Varroa Mite Monitoring - What detergent do I use for a soap wash?

This is a frequently asked question when we’re talking about varroa monitoring. When we need to count mites at the bottom of the container, soaps with suds can trap mites in the foam at the top. The soap suds also cloud up the wash, making mites harder to see. This can skew the accuracy of our mite counts, making varroa control decisions more difficult. We did a quick field test of 10 different soaps for their suds amounts with 60 members from the Far North Coast Beekeepers and the Northern Rivers Amateur Beekeepers clubs in May.

The detergents tested were a mix of dish soaps, laundry detergents, and windscreen washer fluid, bought off the shelf from Woolworths, Aldi, and Supercheap Auto. 

To test, 1 teaspoon of soap was mixed with 500ml water in plastic bottles and shaken each for 20 seconds. As can be seen from the photo, the lowest suds detergent by a long shot was SCA brand windscreen washer. This was the lowest suds version of all, a complete winner. The pre-mixed variety is $5 for 5L, much cheaper than metho.

A beekeeper at a field day suggested that putting a small amount of white vinegar into a soap solution greatly reduced the suds. This was tested by adding vinegar to fresh, unshaken soap/water mixes, starting at 1 teaspoon of vinegar per solution and moving all the way up to 500ml (which works out at equal parts water to vinegar, with 1 tsp soap). At any concentration, the vinegar additive made no difference to the suds in any of the detergents.

Of course, this was not a definitive scientific study; it was just a quick test to get us thinking about trying different soaps to find the best option that meets our own parameters. 

Watering down an alcohol wash
If using methylated spirits for mite monitoring, watering it down could save money and reduce the fire hazard.

This scientific research paper from 1982 by De Jong et al., suggests that alcohol (in the form of ethanol or isopropyl alcohol) can be watered down to a solution of 25% alcohol & 75% water and still achieve a similar mite recovery as a wash containing 100% alcohol. N.b. This experiment was conducted on what was thought to be Varroa Jacobsoni, as Varroa Destructor had yet to be identified.

“Shaking bees in various solutions is an efficient means of detecting the presence of Varroa in samples of freshly killed adult honey bees. 25% solutions of ethanol or isopropyl alcohol were effective, convenient to use, and reasonable in cost. Hand-shaking for one minute removed 79-96% (average 92%) of the mites when 25% alcoholic solutions were used.”

 Watering down the alcohol also seems to reduce the chance of the wash kit catching fire in the truck if it gets close to a lit smoker. In a quick field test, a teaspoon of methylated spirits/water mix was put into a ceramic mug, then lit with a long BBQ lighter.

At 100%, the metho lit very easily and burned for a long time.
A 50/50 mix was harder to light and also burned for less time.
A 25/75 mix would not light at all.