I always treat for mites in late summer, usually in August. Waiting until September to treat for mites may be too late. The bees can be severely damaged by mites at that point and the odds for winter survival may be much less.
I like to use Formic Acid for a mite treatment in August. Formic Acid called Formic Pro or Mite Away Quick Strips. Formic Acid is considered an organic treatment and honey supers can remain on the hive during treatment.
This may be very helpful this year. With the high humidity we have had, honey in the supers may have a high moisture content. By leaving the honey on the hive longer, there may be a better opportunity for the bees to lower the water content of the honey on the hive.
Also, we have had great moisture this year. Goldenrod tends to produce a better nectar flow when there is adequate moisture after July 1st. A good Goldenrod nectar flow may give beekeepers the opportunity of another super or two of honey.
Using Formic Acid in the summer, we are always looking for a proper time to use it. The daily temperatures have to be under 85 degrees for the first three days the Formic Acid is on the hive. So watching the weather is critical to find the proper time to use it. Next week looks great for using Formic acid. Highs in the upper 70's. The hive populations are high, so the bees will be able to deal with the vapors of the Formic Acid.
I have purchased my Formic Pro and I will be putting it on the hives on Monday.