To sugar or not to sugar, that’s the question!
by Dr. Dewey M. Caron — University of Delaware
Using powdered sugar for varroa mite control has been recommended as an IPM tool — to knock mites off workers to help monitor mite levels and as a means of controlling mite buildup in the colonies themselves. Monitoring mite numbers with powdered sugar is a 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 might not be providing the perceived benefit. A newly published six-month study of powder sugaring bees every other week was unable to document any mite reduction!
In nine years of surveying backyard beekeepers in the mid-Atlantic states, I found only a small number — about 10-percent — of beekeepers using powdered sugar for mite control while over 50-percent of beekeepers (who indicated they were monitoring mite levels) prefer to use the powdered sugar roll to determine mite levels. The numbers using powder sugar to control were fairly consistent over the sur-vey years but there has been an increase in use of powdered sugar as a monitoring tool (survey results published on the MARREC web site (MAAREC.psu.edu and in the DE Beekeepers newsletter The Newsy Bee.)
The new study conducted in Florida by Amanda & James Ellis (U Fl) with Gerry Hayes of the Fla. Dept. Apiary Inspection compared mite numbers, adult bee numbers and brood area of colonies treated with powdered sugar 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 also 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. There was significant initial (24h) mite drop following dusting but no overall reduction in mite numbers in this study.
Their conclusion was a surprise negative: "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."
Whether a different method of applying the powdered sugar, such as the newly available powder sugar duster (a converted pesticide applicator from China), would modify the conditions sufficiently to improve overall mite control is unknown. Because powder sugar knocks a large population of mites down within the first few minutes, it is surprising that better overall mite control was not found in this study – it strongly suggests that we should not rely on powder sugaring of bees to reduce mites.
Read these results and parameters of this study in 2009 Journal Apiculture Research & Bee World: Vol 48 (#1), page 72-76 .