If you had an overwintered colony or a nuc you purchased from someone, you may want to treat the colony for mites. Mites build up with time. Keeping their numbers low helps the bees thrive.
Right now the mite treatment that can be used with the honey supers on is Mite Away Quick Strips (MAQS) Formic Acid is the active ingredient. The normal treatment is two strips per hive. A good June treatment is using one strip. Using one strip will knockdown the present mite population. A full treatment again in August is required for proper mite control.
For MAQS application video and general information click the link