Shake a frame from the edge of the brood nest into a plastic dish pan. Be careful not to shake the queen. Scoop 300 bees (1/2 cup) into a wide mouth mason jar. Cap with cover fitted with 1/8 inch hardware cloth (pg 41). Add 2 tablespoons powdered sugar. Roll the jar gently for exactly one minute, set in the shade for exactly two minutes, and shake vigorously over a light colored surface or bowl for exactly one minute (the back of your dishpan works well). Spray with water to dissolve sugar and make mites show up. Count mites. Infection rate is the number counted divided by 3.
The significance of mite levels is debated and varies with season. For a general guideline, we respect and are comfortable with the Varroa Mite Recommendations done by the Ontario Tech Transfer.