There is currently much concern about the health of honey bees. The past decade brought many tales of bees dying at high rates and even disappearing mysteriously. The good news is that we are not in a catastrophic situation – the media likes to hype up things – but it is true that bees are generally less healthy now than they were in the past. This is due to a number of factors: pests, diseases, chemicals used by beekeepers, lack of forage, pesticides, migratory practices, stress and a genetic bottleneck to name a few. Though it is likely a combination of all of them – death by a thousand cuts – it is obvious to any beekeeper that the most major problem of them all is varroa.
Varroa destructor, an apt name if there ever was one, is a tiny, tick-like parasite that lives on the honey bee. I say tiny, for it is to us, but if it was in proportion to a human it would be about the size of a basketball. You can imagine the feelings you would have if a gruesome thing the size of a basketball crawled up your leg and attached itself to your hip.
Varroa was originally a parasite on the Asian honeybee. While it could feed on the European honeybee, it could not reproduce in their hives, and therefore was not very harmful to it. But about 80 years ago, when Russian beekeepers brought hives to Korea on the Trans Siberian railway, European bees came into prolonged contact with their Asian cousins. During this time, one varroa made a genetic switch and could suddenly reproduce on European honey bees. The Russian beekeepers brought varroa back to Europe with their bees, and it quickly spread throughout the continent, and eventually to nearly every corner of the world.
Because the European honey bee had not evolved with varroa, it had no defense against it. Not only does varroa weaken the bees by attaching to them and sucking out their hemolymph, but during that process they also are a vector for diseases like deformed wing virus. As the number of varroa grows, the hive becomes weakened. This allows other stresses, which a healthy hive could normally handle, to take a foothold and eventually cause the hive’s collapse.
There are a number of ways to treat against varroa. Synthetic chemicals are the easiest for a beekeeper but each synthetic chemical seems to be effective only a few years before the varroa evolves a resistance against it. Natural treatments like organic acids or essential oils are less effective and trickier to use. To treat our hives we decided to use formic acid, which can be found naturally in ants. It is put in the hive as a liquid with a paper ‘wick,’ and is slowly vaporized into the hive. If the temperature is correct, it kills many of the varroa while doing little harm to the bees.
One important part of the process is checking how many varroa are in the hive. To do this requires taking 300 bees from the hive and combining them with a scoop of powdered sugar in a jar with a screen lid. The powdered sugar helps dislodge the varroa from the bees and then it is possible to shake the loose varroa through the screen lid onto a plate. If you find more than 6 varroa on 300 bees at the end of summer, it is time to treat. If you don’t, the hive will soon be weakened, overrun by varroa, and will eventually perish.