Varroa Counting Tools

Varroa counting tools are simple pieces of equipment used to measure the load of the Varroa destructor mite in a colony: the sticky board (mite drop tray), the wash jar, the icing sugar jar, the measuring cup, the uncapping fork and the magnifier. A count made with the right tool and always with the same method shows whether treatment is needed and whether the treatment has worked. This page introduces the tools; the details of the methods and the thresholds are on the Varroa Monitoring Methods and Thresholds page.

What tools do you need for a varroa count?

You do not need an expensive set-up to begin with. To get consistent results at the hive, a typical counting kit consists of:

• Sticky board (mite drop tray): A white surface slid under the mesh floor to collect falling mites.
• Wash jar: A double container with a lid and a sieve inside, for washing bees in alcohol or water with detergent.
• Icing sugar jar: A jar with a mesh lid, for counting without killing the bees.
• Measuring cup: For taking the same quantity of about 300 bees (about 120 ml, a little more than half a glass) every time.
• Wide tub or tray: For shaking the bees off the frame and gathering them in one corner.
• Uncapping fork: For opening capped drone brood and looking at the pupae.
• White dish, strainer, magnifier and torch: For making the mites visible and counting them.
• Notebook or app: For recording the date, hive, method and result.

The sticky board: monitoring natural mite drop

The sticky board is a sheet, usually of white plastic or painted metal, placed under the mesh (screened) floor. Mites fall off naturally or after a treatment; the mesh prevents the bees from reaching the board. If the board is coated with a thin layer of oil, petroleum jelly or something sticky, the mites are not blown away by the wind or carried off by ants.

• When choosing: It should sit on the floor without gaps and slide in and out easily; a printed grid makes counting easier.
• Use: It is left for a few days, the fallen mites are counted and the total is divided by the number of days to get the average daily drop.
• Limitation: The drop varies greatly with colony size, amount of brood and season. It is good for following trends and seeing the effect after a treatment; on its own it is weak for deciding whether to treat.

How do you recognise a mite on the sticky board?

Besides mites, wax crumbs, pollen pellets, bee parts and faeces also collect on the board. The female varroa is a reddish-brown, transversely oval, smooth-edged and shiny speck about 1–2 mm across; if it is upside down you can see its legs. Do not confuse it with light-coloured wax crumbs or yellow-orange pollen pellets. A magnifier or the zoom on a phone camera helps a lot.

The wash jar: the most reliable count

A wash jar consists of two nested compartments: the sieve in the upper compartment holds the bees back, while the mites pass with the liquid into the transparent lower compartment. About 300 bees are shaken in alcohol or water with washing-up liquid for at least one minute; the mites are counted and the number divided by three to give the number of mites per 100 bees. The sampled bees die; in return, this method gives the most accurate and repeatable result.

• When choosing: Jars with a transparent lower compartment, a tight lid, a sieve that holds back bees but lets mites through easily, and a 300-bee fill line are practical.
• Home-made: One can also be made from two lidded plastic containers and a wire strainer; what matters is taking the same volume of bees each time.
• Tip: If you wash the bees a second time, you also catch the mites missed in the first wash.

The icing sugar jar: counting without killing bees

About 300 bees are put in a jar with a mesh or perforated lid, icing sugar is added and the jar is gently rolled for about a minute. After waiting a few minutes, the jar is turned upside down and shaken over a white dish; the mites fall out with the sugar. Adding a little water dissolves the sugar and makes the mites visible; the bees are returned to the hive.

It catches somewhat fewer mites than an alcohol wash, and its efficiency drops when the sugar clumps in humid weather. It is a reasonable option for those who do not want to kill bees; but always use the same method, otherwise the results cannot be compared.

Sampling tools: taking the right bees

The accuracy of the count depends on where the sample is taken. Mites are found mostly on nurse bees; so the sample is taken from a frame with open brood. First make sure the queen is not on the frame, shake the bees into a wide tub, tap the tub gently to gather the bees in one corner and scoop them up with the measuring cup.

The uncapping fork: opening drone brood

Varroa prefers drone brood because it stays capped longer. The uncapping fork is pushed into capped drone brood at the pink-eye stage and pulled out in one movement; red-brown mites on the white pupae are easy to see. About a hundred cells are opened and the number with mites is noted. It is a quick early warning tool; its result cannot be converted into mites per 100 bees, and it cannot be used when there is no drone brood.

Comparing the tools

Care, hygiene and common mistakes

• Cleaning: Scrape and wash the boards after every reading; renew the oil or sticky layer. Rinse and dry the wash jar and sieves.
• Hygiene: Clean the tubs and containers used on a hive you suspect of disease before moving on to another hive.
• Consistency: Use the same measuring cup, the same method and the same number of days.
• Mistake: Taking the sample from a super or a broodless frame gives a result that is lower than reality.
• Mistake: Counting one hive and generalising to the whole apiary; each colony should be measured separately.
• Mistake: Not counting again after treatment; resistance can only be noticed by comparing before and after.