I installed some packages this year. I treated them before they had any capped brood, with a single dose of OAV. Most dropped only five or six mites due to treatment. Some dropped as many as 25. Boy, am I glad I treated them all before those 25 could turn into hundreds more.
Since you already have capped brood, that window of opportunity is now closed. But you should begin some kind of mite monitoring treatment program to determine when to threat his summer. The most basic level is sticky boards, if you have screened bottom boards in place. But a better method is to learn to so sugar rolls, and do them monthly on each hive until it becomes too cold in October. Use those numbers to decide when to treat this year, and with what.
Nancy