HI Catherine,
The article is unclear but from other reading I think that they mean that while it is only one mite, Varroa destructor, there are two different strains of mites, one resistant to Amitraz and all the older chemical miticides, and the other strain not resistant. The Australian authorities believe the original strain came in sometime before 2022 when mites were first detected, and the second resistant strain came in later. I'm going to ask Randy about it when he comes down to the workshop because I find this surprising. Why should Varroa not make it to Australia for 40 years and then suddenly have 2 separate incursions in 4 years? Seems possible instead that the mites were already genetically predisposed to develop resistance from pre-existing long term use of miticides in their country of origin.
Mimi:
The southwest of Western Australia, where the beekeeping industry is concentrated, is separated from the rest of Australia by 500 to 1000 miles of desert and has long had biosecurity laws around transport of honey bees and bee products. They remain free of the Small Hive Beetle that has been present in the rest of Australia for 20-25 years. While mite infected honey bees will eventually make it over there it might be decades.
Jim