Hot Rhubarb

danged varroa

Sometimes, help comes from the most unlikely directions.

Of all the stressors bees now face, none is worse, or harder on the bees, than the Varroa destructor mite. Indeed, if you do not face up to the ugly fact of Varroa in your bees early and often, a veritable landslide of Awful Events will gain momentum and crush your colony.

But….many beekeepers are deeply reluctant to treat the bug on their bugs. Some miticides are toxic and migrate into the beeswax, imperiling the next generation of baby bees, whose cradle the wax is. Some treatments are tough on queens, or can’t be used when honey is coming in. Top bar hives are especially tough to treat simply because their configuration is so different from Langstroth hives, and most remedies were developed with Langstroths in mind. Some beekeepers struggle with the idea that all bees who can’t make it make it on their own should just be allowed to die, weeding less than ideal genes out of the system. Some just can’t believe something so tiny, something functionally invisible, can kill their hives. And more than a few just don’t know what to do.

Enter the humble rhubarb plant.

Rhubarb-Plant 2

Rheum rhabarbarum, that delicious copilot in the sensory swoon that is Strawberry-Rhubarb Pie, gets its bite from…wait for it…oxalic acid. Oxalic acid (wood bleach) is a standard Varroa-cide, usually delivered in the form of a solution (dribbled on the bees) or a vapour.

But, for those who are not comfortable with mixing up solutions of weak acids, or wearing full face respirators and lugging car batteries and vapourizers to the beeyard, turns out there is another way…well a couple of ways.

  1. Polish beekeepers Ann and Maciej Winlarski advise the use of rhubarb leaves and stems straight from the garden. In the March 2017 issue of Beekeepers Quarterly, they document their method. Tenderizing a rhubarb leaf and cut off stem with a hammer, the plant material is placed in the hive on the top bars above the brood nest. The worker bees immediately begin to remove the tender parts of the rhubarb and in the process expose the colony to low levels of oxalic acid. Over the next four or five days, the Winlarskis report mite drop increases by a factor of 2x to 7x. They remove the tough bits the bees can’t deal with, and put on a freshly pulverized leaf and stem. This process is repeated 5 times. This season they will test a repeat of 10 times. The method is easy on the bees, non toxic and can be used during a honey flow.
  2. Rhubarb tea. Rhubarb leaves and stems are cut up and brewed into a strong rhubarb tea. Soak shop towels or paper towels in the tea, and place in the hive on the top bars over the brood nest. Again, worker bees will chew up and remove the towelling, exposing the colony to low levels of oxalic acid.

Canada - Honeybee Breeding

Note that Randy Oliver, of, is presently developing a similar method, using shop towels soaked in oxalic acid dissolved in glycerin. He’ll be reporting on the results of his experiments, and his search for the best recipe.

These homely remedies will not result in a 100% kill of Varroa in your hive. But they will  help take the edge off the explosive mite growth curve, and reduce the exposure of your bees to those pesky mites, their viruses and bacteria.

Monitor your mite drop for a few days, and then try one of the above rhubarb remedies. Continue to monitor the mite drop rate and note any effect. Leave a comment below with your results.

Somebody, somewhere is going to find a way to eradicate the Varroa destructor infestation of European honey bees. But until that happy day, it doesn’t hurt to have another weapon in the anti-Varroa arsenal!

rhubarb flower bud




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