Northants Bee Keepers Association

Northamptonshire Beekeepers' Association (NBKA) Registered Charity No. 295593


Northants Bee Keepers Association

Copyright © NBKA 2007-2018

Northants Bee Keepers Association

A member organisation representing beekeepers in the County of Northamptonshire

August 2007

How to test bees for Pyrethroid Resistant Varroa Mites

Apistan and Bayvarol strips both contain Pyrethroid chemicals. If the Varroa mites in a colony of bees have become resistant to this, the strips will not kill the mites and they will build up, together with their associated viruses, causing the rapid death of the colony. Alternative methods to Apistan/ Bayvarol strips, e.g. tubs of Apiguard, will have to be used to control the Varroa mites.


To collect half a container full of bees, without the queen, and to see if the varroa mites on them are resistant to Apistan/Bayvarol strips, or not.


Large tub/honey bucket
Test Kit (ventilated plastic container with mesh lid, suspended Apistan strip, sticky backed plastic covering the mesh lid.)
Indelible marker pen (strips can be used approx. up to 10 times; a tally of use must be kept)
Double sieve (coarse to catch bees, fine to catch Varroa mites)
Shower head
Washing up bowl
Washing up liquid


1. If there are plenty of bees in the supers, shake the bees from 2 or 3 frames into the large plastic bucket/tub. Bang the tub on the ground to amass the bees at the bottom.

2. If there are no supers, or not many bees up there, open the brood box, find the queen and keep her safe (in a cage or on a frame in a nuc box…..) and then shake the bees from a couple of frames into the plastic bucket, amassing the bees in the bottom with a sharp tap.

3. Quickly scoop some bees into the plastic container (the ‘test cage’) to half fill it and quickly screw on the mesh lid.

4. Tip the remaining bees back into the hive.

5. Return the queen to the hive and close it up.

6. Invert the ‘test cage ‘so it is mesh side down and suspend the Apistan strip through the slot in the bottom of the container. Make sure the mesh lid is covered with sticky backed plastic.

7. Leave the test cage for 3-4 hours.

8. Give the ‘cage’ a sharp tap to dislodge any trapped mites.

9. Remove the Apistan strip.

10. Remove the sticky backed plastic covering the mesh lid and count how many mites have been knocked down by the Apistan strip and are stuck to the plastic.. Record this number.

11. Prepare a detergent solution with water (suitable for light washing up) in the washing up bowl.

12. Immerse the test cage in the solution, making sure all the bees are covered. This will rapidly drown the bees.

13. Tip the dead bees, together with the detergent solution, through the double sieve. (This will ensure any mites dislodged during the drowning procedure will not be lost).

14. Wash the bees with a strong flow of water through a shower head to separate any remaining Varroa mites. These will be caught in the fine sieve.

15. Count the number of Varroa mites washed from the bees. Record this number.

16. Calculate how efficient the product (Pyrethroid strip) is as a percentage:

              Varroa mites knocked down x 100 = % efficacy
Total Varroa mites  

17. If the efficacy is above 80% it is assumed the mites are susceptible to Pyrethroids, and killed by the product. If the efficacy is below 60% resistance is likely; contact your seasonal bee inspector who is recording the spread of resistant mites on behalf of the national bee unit.

Bee-Lines (A selection from our quarterly magazine)