A varroa mite is an introduced ectoparasite of the honeybee, Apis mellifera. Mites were first introduced to the Western honeybee when the Apis cerana Fabricius – The eastern European or Asian strain of honeybees – Were introduced to the United States. Since its introduction, the Varroa destructor is believed to be the leading cause of mortality amongst honeybee colonies (Colony Collapse Disorder). Mite cells are most common on the brood and on the belly of worker bees.
HOW ARE MITES TRANSMITTED?
Mites are transmitted when an infected worker bee comes into contact with another hive, either through robbing or drifting. One study by Peck, Smith, and Seeley (2016) showed that mites can also be transmitted from flowers to foraging honeybees.
HOW DO I TEST FOR MITES?
Varroa mite counts can be done via the Powdered Sugar method or through a mite board.
Testing for Mites Using Powdered Sugar:
- Find a frame that is heavy with brood
- Ensure that the queen is not on the frame
- Using a plastic scoop, gently brush horizontally down the brood frame, bringing a sample of bees into the scoop.
You will need ½ cup of bees to adequately test for mites.
- Place bees into a mason jar, and cover with 2 tablespoons of powdered sugar
- Close the jar and gently roll the bees, covering them completely with powdered sugar
- Shake the powdered sugar bees and mites into a clear or white container
- The bees will fly away, leaving the mites behind
- Rinse the mites with 2-3 tablespoons of water, separating the mites from the powdered sugar
- Take count of how many mites you have
Testing for Mites Using a Mite Board:
- Place solid bottom board toward the back of the hive
- Place the screened mite board toward the front of the hive
- Monitor your mite count over a three-day period once per week
While mite boards help beekeepers track Varroa presence in the hive, they do not provide adequate readings of mite counts. Therefore, we recommend powdered sugar or an alcohol wash to measure your mite counts on a regular basis.
HOW DO I CALCULATE THE PERCENTAGE OF MITES IN THE HIVE?
½ cup of bees is approximately 300 bees. Divide the number of mites by 300 to obtain your mite count. 3 varroa in a sample of 300 bees: 3/300 = 1/100. Your mite count is 1%.
CAN I TREAT MY HIVE ON A SCHEDULE WITHOUT CHECKING MITE COUNTS?
Many beekeepers choose to treat their mites on a schedule, rather than tracking mite counts throughout the year. Treating on a schedule without knowing your hive mite count can result in over-treating or under-treating a hive. Varroa infestations have surged in recent years, with notable spikes in the fall timeframe. Beekeepers who treated throughout the summer and early fall lost colonies due to a lack of adequate mite detection and treatment in early winter.
The number one rule of beekeeping is that hives always have mites. Failure to treat will result in a colony absconding or overwinter mortality. We advise beekeepers to regularly monitor their mite counts and treat using the methods outlined in this article.