As the bees come into contact with the Apistan strip, they pick up a minute amount of tau-fluvalinate – whilst another similar minute quantity emerges from within the strip to take its place on the surface becoming available for other passing bees. As the bees interact within the hive, the active ingredient is spread throughout the colony.
How to tackle resistant mites.
Vita has been monitoring the slow spread of mite resistance to pyrethroids for many years. Resistance is an entirely natural phenomenon and there are ways of slowing down its development and even reducing the number of resistant mites so that Apistan can again become effective.
An Integrated Pest Management strategy will vary treatment types from season to season and inhibit the development of resistant mites. Apistan and Apiguard are ideal alternating treatments where resistance has not yet become an issue.
Researchers have shown that the number of mites resistant to pyrethroids drops rapidly if pyrethroid treatments are stopped. Then after a few seasons pyrethroid treatments can be restarted successfully as part of an alternating IPM treatment regime.
This also bears out results of research performed previously in Italy and explains why many UK beekeepers who have used Apistan for the first time in several years are seeing good mite control levels.
No single type of treatment should be used repeatedly, as this can lead to resistance building up in the varroa mite population. Registered (legal) treatment types should be alternated wherever possible.
How to test for resistance
There are two tests for resistance, one based on a rule-of-thumb for very rapid testing, the other more rigorous.
Rule of thumb test
Place an Apistan strip in a colony. If after 24 hours there is a mite drop rate in the hundreds, Apistan’s active ingredient will be having a sufficient effect to enable its use for that season. Of course you need to be sure that the mite drop is not being removed by bees or other creatures before you retrieve it and the assumption is that your bees have a significant population of varroa in the first place.
Field resistance test: Around 300 adult bees are collected in a test container, to which an Apistan Package Bee Strip is inserted. After 3 hours the mite mortality is assessed and the presence or absence of resistance can be determined.