Mite Treatment timing

So a bit of a newbe here, I got a new hive this past year as my last one absconded (indian summer and no forrage for them so they left). I noticed with this hive that there were some plainly visible mites, and when I was pulling off some cross comb that there were mites in the brood.

I know that everyone has different preffered treatments for mites, I'm going to try Apiguard for this particular hive. I just have some questions about when and how to best use it.

I seem to be having a break in the brood cycle at the moment (queen that came with the hive either left of died, not sure which). So I was thinking about treating now, however it is the middle of summer here in southern VT and as such there are a fair bit of flowers and flowering plants around. Apiguard says not to treat during a honey flow. Which I would think that I'm currently in given the abundace of forrage at the moment. So my question would be should I treat now, or wait until the fall and treat then before winter? I will note that I don't plan to harvest the honey this year, but I will harvest what is left in the spring once I start to get a nectar flow going then.

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Thank you in advance for the advice and the help.