This tool calculates the number of varroa mites in a hive (per 100 bees) from a sample of 300 brood bees. It is a quick way to estimate the degree of varroa infestation, even in periods of swarming, through determining which hives are affected or how effective previous treatments were, etc.
Unlike other tests that use ether or drown bees in alcohol or washing detergent, this test allows you to return the bees to their hive unharmed.
Example of how varroa numbers affect honey production (lavender):
A varroa count of 3 mites per 100 bees in one hive at the beginning of the swarming season causes an average loss of 5 Kg of honey.
Note: Only 5% of varroa mites live outside brood cells (phoretic stage). The other 95% live inside capped cells where they reproduce. This measurement only shows the extent of the infestation – not an accurate varroa count.
When should we perform the test?
This test should be performed at the end of a varroa treatment to determine its efficiency, or at the start of an upcoming harvest season to determine the need for a treatment.
-A regular glass jar with a capacity of 1 liter, marked at the 100 ml level (1/10 of its height)
This will be used to measure a bee sample (300 bees = 100 ml = 42 g)
-A screened lid for the jar, big enough to let varroa mites go through, but not bees
-1 tbs of powdered sugar
-Beekeeping equipment (suit, hive tool)
-Reading glasses or magnifying glass (if you need them)
1-2 Select a hive frame with brood bees on it and shake (or brush) the bees off over an upturned hive cover. Fill the jar with these bees up to the mark (around 300 bees or 100 ml). Then close the jar with the screened lid.
3-4 Pour 1 tbs of powdered sugar over the screened lid and sift it by hand or using a hive tool. Shake the jar for 30 seconds, taking care not to let the sugar spill out. This will facilitate the detachment of any varroa mites from the bees in the sample.
5-6 Tip the jar and shake it over a white cloth or beehive cover. Varroa mites will drop while the bees stay inside the jar. This makes it easy to spot the mites and count them.
Getting the varroa count right:
Divide the number of varroa mites (per sample of 300 bees) by 3 to get the number of mites per 100 bees
The test should be performed on at least 8 hives for an apiary of 25-30 hives to get an overall idea of the varroa infestation.
If there are more than 3 varroa mites per 100 bees, the entire apiary should be treated using a method recommended by professionals.