what now? and what do you do?
The Apiarist (aka FS) blog (http://theapiarist.org/) has some informative and thought provoking posts about pyrethroids and resistance; bringing together different strands of the literature. I highly recommend these blogs. It raises the question about whether something like Apistan might be used again for a period since the resistant mite population will have been "evolved" out. And if you think a strategy of mixing up your varroa treatments is beneficial, for example by reducing resistance and allowing treatments at different times of the year then perhaps this miticide is worth consideration again. One issue is that if the miticide residues are present in wax then the resistant mite population will have been selected for and since all of my foundation is from commercial sources then I am a bit hesitant until I find out more. Is the residual miticide present at a significant level?
An issue is also getting everyone in a particular area to treat the same way and at roughly the same time which might reduce the transfer of resistance. Here in Tayside we are all pretty much in flying range of bee farmers and their practice re varroa could influence what we might do. I cannot recall if C4U posted on this issue but, (before we lose him to the season) what is your strategy for varroa management?
I have settled on a mid-winter oxalic acid treatment, and a late summer/autumn Apivar for the past 3 years. In future I'll mix in with Apiguard and if something desperate happened early on I would use formic acid (I have found this harsh on the colonies, but maybe overdid the dose).
The miticide in Apivar is called amitraz - and it is widely used in the US for cattle treatments and drug resistant strains of ticks have been found so at some point also Apivar might be problematic in beekeeping.