Look at the FGMO forum. You can fog anytime you want, and add supers the next day. Some are even considering fogging with supers on. I have not done that, and am not recommending it. Fogging takes only a minute or two and is all food grade.
I would not risk my bees on faith that the package supplier treated for mites. He may have, he may have used a treatment that is not high as far as efficacy goes. Surviving mites in the current atmosphere means checking hives for mites on a regular schedule. We check drone cells or do sugar rolls. We spot check our yards every 2 weeks and monitor levels. You should develop an ongoing IPM plan to deal with ongoing control, preferably one that will include some type of impact during the season. We use tobacco in our smoker judiciously (nicotine in small does kills mites yet will not kill bees) at different times during the season. We pull honey the middle of July and use formic acid or fog with thymol for mid season knock down. Many times even hives that been treated in the early spring then shipped from the South will be heavy with mites towards the end of the summer flow and by the time honey is off and fall treatment is on the damage is done. We've found good mite control is an ongoing task for all season, not a spring/ fall answer.
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