There are several methods to determine the number of mites that are in the colony including uncapping pupae, ether and sugar rolls and using a sticky board.
Uncapping pupae – In this method, pupae are examined for mites by uncapping the cells, extracting the pearly white pupae and looking for the dark brown mites adhering to the surface. Use a capping scratcher or table fork to uncap several cells at a time, and spear the pupae beneath. A pair of tweezers can also be used to extract a single pupa from its cell. Select pupae with pigmented eyes, because these can be extracted from the cell without breaking apart. Select drone pupae if they are present, because Varroa prefer drones. If drone pupae are unavailable, then look at worker pupae. Sample at least 25 drone or 50 worker pupae to determine infestation level.
The ether roll method - is used often because it is quick and easy to perform. All that is needed is a sample of bees, a screw-top glass jar and a can of ether starting fluid. Select a brood frame with worker bees on it. Make sure the queen is not on this frame because the bees will be sacrificed. Shake 200 to 300 bees from the frame into a quart jar. A funnel may aid in this transfer. A temporary funnel can be made using a rolled up piece of paper or a plastic gallon container. Cut the plastic container in half, insert the “mouth” of the container (it becomes the spout of the funnel) into the sample jar. Spray two squirts of ether starting fluid into the jar with bees, cap the jar and shake vigorously. Roll the mass of ether-coated bees in the jar. Observe the inside surface of the jar for the mites that will fall off the bees and stick to glass. Be careful not to confuse wax scales produced by the bees, or lumps of pollen, with Varroa. Wax scales are white. Probe any dark objects of similar size to Varroa. Pollen lumps are soft and will break apart when probed.
Sugar roll - A modification of the ether roll uses powdered sugar, rather than starting fluid, to dislodge mites from bees without harming many bees. The same method described above is used to collect the bees. However, a canning jar should be used so that the solid lid can be replaced with 1/8 inch screen mesh. After collecting bees and capping the jar, 1 tablespoon of powdered sugar is poured through the screen lid and onto the bees. The jar is gently rolled without spilling any of the sugar, then left to sit for a few minutes. Gently shake the sugar and mites from the jar. Brief shaking will recover about 70% of the mites; more shaking will recover 90%. The sugar and mites can be sieved again through a finer screen to separate mites from the sugar and make detection easier.
A sticky board trap - is used to sample a whole colony for mites. A sticky board trap is placed on the bottom board inside the entrance of the bee colony. The board can be used alone or in combination with a treatment to detect mites. Mites die from natural causes, fall off the bees and land on the sticky board. A sticky board is made using stiff cardboard with a smooth, light-colored surface that is cut to fit inside the hive. A sticky substance such as TanglefootTM, clear “contact” shelving paper or spray cooking oil is applied to the upper surface to catch and hold mites. A metal screen made from eight-mesh (per inch) hardware cloth (same dimensions as the sticky board) is placed above the board, to prevent bees from removing the mites, and from becoming trapped on the board. Paper boards coated with sticky material can be purchased from beekeeping suppliers. The sticky board must be examined within two or three days, because other natural debris in the beehive will accumulate on the board, making it difficult to distinguish mites from debris.
-John Skinner, University of Tennessee
Bee Informed Partnership