Considering they have only stubby little legs—and no wings, fins, or driver licenses—Varroa mites have no trouble getting around. In fact, they have an entire public transport system built and maintained by the very host they parasitize. Seems unfair, doesn’t it?
While many routes of migration from colony to colony have been documented, some are more important than others. Here’s a list of common ways mites get around, and there may be others.
- Mites on flowers. Of all the possible methods of mite transmission, this one seems the least likely. Mites are attracted to the pheromones of bees, so it seems far fetched that a mite would jump off a bee onto a flower and wait for another bee to arrive. However, if a Varroa-laden bee lands on a flower and begins to groom, it is possible that she will dislodge a mite. If so, that mite has no choice but to wait for another honey bee to come along and give her a lift. Surely this happens from time to time, but it’s probably not a major means of transmission.
- Beekeeper assist. Beekeepers can easily move mites between colonies when they exchange frames of bees or brood between hives or when they make splits.
- Drifting. Not all honey bees make it back to their own colony. It is well known that if you have a row of hives, the hives on the ends will slowly gain population while the ones in the middle lose it. If these lost bees are carrying pollen, nectar, or other needed stores, they are usually welcomed into the new colony. The unseen gift, though, may be phoretic mites tucked between the bee’s segments which are happy to jump off and make themselves to home.
- Drones. Unlike foragers, drones are not too particular about where they spend the night. Drones are very likely to stop in at any old colony and the foragers usually let them in. Wandering drones may be a major mode of mite transmission.
- Swarming bees. If a colony has mites, so will the swarm. It only takes one mite to begin a new infestation.
- Absconding bees. Bees don’t always abscond in massive groups like a swarm, but may leave a hive in onesies and twosies. This can happen when a colony is collapsing from disease or parasitism, when the bees are starving, when a colony remains queenless for a long period, when a colony is decimated by bears or other predators, after fire or flood, or whenever the bees’ home is destroyed or becomes uninhabitable. The bees fly off and some may be lucky enough to find another colony to join, carrying with them their trove of mites and/or other diseases.
- Robbing bees. Whenever a bee colony becomes weak it is a potential target. Bees from healthy robust hives are often eager to empty out the pantry of a weaker hive and ferry the treasure back home, a form of kleptoparasitism that is greater in some races of honey bee than others. Oftentimes the weak hive is riddled with Varroa mites, and it may even be collapsing for that reason. The robbing bees end up with more than they bargained for, taking home both honey and a blood-thirty population of Varroa mites. Aha! What do they say about greed?
The take-home message is that your colony can pick up an infestation of Varroa at nearly any time of the year. The best practice is to monitor your hives regularly to see if you have a problem, and then decide on a course of action if you do.
Honey Bee Suite