How to Test for Varroa Mites

Why Testing for Varroa Matters?

When should you check your hives for varroa? Unfortunately, testing for varroa mites is not a one and done procedure. If you live in a region with mites (and most folks do), monitoring mite levels is a season long activity.

The only way to know an approximation of varroa mite numbers in the hive is to test. This allows you to decide if treatment is necessary.

Determining when to treat your bees for mites involves many factors beyond just a date on the calendar. But, we do have a bare minimum schedule.

• early Spring (before honey supers)
• early Summer (Late May-June)
• Late Summer (August)
• Late Fall (October)

Another general guideline is to check for varroa mites once a month during the warm season.

And no, you can not rely on visual inspections by the time you see mites on bees – it may be too late to do anything.

Ways to Test for Varroa Mites

The level of mite infestation can be determined by several methods. Each method has benefits, as well as, drawbacks and limitations. Try several until you find the one that fits your style best.

• alcohol wash – soapy water
• sugar shake
• sticky board drop

Powdered Sugar Roll/Shake

For the powdered sugar roll – Harvest 300 bees as above – don’t get the queen!

Pour bees into wide mouth glass jar fitted with a mesh lid. (#8 mesh hardware cloth). Or you can purchase a testing unit from Mann Lake (that’s what I use).

Simply brush the bees off the frame into the cup basket until you get the needed amount. Then, add 1 – 3 Tablespoons of powdered sugar to the container, put on lid and gently shake.

If you need to, set the jar in the sun for a minute (very briefly) to increase humidity. Gently shake the sugar out of the jar (thru the mesh lid) onto a white surface and count the mites.

Release the sugar-coated bees. (Warning – they will be alive but they may not be happy!) Be sure to wear some protective beekeeping wear.

Sticky Board Counts

With bees and mites moving around inside the hive – some mites will fall off during the daily hustle and bustle.

Researchers have determined a guideline for detecting the level of infestation by the number that fall to the bottom.

Screened bottom boards normally come with a white grid board that can be inserted for performing mite checks. (Don’t leave that board in all the time – it cuts down on important hive ventilation.)

Screened bottom boards normally come with a white grid board that can be inserted for performing mite checks. Don’t leave that board in all the time – it cuts down on important hive ventilation.

The numbers seem to change from year to year. But, most experts recommend that more than 30 mites dropped in a 24-hour period is too many. However, this is a highly contested number because there are so many variables.

Mite Drop Counts Can Vary Due to:

• Colony size and behavior
• Weather conditions

While the ideal outcome would be to have colonies with zero mites, that is not usually possible. Most colonies do have some mites and they do deal with the situation well.

Perform a Natural Drop Count

Apply a thin coating of Vaseline or cooking spray to one side of the white board. You can also buy liners that are already sticky if you wish.

The greased sticky board is placed under the screen bottom for 24 hours and then removed. The screen prevents bees from getting stuck on the board.

If you have solid wood bottom boards, you can purchase a special screen insert to allow counting. Inspect your sticky board and look for mites. How many do you see?

Drone Brood Inspection

The life cycle of Varroa Mites and the honey bee life cycle weighs heavily in favor of the mites.  They can identify whether a bee larva is a worker or a drone. They will use both but drone brood is preferred.

The female mite has time to produce 1 mature daughter (maybe 2) in a worker cell. However, if she inhabits a drone cell (with a longer time capped in the cell) she can produce 2 to 3 daughters.

When performing beehive inspections, you may discover drone brood in the stray comb between the boxes. In this case, always check quickly for mites.

Of course, not seeing mites in your exposed drone brood is no guarantee that your colony is safe.  But, it is always a good idea to check for varroa mites.

Why Visual Testing Doesn’t Work

Because varroa are external pests that can be seen with the naked eye, you might think you can just look, right?

Can you check your bees for mites by looking? Well, yes you can but its not easy or reliable.

There is no way you can get a true visual assessment of varroa mite numbers. This is because at any given time the vast majority of mites are inside capped brood cells.

By the time you see adult mites on the bees, it could be too late for the colony to rebound from the infestation.

Once enough bees are sick and enough disease is spread, the colony reaches a point of no return. This is why we use various methods of checking mite levels regularly.

Getting an Accurate Sample

Collect your bee sample from a brood frame where nurse bees are caring for developing brood. These bees are more likely to carry phoretic varroa mites than older foragers.

Most testing methods require a sample of about 300 bees (roughly ½ cup), and always take a moment to locate and avoid accidentally collecting the queen before placing bees in your testing container.

Common Testing Mistakes

It’s hard to do anything to perfection in the bee yard. Bulky bee suit, sweat running in my eyes, thousands of flying stinging insects – it can all be a little disconcerting.

Still, here are some beekeeping mistakes related to varroa counts – you want to avoid.

• collecting forager bees instead of nurse bees
• accidentally including the queen
• estimating instead of measuring 300 bees
• not shaking long enough
• testing only once a year
• relying on seeing mites with your eyes
• testing during poor weather and rushing