'''Mid Summer'''<br />
You can continue removing drone brood for as long as the colony is willing to rear them. The swarms and nucleus can be treated for Varroa with treatments like evaporating [[Formic acid or thymol |thymol]] or trickling [[Oxalic acid in broodless colonies|oxalic acid]] in as early as midsummer if no honey is harvested from these colonies during the same season.
'''Late summer'''<br />
Nordic brown bees have a shorter brood rearing period compared to other subspecies. Brood rearing begins later in the spring and stops earlier in the fall. The broodless period also begins earlier in the fall and gives a good chance for Varroa control on adult bees.