this method for a while now and have not lost a single hive. So until I see that even with dusting I have a mite problem then it works in my opinion. True it will not eliminate the mites but I believe with the mite it is not a matter of eliminating the mite but rather keeping them to a level that the hive can survive and thrive.

[Michael Bush]

http://www.bushfarms.com/beesvarroatreatments.htm

[Robo]

I'm still waiting for a study to address the stress put on a hive by dumping powdered sugar on them.  I know there are all kinds of beliefs about set back to a hive by just opening them up and inspecting,  and one would have to expect dumping powdered sugar would be even greater.

[John Schwartz]

For those of you who dust, 1) how many mites do you see/find that drop subsequently and 2) do you see mite levels drop in general after the dusting?

[Kathyp]

i wonder if using a SBB makes any difference at all?

[challenger]

Too lazy to read the article but I've sort of been treating my bees in a manner that Ross Conrad uses in his book, " The Organic Beekeeper". He maintains that powdered sugar treatments and Drone comb alone can keep hives strong and healthy but he is in VT??? I'm not an organic type of person but I'm also not going to dump chemical in my hives. I use powdered sugar and take all the frames out and dust each one-w-a sifter if I have a large mite problem (like recently). I also just sift over the top bars as "PM" once in a while. I am a strong believer that a screened bottom board is a must and the book states that mites can fall to a solid bottom and hitch a ride back into the hive once they catch their breath but-w-a SBB they are toast.
I had so many Varroa a couple of weeks ago that I could see  a lot of bees-w-one and sometime 2 on their backs. I hate these little bastards and can't wait for a fix.
I also believe firmly that a very heavy smoking of the hives makes mites drop off.
I think I am going to try and put some spearmint leaves in the hives this year once my plants grow and see if this helps. I've read the mites are irritated by mint.
Another curious thing is Succrocide. I think it is Invert sugar-w- some type of soap in it. Any insect-w-a exoskeleton will usually die from having soap applied to it because it makes their "shell" soft and makes them susceptible to infections/damage. I'd love to know about any attempts other may have made at adding a little dish soap to a spray bottle of Honey-B-Healthy (I make my own version) and spraying the bees. I will try this after the honey flow and if anyone else would like to start a trial/error for DIY succrocide using experimental solutions please inform me and we can do some real data gathering. I'm thinking of taking a nuc and trying this. If it fails and kills the bees at least it wouldn't be a full deep hive.
Any takers?
Howard