The A, B, C’s of Bees: Varroa Mites


What’s smaller than a honeybee, but just as devastating as a honey-seeking bear?

Since its first appearance in the US in 1986, the varroa mite has become one of the major killers of bee colonies.  Although it is only about the size of a large pinhead, the varroa mite is devastating.

The varroa life cycle

The varroa mite life cycle is intimately tied to the bee’s life cycle.  A female varroa mite will enter into the cell of a developing larva and hide at the bottom of the food.  This prevents the nurse bees from detecting her and allows her to remain in the cell when it is capped over.  Before the bee larva spins its cocoon for metamorphosis, the varroa mite crawls out of the food and hangs on to the developing bee.  Once the cocoon is spun, the mite will feed on the bee pupa.  After about 30 hours she will begin laying eggs that hatch on the bee.  When the bee emerges from the cocoon as an adult, the mites are released and the cycle starts all over again.

Female mites are strongly attracted to developing drone brood, but will also attack developing worker brood.  Since drones take longer to develop, more mites are produced when drone cells are invaded.

The damage

Varroa mites feed on developing bees, weakening them and might contribute to colony collapse disorder.  They are also believed to be responsible for:

  • Decreased flight activity in foraging bees
  • Weight loss
  • Reduced life span
  • Decreased blood volume
  • Physical damage to the bee with high mite load (>5 mites in one cell)
  • Transmission of other pathogens

Treating for varroa mites

It is probably impossible to prevent varroa mite infection.  The goal of a beekeeper is to keep the number of mites in the hive low to minimize damage.

It is important to check your hives regularly and determine the amount of infestation in the colony.  There are a number of ways to determine pest load.  Probably the most accurate is the washing of adult bees followed by counting the number of mites that are recovered.  This website describes how to do an adult bee wash.

To prevent high mite load in your hive, you are going to have to treat your hive regularly for varroa mites.  Unfortunately, chemical treatments are recommended for controlling mites.  It is important to treat in the spring before the honey flow and again in the fall after the honey flow.  Use two treatments each time to kill the existing mites and then the mites that emerge with the bees later on.  Two of the least noxious treatments are Api Life VAR, which uses thymol (a mouthwash), and MiteAway Quick Strips that uses food grade formic acid.  Formic acid naturally occurs in honey – those smart bees!

I guess beekeeping can’t be all fun and honey.

Blogging my way from A to Z as part of the 2015 April A to Z Challenge!  My theme for this year:  Honeybees


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