[AR1]

Not quite understanding your question. Are you asking if it is normal to have a zero mite count one week after applying formic acid?

 

[JConnolly]

If I understand Randy Oliver correctly, formic acid in high enough concentrations kills most mites even in brood, but the male mites are the most easily killed and are killed off even if the hive was under dosed. So you could still have had unfertilized female mites that survived the formic acid treatment. However since they are unable to reproduce you've still knocked out the mite population. The effect is not apparent for several days as a generation of mites gets skipped and the old survivors die off.

 

[John Davis]

JConnolly you may want to review the varroa life cycle.
You are correct that formic acid forms a true vapor which can penetrate the porous brood capping to kill mites in the capped brood.
The "old survivors" don't die off as quickly as many folks assume - as long as they can feed they survive a long time. The population makes it through the winter with no brood to reproduce in for several months.

 

[dpula2]

Thanks, I didnt know that. I thought that mites came out during broodless period and then when queen started to rear brood again, mites when back to honey comb cells under cappings.