Bee Knowledgeable Answers: Varroa Mites

The honeybee has a specialized enemy called Varroa destructor. This mite can only reproduce and grow in a honeybee colony. 

1) What is a varroa mite?

photo: Agricultural Research Service

These mites are tiny. An adult mite is 1-1.8 mm long and 1.5-2 mm wide, reddish brown in color, and has a flat, round shape.

The adult female mite goes into a honeybee brood cell and lays eggs on the bee larva. The mites develop as the young bee develops and attach themselves to the bee as she hatches from her cell.

This photo shows a Varroa mite on a bee larva:

photo: Pollinator

A Varroa mite on a honeybee pupa:

photo: Agricultural Research Service

2) How does it harm honeybees?

They live attached to the bee, sucking the bee's blood and leaving open sores. This weakens the bee and exposes the bee to diseases. It attaches itself to the body of a honeybee and, like a flea or tick, sucks the hemolymph (honeybee "blood")  from the bee. This weakens the honeybee and spreads disease, called varroatosis. The disease causes deformed wings and the bee is unable to fly.Varroa mites are one of the leading causes of death to a honeybee colony.

Magnified photo of a Varroa mite attached to an adult honeybee:

photo: Christopher Pooley

3) What can humans do to help?

There are many different ways that beekeepers have developed and use to help kill and control the infestation of Varroa destructor.

There are several different miticides that are used to fumigate the bees. These methods can range from strong chemical treatments to all natural solutions. The more natural, organic solutions include the use of essential oils, oxalic acid and formic acid. These do not harm the bees, but kill the mites that are attached to adult bees.

Other methods for eliminating mite problems are the use of screened bottom boards on box hives. When the bee cleans itself and knocks the mite from her body, the mite falls through the screen to the ground and cannot easily climb back up into the main body of the hive to reattach itself to a bee. Small cell foundation is another method of beekeepers. Using a smaller sized base cell foundation encourages the bees to build smaller cells for their brood comb. This gives the mite less room inside the cell with the developing bee and discorages mite reproduction.

Beekeepers also treat their bees with powdered sugar, poofing it onto their bees and into open brood cells. This encourages the bees to clean themseves vigorously, dislodging the mites. The powdered sugar also makes it hard for the mites to hold on and climb, causing them to fall to the bottom of the hive and not be able to climb back up.

Beekeepers and breeders are also breeding bees with more natiral mite resistance. Russian bees are naturally more mite resistant. Breeding these genetic traits into other strains of honeybees helps create new breeds that have a better defence against this old honeybee enemy.