18.104.22.168.2.3. Warm/soapy water or ethanol (75%)
This method follows the protocol by Fries et al. (1991a). Since mites do not have to be collected alive as allows the method described in section 3.1. ‘Collecting mites’, soap can be added to water or ethanol can be used to improve the efficiency of mite dislodging.
1. Warm/soapy water or ethanol is added to jars to cover the 300 honey bees.
2. The jars are shaken for 20 s to dislodge the mites from the adult honey bees.
3. The content of the jar is poured over a first sieve (aperture: 3-4 mm) to collect all the bees.
4. Check the jar for mites sticking to the sides.
5. Place a second sieve (aperture < 0.5 mm) underneath the first to collect the mites.
6. Flush the bees and mites with large amounts of warm water.
Strength of the water stream or volume of water used for rinsing as well as duration of rinsing should be standardised.
7. Count the mites remaining on the second sieve (e.g. 13).
8. Count the bees in the sample washed (e.g. 303).
9. Divide the number of mites counted by the number of bees in the sample to determine the proportion of infested individuals (13/303=0.043).
10. Multiply by 100 to obtain number of mites per 100 bees (4.3).
Pros: water based method: low environmental impact, low cost.
Cons: not practical on remote apiaries (large amount of water for rinsing and heat source needed); alcohol based: expensive, environmentally unfriendly.
None of these three methods is distinctly superior to the other and they can all be considered as reliable given that mite separation is done in a standardised manner (water always at the same temperature, or containing a standardized amount of soap etc.) and that the efficiency of the method is determined as described below.