Hi, Dewey Caron gave me permission to put his latest paper on our website.
Oops, I'm not allowed to put up the webpage, so, I'm going to copy the whole paper.
When an article by Dr. Dewey Caron came out in Oregon’s September 2009 issue of ‘The Bee-Line’ on Powder Sugaring Bees, the news editor, Rosanna Matterly asked for response from beekeepers using powdered sugar.
Hi Rosanna & Dewey, I just read the article, Powder Sugaring Bees by Dewey Caron in the September 09 issue of The Bee Line. I wanted to respond to the editor’s request about beekeepers powdered sugaring bees on a regular basis. Since March of 2005, almost 5 years, we have used nothing but powdered sugar to reduce and control varroa mites in our hives. This year, we had 7 hives and by September, even though we dusted the hives in mid-July, the mite counts were over the threshold (50 mites in 24 hours) in several of the hives. We did 5 applications of powdered sugar in 4 weeks and now our high counts are cut in half and the other hives are very low. Although we do not dust every week, we have someone in our club who dusts weekly and has no varroa. We tend to dust our bees several times a year 3 times, one week apart, mostly March, May and July. In September, with the really high counts we could dust 4 to 6 times in 3 weeks. From November though February, we dust once a month. Here in California, we do get a week of nice weather each winter month and it is a great time to get rid of the phonetic mites. August and September, we always have had high mite counts, and with regular dustings, we have always been able to get them down. Yes, it’s intensive, but not hard on the bees or brood at all. One of the things I noticed is at first, the bees almost sounded angry when you dusted them. Now, almost a curious buzzing, they no longer seemed upset.
Thanks, Janet Brisson
Morris Ostofsky also wrote. Dewey included our information plus response to a letter I wrote to Jerry Hayes of the American Bee Journal, soon to be published in Bee Craft America digital newsletter and gave me permission to post it.
Powder Sugaring Bees – Does it work?
By DEWEY M. CARON
Using powdered sugar (PS) for varroa mite control has been recommended as an IPM tool - to knock mites off workers captured in a jar to monitor mite levels as well as in entire colonies as a way to slow mite buildup in the colonies themselves. Monitoring mite numbers with PS is an relatively easy and helpful tool (see tutorial on MAAREC web site) but a new study suggests adding powdered sugar to a colony to control mites (sometimes called the Dowda method) might not be providing the perceived benefit - a 12-month study of powder sugaring bees every other week was unable to document an overall mite reduction in bee colonies!
The new study conducted in Florida by Amanda & James Ellis (U FL) with Jerry Hayes of FL Dept of Apiary Inspection, compared mite numbers, adult bee numbers and brood area of colonies treated with PS for mite control to untreated controls. Colonies were dusted every other week for 11 months with 120g of powdered sugar. The study found no differences in adult bee populations or amount of brood between treated and control colonies but although there was significant initial (24h) mite drop following dusting, no differences between numbers of mites, numbers of mites prorated to adult bee numbers and no differences in mite numbers per capped brood cells in treated vs untreated colonies.
The study conclusion: “DUSTING COLONIES WITH POWDERED SUGAR DID NOT SIGNIFICANTLY AFFECT COLONY STRENGTH OR MITE POPULATIONS …WE DID NOT FIND THIS METHOD OF DUSTING COLONIES WITH POWDERED SUGAR TO EFFECTIVELY CONTROL VARROA MITES.”
Does this mean PS should not be used in whole colony dustings? In the October 09 in Amer. Bee Jour., Jerry Hayes, one of the authors of the FL study, in his monthly Q&A column answered a letter from Janet Brisson of CA on whether PS works or not as follows:
“Yes research results showed that varroa was not significantly controlled by dusting with
PS. Within the parameters of their research, PS didn’t work great. But that does not mean
that if the research trial were re-structured to treat more often or in a different way that
results would not be different….research shows it doesn’t work long term. But, in real world
situations it does. What to do? I’d treat with PS until research catches up with reality.”
Many beekeepers (including Tom Dowda of FL) dusting whole colonies with PS however believe it is an effective control method. In 9 years of surveying backyard beekeepers in the mid-Atlantic states, I found a growing number of beekeepers using PS for mite control while; over 50% of beekeepers who indicated they were monitoring mite levels prefer to use the PS roll method to determine mite levels vs sticky boards or other methods. In a recent survey of 100 Oregon backyarders (who filled out a survey form during April local association meetings), 65% of the beekeepers who had no over winter losses indicated they used powdered sugar as a control scheme in contrast to 38.5% of beekeeper who did have winter loss (57 of the 100 had a loss; 43 had no loss). Overall colony loss levels were similar for Oregon ( 25.8%) and Mid-Atlantic beekeepers (24 %).
Morris Ostofsky of Eugene OR is one backyard beekeeper who feels PS is effective. He shared with me his success using PS:
“I have successfully used PS to control mites. To give you an example
of the efficacy of the PS treatment here are the results of my
treatment of one of my hives, # 9 - 6, this year. This hive has two
full depth brood boxes.
Date: 8/27 200 mites 24 hr drop using sticky board
8/28 PS dusted
8/31 144 mites on 24 hr on sticky board
9/3 & 9/7 PS dusted
9/10 48 mites on 24 hr sticky board
9/11 & 9/15 PS dusted
9/20 4 mites on 24 hr sticky board
Please note that I would NOT normally treat this often; however,
it was late in the season and I wanted to get the mite count down
before fall. I know this was awfully invasive; however, I felt that
the alternatives were worse. I have used this strategy to reduce
mite loads in other problems hives this year and in previous years.
The fact that I did not lose any hives last winter and had used
powdered sugar to reduce mite counts in fall is an indication that
dusting is effective.
Whether targeted, short time use of PS in spring or fall or using a different method of applying the powdered sugar, such as the newly available powder sugar duster (a converted pesticide applicator from China), modifies the conditions sufficiently to improve overall mite control is unknown. The initial report of mite control using powder sugar (by Nick Aliano in his PhD studies with Marion Ellis at U Neb) utilized the labor-intensive method of shaking adult bees off their comb and powdering them in a shaker box. Up to 35% of mites fall off the adults when the shaking heats the adult bees in the shaker box (and in monitoring a sample mite numbers of 300 adults in a glass jar, it is important that the bees heat up the jar interior to get an accurate mite estimate).
Certainly an initial count of 200 mites in 24 hr drop (as Morris found) should trigger a decision to "do something" (50 or more mites is the widely accepted threshold number from Us and European studies). Morris and other beekeepers have demonstrated that PS can, at least in some instances, reduce the number of mites on adults to a more "reasonable" load. It would seem reasonable that beekeepers using PS should continue to do so – and continue to document and report PS effectiveness.
Read results and parameters of FL study in 2009 Jour Apic. Res & Bee World: Vol 48(#1), page 72-76 .
U Nebraska study is available in: Jour. Apic. Res. Vol 44(#2): 54-57
Randy Oliver is going to do some testing to see if he can duplicate those numbers and see how more intensive dusting reduces mite loads. He talks about it on his website.