After the rain-barrel workshop on Saturday, I dropped by the St. Paul Farmer's Market on my way home.  I was thrilled to stumble across a  local beekeeper who keeps 28 hives without any chemical use at all, resulting in only 10% losses per year.  For non-beekeepers, those are very good stats --- even if you use chemicals, 30% to 50% losses are normal in our area.

I asked the beekeeper what he did about varroa mites, and he shared his home remedy --- rhubarb leaves.  He told me to make a tea out of rhubarb leaves, then to dip in a sheet of plain paper.  After letting the paper dry, you put it in your hive the way you would use mite strips in the fall. 

The internet suggests that the purpose of the rhubarb tea is to extract oxalic acid, which is a proven treatment for mites.  Rhubarb leaves contain 0.2 to 1.3% oxalic acid, and spraying oxalic acid into bee hives does seem to kill varroa mites with only some damage to the bees.  The less-intrusive strips seem much better than spraying if they work, though.  I may have to try that this fall if our mite counts are high.