>Everybody knows the theory. I was looking for _hard evidence_. Without that, it stays in Fantasy Land.

I think this study provides some data that supports varroa populations decline with extended brood breaks alone. But the most effective decline comes from a brood break combined with a treatment at the optimal phoretic period.  


- P/O Summary 
Sixty-two colonies were set up to test the hypothesis that Varroa control with oxalic acid (OA) can be enhanced by combining treatment with late summer requeening. Each colony consisted of two full depth boxes with nine frames per box. All colonies were queen right at the beginning of experiment and had brood present. Approximately 300 adult bees were collected pre- and post- treatment to calculate mites-per-bee. This experiment consisted of four treatment groups, requeen plus OA, requeen only, OA only, and controls (untreated). Queens were caged in the requeen treatment groups five days prior to placing a sealed queen cell in the colonies. This provided a period of 18-21 days without egg lying, which allowed most of the brood present to emerge.

- P/O Results
(Table 1). Post-treatment samples showed that Varroa mite numbers on adult bees decreased significantly in both the requeen only and the requeen plus OA treatment groups. The requeen only treatment was significant at α = 0.05 (t = 2.04, df = 168, P = 0.0429). The requeen plus OA treatment provided the greatest reduction in mite infestation with a drop in infestation from 0.2 ± 0.05 to 0.04 ± 0.05 mites-per-bee (t = 2.65, df = 168, P = 0.008)(Figure 1).


Combining An Artificial Break In Brood Rearing With Oxalic Acid Treatment To Reduce Varroa Mite Levels
Jeremy J. Wagnitz and Marion D. Ellis
University of Nebraska-Lincoln, Department of Entomology, Lincoln, NE 68583

http://www.academia.edu/download/31046556/ScienceJournalDec2010.pdf#page=6

Bill Hesbach

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