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How to treat Varroa Mites

How to treat Varroa Mites

TREATING VARROA MITES

Western Honey Bee (Apis mellifera) with attached Varroa Mites (Varroa destructor)” by AbsoluteFolly is licensed under CC BY-NC-ND 2.0

The detection and timely treatment of varroa mites is critical in preventing mite infestation, a principal cause of colony collapse disorder (CCD). One of the most common misconceptions among beekeepers is that a thriving hive does not need treatment. If their population is growing, they must be healthy, right? This assumption can lead to heartbroken beekeepers – Realizing that their hive absconded or died due to mite overload. Continuing to monitor and treat for mites can help to ensure the continued health of your hive.

To determine which treatment is best for you, one must consider the implications of treatment on mites, bees, and the honey itself. There is no ‘low maintenance’ mite treatment. There are, however, some treatments that require less time or less harm to bees or honey than others.

SCHEDULING YOUR TREATMENTS

Mite counts and treatment should be an ongoing project for beekeepers to ensure a healthy and prosperous apiary. Your geographic location, weather, humidity, and presence of other neighborhood hives will influence the type and frequency of mite treatments.

For example, beekeepers in northern climates should account for drastic weather changes in September and October, which will make accessing the hive and treating for mites harder. The presence of other hives in the area – especially a large apiary – should alert beekeepers to continually check and treat their hives for mites, as they will be transmitted from one apiary to another.

female varroa mite

“Varroa destructor female” by Gilles San Martin is licensed under CC BY-SA 2.0

POWDERED SUGAR

Natural beekeepers have long used powdered sugar to control mite populations. It is theorized that the bees will groom themselves of the powdered sugar, and in this process, the mites will fall off, dropping to the sticky board and or out of the hive, if using only a screened bottom board.

While the use of powdered sugar is a harmless treatment to the bees and honey, it is only useful in treating phoretic mites. Phoretic mites are mites that have adhered to the honeybee itself. Powdered sugar does not treat the mites that are on brood cells. Beekeepers looking to treat mites using powdered sugar should remain vigilant in assessing the mite loads and treating them every week to prevent infestation.

This treatment should not be performed in humid climates, as powdered sugar attracts water, encouraging excess humidity in the hive.

Treating Using Powdered Sugar:

  1. Fill 1 cup with powdered sugar
  2. Place a window screen or mesh over the top of frames
  3. Dust colonies with powdered sugar, using a hive brush to ensure all frames below are coated with sugar

While some ‘beeks’ will opt for a natural treatment method, such as powdered sugar, the most common methods for treating mites include Oxalic Acid or Formic Acid. We’ve outlined the two options below to help you determine the treatment that is best for you.

OXALIC ACID

Oxalic Acid can be applied in three ways: vaporization, fogging, or trickling. Trickling preserves honey, however, the volume of OA absorbed by the bees can be harmful to the colony. Therefore, we recommend either vaporization or fogging.

Vaporization

Oxalic Acid Vaporization treatment includes heating the OA to a point of sublimation. Beekeepers will need a vaporization tool, such as this one, that uses either an AC or DC battery source. A single hive generally requires 1 gram of fully vaporized OA.

When ready to apply, the ambient temperature of the tool must be between 315 °F (157 °C) and 370 °F (189 °C) to reach the point of sublimation. If the OA is not fully vaporized, the bees will not receive the full dose and the treatment will be ineffective. After 370 °F, the OA deteriorates into harmful formic acid and carbon monoxide.

Oxalic acid vapor released into the hive covers all of the frames within the boxes. The vapor then cools and adheres to the surfaces within the hive. Mites moving within the hive, on the brood, and on the bellies or backs of bees will die once in contact with the OA.

The oxalic acid treatment will result in a steep death rate in the first 2-3 days of the application. After three days, the vapor is no longer effective. Another mite count and treatment should be performed in 5-7 days. The vaporization treatment should be continued weekly for 3 weeks.

Fogging

treating honey bees for varroa mites

“Treating Honeybees” by Scott Barlow is licensed under CC BY-NC-ND 2.0

Fogging combines ethyl alcohol and oxalic acid. Fogging treatment delivers a strong dosage of the oxalic acid in a single application, and is best for beekeepers with multiple hives. For apiaries of 20 – 45 hives: Add 25 grams of the OA powder to 100ml of ethyl alcohol. Stir the mixture until the oxalic acid dissolves into the ethyl alcohol.

Note: The size of the nozzle will determine where your tool be inserted. Devices with a small nozzle require the beekeepers to drill a small hole into the back of the beehive, which is plugged following the treatment. Wider nozzles can be applied directly through the hive entrance.

The fogging treatment should be continued weekly for 3 weeks.

Beekeepers should use extreme caution when vaporizing or fogging with Oxalic acid. The temperature of the oxalic acid can lead to burns. Beekeepers should wear proper equipment when treating with oxalic acid through fogging or vaporization.

Why treat for 3 weeks with Oxalic acid?

Oxalic acid is only effective in treating mites that are on uncapped brood cells or on the bellies or backs of the honeybee. A worker bee remains in their brood cell for 11 days, and a drone for 14 days. Therefore, a beekeeper must complete three weeks of treatment to reduce the overall mite count within a hive.

FORMIC ACID

Formic acid, also known as MiteAway Quick Strips (MAQs), is a common mite treatment for beekeepers when temperatures are between 50 – 85oF. Formic Acid should not be used in temperatures below 50oF or over 85oF, as bees must be actively moving within the hive to move the formic acid between the frames.

To use the strips, insert a solid board in lieu of or below a screened bottom board, to prevent the formic acid from leaving the hive. Place the strips beneath the brood frames. Remove MAQs after 1 week, and re-check mite count.

Whichever, the method you choose, be sure to continue to monitor your mite counts and treat hives as needed.

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